medicina

Review CT and MRI in Urinary Tract Infections: A Spectrum of Different Imaging Findings

Mohamed Abou El-Ghar, Hashim Farg *, Doaa Elsayed Sharaf and Tarek El-Diasty

Radiology Department, Urology and Nephrology Center, Mansoura University, 35516 Mansoura, Egypt; [email protected] (M.A.E.-G.); [email protected] (D.E.S.); [email protected] (T.E.-D.) * Correspondence: [email protected]

Abstract: There are many acute and chronic infections affecting the urinary tract including bacterial, fungal and viral infections. Urinary tract infections (UTIs) can present in many different patterns with variable degrees of severity varying from asymptomatic and uncomplicated forms to life threatening complicated infections. Cross-sectional imaging techniques—including both computed tomography (CT) and magnetic resonance imaging (MRI)—have become very important tools not only for evalu- ation of UTIs, but also for detection of associated complications. Selection of either CT or MRI in the UTI evaluation depends on several factors such as the presence of contraindication, experience, cost and availability. CT and MRI help in early detection and management of UTIs that reduce the prevalence and severity of complications. In this article we will present the radiologic findings at CT and MRI in different types of upper and lower UTIs including acute pyelonephritis, intrarenal and perinephric abscesses, pyonephrosis, chronic pyelonephritis, emphysematous UTIs, xanthogranulo- matous pyelonephritis, tuberculosis (TB), bilharziasis, fungal infection, corynebacterium infection, ureteritis, cystitis, prostatitis, prostatic abscess and urethritis.

Keywords: urinary tract; infection; pyelonephritis; cystitis; CT; MRI





Citation: El-Ghar, M.A.; Farg, H.; Sharaf, D.E.; El-Diasty, T. CT and 1. Introduction MRI in Urinary Tract Infections: A Spectrum of Different Imaging Worldwide, urinary tract infection (UTI) is considered the commonest urologic prob- Findings. Medicina 2021, 57, 32. lem, affecting about 150 million patients annually [1]. UTIs account for the greatest https://doi.org/10.3390/medicina proportion (31%) of nosocomial infections in American medical intensive care units while 57010032 it represents the second most common nosocomial infection after respiratory infection in Europe [2]. The anatomic structure of the urinary tract increases its susceptibility for Received: 20 November 2020 colonization by several microbial agents [3,4]. UTIs can be caused by many types of micro- Accepted: 29 December 2020 organisms, including Gram-positive bacteria, Gram-negative bacteria and certain fungi. Published: 1 January 2021 Uropathogenic Escherichia coli (UPEC) is the commonest causative organism for both com- plicated and uncomplicated UTIs [5–8]. Undetected and untreated acute pyelonephritis Publisher’s Note: MDPI stays neu- may lead to renal hypertension, renal scarring, and even renal failure [9]. tral with regard to jurisdictional clai- Diagnostic imaging for evaluation of UTI is mandatory in the following conditions: ms in published maps and institutio- (a) uncertainty of symptoms; (b) assessment of the complicated UTI causes such as tumors nal affiliations. and strictures; (c) persistent and recurrent symptoms despite adequate treatment; (d) assessment of complications that need urgent intervention and management, such as renal abscess [10]. Copyright: © 2021 by the authors. Li- Cross-sectional imaging including both computed tomography (CT) and magnetic censee MDPI, Basel, Switzerland. resonance imaging (MRI) becomes a part of a routine study of patients with symptomatic This article is an open access article and complicated UTIs. distributed under the terms and con- Both MRI and CT provide high image quality, allowing easy diagnosis of urinary tract ditions of the Creative Commons At- infections. CT is usually readily available than MRI [11], however both modalities allow tribution (CC BY) license (https:// comprehensive evaluation of the renal parenchyma, surrounding structures and spaces, creativecommons.org/licenses/by/ and better evaluation of the urothelial wall [12,13]. 4.0/).

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CT is the ideal imaging modality in the assessment of most cases of UTI as it is a fast technique and provides adequate anatomical and physiological details, identifies both renal and extra-renal pathologies, and provides different phases to be evaluated after intravenous contrast injection. Other CT advantages include the use of multiplanar reconstruction (MPR), curved planar reformatted images, maximum intensity projection (MIP) and three-dimensional (3D) reconstruction. The detectability of air and calcifications is usually better using CT scan than MRI, although these conditions can also be detected on MRI [2,11,13–15]. MRI is currently considered as a problem-solving imaging technique if CT is not diagnostic. MRI is recommended also when CT cannot be performed such as in pregnant women and in patients with contrast medium contraindication. Additionally, MRI can be used for diagnosing chronic UTI with or without using contrast material. MRI has also the advantage of high soft-tissue resolution and no radiation exposure [11,16]. Better tissue characterization can be obtained using dynamic contrast enhanced MRI and diffusion weighted MRI [16,17]. Diffusion-weighted imaging (DWI) can eas- ily diagnose pyelonephritis based on renal parenchymal apparent diffusion coefficient (ADC) values, which are usually found to be lower than those of the unaffected renal parenchyma [11,18,19]. MRI is ideal for detection of complications related to UTIs such as renal abscess and also to follow up the response to medical treatment and percutaneous drainage, especially in young patients. Sometimes, delayed excretory phase imaging (either with CT or MRI) is required to evaluate the urinary collecting system [16,20]. CT carries the risk of radiation exposure and side effects of iodinated contrast medium [21]. On the other hand, MRI is not routinely used in the evaluation of UTIs and is reserved for problematic cases due to high cost, limited availability, and scanning duration [22]. In this review, we will explore the respective role of CT and MRI in the evaluation of UTIs. The role of MRI will be highlighted in the diagnosis of UTIs and associated complications, especially when there is a contraindication to CT.

2. Cross-Sectional Imaging Features of Urinary Tract Infections 2.1. Acute Pyelonephritis Acute pyelonephritis (APN) is an acute infection of the renal parenchyma and collect- ing system. Pathophysiology of APN explains its symptoms. It usually results from either ascending infection from the bladder or by hematogenous spread that is why the patients presented with high-grade fever, flank or suprapubic pain, dysuria, urinary frequency, nausea, or vomiting [2]. APN usually responds to adequate antibiotic treatment [23]. A non-contrast CT scan is important for detecting air bubbles in the urinary tract, hydronephrotic changes, and stones. High attenuation areas on non-contrast CT represent hemorrhage, while low attenuation areas represent edema. In early contrast-enhanced CT scan, there is a loss of corticomedullary differentiation associated with wedge-shaped hypo- enhancing areas or striated nephrogram pattern of linear alternating streaks of increased and decreased attenuation extending from the renal sinus to the renal cortex (Figure1)[ 11]. The pathophysiology of these radiological features may be due to poorly functioning renal parenchyma caused by vasospasm, tubular obstruction, or interstitial edema [10,24]. Additionally, perinephric fat stranding and renal abscess formation may be noted at CT imaging [23]. Medicina 2021, 57, x FOR PEER REVIEW 3 of 22 Medicina 2021, 57, x 32 FOR PEER REVIEW 3 3of of 22 23

(a) (b) (c) (a) (b) (c) Figure 1. Acute right pyelonephritis. (a) Axial non-contrast computed tomography (CT) image shows enlarged right kid- neyFigure with 1. anAcuteAcute irregular right right pyelonephritis.outline, pyelonephritis. thickened (a) ( aAxialperineph) Axial non-contrast non-contrastric fascia, computedand computed distorted tomography tomographyperinephric (CT) fat. (CT) image Axial image shows (b) showsearly enlarged and enlarged (c right) delayed right kid- ney with an irregular outline, thickened perinephric fascia, and distorted perinephric fat. Axial (b) early and (c) delayed post-contrastkidney with an CT irregular images outline,show linear thickened streaks perinephric extending fascia,from th ande papillae distorted to perinephric the cortex with fat.Axial an impaired (b) early enhancement and (c) delayed of post-contrast CT images show linear streaks extending from the papillae to the cortex with an impaired enhancement of thepost-contrast parenchyma. CT images show linear streaks extending from the papillae to the cortex with an impaired enhancement of the the parenchyma. parenchyma. Some radiological features may suggest specific pathologies, for example, the thick Some radiological features may suggest specific pathologies, for example, the thick enhancingSome wall radiological of the renal features pelvis may without suggest renal specific parenchymal pathologies, affection for example, indicates the thickpyelitis en- enhancing wall of the renal pelvis without renal parenchymal affection indicates pyelitis [25].hancing wall of the renal pelvis without renal parenchymal affection indicates pyelitis [25]. [25]. TheThe presence presence of of round round peripheral peripheral hypo-e hypo-enhancingnhancing parenchymal parenchymal renal renal lesions with a clinicalclinicalThe presentation presentation presence of of ofround pyelonephritis pyelonephritis peripheral favors favorshypo-e the thenhancing diagnosis diagnosis parenchymal of of the hematogenous renal lesions route route with of a infectionclinicalinfection presentation (Figure (Figure 22),), howeverhowever of pyelonephritis thethe ascendingascending favors infectioninfection the diagnosis usuallyusually of presentspresents the hematogenous withwith wedge-shapedwedge-shaped route of areasinfectionareas (Figure (Figure (Figure 33).). WhenWhen2), however thethe entireentire the ascending kidneykidney isis involvedinfectioninvolved usually thethe differentiationdifferentiation presents with betweenbetween wedge-shaped thethe twotwo routesareasroutes (Figure is is difficult difficult 3). When [24]. [24]. the entire kidney is involved the differentiation between the two routes is difficult [24].

(a) (b) (c) (a) (b) (c) Figure 2. 2. LeftLeft hematogenous hematogenous acute acute pyelonephritis. pyelonephritis. (a) (Axiala) Axial non-contrast non-contrast CT CTimage image shows shows focal focal contour contour bulge bulge at the at pos- the Figure 2. Left hematogenous acute pyelonephritis. (a) Axial non-contrast CT image shows focal contour bulge at the pos- teriorposterior parapelvic parapelvic region region of the of the left left kidney. kidney. (b) ( bAxial) Axial and and (c ()c coronal) coronal reformatted reformatted post-contrast post-contrast CT CT images images show show mildly mildly enhancingterior parapelvic rounded region lesion of at the the left mid-zone kidney. of (b the) Axial kidney and with (c) coronaladhesion reformatted to the left psoas post-contrast muscle mimicking CT images renal show tumor. mildly enhancing rounded lesion at the mid-zone of the kidney with adhesion to the left psoas muscle mimicking renal tumor. enhancing rounded lesion at the mid-zone of the kidney with adhesion to the left psoas muscle mimicking renal tumor. CT is also important for differentiating pyelonephritis from tumor and renal infarction. In certain cases, if the diagnosis is not established, a delayed CT scan after three hours should be performed to assess retention of contrast that differentiates pyelonephritis from renal tumors and renal infarctions. Imaging features of acute pyelonephritis usually show significant improvement after appropriate medical treatment but the tumor will not. Sometimes, radiological signs of APN lag behind clinical improvement and this can create clinical uncertainty and require histopathological confirmation. Extrarenal manifestations of APN that are observed on CT include periportal edema, gall bladder wall thickening, and renal vein or inferior vena cava thrombosis [2], but are rarely observed.

(a) (b) (c) (a) (b) (c)

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(a) (b) (c) Figure 1. Acute right pyelonephritis. (a) Axial non-contrast computed tomography (CT) image shows enlarged right kid- ney with an irregular outline, thickened perinephric fascia, and distorted perinephric fat. Axial (b) early and (c) delayed post-contrast CT images show linear streaks extending from the papillae to the cortex with an impaired enhancement of the parenchyma.

Some radiological features may suggest specific pathologies, for example, the thick enhancing wall of the renal pelvis without renal parenchymal affection indicates pyelitis [25]. The presence of round peripheral hypo-enhancing parenchymal renal lesions with a clinical presentation of pyelonephritis favors the diagnosis of the hematogenous route of infection (Figure 2), however the ascending infection usually presents with wedge-shaped areas (Figure 3). When the entire kidney is involved the differentiation between the two routes is difficult [24].

(a) (b) (c)

MedicinaFigure2021 ,2.57 Left, 32 hematogenous acute pyelonephritis. (a) Axial non-contrast CT image shows focal contour bulge at the pos-4 of 23 terior parapelvic region of the left kidney. (b) Axial and (c) coronal reformatted post-contrast CT images show mildly enhancing rounded lesion at the mid-zone of the kidney with adhesion to the left psoas muscle mimicking renal tumor.

(a) (b) (c)

Figure 3. Left acute pyelonephritis. (a) Axial non-contrast CT image shows a slight focal contour bulge at the middle of the kidney. (b) Axial and (c) coronal reformatted post-contrast CT images show mildly enhancing subcapsular lesion of relative wedge shape extending to the medulla with thickened related perinephric fascia with distorted perinephric fat.

MRI signs of acute pyelonephritis are similar to those detected at CT scan; renal enlargement, alterations of signal intensity due to hemorrhage or edema, striated nephro- gram, and perinephric fluid reaction. On MRI, signal void lesions detected in the urinary tract may be due to either calculi or air bubbles. With MRI, APN shows a heterogeneous lesion of hypointense signal intensity on T1-WI and hyperintense signal intensity on T2-WI. MRI provides high soft-tissue contrast resolution, facilitating differentiation of APN from renal scarring, and detection of the extrarenal extension [1,2]. MRI with contrast helps to depict areas of renal parenchyma involvement. Gadolinium- enhanced inversion recovery imaging can help to detect APN accurately in children com- pared with dimercaptosuccinic acid (DMSA) scintigraphy. This method accentuates con- trast differences as unaffected renal tissue enhances normally. However, APN remains hypointense after the administration of intravenous contrast media. MR urography (MRU) using heavy T2 weighted sequence can detect hydronephrotic changes in cases of uri- nary tract obstruction and extension of perirenal inflammation, particularly when fat suppression sequence is used. DWI can characterize lesions without contrast injection or ionizing radiation. On DWI, APN can be more confidently diagnosed when areas of restricted diffusion are demonstrated; these areas are hyperintense on high b-value DWI, and hypointense on ADC map which accurately differentiate between unaffected renal parenchyma, abscesses and nephritis. DW-MRI demonstrated very high accuracy and diagnostic agreement (~95%) with gadolinium-enhanced MRI [2,26–28]. There are two types of pyelonephritis; diffuse type and focal type. The focal type is limited to a mass-like or localized peripheral wedge-shaped hypo-enhancing lesion associated with adjacent fat stranding. In the diffuse form of pyelonephritis, kidney en- largement, poor parenchymal enhancement (delayed nephrogram), perirenal fat stranding, and thickened fascia are usually noted [14].

2.2. Renal and Perinephric Abscesses An abscess may occur secondary to aggregating lesions of infection in pyelonephritis or superimposed infection of a pre-existing urinoma or hematoma [10]. The risk of abscess formation increases in the presence of obstructive uropathy and immunosuppression conditions. Diabetes is also a major risk factor for complicated UTIs including renal abscess and emphysematous pyelonephritis [29]. The commonest infectious organisms in renal abscesses are Escherichia coli, and Staphylococcus Aureus [14], while Candida species are more commonly detected in diabetic patients. About 20% of patients with a renal abscess may have a negative urine culture [14,25]. The renal abscess appears as hypodense geographic or rounded non-enhancing fluid collection at contrast-enhanced CT. However, the fluid contents may have high attenuation than the clear fluid in early stages. The enhancing margin of abscess represents a pseu- docapsule with variable degrees of wall thicknesses and nodularity. A halo of reduced Medicina 2021, 57, 32 5 of 23

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Medicina 2021, 57, x FOR PEER REVIEWenhancement may surround the abscess during the nephrographic phase. Sometimes,5 of 22

air bubbles may be seen within the abscess and appear as locules of low density at non- contrastnon-contrast CT scan. CT The scan. renal The fascia renal isfascia often is thickenedoften thickened with soft-tissuewith soft-tissue stranding; stranding; septal septal thickeningthickening and and perinephric perinephric fat fat obliteration obliteration (Figure (Figure4). 4). CT CT can can easily easily detect detect extrarenal extrarenal ex- non-contrast CT scan. The renal fascia is often thickened with soft-tissue stranding; septal extensiontension of of the the abscess abscess into into the the perinephric perinephric spaces, spaces, psoas psoas muscle,muscle, andand thethe adjacentadjacent or-organs thickening and perinephric fat obliteration (Figure 4). CT can easily detect extrarenal ex- gans(Figures (Figures 55 andand 66).). CT CT guided guided aspiration aspiration and and tube tube drain drain is isa apreferable preferable method method for for mini- tension of the abscess into the perinephric spaces, psoas muscle, and the adjacent organs minimallymally invasive invasive treatment treatment of of renal renal abscess abscess in incase case of ofdifficult difficult ultrasound ultrasound approach approach (Figure (Figures 5 and 6). CT guided aspiration and tube drain is a preferable method for mini- (Figure7) [1,2,24,25].7)[1,2,24,25 ]. mally invasive treatment of renal abscess in case of difficult ultrasound approach (Figure 7) [1,2,24,25].

(a) (b)

Figure 4. Left renal andFigure perirenal 4. Left abscess.(a) renal Axial and perirenal(a) non-contrast abscess. and Axial (b) post-contrast ((ab)) non-contrast CT andimages (b) show post-contrast multilocular CT images cystic lesion at the posterior aspect of the mid-zone of the left kidney with enhancing septa, it extends to the posterior perirenal show multilocular cystic lesion at the posterior aspect of the mid-zone of the left kidney with Figurespace 4. Left involving renal and the perirenal left crus abscess.of the diaphragm Axial (a) non-contrast and posterior and abdominal (b) post-contrast wall. CT images show multilocular cystic lesion at the posterior aspectenhancing of the mid-zone septa, itof extends the left tokidn theey posterior with enhancing perirenal septa, space it involving extends to the the left posterior crus of theperirenal diaphragm space involving the left crusand of the posterior diaphragm abdominal and posterior wall. abdominal wall.

(a) (b) (c) Figure 5. Right renal(a) abscess. (a) Axial non-contrast CT(b image) shows right upper polar cystic(c) lesion with a thick wall. (b) Axial and (c) coronal reformatted post-contrast CT images show upper polar abscess extending to the right psoas muscle Figurewith 5. Right a thick renal enhancing abscess. wall. ( (aa)) Axial Axial non-contrast non-contrast CT CT image image shows shows right right upper upper polar polar cystic cystic lesion lesion with with a a thick thick wall. wall. ( (bb)) Axial and (c) coronal reformatted post-contrast CT images show upper polar abscess extending to the right psoas muscle Axial and (c) coronal reformatted post-contrast CT images show upper polar abscess extending to the right psoas muscle with a thick enhancing wall. with a thick enhancing wall. The appearance of renal abscess at MRI study depends upon the amount of fluid, cellular debris, and protein. So, it appears as a complex cystic lesion with heterogeneous low signal intensity on T1-WI and high signal intensity on T2-WI (Figure8a,b). The wall of the abscess is usually thick and irregular with a little enhancement on the delayed excretory phase [30]. Renal parenchyma adjacent to the abscess can demonstrate low signal intensity on early phases with subsequently delayed enhancement [15]. Perinephric fat stranding is usually seen adjacent to the renal abscess [31]. Air bubbles can be rarely seen within the cystic lesion and strongly suggests abscess formation. Gadolinium-enhanced MRI can differentiate enhancing lesions from the non-enhancing soft tissue edema (Figure8c,d).

(a) (b) (c) (a) (b) (c)

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non-contrast CT scan. The renal fascia is often thickened with soft-tissue stranding; septal thickening and perinephric fat obliteration (Figure 4). CT can easily detect extrarenal ex- tension of the abscess into the perinephric spaces, psoas muscle, and the adjacent organs (Figures 5 and 6). CT guided aspiration and tube drain is a preferable method for mini- mally invasive treatment of renal abscess in case of difficult ultrasound approach (Figure 7) [1,2,24,25].

(a) (b) Figure 4. Left renal and perirenal abscess. Axial (a) non-contrast and (b) post-contrast CT images show multilocular cystic lesion at the posterior aspect of the mid-zone of the left kidney with enhancing septa, it extends to the posterior perirenal space involving the left crus of the diaphragm and posterior abdominal wall.

(a) (b) (c)

MedicinaFigure2021 ,5.57 Right, 32 renal abscess. (a) Axial non-contrast CT image shows right upper polar cystic lesion with a thick wall. (b)6 of 23 Axial and (c) coronal reformatted post-contrast CT images show upper polar abscess extending to the right psoas muscle with a thick enhancing wall.

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Figure 6. Right renal abscess with hepatic extension. (a) Axial non-contrast CT image shows right upper polar isodense lesion with irregular renal contour. (b) Axial and (c) coronal reformatted post-contrast CT images show multilocular ab- scess extending to the perirenal space and the liver.

Medicina 2021, 57, x FOR PEER REVIEW 6 of 22 (a) (b) (c)

Figure 6. Right renal abscess with hepatic extension. (a) Axial non-contrast CT image shows right upper polar isodense lesionFigure with 6. Right irregular renal renal abscess contour. with (b hepatic) Axial andextension. (c) coronal (a) Axial reformatted non-contrast post-contrast CT image CT imagesshows showright upper multilocular polar isodense abscess lesion with irregular renal contour. (b) Axial and (c) coronal reformatted post-contrast CT images show multilocular ab- extending to the perirenal space and the liver. scess extending to the perirenal space and the liver.

Figure 7. CT guided tube drain of the right renal abscess of the case number 5.

The appearance of renal abscess at MRI study depends upon the amount of fluid, cellular debris, and protein. So, it appears as a complex cystic lesion with heterogeneous low signal intensity on T1-WI and high signal intensity on T2-WI (Figure 8a,b). The wall of the abscess is usually thick and irregular with a little enhancement on the delayed ex- cretory phase [30]. Renal parenchyma adjacent to the abscess can demonstrate low signal intensity on early phases with subsequently delayed enhancement [15]. Perinephric fat stranding is usually seen adjacent to the renal abscess [31]. Air bubbles can be rarely seen within the cystic lesion and strongly suggests abscess formation. Gadolinium-enhanced

MRI can differentiate enhancing lesions from the non-enhancing soft tissue edema (Figure 8c,d).FigureFigure 7. 7.CT CT guided guided tube tube drain drain of of the the right right renal renal abscess abscess of of the the case case number number 5. 5. The appearance of renal abscess at MRI study depends upon the amount of fluid, cellular debris, and protein. So, it appears as a complex cystic lesion with heterogeneous low signal intensity on T1-WI and high signal intensity on T2-WI (Figure 8a,b). The wall of the abscess is usually thick and irregular with a little enhancement on the delayed ex- cretory phase [30]. Renal parenchyma adjacent to the abscess can demonstrate low signal intensity on early phases with subsequently delayed enhancement [15]. Perinephric fat stranding is usually seen adjacent to the renal abscess [31]. Air bubbles can be rarely seen within the cystic lesion and strongly suggests abscess formation. Gadolinium-enhanced MRI can differentiate enhancing lesions from the non-enhancing soft tissue edema (Figure 8c,d).

(a) (b) (c) (d)

Figure 8. Multiple right renal abscesses. Axial ( a) T1 and ( b) T2 weighted images show two cystic lesions at the posterior aspect of the renal lower pole. ( c) Axial and ( d) coronal post-contrast GRE T1 weighted images show multiple marginally enhancing abscesses with enhancing septum at the later one at the lower pole. enhancing abscesses with enhancing septum at the later one at the lower pole.

The fluid fluid contents show characteristically marked and heterogeneous restricted restricted dif- dif- fusion on on DWI due to the presence of viscousviscous pus, which favors the diagnosis of renal abscess rather than renal tumor [[30]30] (Figure 9 9)).. DWIDWI alsoalso usefuluseful inin patients’patients’ follow-upfollow-up withwith the absence of diffusion restriction indicates a resolution ofof thethe infectioninfection [[2,30].2,30].

(a) (b) (c) (d) Figure 8. Multiple right renal abscesses. Axial (a) T1 and (b) T2 weighted images show two cystic lesions at the posterior aspect of the renal lower pole. (c) Axial and (d) coronal post-contrast GRE T1 weighted images show multiple marginally enhancing abscesses with enhancing septum at the later one at the lower pole.

The fluid contents show characteristically marked and heterogeneous restricted dif- fusion on DWI due to the presence of viscous pus, which favors the diagnosis of renal abscess rather than renal tumor [30] (Figure 9). DWI also useful in patients’ follow-up with the absence of diffusion restriction indicates a resolution of the infection [2,30].

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Figure 9. Diffusion-weighted image (DWI) of right renal and perirenal abscess with diffusion re- FigureFigure 9.9. Diffusion-weightedDiffusion-weighted image image (DWI) (DWI) of ofright right renal renal and and perire perirenalnal abscess abscess with with diffusion diffusion re- striction. restriction.striction.

2.3.2.3.2.3. Pyonephrosis PyonephrosisPyonephrosis PyonephrosisPyonephrosisPyonephrosis is isis the thethe collection collectioncollection of of pusof puspus in aninin an obstructedan obstructedobstructed collecting collectincollectin system;gg system;system; the obstructionthethe obstruc-obstruc- maytiontion bemaymay due bebe toduedue stricture, toto stricture,stricture, stone, stone,stone, congenital congenitalcongenital anomaly, anomaly,anomaly, or tumororor tumortumor [14 [14].[14].]. Pyonephrosis PyonephrosisPyonephrosis is isis an anan urgenturgenturgent diagnosis diagnosisdiagnosis and andand it itit requires requiresrequires urgent urgenturgent urinary urinaryurinary drainage. drainage.drainage. On OnOn CT CTCT scan, scan,scan, signs signssigns of ofof infection infectioninfection includeincludeinclude high highhigh urine urineurine attenuation attenuationattenuation and andand contrast contrastcontrast layering layeringlayering in inin the thethe dilated dilateddilated collecting collectingcollecting system, system,system, thickeningthickeningthickening and and and hyperenhancement hyperenhancement hyperenhancement of of of renal renal renal pelvis pelv pelvisis wall, wall, wall, perinephric perinephric perinephric inflammatory inflammatory inflammatory lesions, lesions, lesions, andandand renal renalrenal cortical corticalcortical thinning thinningthinning [[1,14].[1,14].1,14]. ContraryContrary to toto other otherother types types ofof UTIs,UTIs, UTIs, CTCT CT hashas has limitedlimited limited valuevalue value inin indifferentiationdifferentiation differentiation betweenbetween between pyonephrosispyonephrosis pyonephrosis andand and hydrhydr hydronephrosisonephrosisonephrosis [10,24].[10,24]. [10,24 BothBoth]. Both urinaryurinary urinary tracttract tract dis-dis- disordersordersorders maymay may presentpresent present withwith with thethe the samesame same radiologicradiologic radiologicalalal signs signs which which maymay bebebe moremoremore prominent prominentprominent in inin pyonephrosispyonephrosispyonephrosis [ 25 [25].[25].]. MRIMRIMRI is isis preferredpreferredpreferred overover CT CT in in thethe diagnosisdiagnosis diagnosis ofof of pyonephrosispyonephrosis pyonephrosis asas as thethe the delineationdelineation delineation ofof ob- ofob- obstructionstructionstruction causecause cause andand and thethe the degreedegree degree ofof ofcollectingcollecting collecting systemsystem system dilatationdilatation dilatation cancan can bebe obtained beobtained obtained usingusing using con-con- conventionalventionalventional MRIMRI MRI sequencessequences sequences withoutwithout without contrast.contrast. contrast. AtAt At T1T1 T1-WI,-WI,-WI, the the signal signalsignal intensityintensity of ofof the thetheinfected infectedinfected fluidfluidfluid will willwill be bebe low lowlow or oror slightly slightlyslightly high highhigh however, however,however, it will itit willwill be intermediate bebe intermediateintermediate to low toto low atlow T2-WI. atat T2-WI.T2-WI. MRI canMRIMRI alsocancan detect alsoalso detectdetect the fluid–fluid thethe fluid–fluid fluid–fluid layering layeringlayering and theand and presence ththee presencepresence of renal ofof renalrenal pelvis pelvpelv thickeningisis thickeningthickening (Figure (Figure (Figure 10). DWI10).10). DWI mayDWI may havemay havehave an added anan addedadded role inrolerole differentiating inin differedifferentiatingntiating pyonephrosis pyonephrosispyonephrosis from fromfrom hydronephrosis hydronephrosishydronephrosis as pyonephrosisasas pyonephrosispyonephrosis demonstrates demonstratesdemonstrates characteristic characteristiccharacteristic diffusion diffusiondiffusion restriction. restriction.restriction. MRI MRIMRI with withwith contrast contrastcontrast may maymay showshowshow mural muralmural enhancement enhancementenhancement and andand thickening thickeningthickening of ofof the thethe renal renalrenal pelvis pelvispelvis [ 14 [14].[14].].

FigureFigure 10.10. RightRight pyonephrosis.pyonephrosis. AxialAxial T2T2 weightedweighted imimageage showsshows hydronephrotichydronephrotic changes changes with with Figure 10. Right pyonephrosis. Axial T2 weighted image shows hydronephrotic changes with fluid–fluidfluid–fluid layeringlayering insideinside thethe dilateddilated calyces.calyces. fluid–fluid layering inside the dilated calyces.

2.4.2.4.2.4. Chronic ChronicChronic Pyelonephritis PyelonephritisPyelonephritis ChronicChronicChronic pyelonephritis pyelonephritispyelonephritis may maymay result resultresult from fromfrom recurrent recurrentrecurrent infections infectionsinfections or reflux oror refluxreflux of infected ofof infectedinfected urine inurineurine childhood inin childhoodchildhood [32]. It is [32].[32]. characterized ItIt isis characterizedcharacterized by parenchymal byby parenchymalparenchymal atrophy of atrophyatrophy the affected ofof thethe areas, affectedaffected hypertro- areas,areas, phyhypertrophyhypertrophy of residual ofof normal residualresidual parenchymal normalnormal parenchymalparenchymal tissue, clubbing titissue,ssue, of clubbingclubbing the calyces ofof the secondarythe calycescalyces tosecondarysecondary retraction toto ofretractionretraction the papilla ofof fromthethe papillapapilla adjacent fromfrom overlying adjacentadjacent renal overlyingoverlying scarring, renalrenal dilatation scarring,scarring, of dilatation thedilatation calyces, ofof and thethe overallcalyces,calyces, renalandand overall asymmetry.overall renalrenal CT asymmetry.asymmetry. with contrast CTCT is withwith important contrastcontrast to is differentiateis importantimportant thetoto differentiatedifferentiate non-enhancing thetheareas non-en-non-en- of hancinghancing areasareas ofof infarctioninfarction fromfrom thethe scarscar titissue;ssue; itit alsoalso cancan diagnosediagnose thethe pseudotumorspseudotumors

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infarction from the scar tissue; it also can diagnose the pseudotumors due to focal parenchy- due to focal parenchymal hypertrophy from renal neoplasm, MRI can provide the same duemal to hypertrophy focal parenchymal from renal hypertrophy neoplasm, from MRI canrenal provide neoplasm, the sameMRI can information provide obtainedthe same informationfrom CT without obtained the need from of CT contrast without in the most need the casesof contrast (Figures in most11 and the 12 cases) [2,25 (Figures,33]. Lobar 11 information obtained from CT without the need of contrast in most the cases (Figures 11 andinfarcts 12) [2,25,33]. are characterized Lobar infarcts by their are lack characterized of calyceal affection.by their lack Persistent of calyceal fetal lobulationsaffection. Per- are and 12) [2,25,33]. Lobar infarcts are characterized by their lack of calyceal affection. Per- sistentcharacterized fetal lobulations by parenchymal are characterized depressions by lying parenchymal betweenthe depressions calyces rather lying than between opposite the sistent fetal lobulations are characterized by parenchymal depressions lying between the calycesthe calyces rather [14 than]. opposite the calyces [14]. calyces rather than opposite the calyces [14].

(a) (b) (a) (b) Figure 11. Bilateral chronic pyelonephritis. (a) Axial and (b) coronal CTU images show small-sized kidneys with irregular Figure 11. Bilateral chronic pyelonephritis. ( a) Axial and ( (b) coronal coronal CTU images show small-sized kidneys with irregular contours and localized left upper and middle hydrocalycosis. contours and localized left upper and middlemiddle hydrocalycosis.hydrocalycosis.

(a) (b) (a) (b) Figure 12. Bilateral chronic pyelonephritis. (a) Axial and (b) coronal T2 weighted images show renal scarring, and paren- Figure 12. Bilateral chronic pyelonephritis. (a) Axial and (b) coronal T2 weighted images show renal scarring, and paren- chymalFigure 12.atrophyBilateral with chronicirregular pyelonephritis. dilated calyces and (a) Axialirregular and contour (b) coronal of both T2 kidneys. weighted images show renal scarring, and chymal atrophy with irregular dilated calyces and irregular contour of both kidneys. parenchymal atrophy with irregular dilated calyces and irregular contour of both kidneys. Renal replacement lipomatosis is seen when there is total atrophy of the renal paren- Renal replacement lipomatosis is seen when there is total atrophy of the renal paren- chymaRenal and replacementcomplete fibrofatty lipomatosis replacement is seen when of renal there sinus. is total It atrophy is associated of the renalwith stag parenchyma horn chyma and complete fibrofatty replacement of renal sinus. It is associated with stag horn stoneand complete in more than fibrofatty 70% of replacement cases. CT and of renal MRI sinus.confirmed It is associatedthe presence with of fat stag in horn the atrophic stone in stone in more than 70% of cases. CT and MRI confirmed the presence of fat in the atrophic kidneymore than and 70% its extension of cases. CT outside and MRI the confirmedkidney [1]. the The presence calyces of are fat usually in the atrophic stretched kidney and kidney and its extension outside the kidney [1]. The calyces are usually stretched and elongatedand its extension without outside hydronephrosis the kidney (Figure [1]. The 13) calyces. are usually stretched and elongated elongatedwithout hydronephrosis without hydronephrosis (Figure 13). (Figure 13).

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(a) (b) Figure 13. Right renal sinus lipomatosis. (a) Axial and (b) coronal reformatted non-contrast CT images show small chronic pyelonephritic right kidney with branched hyperdense stone at the renal pelvis and(a) middle calyx. There is a large( bfatty) area of low density replacing the renal sinus and involving the renal parenchyma and the perirenal space. FigureFigure 13. 13. RightRight renal renal sinus sinus lipomatosis. lipomatosis. (a) Axial (a) Axial and and(b) coronal (b) coronal reformatted reformatted non-contrast non-contrast CT CT images show small chronic pyelonephritic right kidney with branched hyperdense stone at the 2.5.images Xanthogranulomatous show small chronic pyelonephriticPyelonephritis right (XGP) kidney with branched hyperdense stone at the renal renalpelvis pelvis and and middle middle calyx. calyx. There There is ais largea large fatty fatty area area of of low low density density replacing replacingthe the renalrenal sinussinus and and involvingXanthogranulomatous the renal parenchyma pyelonephr and the perirenalitis can bespace. considered as an atypical immune re- involving the renal parenchyma and the perirenal space. sponse to chronic infected urinary tract obstruction occurring secondary to staghorn cal- 2.5.culus.2.5. Xanthogranulomatous Xanthogranulomatous Infectious organisms Pyelonephritis Pyelonephritis are commonly (XGP) (XGP) Escherichia coli and Proteus mirabilis. There is no specificXanthogranulomatousXanthogranulomatous symptom of XGP. Itpyelonephr usually pyelonephritis affectsitis can pe can rimenopausalbe be considered considered females as as an an atypical with atypical a past immune immune history re- re-of sponserecurrentsponse to tochronic UTI, chronic urinary infected infected obstruction urinary urinary tract or tractdiabetes obst obstructionruction [2,4,10,24]. occurring occurring The immunesecondary secondary response to staghorn to to staghorn chronic cal- culus.infectioncalculus. Infectious Infectiousconsists organisms of organisms renal are parenchyma commonly are commonly EscherichiareplacementEscherichia coli by and coli lipid-laden andProteusProteus mirabilis macrophages mirabilis. There. There is noand is specificchronicno specific symptom destructive symptom of XGP.granulomatous of XGP. It usually It usually affects infection. affects perimenopausal The perimenopausal condition females usually females with involves with a past athe past history renal history pel-of recurrentvisof recurrentand UTI,extends UTI,urinary into urinary obstruction the renal obstruction medulla, or diabetes or diabetescort [2,4,10,24].ex, perirenal [2,4, The10,24 immunespace,]. The and immune response retroperitoneum. response to chronic to infectionTherechronic are infectionconsists two different of consists renal forms ofparenchyma renal of XGP; parenchyma a diffusreplacemente replacementtype andby alipid-laden localized by lipid-laden type,macrophages the macrophages latter beingand chroniclessand common chronic destructive destructive [2,3,15,24]. granulomatous granulomatous infection. infection. The condition The condition usually usually involves involves the renal the pel- renal vispelvis andContrast-enhanced andextends extends into into the theCTrenal renalis themedulla, medulla,technique cort cortex, ofex, choice perirenal perirenal in the space, assessment space, and and retroperitoneum. retroperitoneum.of Xanthogranu- TherelomatousThere are are two twopyelonephritis; different different forms forms however, of of XGP; XGP; MRI a adiffus diffuse can ebe type typea useful and and a alternative alocalized localized type, when type, the theiodinated latter latter being being con- lesstrastless common common is contraindicated. [2,3,15,24]. [2,3,15,24 ]. CT may demonstrate an enlarged kidney replaced with low at- tenuationContrast-enhancedContrast-enhanced dilated calyces CT CTresulting is isthe the technique techniquein parenchymal of ofchoice choice atrophy in inthe the assessment and assessment the classic of Xanthogranu- of bear Xanthogran- paw sign lomatous[4].ulomatous These pyelonephritis; dilated pyelonephritis; calyces however, are however, thought MRI MRI tocan be be canfilled a beuseful with a useful alternativedebris, alternative hemorrhage, when wheniodinated or iodinated pus. con- The trastcombinationcontrast is contraindicated. is contraindicated. of a non-functioning CT may CT maydemonstrate enlarged demonstrate kidney, an enlarged an obstructing enlarged kidney kidney stone replaced within replaced with non withlow dilated at- low tenuationrenalattenuation pelvis, dilated dilateddilated calyces calycescalyces, resulting resultingand perinephricin parenchymal in parenchymal fat stranding atrophy atrophy and is strongly the and classic the suggestive classic bear paw bear of sign XGP paw [4].(Figuressign These [4]. These14dilated and dilated 15) calyces [4,24]. calyces are thought are thought to be to filled be filled with with debris, debris, hemorrhage, hemorrhage, or or pus. pus. The The combinationcombinationExtrarenal of of a XGP anon-functioning non-functioning extension can enlarged be enlarged detected kidney, kidney, with obstructing perirenal obstructing soft stone stone tiss uewithin within inflammation non non dilated dilated and renalabscessrenal pelvis, pelvis, formation dilated dilated that calyces, calyces, extend and and from perinephric perinephric the kidney fat fat and stranding stranding dissect is through is strongly strongly the suggestive suggestiveperinephric of of space,XGP XGP (Figuresadjacent(Figures 14 14viscera, and and 15) 15 and )[[4,24].4 ,psoas24]. muscle [1]. Extrarenal XGP extension can be detected with perirenal soft tissue inflammation and abscess formation that extend from the kidney and dissect through the perinephric space, adjacent viscera, and psoas muscle [1].

(a) (b) (c) (d) Figure 14. Left xanthogranulomatous pyelonephritis (XGP): (a) axial non-contrast CT image shows an enlarged left kidney Figure 14. Left xanthogranulomatous pyelonephritis (XGP): (a) axial non-contrast CT image shows an enlarged left kidney with hyperdense stone at the renal pelvis and multiple fluid locules at the renal parenchyma. (b,c) Contrast-enhanced with hyperdense stone at the renal pelvis and multiple fluid locules at the renal parenchyma. (b,c) Contrast-enhanced axial (a) (b) (c) (d) and (d) coronal reformatted CT images show multiple stones with multiple cavities at the renal parenchyma and irregular Figureinflammatory 14. Left xanthogranulomatous lesion at the lower pole pyelonephritis of the kidney. (XGP): (a) axial non-contrast CT image shows an enlarged left kidney with hyperdense stone at the renal pelvis and multiple fluid locules at the renal parenchyma. (b,c) Contrast-enhanced

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Medicina 2021, 57, 32 10 of 23 axial and (d) coronal reformatted CT images show multiple stones with multiple cavities at the renal parenchyma and irregular inflammatory lesion at the lower pole of the kidney.

(a) (b)

FigureFigure 15. Right 15. Right XGP. XGP. (a) Non-contrast (a) Non-contrast and and (b) post-contrast (b) post-contrast coronal coronal refo reformattedrmatted CT images CT images show show stonesstones at the at therenal renal pelvis pelvis and and middle middle calyx calyx with with multiple multiple parenchymal parenchymal cavities. cavities.

2.6. EmphysematousExtrarenal XGP Urinary extension Tract Infection can be detected with perirenal soft tissue inflammation and abscessEmphysematous formation thatUTI extendis a life-threatening from the kidney necrotizing and dissect infection through seen the commonly perinephric in space,di- abeticadjacent or immunosuppressed viscera, and psoas patients muscle secondary [1]. to infection with gas-forming organisms, such as Escherichia coli. Patients with bladder outlet obstruction, neurogenic bladder, and chronic2.6. Emphysematous pyelonephritis Urinaryalso represent Tract Infection a high risk group. Emphysematous UTI includes emphysematousEmphysematous pyelonephritis UTI is aand life-threatening emphysematous necrotizing cystitis infection [25,34]. The seen clinical commonly presen- in dia- tationbetic is orvariable, immunosuppressed ranging from patientsno sympto secondaryms to marked to infection septicemia. with gas-forming Pneumaturia organisms, repre- sentssuch the as mostEscherichia specific colisymptom. Patients however, with bladder it is rarely outlet reported. obstruction, Early neurogenic diagnosis of bladder, emphy- and sematouschronic UTI pyelonephritis is very important, also represent as rapid a trea hightment risk group.with intravenous Emphysematous antibiotic UTI therapy includes is em- criticalphysematous to avoid associated pyelonephritis morbidity and emphysematous and mortality [35–38]. cystitis [25,34]. The clinical presentation isNon-contrast variable, ranging CT scan from is no the symptoms key imagin tog marked modality septicemia. for diagnosis Pneumaturia of emphysematous represents the UTIs,most based specific on the symptom detection however, of air bubbles it is rarely in reported.the renal Earlyparenchyma, diagnosis collecting of emphysematous system, bladderUTI is lumen very important,and sometimes as rapid in the treatment perirenal with and intravenous perivesical antibiotictissue (Figure therapy 16). isCT critical find- to ingsavoid of emphysematous associated morbidity pyelonephritis and mortality include [35– diffuse38]. renal enlargement and destruc- tion, linearNon-contrast streaks of air CT bubbles scan is theradiating key imaging from the modality renal papillae, for diagnosis air-fluid of emphysematouslayering, and focalUTIs, tissue based liquefaction on the detection which may of airbe bubblesassociated in with the renal renal parenchyma, and perirenal collecting abscess. Con- system, trastbladder injection lumen is often and contraindicated sometimes in the in perirenal patients andwith perivesical renal impairment tissue (Figure however, 16). it CT can find- ings of emphysematous pyelonephritis include diffuse renal enlargement and destruction, be used to evaluate the extent of renal parenchyma destruction. If air locules are only con- linear streaks of air bubbles radiating from the renal papillae, air-fluid layering, and focal fined to the collecting system, this may suggest emphysematous pyelitis. Sometimes, the tissue liquefaction which may be associated with renal and perirenal abscess. Contrast isolated distribution of gas in the collecting system may be related to urethral catheteriza- injection is often contraindicated in patients with renal impairment however, it can be used tion or uro-intestinal fistula [4,10,24,33,39]. to evaluate the extent of renal parenchyma destruction. If air locules are only confined to the collecting system, this may suggest emphysematous pyelitis. Sometimes, the isolated distribution of gas in the collecting system may be related to urethral catheterization or uro-intestinal fistula [4,10,24,33,39]. Based on radiological findings, emphysematous pyelonephritis can be classified into two types. Type 1 emphysematous pyelonephritis demonstrates necrosis of renal parenchyma with mottled or streaky areas of air locules without an extrarenal fluid col- lection. Type 2 emphysematous pyelonephritis demonstrates intrarenal or perirenal fluid collections that are often associated with air locules or air within the collecting system. Type 1 and type 2 mortality rates are reported to be 69% and 18%, respectively [1]. CT-guided drainage followed by intravenous antibiotics can be used for adequate management of emphysematous pyelonephritis particularly in solitary kidney patients, (a) absence of severe toxicity,( andb) in the localized affected kidney(c) part [29]. MRI is not the imaging modality of choice for the diagnosis of emphysematous Figure 16. Emphysematous pyelonephritis and cystitis. Axial non-contrast CT images of the abdomen (a), pelvis (b), and pyelonephritis, it is used if there is a contraindication to CT. At MRI, the air bubble appears coronal reformatted non-contrast CT image (c) show right emphysematous pyelonephritis in the form of diffuse paren- as a signal void on both T1- and T2-WI, but this may mistake with calculi or rapid-flowing chymal enlargement and destruction, multiple bubbly air locules involving the renal parenchyma and extends to the blood. Perinephric and intrarenal fluid collections are better delineated on MRI [39].

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axial and (d) coronal reformatted CT images show multiple stones with multiple cavities at the renal parenchyma and irregular inflammatory lesion at the lower pole of the kidney.

(a) (b) Figure 15. Right XGP. (a) Non-contrast and (b) post-contrast coronal reformatted CT images show stones at the renal pelvis and middle calyx with multiple parenchymal cavities.

2.6. Emphysematous Urinary Tract Infection Emphysematous UTI is a life-threatening necrotizing infection seen commonly in di- abetic or immunosuppressed patients secondary to infection with gas-forming organisms, such as Escherichia coli. Patients with bladder outlet obstruction, neurogenic bladder, and chronic pyelonephritis also represent a high risk group. Emphysematous UTI includes emphysematous pyelonephritis and emphysematous cystitis [25,34]. The clinical presen- tation is variable, ranging from no symptoms to marked septicemia. Pneumaturia repre- sents the most specific symptom however, it is rarely reported. Early diagnosis of emphy- sematous UTI is very important, as rapid treatment with intravenous antibiotic therapy is critical to avoid associated morbidity and mortality [35–38]. Non-contrast CT scan is the key imaging modality for diagnosis of emphysematous UTIs, based on the detection of air bubbles in the renal parenchyma, collecting system, bladder lumen and sometimes in the perirenal and perivesical tissue (Figure 16). CT find- ings of emphysematous pyelonephritis include diffuse renal enlargement and destruc- tion, linear streaks of air bubbles radiating from the renal papillae, air-fluid layering, and focal tissue liquefaction which may be associated with renal and perirenal abscess. Con- trast injection is often contraindicated in patients with renal impairment however, it can be used to evaluate the extent of renal parenchyma destruction. If air locules are only con- fined to the collecting system, this may suggest emphysematous pyelitis. Sometimes, the Medicina 2021, 57, 32 11 of 23 isolated distribution of gas in the collecting system may be related to urethral catheteriza- tion or uro-intestinal fistula [4,10,24,33,39].

(a) (b) (c)

Figure 16. EmphysematousEmphysematous pyelonephritis pyelonephritis and and cystitis. cystitis. Axial Axial non-contrast non-contrast CT CTimages images of the of theabdomen abdomen (a), pelvis (a), pelvis (b), and (b), andcoronal coronal reformatted reformatted non-contrast non-contrast CT image CT image (c) show (c) showright emphysematous right emphysematous pyelonephr pyelonephritisitis in the form in the of form diffuse of diffuseparen- chymal enlargement and destruction, multiple bubbly air locules involving the renal parenchyma and extends to the parenchymal enlargement and destruction, multiple bubbly air locules involving the renal parenchyma and extends to the pelvicalyceal system with perirenal inflammatory fat strands and thickened fascia. Emphysematous cystitis can also be detected in the form of intramural air, and air within the bladder lumen with minimal perivesical extension.

The classic imaging feature of emphysematous cystitis is the presence of air bubbles in the bladder wall or lumen without a recent history of instrumentation. As mentioned before, CT has high sensitivity in the detection of intramural or intraluminal gas. CT can also evaluate the other causes for intravesical air bubbles, such as a colovesical fistula [37,40]. MRI findings of emphysematous cystitis include inflammatory findings of concurrent cystitis or entero-vesical fistula [36].

2.7. Urinary Tuberculosis The urinary tract is the second most common site affected by tuberculosis after the lungs [41]. In urinary tuberculosis, the urinary bladder is normally involved in a later stage after renal involvement and through the descending route [42]. Symptoms of urinary tuberculosis are nonspecific and include frequency, dysuria, and hematuria. Tuberculosis should be considered in patients with sterile pyuria, and persistent cystitis [41]. The kidneys can be affected in miliary tuberculosis due to the hematogenous spread of Koch’s bacillus. It can produce renal parenchyma ulceration, leading to cavity formation. The spread of bacilli in the urine can also lead to urothelial ulceration, followed by fibrosis and stenosis which are usually located at either the vesicoureteric junction or pelviureteric junction [24]. At a later stage, the reduction in bladder volume, vesical wall calcifications sparing the bladder mucosa, are combined with renal and ureteric calcifications [42]. The earliest radiological finding of TB which can be detected in CT urography (CTU) is dilated calyx with a feathery appearance, which can be seen as a cavity communicating with a deformed calyx or a phantom calyx in later phase [14]. Delayed CTU demonstrates accumulation in the calyces, stenosis of calyceal infundibulum due to fibrosis with proximal ball-shaped hydrocalyx, ureteral stricture and, calcifications of the renal parenchyma with a putty kidney appearance [33]. MRI features of renal macronodular tuberculoma include hypointensity on T1weighted images and a thick, irregular, hypointense peripheral wall with intralesional fluid–fluid lay- ering on T2 weighted images. TB granulomas may appear as mildly enhancing soft-tissue masses on MRI [2]. Ureteric affection may be seen as mural thickening causing strictures, shortening, and beaded appearance. The extra-renal extension can involve periureteric and retroperitoneal tissues (Figure 17)[2,14]. In the acute phase of bladder tuberculosis, CT and MRI features include diffuse irregular bladder wall thickening, irregular mucosal masses due to coalescing tubercles with edema, ulceration, and trabeculation [43]. Vesicoureteric junction orifice may be fixed and patulous, leading to vesicoureteric reflux. In the chronic phase, radiologic findings are a thick-walled contracted bladder due to fibrosis [44]. Associated seminal vesicles Medicina 2021, 57, 32 12 of 23 Medicina 2021, 57, x FOR PEER REVIEW 12 of 22

calcification also may be detected, but the urinary bladder wall calcification is rare and seen only only after after healing healing [43–45]. [43–45]. Bladder Bladder tuberculosis tuberculosis may may be be complicated complicated by by sinus sinus tract tract or fistulaor fistula formation formation however, however, these these complication complicationss are arenot notfrequent frequent and and can canbe detected be detected ac- curatelyaccurately on on MRI MRI and and CT CT [41]. [41 ].

(a) (b) (c)

Figure 17. UrinaryUrinary tuberculosis tuberculosis.. (a, (ba), bCoronal) Coronal T2-WI T2-WI and and (c) axial (c) axial T2-WI T2-WI show show small small size right size kidney right kidney with chronic with chronic pyelo- nephritic changes in the form of renal scarring and cortical thinning. There is mild hydroureteronephrosis down to the pyelonephritic changes in the form of renal scarring and cortical thinning. There is mild hydroureteronephrosis down to the pelvic segment of the ureter with mural thickening of the pelvicalyceal system and ureter associated with clubbing of pelvic segment of the ureter with mural thickening of the pelvicalyceal system and ureter associated with clubbing of dilated dilated calyces and dilated ureter with beaded appearance. There is diffuse circumferential periureteric soft tissue mass calycesof low T2 and weighted dilated uretersignal intensity with beaded surrounding appearance. the Therelumber is ur diffuseeter associated circumferential with retroper periuretericitoneal soft fat tissue stranding mass and of low thick- T2 weightedened fascia. signal intensity surrounding the lumber ureter associated with retroperitoneal fat stranding and thickened fascia.

2.8. Urinary Urinary Bilharziasis Bilharziasis Urinary bilharziasis bilharziasis or or schistosomiasis schistosomiasis is isthe the most most common common parasitic parasitic infection infection of the of urinarythe urinary tract tract caused caused by Schistosoma by Schistosoma haematobium haematobium [42]. It[42 is]. considered It is considered a major a majorhealth health prob- lemproblem in developing in developing countries countries predisposing predisposing patients patients to squamous to squamous cell carcinoma. cell carcinoma. This Thispar- asiticparasitic infection infection generally generally occurs occurs in inthe the urinary urinary bladder bladder but but can can spread spread via via reflux reflux to the ureters and kidneys [33,36]. [33,36]. Symptoms of of urinary schistosomiasis are are usually non-specific non-specific and include dysuria, suprapubicsuprapubic pain, and microscopic hematuria. Red and white cells can be detected in urine however, the diagnosis is confirmedconfirmed only by microscopic detectiondetection ofof eggseggs inin urineurine [[41].41]. ImagingImaging findings findings mirror the pathologic course.course. In the the acute acute stage, stage, nodular nodular thickening thickening of the the urinary urinary bladder bladder wall wall is isdetected detected easily easily in MRI. in MRI. Curvilinear Curvilinear mural mural calcifications, calcifications, best visualizedbest visualized on CT on scan, CT scan, in the in wall the wallof the of bl theadder bladder or ureter or ureter are frequent are frequent findings findings and andare mainlyare mainly caused caused by calcified by calcified dead dead ova. ova.Typical Typical additional additional features features are strictures are strictures of the of ure- the tersureters or reflux or reflux [36,42]. [36,42 The]. The chronic chronic stage stage is ischaracterized characterized by by a a contracted, contracted, thick thick calcified calcified bladder wall with ureteric stenosis and calcification calcification (Figure 1818).). An intravesical mass may also be present secondary to complicating blad bladderder carcinoma, particularly squamous cell carcinoma [24,33,41] [24,33,41].. InIn the the majority majority of of patients, patients, the the calcificatio calcificationsns affect affect only only the the bladder bladder mucosa mucosa however, however, inin the the most most severe severe cases, they reach the musc muscularular layer and the tunica adventitia, leading toto fibrosis fibrosis of the the whole whole urinary urinary bladder, bladder, leading to bladder wall deformity. The collection of several granulomas can can cause cause a a bilharzioma, taking taking the the appearance appearance of of pseudotumor. pseudotumor. Lesions are are commonly present in the posterior posterior surface surface of of the the bladder, bladder, the vesical triangle, triangle, and around the neck of the the bladder. bladder. In later later stages stages of of urinary urinary bilharziasis, bilharziasis, the distal ureters may be involved; renal affection occurs later,later, secondarysecondary toto ascendingascending infectioninfection [[42].42].

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(a) (a) (b)( b) FigureFigureFigure 18. 18. Urinary18.Urinary Urinary bilharziasis. bilharziasis. ( (aa,b ,(ba)) ,Coronalb Coronal) Coronal reformatted reformatted reformatted CT CT CTimages images images without without without contrast contrast contrast showing showingshowing diffusediffusediffuse mural mural mural calcifications calcifications calcifications of of the theof bladder, the bladder, bladder, and and both and both uretersboth ureters ureters with with bilateralwith bilateral bilateral hydroureteronephrosis hydroureteronephrosis hydroureteronephrosis and and multiple bilateral ureteric strictures associated with secondary stone at right pelvic ureter. multipleand multiple bilateral bilateral ureteric ureteric strictures strictures associated associat withed secondarywith secondary stone stone at right at pelvicright pelvic ureter. ureter.

2.9.2.9.2.9. Corynebacterium Corynebacterium Corynebacterium Infection: Infection: Infection: EncrustedEncrusted Encrusted Pyelitis Pyelitis Pyelitis and and and Cystitis Cystitis Cystitis ThisThisThis is is a ais nosocomial nosocomial a nosocomial type type type of of infection infectionof infection caused caus caused by edby urealyticum byurealyticum urealyticum bacteria bacteria bacteria colonizing colonizing colonizing the the the urinaryurinaryurinary tractstracts tracts ofof immune-compromisedimmune-compromisedof immune-compromised patients.patients patients. This This. This type type type of of ofinfection infection infection usually usually usually leads leads leads to to tothe thethe formation formation formation of of ofammonium ammonium ammonium magnesium magnesium magnesium phosphate phosphate phosphate calculi calculi calculi which which which become become become encrusted encrusted encrusted in in in the urothelium of the collecting system and ureter. Non-contrast CT scan is the best thethe urothelium urothelium of theof the collecting collecting system system and and ur eter.ureter. Non-contrast Non-contrast CT CT scan scan is theis the best best im- im- imaging technique for visualizing linear hyperdense calcifications along the thickened agingaging technique technique for for visualizing visualizing linear linear hyperdense hyperdense calcifications calcifications along along the the thickened thickened urothelium (Figure 19). MRI can easily detect mural thickening, perirenal, and periureteric urotheliumurothelium (Figure (Figure 19). 19). MRI MRI can can easily easily detect detect mural mural thickening, thickening, perirenal, perirenal, and and periureteric periureteric fat stranding [33,46,47]. fat fatstranding stranding [33,46,47]. [33,46,47].

FigureFigure 19. 19.Encrusted Encrusted pyelitis pyelitis in horseshoein horseshoe kidney. kidney. Ax ialAx non-contrastial non-contrast CT CTimage image shows shows horseshoe horseshoe Figure 19. Encrusted pyelitis in horseshoe kidney. Axial non-contrast CT image shows horseshoe kidneykidney with with malrotation malrotation of bothof both compartm compartmentsents and and marginally marginally calcified calcified calyces. calyces. kidney with malrotation of both compartments and marginally calcified calyces. 2.10. Urinary Candidiasis: 2.10.2.10. Urinary Urinary Candidiasis: Candidiasis: The urinary tract can be colonized by Candida albicans either via hematogenous TheThe urinary urinary tract tract can can be colonizedbe colonized by Candida by Candida albicans albicanseither viaeither hematogenous via hematogenous spread spread or ascending infection in immune-compromised patients. It may complicate gram- orspread ascending or ascending infection infection in immune-compromised in immune-compromised patients. Itpatients. may complicate It may complicate gram-negative gram- negative UTIs. On contrast-enhanced CT, the mycelial aggregation does not demonstrate UTIs.negative On contrast-enhancedUTIs. On contrast-enhanced CT, the mycelial CT, the aggregation mycelial aggregation does not demonstrate does not demonstrate enhance- enhancement. It has a rolled appearance when it contains gas between the layers of fungal ment.enhancement. It has a rolled It has appearance a rolled appearance when it contains when itgas contains between gasthe between layers the of fungal layers colonies.of fungal Calcifiedcolonies.colonies. lesions Calcified Calcified indicate lesions lesions healing. indicate indicate Thickening healing. healing. ofThickening theThickening renal pelvisof ofthe the andrenal renal hydronephrosis pelvis pelvis and and hydro- duehydro- tonephrosis uretericnephrosis obstructiondue due to uretericto ureteric by the obstruction fungusobstruction ball by may bythe the befungus seenfungus onball ball CT may (Figuremay be beseen 20 seen)[ on1, 33onCT]. CT (Figure (Figure 20) 20) [1,33].[1,33].At MRI, renal fungal infections usually manifest as parenchymal micro-abscesses demonstratingAt AtMRI, MRI, renal high renal fungal signal fungal intensityinfections infections on usually T2-WI.usually manifest Coalescingmanifest as asparenchymal of parenchymal small abscesses micro-abscesses micro-abscesses leads to thedemonstratingdemonstrating formation of high a largerhigh signal signal parenchymal intensity intensity on abscess onT2-WI. T2-WI. withCoalescing Coalescing or without of smallof hydronephrotic small abscesses abscesses leads changes.leads to theto the Fungusformationformation balls of are aof larger a seen larger asparenchymal non-enhancingparenchymal abscess abscess soft with tissue with or masswithoutor without occupying hydronephrotic hydronephrotic the collecting changes. changes. system, Fun- Fun- thatgusgus oftenballs balls isointenseare are seen seen as on non-enhancingas T1-WInon-enhancing and hyperintense soft soft tissue tissue mass on mass T2-WI. occupying occupying Fungal the infectionsthe collecting collecting may system, system, lead that to that localoftenoften vascular isointense isointense inflammation on onT1-WI T1-WI and and and hyperintense thrombosis. hyperintense Parenchymalon onT2-WI. T2-WI. Fungal Fungal calcifications infections infections may may may also lead lead occur to localto in local chronic fungal infections [48].

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Medicina 2021, 57, 32 14 of 23 vascularvascular inflammation inflammation and and thrombosis. thrombosis. Parenchymal Parenchymal calcifications calcifications may may also also occur occur in in chronicchronic fungal fungal infections infections [48]. [48].

Figure 20. Left renal fungus infection. Axial non-contrast CT image shows hyperdense lesion at FigureFigure 20. 20.Left Left renal renal fungus fungus infection. infection. Axial Axial non-contrast non-contrast CT CT image image shows shows hyperdense hyperdense lesion lesion at at the thethe renal renal pelvis pelvis with with calcific calcific foci foci inside. inside. renal pelvis with calcific foci inside.

2.11.2.11.2.11. Ureteritis Ureteritis Ureteritis UreteritisUreteritisUreteritis refers refers to to ureteric ureteric inflammation,inflammation, inflammation, which which which usually usually usually occurs occurs occurs as as aas a result aresult result of of ascending of ascend- ascend- inginfectioning infection infection secondary secondary secondary to cystitis to to cystitis cystitis [49]. [49]. Other[49]. Other Other rare rare causesrare causes causes include include include hematogenous hematogenous hematogenous spread spread spread and andchronicand chronic chronic infection infection infection in a in patient in a apatient patient with with awith ureteral a auret ureteral stent.eral stent. stent. CT andCT CT and MRI and MRI demonstrateMRI demonstrate demonstrate diffuse diffuse diffuse mu- mucosalcosalmucosal urothelial urothelial urothelial thickening, thickening, thickening, often often often with with associatedwith associated associated periureteric periureteric periureteric stranding stranding stranding and inflammatory and and inflam- inflam- matoryreactionmatory reaction (Figurereaction (Figure21 (Figure)[37]. 21) 21) [37]. [37]. UreteritisUreteritisUreteritis cystica cystica is is a verya very rarerare rare benignbenign benign condition condition condition characterized characterized characterized by by cysticby cystic cystic degeneration degeneration degeneration of ofepithelialof epithelial epithelial cell cell nestscell nests nests invaginating invaginating invaginating into theinto into lamina the the lamina lamina propria propria propria leading leading toleading the formation to to the the formation formation of multiple of of multiplesmallmultiple submucosal small small submucosal submucosal epithelial-lined epithelial-lined epithelial-lined cysts. This cysts. cysts. condition This This condition condition may present may may withpresent present hematuria with with hema- hema- and turiaisturia often and and associated is is often often associated associated with recurrent with with recurrent recurrent or chronic or or chronic UTI. chronic On UTI. CTUUTI. On On or CTU MRU,CTU or or multipleMRU, MRU, multiple multiple tiny filling tiny tiny fillingdefectsfilling defects defects are usually are are usually usually seen, andseen, seen, associated and and associated associated hydronephrotic hydronephrotic hydronephrotic changes changes changes may coexist may may coexist [coexist49]. [49] [49]. .

(a()a ) (b()b ) (c()c )

FigureFigureFigure 21. 21. Cystitis Cystitis and and ureteritis.ureteritis. ureteritis. (a(a )() Axiala Axial) Axial and and and (b ()b ( coronal)b coronal) coronal T2–W T2–W T2–W images images images show show show diffuse diffuse diffuse thickened thickened thickened irregular irregular irregular bladder bladder bladder wall, wall, with wall, with multiple intramural trabeculation, perivesical fat stranding, and inflammatory reaction. (c) Sagittal T2–WI demon- multiplewith multiple intramural intramural trabeculation, trabeculation, perivesical perivesical fat stranding, fat strandin andg, inflammatory and inflammatory reaction. reaction. (c) Sagittal (c) Sagittal T2–WI T2–WI demonstrates demon- stratesstrates diffuse diffuse mural mural thickening thickening of of the the left left ureter ureter with with periureteric periureteric fat fat stranding. stranding. diffuse mural thickening of the left ureter with periureteric fat stranding. 2.12.2.12. Cystitis Cystitis 2.12.Cystitis CystitisCystitis refers refers to to bladder bladder inflammation. inflammation. It It may may be be isolated isolated or or combined combined with with the the in- in- volvementvolvementCystitis of of refersthe the whole towhole bladder urinary urinary inflammation. tract tract or or ad adjacent Itjacent may organs beorgans isolated [42]. [42]. orSymptoms Symptoms combined include withinclude the fre- in-fre- quency,volvementquency, dysuria, dysuria, of the hematuria, whole hematuria, urinary urgency, urgency, tract or or or adjacent suprapubic suprapubic organs pain. pain. [42 Sources]. Sources Symptoms include include include infection infection frequency, (bac- (bac- terial,dysuria,terial, schistosomiasis, schistosomiasis, hematuria, urgency, TB, TB, parasites, parasites, or suprapubic or or my mycosis), pain.cosis), Sourcesmedications medications include (cyc (cyc infectionlophosphamide)lophosphamide) (bacterial, orschis- or ra- ra- diationtosomiasis,diation [2]. [2]. Cystitis TB,Cystitis parasites, usually usually or results mycosis),results from from medications ascending ascending urethral (cyclophosphamide)urethral infection, infection, such such or as radiationas Escherichia Escherichia [2]. coliCystitiscoli [37]. [37]. It usually It is is more more results common common from in in ascendingfemales females due due urethral to to short short infection, urethral urethral length such length as and andEscherichia urethral urethral coliproximity proximity[37]. It toisto the more the anus anus common [42]. [42]. in females due to short urethral length and urethral proximity to the anus [42]. On CT, radiologic findings of acute uncomplicated bacterial cystitis include either diffuse or focal mural hypertrophy, periserosal edema, and mucosal urothelial irregularity.

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Medicina 2021, 57, 32 15 of 23 On CT,On radiologic CT, radiologic findings findings of acute of uncomplicated acute uncomplicated bacterial bacterial cystitis cystitisinclude include either either diffuse diffuseor focal or mural focal hypertrophy, mural hypertrophy, perisero periserosal edema,sal edema,and mucosal and mucosal urothelial urothelial irregular- irregular- ity. Layeringity. Layering debris candebris also can be alsodetected be detected and best and demonstrated best demonstrated by sonography. by sonography. Some- Some- timesLayering focal,times debris protruding focal, can protruding also pseudotumors be detected pseudotumors and are best repo are demonstratedrted repo [34,37,42].rted [34,37,42]. by MRI sonography. can MRI detect can Sometimes diffusedetect diffuseor or focalfocal, irregular protrudingfocal irregular mural pseudotumors thickeningmural thickening aredue reported to edemadue to [34 edemaof,37 the,42 urinary]. of MRI the canurinary bladder detect bladder wall. diffuse Gadolinium- wall. or focal Gadolinium- ir- enhancedregularenhanced mural MRI thickening of MRIthe bladder of the due bladder shows to edema differentia shows of the differentia urinaryl enhancement bladderl enhancement wall.proportional Gadolinium-enhanced proportional to the severity to the severity ofMRI inflammation ofof the inflammation bladder but generally shows but generally differential less than less that enhancement than of the that tumor of the proportional [2,36,50]. tumor [2,36,50]. Radiological to the Radiological severity evaluation of evaluation in- offlammation recurrentof recurrent butcystitis generally cystitisis indicated less is indicated than using that CT ofusing theand tumorCT MRI, and to [2 MRI,, 36check,50 to]. for Radiologicalcheck bladder for bladder tumor, evaluation tumor,foreign of foreign body,recurrent diverticulabody, cystitis diverticula is(Figure indicated (Figure22), usingor fistulae 22), CT or and fistulaebetween MRI, between the to check gastrointestinal the for gastrointestinal bladder tract tumor, and tract foreign the and bladder body, the bladder [42].diverticula [42]. (Figure 22), or fistulae between the gastrointestinal tract and the bladder [42].

(a) (a) (b) (b) Figure 22. 22.Figure RecurrentRecurrent 22. Recurrent cystitis cystitis with cystitis with right rightwith vesical vesicalright wall vesical wall diverticulum. diverticulum.wall diverticulum. (a) Axial (a) Axial( aand) Axial ( andb) sagittaland (b) ( sagittalb) T2sagittal T2 T2 weightedweighted images ofimages the pelvis of the demonstrate pelvis demonstrate diffuse irregular diffuse irregular bladder bladderwall thickening, wall thickening, and irregular and irregular mucosal thickening. Right lateral wall narrow neck diverticulum with fluid–fluid layering inside mucosal thickening. thickening. Right Right lateral lateral wall wall narrow narrow neck neck diverticulum diverticulum with with fluid–fluid fluid–fluid layering layering inside inside denoting infected urine. Enlarged prostate with median lobe hypertrophy projecting inside the denoting infected infected urine. urine. Enlarged Enlarged prostate prostate with with median median lobe lobe hypertrophy hypertrophy projecting projecting inside inside the the bladder bladderand Foley’s and catheterFoley’s cathetercould be could noted. be noted. bladder and Foley’s catheter could be noted.

Sometimes,Sometimes, acute infectious acute infectious cystitis cystitismay be maycomplicated be complicated by a mural by a bladdermural bladder abscess abscess formation,formation,formation, which which can canwhich be be candemonstrated demonstrated be demonstrated by by MRI MRI by and and MRI CT CT and as anCT intramural as an intramural (Figure (Figure 23)23) or 23) or exophyticexophytic (Figure(Figure 24 (Figure24)) non-enhancing non-enhancing 24) non-enhancing cystic cystic collection co cysticllection co withllection with marginal marginal with irregular marginal irregular enhancement, irregular enhance- enhance- ment,commonly commonlyment, developing commonly developing at developing the bladderat the bladder at dome. the bladder Thedome. absence Thedome. absence of The an appreciable absence of an appreciable of connectionan appreciable connec- with connec- tionthe urinarywithtion the with bladder urinary the urinary lumenbladder allows bladder lumen the allowslumen differentiation theallows differentiation the ofdifferentiation an infected of an infected diverticulum of an infected diverticulum from diverticulum a frommural a abscessmuralfrom a abscess mural [50]. abscess [50]. [50].

(a) (a) (b) (b) (c) (c)

Figure 23.Figure Cystitis 23. Cystitis complicated complicated by mural by bladder mural bladder abscess. abscess.( a) Axial ( aT2–WI, ) Axial ( T2–WI,b) axial ( post-contrastb) axial post-contrast T1–WI, and T1–WI, ( c) coronaland (c) coronal post-contrast T1–WI show circumferential thickened irregular bladder wall. The right aspect of the bladder dome shows post-contrast T1–WI show circumferential thickened irregular bladder wall. The ri rightght aspect of the bladder dome shows marked markedmural thickening mural thickening with underlying with underlying intramural intramural marginally marg enhancinginally enhancing small fluid small locules fluid andlocules distorted and distorted related related marked mural thickening with underlying intramural marginally enhancing small fluid locules and distorted related perivesicalperivesical fat, the radiological fat, the radiological features featuressuggest suggestbladder bladderwall abscesses. wall abscesses. perivesical fat, the radiological features suggest bladder wall abscesses.

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(a) (b) (c) (d) (a) (b) (c) (d) Figure 24. Cystitis complicated by an exophytic bladder wall abscess in a patient with colonic diverticulitis. ( (aa)) Sagittal, Sagittal, (b) coronal, (c) axial T2-W images and (d) post-contrast axial T1–WI show diffuse irregular bladder wall thickening with Figure 24. Cystitis(b) coronal, complicated (c) axial by T2-W an exophytic images and bladder (d) post-contrast wall abscess axial in a T1–WI patient show with diffusecolonic irregular diverticulitis. bladder (a) wallSagittal, thickening with contiguous soft tissue inflammatory thickening closely related to adjacent margin of a thick-walled sigmoid colon associ- (b) coronal, (contiguousc) axial T2-W soft images tissue inflammatoryand (d) post-contrast thickening axial closely T1–WI related show to diffuse adjacent irregular margin bladder of a thick-walled wall thickening sigmoid with colon associated contiguous softated tissue with inflammatoryfluid-like collection thickening demonstrating closely relate irregulard to adjacent periph margineral enhancement of a thick-walled along thesigmoid supe riorcolon aspect associ- of the urinary with fluid-like collection demonstrating irregular peripheral enhancement along the superior aspect of the urinary bladder. ated with fluid-likebladder. collection Diffusely demonstratingthickened adjacent irregular intestinal periph loopseral enhancementwith multiple alongdiverticulitis the supe showingrior aspect peridiverticular of the urinary fat stranding Diffusely thickened adjacent intestinal loops with multiple diverticulitis showing peridiverticular fat stranding and mural bladder. Diffuselyand mural thickened enhancemen adjacentt could intestinal be noted. loops with multiple diverticulitis showing peridiverticular fat stranding and mural enhancemenenhancementt could could be be noted. noted. 2.13. Eosinophilic Cystitis 2.13. Eosinophilic2.13.Eosinophilic EosinophilicCystitis Cystitiscystitis represents a rare chronic inflammatory condition of the urinary Eosinophilicbladder.Eosinophilic cystitis It is characterized represents cystitis a representsraremainly chronic by athe inflammatory rare infiltration chronic of inflammatory condition the urinary of the bladder condition urinary wall of with the uri-eo- bladder. It sinophilsisnary characterized bladder. associated It mainly is characterized with by variable the infiltration mainly degrees of by of the the fibrosis urinary infiltration and bladder muscle of the wall necrosis urinary with eo- bladder[51]. Eosino- wall sinophils associatedphilicwith eosinophilscystitis with may variable associated occur degrees in patients with of variablefibrosis with peripheral degreesand muscle of eosinophilia fibrosis necrosis and [51]. or muscle allergy. Eosino- necrosis Hematuria, [51]. philic cystitisfrequency,Eosinophilic may occur and cystitis in dysuria patients may are occurwith the peripheralmost in patients common eosinophilia with associated peripheral or symptoms allergy. eosinophilia Hematuria, [52,53]. or allergy. At the Hema-radio- frequency, logicandturia, dysuria assessment, frequency, are the anda single most dysuria commonbladder are themass associated most maybe common symptoms visualized associated [52,53]. more symptomsfrequently At the radio- [than52,53 multiple]. At the logic assessment,massesradiologic a and single assessment, may bladder be sessile amass single [51,53]. maybe bladder MRI visualized shows mass maybe mural more visualized bladderfrequently wall more than thickening frequentlymultiple with than a mass mul- masses anddisplayingtiple may massesbe sessile inhomogeneous and [51,53]. may beMRI sessile showsvariable [51 mural,53 signal]. MRI bladder intensity shows wall muralon thickening T1 bladderand T2–WI with wall a (Figuremass thickening 25). withThe displaying massainhomogeneous mass is displayingusually enhanced vari inhomogeneousable signalafter intravenous intensity variable on signalad T1ministration and intensity T2–WI of on (Figure contrast T1 and 25). T2–WImaterial. The (Figure A cystic 25). mass is usuallyvariantThe massenhanced with is an usually enhancingafter intravenous enhanced wall may after ad beministration intravenous seen. In the of administrationfibrotic contrast stage material. of ofthe contrast disease,A cysticmaterial. the urinary A variant withbladdercystic an enhancing variant is small with wall and an may contracted, enhancing be seen. and wallIn the there may fibrotic may be seen. stage be resultant In of the the fibrotic disease, hydronephrosis stage the urinary of the [41,54] disease, . the bladder is smallurinary and bladder contracted, is small and and there contracted, may be resultant and there hydronephrosis may be resultant [41,54] hydronephrosis. [41,54].

(a) (b) Figure 25.( aEosinophilic) cystitis. (a) Axial and (b) sagittal(b T2) weighted images show diffuse bladder Figure 25. EosinophilicFigure 25. cystitis. Eosinophilicwall (thickeninga) Axial cystitis. and with (b ()a sagittalan) Axial intravesical T2and weighted (b) superficialsagittal images T2 maweighted showss displaying diffuse imag bladderes heterogeneous show wall diffuse thickening bladder signal intensity. with an It is seen related to the posterior bladder wall with intact muscle layer; the lesion encroaches upon intravesical superficialwall thickening mass displaying with an intravesical heterogeneous superficial signal intensity. mass displaying It is seen heterogeneous related to the posterior signal intensity. bladder It wall with ureteric orifices and bladder neck. It was proved as eosinophilic cystitis by histopathology. intact muscle layer;is seen the related lesion encroachesto the posterior upon bladder ureteric wall orifices with and intact bladder muscle neck. layer; It wasthe lesion proved encroaches as eosinophilic upon cystitis by ureteric orifices and bladder neck. It was proved as eosinophilic cystitis by histopathology. histopathology. 2.14. Cystitis and Fistula 2.14. Cystitis andColovesical Fistula fistulas occur most commonly in association with Crohn’s disease and Colovesicaldiverticulitis.2.14. Cystitisfistulas andoccurIn smaller Fistula most fistulae,commonly the inonly association clinical presentation with Crohn’s may disease be chronic and cystitis. diverticulitis.Bladder InColovesical smaller cancer, fistulae, iatrogenic fistulas the occur onlyinjuries, mostclinical and commonly presentationradiotherapy in association may may be also chronic with favor Crohn’s cystitis.colovesical disease fistula and Bladder cancer,formation.diverticulitis. iatrogenic Frequently, In injuries, smaller largerand fistulae, radi fistulaeotherapy the only lead may clinical to alsoair presentation orfavor feces colovesical excretion may be fistula chronicvia the cystitis.urine. formation. [3,34,36,55].BladderFrequently, cancer, larger iatrogenic fistulae injuries, lead to and air radiotherapy or feces excretion may also via favor the colovesicalurine. fistula [3,34,36,55].formation. Frequently, larger fistulae lead to air or feces excretion via the urine [3,34,36,55].

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InIn CT CT and and MRI, MRI, fistula fistula detection detection can can be be reached reached either either directly directly (by (by filling filling the the fistulous fistulous tracttract with with contrast contrast medium) medium) or or indirectly indirectly (only by showing the communication of two organsorgans or or by air detection in the fistulous fistulous trac tract)t) (Figure 2626).). For fistula fistula detection, MRI is betterbetter than than CT, CT, since the fistulae fistulae can be detected at T2–WI with fat suppression sequence andand after after Gadolinium Gadolinium administration administration in in fat-sa fat-saturatedturated T1–WI. T1–WI. Moreover, Moreover, MRI can be used toto detect detect a a coexisting coexisting abscess abscess via via DWI DWI with with high high specificity specificity [34,36]. [34,36]. CT CT findings findings are are usually usually diagnostic,diagnostic, in in 90–100% 90–100% of of cases, cases, and and include endoluminal air, mural thickening, mucosal hyperemia,hyperemia, tethering tethering of of adjacent adjacent thick-walled thick-walled bowel bowel as as well well as the presence of pericolic fatfat stranding stranding and and dissecting inflammatory inflammatory fi fistulastula tract. Multiplanar coronal and sagittal reformattedreformatted images, images, as as well well as as three-dimensional reconstructions, are usually invaluable inin detecting detecting the the fistula fistula tract, tract, particularly particularly at at the the level level of of the bladder dome where partial volumevolume averaging may potentially obscure the findingsfindings seen on axial images [[34,41]34,41]..

(a) (b) (c)

Figure 26. 26. ColovesicalColovesical fistula. fistula. (a) (Sagittala) Sagittal and and (b) (coronalb) coronal T2 weighted T2 weighted images images show show marked marked irregular irregular bladder bladder wall thick- wall eningthickening at the at bladder the bladder dome domewith related with related inflammatory inflammatory soft tissu softe tissueclosely closely related related to the adjacent to the adjacent thick-walled thick-walled sigmoid sigmoid colon. Intravesical signal void air locules also could be noted. (c) Coronal reformatted CT cystography confirms the presence of colon. Intravesical signal void air locules also could be noted. (c) Coronal reformatted CT cystography confirms the presence colovesical fistula. of colovesical fistula. 2.15. Acute Bacterial Prostatitis and Prostatic Abscess 2.15.Prostatitis Acute Bacterial has a Prostatitis prevalence and of Prostatic 9% among Abscess adult male patients. The route of contami- nationProstatitis is usually has ascending. a prevalence Prostatitis of 9% can among be classified adult maleinto 4 patients.categories The[56] routeas following: of con- I.tamination Acute bacterial is usually prostatitis, ascending. II. Chronic Prostatitis bacterial can be classifiedprostatitis, into III. 4 Chronic categories prostati- [56] as tis/chronicfollowing: I.pelvic Acute pain bacterial syndrome prostatitis, (CPPS); II. Chronic inflammatory bacterial prostatitis,(IIIA) and III.non-inflammatory Chronic prostati- (IIIB),tis/chronic IV. Asymptomatic pelvic pain syndrome inflammatory (CPPS); prostatitis inflammatory [42]. Fever, (IIIA) anddysuria, non-inflammatory frequency, and (IIIB), pel- vicIV. pain Asymptomatic are common inflammatory presentation prostatitiss. The prostate [42]. is Fever, usually dysuria, enlarged frequency, and tender and during pelvic thepain digital are common rectal examination. presentations. About The 10% prostate of patients is usually with enlarged acute bacterial and tender prostatitis during pro- the gressdigital to rectal chronic examination. bacterial prostatitis About 10% and of patientsa further with 10% acute of cases bacterial progress prostatitis to CPPS. progress Risk factorsto chronic for bacterialacute bacterial prostatitis prostatitis and a furtherinclude 10% urethral of cases catheterization progress to CPPS. and prostate Risk factors biopsy for [37].acute bacterial prostatitis include urethral catheterization and prostate biopsy [37]. TheThe prostatic prostatic abscess abscess requires requires early early diagnosis diagnosis and and management management to to avoid avoid severe severe com- com- plications.plications. Most Most prostatic prostatic abscesses abscesses occur occur secondary secondary to lower urinary tract obstruction or hematogenoushematogenous spread of infection infection in patients patients with with pre-existing pre-existing prostatitis. The The nonspecific nonspecific symptomssymptoms of of prostatic prostatic abscess often ma makeke the diagnosis difficult difficult [[37,57].37,57]. TransrectalTransrectal ultrasound (TRUS) is indicated for patients who fail initial treatment for prostatitisprostatitis and particularly for suspected pros prostatictatic abscess. TRUS can also guide abscess drainagedrainage and and provide provide samples samples for for culture [37]. [37]. CT CT has has no no role in the diagnosis of acute prostatitisprostatitis however, however, it it may may diagnose diagnose an an absces abscesss or extraprostatic or extraprostatic extension. extension. Although Although MRI canMRI detect can detect the diffuse the diffuse asymmetric asymmetric prostate prostate enlargement, enlargement, it is usually it is usually indicated indicated for sus- for pectedsuspected prostatic prostatic abscess, abscess, which which appears appears as a cy asstic a cysticlesion lesionwith thick with walls, thick septae, walls, septae,or het- erogeneousor heterogeneous contents. contents. Signal intensity Signal intensity is usually is usuallyisointense isointense to hyperintense to hyperintense on T1-WI, on and T1- isointenseWI, and isointense to hypointense to hypointense on T2-WI ondue T2-WI to pus due and to debris. pus and Thick-walled debris. Thick-walled fluid collections fluid duecollections to abscess due toformation abscess formationare well seen are well at co seenntrast-enhanced at contrast-enhanced MRI. Excellent MRI. Excellent soft-tissue soft-

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characterization provided by MRI is useful to assess the prostatic abscess extension and extraprostatictissue characterization involvement. provided Diffusion-weighted by MRI is useful MRI to assess will detect the prostatic the prostatic abscess abscess extension as anand area extraprostatic of diffusion involvement. restriction that Diffusion-weighted correlates with MRIT2 weighted will detect abnormality the prostatic (Figure abscess 27) as [2]an. area of diffusion restriction that correlates with T2 weighted abnormality (Figure 27)[2].

(a) (b) (c)

(d) (e) (f)

Figure 27. ProstaticProstatic abscess. abscess. (a) ( aAxial,) Axial, (b) ( bsagittal,) sagittal, (c) (coronalc) coronal T2 weighted T2 weighted images images and and(d) Axial (d) Axial T2 weighted T2 weighted image image with fat suppression show that the enlarged prostate is a seat of a multilocular cystic lesion with thick wall and thick septae, with fat suppression show that the enlarged prostate is a seat of a multilocular cystic lesion with thick wall and thick displaying fluid signal intensity, showing extraprostatic extension with periprostatic fat stranding and inflammatory re- septae, displaying fluid signal intensity, showing extraprostatic extension with periprostatic fat stranding and inflammatory action, it is seen indenting the right lateral wall of the rectum, and extends to the left obturator internus muscle. The DWI (reaction,e) and apparent it is seen diffusion indenting coefficient the right lateral(ADC) wall map of (f the) show rectum, the abscess and extends as an toarea the of left restricted obturator diffusion; internus high muscle. signal The inten- DWI sity(e) and (SI) apparentat DWI and diffusion low SI coefficient at ADC map. (ADC) map (f) show the abscess as an area of restricted diffusion; high signal intensity (SI) at DWI and low SI at ADC map. 2.16. Chronic Prostatitis 2.16.TRUS Chronic is usually Prostatitis normal in most cases of chronic prostatitis. Calcification can be easily detectedTRUS by isCT usually but it is normal not specific in most for chronic cases of prostatitis. chronic prostatitis. Overlapping Calcification features between can be chroniceasily detected prostatitis by and CT butprostate it is not cancer specific are foralso chronic seen on prostatitis. MRI. Diffusion-weighted Overlapping features MRI showsbetween restricted chronic diffusion prostatitis in and both prostate cancer cancerand prostatitis, are also seen but onusing MRI. the Diffusion-weighted ADC value < 1.2 × −3 2 10MRI mm shows/sec restricted as a cutoff diffusion point for in boththe diagnosis cancer and of prostatitis,cancer increased but using the theDWI ADC sensitivity value < and1.2 × specificity10−3 mm 2[2]./s as a cutoff point for the diagnosis of cancer increased the DWI sensitivity and specificity [2]. 2.17. Urethritis 2.17.Urethritis Urethritis is commonly caused by a sexually transmitted infections. Urethritis from chlamydia,Urethritis trachomatis, is commonly and causedgonorrhea by ais sexually favored transmittedby low socioeconomic infections. status. Urethritis Alterna- from tively,chlamydia, urethral trachomatis, infection andresults gonorrhea from permanent is favored or by intermittent low socioeconomic catheterization status. Alterna-or from urologictively, urethral instrumentation. infection results Symptoms from include permanent dysuria, or intermittent mucopurulent catheterization discharge, and or fromure- thralurologic pruritus instrumentation. [50,58]. Symptoms include dysuria, mucopurulent discharge, and ure- thralAcute pruritus urethritis [50,58]. is often diagnosed on the background of clinical and laboratory find- ings however,Acute urethritis imaging is may often be diagnosed required to on exclude the background associated of complications clinical and laboratorysuch as a periurethralfindings however, abscess. imaging At MRI, may acute be requiredurethritis to appears exclude as associated diffuse thic complicationskening of the such urethra as a asperiurethral well as periurethral abscess. At tissues, MRI, acute with urethritis intermediate appears to high as diffuse signal thickening intensity on of theT2-WI urethra and intenseas well contrast as periurethral enhancement tissues, (Figure with intermediate 28). The use of to MRI high can signal effectively intensity visualize on T2-WI differ- and entintense abnormalities contrast enhancement related to the (Figure urethra 28 such). The as use perineal of MRI and can periurethral effectivelyvisualize abscesses different [50,59]. abnormalities related to the urethra such as perineal and periurethral abscesses [50,59].

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Figure 28. Cystitis and urethritis. Sagittal post-contrast T1 weighted image shows diffuse thick Figure 28. Cystitis and urethritis. Sagittal post-contrast T1 weighted image shows diffuse thick enhancing urethra suggesting urethritis. There is also cystitis complicated by an exophytic bladder enhancing urethra suggesting urethritis. There is also cystitis complicated by an exophytic bladder wall abscess showing a thick enhancing wall. wall abscess showing a thick enhancing wall. A periurethral abscess is a life-threatening condition of the male urethra which may A periurethral abscess is a life-threatening condition of the male urethra which may result from gonococcal infection, urethral stricture, or urethral catheterization. CT and result from gonococcal infection, urethral stricture, or urethral catheterization. CT and MRIMRI can can demonstrate demonstrate the the presence presence and and extension extension of of a a periurethral periurethral abscess abscess and and can can assess assess thethe associatedassociated complicationscomplications suchsuch asas urethroperineal urethroperineal fistulas,fistulas, Fournier Fournier gangrene, gangrene, and and fasciitis.fasciitis. Urethroperineal Urethroperineal fistulas fistulas are are usually usually the the consequence consequence of a periurethralof a periurethral abscess. abscess. The initialThe initial cavity cavity of the of abscess the abscess contracts contracts due to due fibrosis, to fibrosis, leaving leaving only the only narrow the narrow fistulous fistulous tract extendingtract extending from the from urethra the urethra to the perineum.to the perine Urethroperinealum. Urethroperineal fistulas fistulas are usually are usually the result the ofresult urinary of urinary tuberculosis tuberculosis and schistosomiasis and schistosomiasis infections infections [60]. [60]. TheThe characteristic characteristic cross-sectional cross-sectional imaging imaging features features of of different different types types of of UTIs UTIs affecting affecting thethe upper upper and and lower lower urinary urinary tracts tracts are are summarized summarized in in Table Table1. 1.

TableTable 1. 1.Cross-sectional Cross-sectional imaging imaging signs signs of of different different types types of of urinary urinary tract tract infections. infections.

Infectious Conditions Conditions Cross-Sectional Cross-Sectional Imaging Imaging Signs Signs Wedge shaped hypo-enhancing areas or stri- Wedge shaped hypo-enhancing areas or striated AcuteAcute pyelonephritispyelonephritis nephrogramated nephrogram pattern. pattern. Perinephric Perinephric fat stranding fat and thickeningstranding ofand Gerota’s thickening fascia. of Gerota’s fascia. RoundRound or or geographic geographic non-enhancing non-enhancing central central fluid Renal abscesses collectionfluid collection and enhancing and enhancing rim. Perinephric rim. Perineph- fat Renal abscesses strandingric fat stranding and thickening and thickening of Gerota’s of fascia. Gerota’s Gasfascia. in the renal parenchyma, collecting system, Emphysematous UTIs bladderGas in the lumen renal and parenchyma, sometimes in thecollecting perirenal sys- and Emphysematous UTIs perivesicaltem, bladder tissue. lumen and sometimes in the Dilatedperirenal thick-walled and perivesical hyperenhancing tissue. collecting system, distended with high attenuation pus-filled Pyonephrosis Dilated thick-walled hyperenhancing collect- fluid, fluid—fluid layering at T2WI, and thinning ing system, distended with high attenuation Pyonephrosis of the renal cortex. pus-filled fluid, fluid—fluid layering at T2WI, Renal scarring, cortical atrophy, calyceal clubbing, Chronic pyelonephritis thickeningand thinning and of dilatation the renal of thecortex. calyceal system andRenal overall scarring, renal asymmetry.cortical atrophy, calyceal club- Chronic pyelonephritis Non-functioningbing, thickening enlarged and dilatation kidney,obstructing of the calyceal stone within a non-dilated renal pelvis, expansion Xanthogranulomatous Pyelonephritis system and overall renal asymmetry. ofNon-functioning the calyces, and inflammatoryenlarged kidney, changes obstructing in the perinephric fat. stone within a non-dilated renal pelvis, expan- Xanthogranulomatous Pyelonephritis sion of the calyces, and inflammatory changes in the perinephric fat. Calyx stem stenosis with proximal ball-shaped Urinary tuberculosis hydrocalyx, cavity communicating with a

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Table 1. Cont.

Infectious Conditions Cross-Sectional Imaging Signs Calyx stem stenosis with proximal ball-shaped hydrocalyx, cavity communicating with a Urinary tuberculosis deformed calyx, putty kidney, ureteric strictures and shortening with beaded appearance, thick-walled contracted bladder. Total atrophy of the renal parenchyma with complete fibrofatty replacement associated with Renal replacement lipomatosis stag horn stone. Stretched calyces without hyronephrosis. Contracted, fibrotic, thick calcified bladder wall Urinary Bilharziasis with ureteric stenosis and calcifications. Rolled appearance when it contains air bubbles between the layers of fungal colonies. If air Urinary candidiasis bubbles are not present, it appears as non-enhancing solid mass. Diffuse mucosal urothelial thickening, often with Ureteritis associated periureteric fat stranding. Linear hyperdense calcifications along the Encrusted pyelitis and cystitis thickened urothelium. Diffuse bladder wall thickening, especially if Acute infectious cystitis oedematous at T2 weighted image, urothelial hyperenhancement, perivesical fat stranding. Intramural/exophytic non-enhancing fluid collection, irregular wall, often thick peripheral Mural bladder abscess enhancement, usually affecting the upper bladder aspect. Non enhancing fluid collection with peripheral or Prostatic abscess septal enhancement and non-enhancing central fluid. Possible extraprostatic extension Thickened urethra and surrounding soft tissues, Acute urethritis high T2 weighted signal intensity, corresponding intense contrast enhancement.

3. Conclusions This is an excellent review of the CT and MRI in urinary tract infections. It should interest most of the readers of Medicina including radiologists, urologists, and nephrologists. We should be familiar with the CT and MRI signs of these common and potentially severe disorders, which may require early diagnosis and appropriate management that decrease the incidences and degree of complications.

Author Contributions: Conceptualization, M.A.E.-G. and H.F.; software, H.F.; validation, M.A.E.-G. and T.E.-D.; formal analysis, H.F. and D.E.S.; investigation, D.E.S.; resources, D.E.S.; data curation, M.A.E.-G. and Sharaf.; writing—original draft preparation, M.A.E.-G.; H.F. and D.E.S.; writing— review and editing, M.A.E.-G.; H.F. and D.E.S.; visualization, T.E.-D.; supervision, M.A.E.-G. and T.E.-D. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest. Medicina 2021, 57, 32 21 of 23

References 1. Nicola, R.; Menias, C.O. Urinary Obstruction, Stone Disease, and Infection. In Diseases of the Abdomen and Pelvis 2018–2021: Diagnostic Imaging—IDKD Book; Hodler, J., Kubik-Huch, R.A., von Schulthess, G.K., Eds.; Springer: Cham, Switzerland, 2018; pp. 223–228. 2. O’Connor, O.J.; El-Diasty, T.; Abou-El-Ghar, M.; Maher, M.M. Common Uroradiological Referrals: Haematuria, Loin Pain, Renal Failure and Infection Haematuria, Loin Pain, Renal Failure and Infection. In Grainger and Allison’s Diagnostic Radiology, 6th ed.; Adam, A., Dixon, A., Gillard, J., Schaefer-Prokop, C., Grainger, R., Eds.; Elsevier Publishing: London, UK, 2015; pp. 832–858. 3. Foxman, B. Epidemiology of urinary tract infections: Incidence, morbidity, and economic costs. Dis.-A-Mon. DM 2003, 49, 53–70. [CrossRef][PubMed] 4. Nicolle, L.E. The chronic indwelling catheter and urinary infection in long-term-care facility residents. Infect. Control Hosp. Epidemiol. 2001, 22, 316–321. [CrossRef][PubMed] 5. Flores-Mireles, A.L.; Walker, J.N.; Caparon, M.; Hultgren, S.J. Urinary tract infections: Epidemiology, mechanisms of infection and treatment options. Nat. Rev. Microbiol. 2015, 13, 269–284. [CrossRef][PubMed] 6. Sarshar, M.; Behzadi, P.; Ambrosi, C.; Zagaglia, C.; Palamara, A.T.; Scribano, D. FimH and Anti-Adhesive Therapeutics: A Disarming Strategy against Uropathogens. Antibiotics 2020, 9, 397. [CrossRef] 7. Scribano, D.; Sarshar, M.; Prezioso, C.; Lucarelli, M.; Angeloni, A.; Zagaglia, C.; Palamara, A.T.; Ambrosi, C. d-Mannose Treatment neither Affects Uropathogenic Escherichia coli Properties nor Induces Stable FimH Modifications. Molecules 2020, 25, 316. [CrossRef] 8. Terlizzi, M.E.; Gribaudo, G.; Maffei, M.E. UroPathogenic Escherichia coli (UPEC) Infections: Virulence Factors, Bladder Responses, Antibiotic, and Non-antibiotic Antimicrobial Strategies. Front. Microbiol. 2017, 8, 1566. [CrossRef] 9. Jung, H.J.; Choi, M.H.; Pai, K.S.; Kim, H.G. Diagnostic performance of contrastenhanced ultrasound for acute pyelonephritis in children. Sci. Rep. 2020, 10, 10715. [CrossRef] 10. Demertzis, J.; Menias, C.O. State of the art: Imaging of renal infections. Emerg. Radiol. 2007, 14, 13–22. [CrossRef] 11. Sriman, R.; Venkatesh, K.; Mathew, C.; Pankaj, M.; Shankar, R. Validity of diffusionweighted magnetic resonance imaging in the evaluation of acute pyelonephritis in comparison with contrast-enhanced computed tomography. Pol. J. Radiol. 2020, 85, e137–e143. 12. Sallami, S.; Ghariani, R.; Hichri, A.; Zrayer, O. Imaging findings of urinary tuberculosis on computerized tomography versus excretory urography: Through 46 confirmedcases. La Tunis. Med. 2014, 92, 743–747. 13. Gaudiano, C.; Tadolini, M.; Busato, F.; Vanino, E.; Pucci, S.; Corcioni, B.; Golfieri, R. Multidetector CT urography in urogenital tuberculosis: Use of reformatted images for the assessment of the radiological findings. A pictorial essay. Abdom. Radiol. (N. Y.) 2017, 42, 2314–2324. [CrossRef][PubMed] 14. Das, C.J.; Ahmad, Z.; Sharma, S.; Gupta, A.K. Multimodality imaging of renal inflammatory lesions. World J. Radiol. 2014, 6, 865–873. [CrossRef][PubMed] 15. Kawashima, A.; Sandler, C.M.; Goldman, S.M. Imaging in acute renal infection. BJU Int. 2000, 86 (Suppl. 1), 70–79. [CrossRef] 16. Udare, A.; Abreu-Gomez, J.; Krishna, S.; McInnes, M.; Siegelman, E.; Schieda, N. Imaging Manifestations of Acute and Chronic Renal Infection That Mimics Malignancy: How to Make the Diagnosis Using Computed Tomography and Magnetic Resonance Imaging. Can. Assoc. Radiol. J. J. L’assoc. Can. Des. Radiol. 2019, 70, 424–433. [CrossRef][PubMed] 17. Chung, A.D.; Schieda, N.; Shanbhogue, A.K.; Dilauro, M.; Rosenkrantz, A.B.; Siegelman, E.S. MRI Evaluation of the Urothelial Tract: Pitfalls and Solutions. AJR Am. J. Roentgenol. 2016, 207, W108–W116. [CrossRef][PubMed] 18. Yoshikawa, T.; Kawamitsu, H.; Mitchell, D.G.; Ohno, Y.; Ku, Y.; Seo, Y.; Fujii, M.; Sugimura, K. ADC measurement of abdominal organs and lesions using parallel imaging technique. AJR Am. J. Roentgenol. 2006, 187, 1521–1530. [CrossRef] 19. Matsuoka, A.; Minato, M.; Harada, M.; Kubo, H.; Bandou, Y.; Tangoku, A.; Nakano, K.; Nishitani, H. Comparison of 3.0-and 1.5-tesla diffusion-weighted imaging in the visibility of breast cancer. Radiat. Med. 2008, 26, 15–20. [CrossRef] 20. Abreu-Gomez, J.; Udare, A.; Shanbhogue, K.P.; Schieda, N. Update on MR urography (MRU): Technique and clinical applications. Abdom. Radiol. (N. Y.) 2019, 44, 3800–3810. [CrossRef] 21. Kraus, S.J. GENITOURINARY IMAGING IN CHILDREN. Pediatr. Clin. N. Am. 2001, 48, 1381–1424. [CrossRef] 22. Majd, M.; Nussbaum Blask, A.R.; Markle, B.M.; Shalaby-Rana, E.; Pohl, H.G.; Park, J.S.; Chandra, R.; Rais-Bahrami, K.; Pandya, N.; Patel, K.M.; et al. Acute pyelonephritis: Comparison of diagnosis with 99mTc-DMSA, SPECT, spiral CT, MR imaging, and power Doppler US in an experimental pig model. Radiology 2001, 218, 101–108. [CrossRef] 23. Johnson, J.R.; Russo, T.A. Acute Pyelonephritis in Adults. N. Engl. J. Med. 2018, 378, 48–59. [CrossRef][PubMed] 24. Browne, R.F.; Zwirewich, C.; Torreggiani, W.C. Imaging of urinary tract infection in the adult. Eur. Radiol. 2004, 14 (Suppl. 3), E168–E183. [CrossRef] 25. Patiño, A.; Martinez-Salazar, E.L.; Tran, J.; Sureshkumar, A.; Catanzano, T. Review of Imaging Findings in Urinary Tract Infections. Semin. Ultrasound Ct MR 2020, 41, 99–105. [CrossRef][PubMed] 26. Rathod, S.B.; Kumbhar, S.S.; Nanivadekar, A.; Aman, K. Role of diffusion-weighted MRI in acute pyelonephritis: A prospective study. Acta Radiol. (Stockh. Swed. 1987) 2015, 56, 244–249. [CrossRef][PubMed] 27. Faletti, R.; Cassinis, M.C.; Fonio, P.; Grasso, A.; Battisti, G.; Bergamasco, L.; Gandini, G. Diffusion-weighted imaging and apparent diffusion coefficient values versus contrast-enhanced MR imaging in the identification and characterization of acute pyelonephritis. Eur. Radiol. 2013, 23, 3501–3508. [CrossRef][PubMed] Medicina 2021, 57, 32 22 of 23

28. De Pascale, A.; Piccoli, G.B.; Priola, S.M.; Rognone, D.; Consiglio, V.; Garetto, I.; Rizzo, L.; Veltri, A. Diffusion-weighted magnetic resonance imaging: New perspectives in the diagnostic pathway of non-complicated acute pyelonephritis. Eur. Radiol. 2013, 23, 3077–3086. [CrossRef][PubMed] 29. Chauhan, V.; Sharma, R. Emphysematous pyelonephritis (class IIIa) managed with antibiotics alone. Hong Kong Med. J. Xianggang Yi Xue Za Zhi 2015, 21, 363–365. [CrossRef][PubMed] 30. Goyal, A.; Sharma, R.; Bhalla, A.S.; Gamanagatti, S.; Seth, A. Diffusion-weighted MRI in inflammatory renal lesions: All that glitters is not RCC! Eur. Radiol. 2013, 23, 272–279. [CrossRef] 31. Katabathina, V.S.; Kota, G.; Dasyam, A.K.; Shanbhogue, A.K.; Prasad, S.R. Adult renal cystic disease: A genetic, biological, and developmental primer. Radiographics 2010, 30, 1509–1523. [CrossRef] 32. Stunell, H.; Buckley, O.; Feeney, J.; Geoghegan, T.; Browne, R.F.; Torreggiani, W.C. Imaging of acute pyelonephritis in the adult. Eur. Radiol. 2007, 17, 1820–1828. [CrossRef] 33. Ifergan, J.; Pommier, R.; Brion, M.C.; Glas, L.; Rocher, L.; Bellin, M.F. Imaging in upper urinary tract infections. Diagn. Interv. Imaging 2012, 93, 509–519. [CrossRef][PubMed] 34. Hirshberg, B.; Rheinboldt, M. MDCT Imaging of Acute Bladder Pathology. Curr. Probl. Diagn. Radiol. 2019, 49, 422–430. [CrossRef] [PubMed] 35. Eken, A.; Alma, E. Emphysematous cystitis: The role of CT imaging and appropriate treatment. Can. Urol. Assoc. J. J. L’assoc. Des. Urol. Can. 2013, 7, E754–E756. [CrossRef][PubMed] 36. Schönberg, S.O.; Budjan, J.; Hausmann, D. Urinary Obstruction, Stone Disease, and Infection. In Diseases of the Abdomen and Pelvis 2018–2021: Diagnostic Imaging—IDKD Book; Hodler, J., Kubik-Huch, R.A., von Schulthess, G.K., Eds.; Springer: Cham, Switzerland, 2018; pp. 247–255. 37. Steinkeler, J.A.; Sun, M.R.M. Imaging of Infections of the Urinary and Male Reproductive Tracts. Semin. Roentgenol. 2017, 52, 83–89. [CrossRef] 38. Bobba, R.K.; Arsura, E.L.; Sarna, P.S.; Sawh, A.K. Emphysematous cystitis: An unusual disease of the Genito-Urinary system suspected on imaging. Ann. Clin. Microbiol. Antimicrob. 2004, 3, 20. [CrossRef] 39. Huang, J.J.; Tseng, C.C. Emphysematous pyelonephritis: Clinicoradiological classification, management, prognosis, and patho- genesis. Arch. Intern. Med. 2000, 160, 797–805. [CrossRef] 40. Grayson, D.E.; Abbott, R.M.; Levy, A.D.; Sherman, P.M. Emphysematous infections of the abdomen and pelvis: A pictorial review. Radiographics 2002, 22, 543–561. [CrossRef] 41. Wong-You-Cheong, J.J.; Woodward, P.J.; Manning, M.A.; Davis, C.J. From the archives of the AFIP: Inflammatory and nonneo- plastic bladder masses: Radiologic-pathologic correlation. Radiographics 2006, 26, 1847–1868. [CrossRef] 42. Schull, A.; Monzani, Q.; Bour, L.; Barry-Delongchamps, N.; Beuvon, F.; Legmann, P.; Cornud, F. Imaging in lower urinary tract infections. Diagn. Interv. Imaging 2012, 93, 500–508. [CrossRef] 43. Vijayaraghavan, S.B.; Kandasamy, S.V.; Arul, M.; Prabhakar, M.; Dhinakaran, C.L.; Palanisamy, R. Spectrum of high-resolution sonographic features of urinary tuberculosis. J. Ultrasound Med. Off. J. Am. Inst. Ultrasound Med. 2004, 23, 585–594. [CrossRef] 44. Muttarak, M.; ChiangMai, W.N.; Lojanapiwat, B. Tuberculosis of the genitourinary tract: Imaging features with pathological correlation. Singap. Med. J. 2005, 46, 568–574. 45. Dyer, R.B.; Chen, M.Y.; Zagoria, R.J. Classic signs in uroradiology. Radiographics 2004, 24 (Suppl. 1), S247–S280. [CrossRef] 46. Thoumas, D.; Darmallaicq, C.; Pfister, C.; Savoye-Collet, C.; Sibert, L.; Grise, P.; Lemaitre, L.; Benozio, M. Imaging characteristics of alkaline-encrusted cystitis and pyelitis. AJR Am. J. Roentgenol. 2002, 178, 389–392. [CrossRef][PubMed] 47. Hertig, A.; Duvic, C.; Chretien, Y.; Jungers, P.; Grünfeld, J.P.; Rieu, P. Encrusted pyelitis of native kidneys. J. Am. Soc. Nephrol. JASN 2000, 11, 1138–1140. [PubMed] 48. Orlowski, H.L.P.; McWilliams, S.; Mellnick, V.M.; Bhalla, S.; Lubner, M.G.; Pickhardt, P.J.; Menias, C.O. Imaging Spectrum of Invasive Fungal and Fungal-like Infections. Radiographics 2017, 37, 1119–1134. [CrossRef] 49. Wasnik, A.P.; Elsayes, K.M.; Kaza, R.K.; Al-Hawary, M.M.; Cohan, R.H.; Francis, I.R. Multimodality imaging in ureteric and periureteric pathologic abnormalities. AJR Am. J. Roentgenol. 2011, 197, W1083–W1092. [CrossRef] 50. Tonolini, M.; Ippolito, S. Cross-sectional imaging of complicated urinary infections affecting the lower tract and male genital organs. Insights Imaging 2016, 7, 689–711. [CrossRef] 51. Teegavarapu, P.S.; Sahai, A.; Chandra, A.; Dasgupta, P.; Khan, M.S. Eosinophilic cystitis and its management. Int. J. Clin. Pract. 2005, 59, 356–360. [CrossRef] 52. van den Ouden, D. Diagnosis and management of eosinophilic cystitis: A pooled analysis of 135 cases. Eur. Urol. 2000, 37, 386–394. [CrossRef] 53. Itano, N.M.; Malek, R.S. Eosinophilic cystitis in adults. J. Urol. 2001, 165, 805–807. [CrossRef] 54. Verhagen, P.C.; Nikkels, P.G.; de Jong, T.P. Eosinophilic cystitis. Arch. Dis. Child. 2001, 84, 344–346. [CrossRef][PubMed] 55. Najjar, S.F.; Jamal, M.K.; Savas, J.F.; Miller, T.A. The spectrum of colovesical fistula and diagnostic paradigm. Am. J. Surg. 2004, 188, 617–621. [CrossRef][PubMed] 56. Krieger, J.N.; Nyberg, L., Jr.; Nickel, J.C. NIH consensus definition and classification of prostatitis. JAMA 1999, 282, 236–237. [CrossRef][PubMed] 57. Ren, J.; Huang, X.; Wang, H.; Liu, H.; Ren, F.; Zhang, Z.; Yang, Y.; Yin, H.; Huan, Y. Prostatic abscess and seminal vesicle abscess: MRI findings and quantitative analysis of apparent diffusion coefficient values. Radiol. Infect. Dis. 2015, 2, 27–32. [CrossRef] Medicina 2021, 57, 32 23 of 23

58. Barozzi, L.; Valentino, M.; Menchi, I.; Pavlica, P. Clinical uroradiology: The standardisation of terminology for lower urinary tract function and dysfunction. La Radiol. Med. 2010, 115, 272–286. [CrossRef] 59. Del Gaizo, A.; Silva, A.C.; Lam-Himlin, D.M.; Allen, B.C.; Leyendecker, J.; Kawashima, A. Magnetic resonance imaging of solid urethral and peri-urethral lesions. Insights Imaging 2013, 4, 461–469. [CrossRef] 60. Kawashima, A.; Sandler, C.M.; Wasserman, N.F.; LeRoy, A.J.; King, B.F., Jr.; Goldman, S.M. Imaging of urethral disease: A pictorial review. Radiographics 2004, 24 (Suppl. 1), S195–S216. [CrossRef]