JULY 2021 | Supplement Issue THE SOUTH AFRICAN RADIOGRAPHER

Peer Reviewed Article of Interest

A PICTORIAL PRESENTATION OF CT LESIONS IN ADULTS, PARTICULARLY KIDNEY CANCER: PART 1

Joel Harold Bortz1 MB ChB [Cape Town]; DMRD [London]; FRCR [London]; FFRRCS [Ireland] Riaan van de Venter2 DRad, MTech:Rad (research), PDTE Leonie Munro3 ND Rad (D), MA, P Grad Dip: Public Admin, Cert for trainers 1LSG Imaging, Los Angeles, California, America 2Lecturer, Nelson Mandela University, Port Elizabeth, South Africa 3Durban, South Africa

ABSTRACT There are many pathologies that affect the kidneys. The focus of this paper is computed tomography of kidney cancer. Other imaging modalities for kidney pathologies are briefly discussed. A few examples of benign tumours and masses are presented. The bulk of the paper is a pictorial presentation of kidney cancer and its spread to other organs and . A range of unen- hanced and enhanced CT images are included for self-assessment. Keywords: renal cell carcinoma, lymphadenopathy, oncocytoma, imaging modalities

LAY ABSTRACT Imaging of the kidneys is done to find out whether a mass in a kidney may be a benign tumour, cyst or cancer. If it is a cancer then it is important to check whether there is spread to other organs. Examples of computed tomography (CT) are used to de- scribe the different patterns of benign and cancer lesions.

1. INTRODUCTION The focus of this paper is on computed es of kidney cancer and its spread to tomography (CT) images of cancer of other organs and bones. A pictorial Kidney pathologies may be congenital, the kidney in adults, excluding hered- presentation is used to illustrate the such as horseshoe kidney, or acquired, itary kidney cancers and kidney cancer different CT patterns of kidney cancer. such as renal tumours.[1] The latter in children. It is important to also recognise the may be benign or malignant. Kidney patterns of cysts and benign tumours cancer affects all age groups. In adults Knowledge of anatomy of the kidney is therefore several examples of these it is the sixth most common cancer in important when interpreting CT imag- pathologies are presented. Table 1 men, and the eighth most common in es. Other modalities are used to visual- presents the headings and sub-head- women.[2, 3] Radiology plays an impor- ise kidney pathology. A brief overview ings of this article. Box 1 presents the tant role in imaging of kidney cancer is presented of those that may be used objectives of this paper. for kidney cancer patterns. as there are no routine screening tests The article is presented in five parts. for early detection of kidney cancer.[4] The bulk of the paper is of CT imag- The references are listed in Part 5.

Table 1. Headings and sub-headings Number Heading Sub-heading 1 Introduction 2 Anatomy 3 Definitions 4 Overview of imaging modalities to visualise kidney 4.1 Plain-film abdominal radiography pathology 4.2 Ultrasonography 4.3 CT 4.4 MRI 4.5 Nuclear medicine 5 Kidney cancer: risk factors and treatment 5.1 Benign tumours vs RCC 5.1.2 (AML) 6 Renal lesions: CT of the abdomen 6.1 Malignant renal tumours 6.2 Role of unenhanced CT for visualisation of renal le- sions

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Table 1 continued ... Number Heading Sub-heading 7 Varied appearances of kidney cancer on CT 7.1 Small versus large tumours 7.2 Chromophobe and papillary RCC 7.3 Collecting duct cancer 7.4 Intrarenal transitional cell carcinoma 7.5 Metastases to the kidney 7.6 Transitional cell carcinoma (TCC) 7.7 Anatomic extent of tumour 8 Renal cysts and renal malignancies 9 Lymphoma 10 Multiphase CT for examination of the abdomen for lesions in the kidney and spread to adjacent organs 11 Pictorial presentation of enhanced CT cases of 11.1 Tips to evaluate 2D CT images for cancer of the kidney kidney lesions and spread to other regions 11.2 and ribs 11.3 11.4 Spleen and pancreas 11.5 Venous system 11.6 Kidneys 11.7 Adrenal glands 11.8 Lymph nodes 11.9 Bony structures 11.10 Post-nephrectomy patients Kidney cancer treatment, fusion imaging and dual 12 energy CT 13 Key points 14 Conclusion 15 Self-assessment

Box 1

Nine objectives underpin the overarching aim of this paper, which is to provide a range of CT imag- es for radiographers to be able to perform pattern recognition of normal kidneys, benign kidney pa- thology, kidney cancer and its spread, and post-ne- phrectomy cases. • Present a summary of the anatomy of the kidney • Provide a list of definitions that pertain to kid- ney lesions and CT of the kidney Figure 2.1. Axial CT scan showing right kidney (RK) and left • Provide examples of benign kidney masses kidney (LK). Right renal artery (yellow arrow) and left renal artery (yellow) arise from the aorta (A). The upper poles are • Present a summary of different imaging mo- deviated medially (red arrows) and the lower poles laterally dalities for kidney pathology (black arrows). Inferior vena cava = IVC. • Briefly discuss causes of cancer of the kidney and its spread • Discuss the use of multiphase CT for examina- tion of the abdomen for lesions in the kidney and spread to adjacent organs • Provide tips on how to evaluate CT images of kidney cancer and its spread • Present a range of un-enhanced and enhanced CT images showing benign and malignant kidney tumours • Provide a range of CT images for self-assess- Figure 2.2. Axial CT scan showing right kidney (RK), ment left kidney (LK), left renal vein (red arrow), and renal artery (yellow arrow).

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Figure 2.3a. Unenhanced axial CT scan showing right kidney Figure 2.3b. Unenhanced axial CT scan showing left renal (RK) and left kidney (LK). Left renal vein (white arrow) is above vein below the aorta. Green arrow = IVC. the aorta (A).

Figure 2.4a. Unenhanced axial CT scan showing the adrenal Figure 2.4b. Enhanced axial CT scan glands above the kidneys. Right adrenal (black arrow) and left showing the right adrenal (red arrow) and adrenal (red arrow). RK = right kidney, LK = left kidney, aorta (A). Aorta = A.

2. ANATOMY Figures 2.3a and b are unenhanced • Benign is the opposite of malig- CT scans showing the normal position nant; it refers to a non-cancerous The kidneys normally lie on either of the left renal vein and a retroaor- tumour that does not spread to side of the vertebrae in the abdomen. tic left renal vein. As shown in Figure other organs or parts of the body.[9] They are paired retroperitoneal bean- 2.4a the suprarenal glands (adrenals) • Cancer is the opposite of benign as shaped organs. There are three distinct are in the perinephric space and are the neoplastic cells can spread and spaces in the retroperitoneum, name- situated on top of each kidney.[1,5] Fig- metastasise. Renal cell cancer (RCC) ly, anterior and posterior para-renal occurs in the renal tissue that filters spaces, and the perinephric space. ure 2.4b shows an enhanced right ad- and produces urine. Transi- The latter has an inverted cone shape renal gland. The right adrenal on CT tional cell cancer occurs in the renal which contains the kidneys, proximal has an inverted y-shape with two limbs pelvis.[10] ureters, adrenal glands, vessels and and the left has a lambda shape and • Cannonball lesions refer to well-cir- lymphatics.[5] The upper poles of the two limbs. cumscribed, spherical, metastatic kidneys are deviated medially and the lesions found in the fields. This lower ones laterally (Figure 2.1).[1] The 3. DEFINITIONS is typical of haematogenous spread right kidney is below the liver. It is low- • Adenopathy means any inflamma- of malignancies.[11] er than the left kidney.[1] The renal ar- tion or disease that involves lymph • Contrast enhanced CT (CECT) scan tery and vein, ureter and nerves enter nodes or glandular tissue. It usually refers to a CT scan examination the kidney via the hilum at the level of refers to swollen lymph nodes or during which one or more con- the first lumbar vertebra.[1] Figure 2.2 lymphadenopathy.[7] trast agents are administered to shows the renal arteries which are be- • Angiomyolipoma is a benign tu- a patient in order to visualise and low the renal vein.[6] mour of the kidney. It comprises differentiate between different In approximately 3% of the popula- blood vessels (angio), muscle (myo) normal and abnormal tissues and tion the left renal vein is retroaortic.[6] and (lipoma).[8] viscera.[12]

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• Cyst refers to closed cavity (sac/ but the ureters are not frequently seen. pathologies.[21] Imaging of smaller re- pouch) lined by epithelium and US can assist in determining the size nal masses with CT has been reported containing fluid.[13] A kidney cyst is a of the kidneys and any obstruction to to pose challenges.[22] fluid-filled sac. There are two types: renal outflow, and is used to differen- simple cyst or complex cyst that tiate solid, cystic and complex masses/ 4.4 MRI contains semisolid material. tissues as well as where they are locat- MRI is a useful imaging tool in charac- [20, 21] • Hounsfield unit refers to x-ray at- ed and their dimensions. US is not terising renal masses and for staging tenuation coefficients of tissue a reliable imaging modality to differen- of neoplasia, as an adjuvant to US and [22] compared to on a CT scan. tiate renal tumour sub-types. Renal CT. MRI appearances of renal masses On the Hounsfield scale water is as- vasculature and associated conditions assist in more accurate diagnoses and signed a value of 0 HU; air has a val- can be assessed and visualised using subsequent patient management. MRI ue of -1000 HU; dense +1000 vascular and colour-flow Doppler US is used when US and CT findings ap- [19] HU; fatty tissue of approximately techniques. US is readily available, pear to be inconclusive and to assess [22] -100 HU.[14] cheap and regarded as a first-line in- renal tumours ≤20mm in diameter. vestigation for renal tumour screening To achieve optimal characterisation of • Metastases refers to growth of but is highly operator-dependent.[12, 22- renal masses it is recommended that abnormal cells distant from the 24] It has limitations in terms of further MRI protocols cover (i) techniques to primary site.[15] Kidney cancer may characterisation of both solid tumours ensure maximum soft-tissue contrast, metastasise to adrenal glands, liv- and staging of malignancy.[24] In view of and (ii) multiplanar imaging.[16] er, chest, vertebrae, ribs, brain, for these limitations CT and MRI should be example.[16] used for screening and imaging of kid- 4.5 Nuclear medicine • Oncocytoma is a benign epithelial [24] ney cancer. Nuclear medicine plays a role in imag- renal tumour.[17] It usually presents ing of renal pathology as isotope scans as a solid tumour with a central 4.3 CT provide valuable information about re- star-shaped (stellate) scar, but may CT is considered the gold standard due nal anatomy and function. A DMSA (di- have central cyst degeneration or to is ability to provide high resolution mercaptosuccinic acid) scan provides multilocular cyst.[17] cross-sectional images of the area of information about renal size, location interest in various body planes and and shape in cases where congenital 4. OVERVIEW OF IMAGING the ability to differentiate benign from renal abnormalities/anomalies are MODALITIES TO VISUALISE KIDNEY malignant masses, staging of malig- investigated, and useful information PATHOLOGY nancies, and providing in-depth infor- related to acute pyelonephritis and Plain-film radiography, ultrasound mation about the impact renal masses renal scarring. The isotope 18F-fluo- (US), computed tomography (CT), mag- have on surrounding anatomy.[21, 22] rodeoxyglucose (18F-FDG) is used for netic resonance imaging (MRI), and positron emission tomography CT Renal pathologies, like renal neopla- (PET/CT) for investigating renal mass- nuclear medicine (NM), are covered in sia and cysts, can be investigated us- this overview. es that are metabolically active and ing CT. Contrast enhanced CT (CECT) sensitive to 18F-FDG uptake. However, is used to visualise kidneys, invasion 4.1 Plain-film abdominal some authors argue that 18F-FDG PET/ of other organs, and lymphadenopa- radiography CT should not be used as the primary thy, and also allows for differentiation diagnostic imaging modality due to its Plain abdominal radiography is an of benign lesions such as renal cysts, low sensitivity.[22] Single-photon emis- easily accessible and quick imaging [12] and oncocytoma. Imaging protocols sion computed tomography (SPECT- investigation for non-specific abdom- should include both pre- and post-con- CT) using technetium-99m-sestamibi inal pain and can be used to visualise [16] trast images. According to de Leon has demonstrated promise in accu- the size, shape and location of the [16] and Pedrosa pre-contrast images rately differentiating oncocytomas and [18-20] kidneys. However, accurate differ- are used to provide baseline attenu- hybrid oncocytic/chromophobe tu- entiation between the various abdom- ation values in regions of interest as mours from other RCC subtypes.[22] ino-pelvic viscera and their associated well as to help identify the presence pathologies is not possible due to a of fat, calcification, or haemorrhage. low inherent subject contrast on plain- To provide more information scanning REFERENCES film abdomens.[19] Ultrasound and CT of the abdomino-pelvic region may See Part 5. are considered first-line imaging in- also occur at various time settings af- vestigations for renal pathologies.[18,19] ter contrast medium administration by using biphasic, triphasic or four- 4.2 Ultrasonography phase imaging techniques. This allows US can demonstrate renal tissue well. the contrast media to be visualised in One can readily demonstrate the renal different parts of the vascular system parenchyma and pelvicalyceal system; and aids in better diagnosis of specific

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