The Egyptian Journal of and (2013) 44, 893–899

Egyptian Society of Radiology and Nuclear Medicine The Egyptian Journal of Radiology and Nuclear Medicine

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ORIGINAL ARTICLE Assessment of ureteral obstruction in patients with compromised renal function: Value of Curved Planar Reformations in MDCT

Mohamed Ahmed Youssef a,*, Aly Aly Elbarbary b a Radiodiagnosis Department, Tanta Faculty of Medicine, 72 Elnady Street, Tanta, Gharbeya 31111, Egypt b Radiodiagnosis Department, Tanta Faculty of Medicine, Saeed Street, Tanta, Gharbeya, Egypt

Received 3 May 2013; accepted 20 July 2013 Available online 13 August 2013

KEYWORDS Abstract Objective: To evaluate the usefulness of MDCT using a curved planar reformation tech- MDCT; nique for the noninvasive assessment of the causes and level of ureteral obstruction in patients with Ureteric obstruction; compromised renal function. Curved planar reformation Patients and methods: Between January 2012 and February 2013, 50 patients with clinical and sonographic manifestations of ureteral obstruction underwent non-contrast multidetector CT (MDCT) using a 16-slice machine. A total of 65 were examined. Curved planar reformation images were performed to display the entire course of ureters in the same image. All patients had renal impairment with serum creatinine greater than 2.0 mg/dl. The gold standard for diagnosis of the cause of obstruction was and/or open surgery. The sensitivity, specificity and overall accuracy of MDCT using curved planar reformation in the diagnosis of ureteral obstruction were calculated in comparison with the gold standard. Results: A total of 65 ureters were examined (35 unilateral, 15 bilateral). The most common cause of ureteric obstruction was ureteric stone representing 27/65 (41.5%), followed by ureteric stricture representing 23/65 (35.4%). The lower third was the most affected in our study, it was encountered

Abbreviations: MDCT, multidetector CT; CPR, curved planar reformation * Corresponding author. Tel.: +20 1227446621. E-mail address: [email protected] (M.A. Youssef). Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine.

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0378-603X 2013 Production and hosting by Elsevier B.V. on behalf of Egyptian Society of Radiology and Nuclear Medicine. http://dx.doi.org/10.1016/j.ejrnm.2013.07.008 894 M.A. Youssef, A.A. Elbarbary

in 38/65 ureters (58.46%). The total sensitivity, specificity and accuracy of CPR for the cause of the ureteric obstruction were 98.5%, 98.5% and 97.8%, respectively (P value >0.05). CPR also was more sensitive and accurate for the level of ureteral obstruction with a total sensitivity of 100% and accuracy of 100% (P value >0.001). Conclusion: Curved planar reformation MDCT is a useful noninvasive technique which is accurate in diagnosing the cause and level of ureteral obstruction in patients with compromised renal func- tions and is helpful for planning the therapeutic management of such patients. 2013 Production and hosting by Elsevier B.V. on behalf of Egyptian Society of Radiology and Nuclear Medicine.

1. Introduction tector CT urography is its ability to provide a detailed anatomic depiction of each part of the urinary tract (8). It also offers sev- Ureteric obstruction with subsequent is the eral advantages for imaging of the includ- terminal outcome of most urological disorders. It can be clas- ing: single breath-hold coverage of whole urinary tract and the sified into congenital and acquired, intraluminal or extralumi- possibility to use different post processing techniques in addi- nal. Many imaging modalities are used to evaluate the tion to native axial images such as multiplanar reformation, obstructive uropathy such as plain X-ray of the urinary tract curved planar reformations, maximum intensity projections combined with abdominal gray-scale ultrasonography and and volume rendering technique (9,10). excretory urography, other methods of visualizing the ureteric MDCT has gradually evolved as an accepted method for an obstruction e.g. retrograde or antegrade pyelography or urete- assessment of patients with flank pain or hematuria (11,12). ropyeloscopy, are invasive (1). In the last decades some recent The main advantage of CT urography over excretory urogra- noninvasive investigations have been introduced for the diag- phy is its ability to show the intraluminal, mural and extralu- nosis of ureteral obstruction, e.g. the renal resistive index, (2) minal of the urinary tract (13,14). non-contrast MDCT (3–5) and magnetic resonance urography Curved planar reformations are single images obtained by with their ability to image the urinary tract in ways that exceed tracing a curved path through the imaging volume along the the excretory urography (6). course of a particular anatomic structure of interest. The vol- With the revolution of multidetector technology, multidetec- umetric data set is displayed by a path-tracing tool into a 2D tor CT urography has become the imaging modality of choice image representing the tortuous plane described by the struc- for many urologic problems (7). The main advantage of multide- ture of interest. The exact algorithm used to create the image

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Fig. 1 59-Year-old male patient with right loin pain. Multidetector computed tomography axial (A and B) and curved planar reformation images (C) show atrophic left , dilated right pelvicaliceal system and right down to the lower third due to obstructing radiodense stone. Assessment of ureteral obstruction in patients with compromised renal function 895

data sets of the native acquisition, and curved planar reforma- Table 1 Clinical data and past history of the studied group tions have become essential for that purpose (15). The aim of (n = 50). our study was to evaluate the usefulness of MDCT using a Presenting renal symptoms No. of patients Percent (%) curved planar reformation technique for the noninvasive Loin Pain 35/50 70 assessment of the causes and level of ureteral obstruction in Acute 21/35 60 patients with compromised renal function. Chronic 14/35 40 Hematuria 12/50 24 2. Patients and methods Dysuria 5/50 10 History of 2.1. Patient population Bilharziasis 21/50 42 Urinary tract operation 7/50 14 This study was approved by the local research ethics commit- Stone passing 10/50 20 tee of our institution, and informed consent for the procedure Previous pelvic surgery 4/50 8 was obtained from each patient. Between January 2012 and February 2013, 50 patients (30 males and 20 females, age range, 28–64 years; mean age, Table 2 Causes of ureteric obstruction as detected by 45.0 years ± 12.8[SD], were referred from Clinic with MDCTU (n = 65 ureter). a diagnosis of un-explained ureteral obstruction based on Causes NO (ureters) Percent (%) ultrasound and plain radiography findings, with unilateral or bilateral ureteral obstruction and IVP was contraindicated Ureteric stone 27 41.5 due to renal impairment with elevated renal function tests (ser- Ureteric stricture 23 35.4 Ureteric compression 6 9.3 um creatinine level >2.0 mg/dL). Patients were referred for UB masses involving ureteric orifice 4 6.2 MDCT as a part of investigatory work up. PUJ 3 4.6 Ureteric mass 1 1.5 2.2. MDCT technique 1 1.5 Total 65 100 MDCT examinations were performed for all patients using a 16- detector CT scanner (Somatom, E-motion 16, Siemens Health- care; Germany). Patients were prepared by giving 800–1000 mL of water over a 20- to 30-min period before the start of a renal Table 3 Level of ureteric obstruction as detected by MDCTU CT examination and no intravenous contrast material was (n = 65 ureter). administered. The acquisition parameters were 120 kVp, Level No (ureters) Percent (%) 350 mAs, a helical pitch of 1.375:1, 0.6-s gantry rotation time, PUJ 3 4.61 table speed of 53 mm per rotation, 16 · 0.625 mm detector con- Upper ureter 4 6.17 figuration, 18.4-s total exposure time, 0.625 mm helical slice Middle ureter 12 18.46 thickness, and 0.625 mm reconstruction interval with a large Lower ureter 38 58.46 FOV. The axial source images with a 0.625-mm slice were trans- Ureteric orifice 8 12.30 ferred to a dedicated workstation (Wizard, Siemens Health- Total 65 100 care), and curved planar reconstructions were performed by specially trained CT technologists. Curved planar reformatted (CPR) images were performed to display the entire length of ure- can vary, but in general, once a path has been traced, data ters in the same image. It was obtained manually by drawing a points for the image are generated using linear interpolation line over the course of the ureter. in three dimensions. The output is a single image in which the resultant pixel dimension is equal to the smallest pixel 2.3. Image analysis dimension in the native acquisition (15). Curved planar reformations permit even the most tortuous The non-contrast axial, coronal and post-processing images of anatomy to be unwound and displayed along its long axis CPR were reviewed for the detection of the cause and level of while preserving the gray-scale contrast of the original data ureteral obstruction. There were certain diagnostic criteria to acquisition. Curved planar reformations can illustrate complex differentiate intrinsic from extrinsic causes of ureteral obstruc- anatomy and in a single image, thus serving as a tion as reported by Shokeir et al. (1): an abrupt change in useful tool. Our referring clinicians typically want to view only ureteral caliber on axial as well as reconstructed images was a few illustrative images of their patients rather than the large suggestive of intraluminal lesion, while gradual tapering of

Table 4 Total sensitivity, specificity and accuracy of CPR, in detecting the cause and level of ureteral obstruction (n = 65). Ureteric obstruction Sensitivity (%) Specificity (%) Accuracy (%) P value Cause 98.5 98.5 97.8 0.05 Level 100 100 100 0.001 896 M.A. Youssef, A.A. Elbarbary

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Fig. 2 60-Year-old female patient with bilateral loin pain. Multidetector computed tomography axial (A and B) and curved planar reformation images (C) show radiodense stone in the right pelvi-ureteric junction, two radiodense stones in the left collecting system with moderate left hydro-uretro-nephrosis secondary to bladder mass obliterating the left ureteric orifice (black arrows). the ureter with no intraluminal mass or filling defect was indic- teric obstruction was loin pain representing 70%. The clinical ative of mural or extraurinary cause. On NCCT a hyperdense data and relevant patient’s past history are listed in Table 1. focus within the ureter was diagnostic of a calculus, while an A total of 65 ureters were examined (35 unilateral, 15 bilat- intraluminal mass of soft tissue density was considered a sign eral). The most common cause of ureteric obstruction was ure- of tumor. Extra-ureteral lesion was diagnosed according to teric stone representing 27/65 (41.5%), followed by ureteric the mass effect, and the specific density on NCCT. stricture representing 23/65 (35.4%). The lower third was the most affected in our study, it was encountered in 38/65 ureters 2.4. Statistical analysis (58.46%). The cause and level of ureteral obstruction as de- tected by MDCTU are listed in Tables 2 and 3. The diagnostic efficacy of the MDCT with curved planar ref- According to the final ureteroscopy and surgical findings, ormation images was evaluated and compared with ureteros- the sensitivity, specificity and accuracy of CPR in detecting copy and/or open surgery findings, which is considered the the cause and level of ureteric obstruction were calculated. gold standard of reference. The sensitivity, specificity and over- The total sensitivity, specificity and accuracy of CPR for all accuracy of CPR in the assessment of the cause and level of detecting the cause of ureteral obstruction were 98.5%, ureteral obstruction were calculated in comparison with the 98.5% and 97.8%, respectively (P value <0.05). Regarding gold standard. Data entry was done by SPSS version 13 and the detection of ureteral obstruction level, CPR was more sen- analyzed by the same software. A P value >0.05 was sitive and accurate with a sensitivity of 100% and accuracy of considered significant. 100% (P value >0.001) Results are listed in Table 4, Figs. 1–5.

3. Results 4. Discussion

This study included 50 patients (30 males, 20 females), age range Since the introduction of MDCT technology, CT urography is was from 28 to 64 years (mean age was 45 years). All patients gaining a dominant role as fast, accurate, and comprehensive had renal impairment with serum creatinine greater than imaging technique for the entire , including 2.0 mg/dl. Therefore, IVP and CT with contrast medium were native and transplanted kidneys, collecting systems, ureters, contraindicated. The most common clinical presentation of ure- and the urinary bladder (12). Assessment of ureteral obstruction in patients with compromised renal function 897

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Fig. 3 75-Year-old female patient with left loin pain. Multidetector computed tomography axial (A–C) and curved planar reformation images (D) show atrophic right kidney with marked left hydro-uretero-nephrosis and curved planar reformation determines clearly the cause and level of obstruction (stricture lower third left ureter). Non obstructing two stones; seen at the mid-third and lower third left ureter.

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Fig. 4 35-Year-old female patient with bilateral loin pain. Multidetector computed tomography axial (A and B) and curved planar reformation images (C) shows atrophic hydronephrotic left kidney, hyperdense stone impacted in the upper third right ureter with proximal marked hydro-ureteronephrosis. 898 M.A. Youssef, A.A. Elbarbary

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Fig. 5 74-Year-old male patient with left loin pain. Multidetector computed tomography axial (A and B) and curved planar reformation images (C and D) show atrophic right kidney with radiodense branching stone in the left pelvi-ureteric junction with moderate left hydronephrosis.

A wide variety of pathological processes, intrinsic and extrin- 20%, this discrepancy can be explained by the fact that sic to the ureter can cause ureteric obstruction, the kidneys and 42.0% of our patients had a previous history of bilharziasis, bladder are commonly well seen in a variety of planes, but the a common association of bilharziasis and stones was addressed ureter is rarely seen in its entirety on a single image. Curved pla- by Shokeir et al., and Ghoneim, (1,19) who reported that uri- nar reformations can be useful in illustrating the presence of nary stasis in dilated atonic ureter invites secondary bacterial stones, intraluminal and extraluminal lesions in the ureters (15). infection and stone formation. In the present study, curved planar reformatted images The second most common cause of obstructive uropathy in were used to display the entire course of the dilated ureters our study was the ureteric stricture with an incidence of 35.4%, in a single longitudinal uninterrupted image and hence better this can be attributed to the high incidence of bilharziasis intraluminal and extraluminal assessment and accurate detec- (42.0%). In Egypt; the prevalence of Schistosomiasis hemato- tion of the level of obstruction. Cademartiri et al., (16) stated bium in endemic areas in Egypt ranged from 4.8% to 13.7% that the most important advantage of this technique is visual- and averaged 7.8% (20). Ghoneim, (19) postulated that bilhar- ization of both opacified and unopacified ureters. He postu- zial healed with variable degrees of mural fibrosis lated that CPR images could be obtained manually by with a loss of muscle and peri-ureteric adhesions that lead to drawing a line over a structure of interest or it can be produced ureteric stricture. automatically by a dedicated software. In this study curved In the current study, the lower third ureter was the most planar reformatted images were obtained only manually by common level of obstruction (58.46%), this was in agreement drawing a line over the dilated ureters using workstation (Wiz- with several authors who reported that the main site of bilhar- ard, Siemens Healthcare). zial strictures occurred in the lower third of the ureter (20–22). In this study the most common cause of ureteric obstruc- The current study demonstrated that CPR exhibits a higher tion was the ureteral stone which represented 41.5% of all sensitivity and accuracy in depicting the cause of ureteric cases. This was in agreement with Chevalier et al., and Shokeir obstruction, this was statistically significant (P > 0.05). The et al., (17,1) who reported that ureteral obstruction is usually a total sensitivity and accuracy of CPR for the determination of consequence of nephrolithiasis which is the most common the cause of the ureteric obstruction were 98.5% and 98.5%, cause of urinary obstruction. respectively. We believe that the most important advantage This not in agreement with Basiri, et al. (18) who reported of CPR is that it could clarify the unopacified ureters, thus it that the incidence of ureteral stones ranges between 2% and could be used in the case of severe urinary obstruction with Assessment of ureteral obstruction in patients with compromised renal function 899 non-excretory function, in addition to visualization of the ure- (7) Ghersin E, Brook OR, Meretik S, Kaftori JK, Ofer A, teral environment including, soft tissue and associated extralu- Amendola MA, et al. Antegrade MDCT pyelography for the minal pathology. evaluation of patients with obstructed urinary tract. AJR In this study, CPR could not detect the cause of obstruction 2004;183:1691–6. (8) Chow LC, Sommer FG. Multidetector CT urography with in one patient (false negative) which is interpreted as normal, abdominal compression and three-dimensional reconstruction. showed normal ureteric wall, with no thickening or evident AJR Am J Roentgenol 2001;177:849–55. stricture and mild backpressure changes, by ureteroscopy ure- (9) Kim JK, Ahn JH, Park T, Ahn HJ, Kim KS, Cho KS. Virtual teric stricture was detected. cystoscopy of the contrast-filled bladder in patients with gross CPR was highly sensitive (100%) in detecting the level of hematuria. AJR Am J Roentgenol 2002;179:763–8. ureteric obstruction with an accuracy of 100%, this was statis- (10) Maher MM, Kalra MK, Rizzo S, Mueller PR, Saini S. Multi- tically highly significant (P < 0.001). 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