CT Urography Findings of Upper Urinary Tract Carcinoma and Its Mimickers: A Pictorial Review

Abstract

Urothelial carcinoma (UC) is the fourth most frequent tumor in Western countries and upper tract urothelial carcinoma (UTUC), affecting pyelocaliceal cavities and ureter, accounts for 5-10% of all UCs. Computed tomography urography (CTU) is now considered the imaging modality of choice for diagnosis and staging of UTUC, guiding disease management. Although its specificity is very high, both benign and malignant diseases could mimic UTUCs and therefore have to be well-known to avoid misdiagnosis. We describe CTU findings of upper urinary tract carcinoma, features that influence disease management, and possible differential diagnosis.

Keywords: CT urography; benign urinary tract lesions; upper tract urothelial carcinoma; urinary tract imaging; urinary tract inflammatory disease; urinary tract tumor; urothelial carcinoma.

Figure 1

Computed tomography urography (CTU): MIP (maximum intensity projection) (a) and coronal (b) images. Furosemide administration allows distention of the entire urinary tract, without blooming artifacts due to high attenuation of intraluminal contrast medium; the split-bolus technique allows simultaneous luminal and parenchymal assessment.

Figure 2

Small renal pelvis UTUC: a soft tissue lesion on unenhanced scan (arrow in (a)), shows homogeneous enhancement in the cortico-medullary phase (arrow in (b)) and appears as a filling defect in the nephrographic-excretory phase using a wide window setting (arrow in (c)). With wrong imaging settings, it results hardly recognizable (d).

Figure 3

Pyelocaliceal papillary tumors: coronal nephrographic-excretory images (a,b). Solid tissue enlarges and obscures the superior calyx (arrow in (a)), the so-called oncocalyx. Solid pelvic-infundibular tissue (empty arrow in (b)) causes upstream non-opacified dilation (*), the so-called phantom calyx.

Figure 4

Ureteral papillary upper tract urothelial carcinoma (UTUC): nephrographic-excretory coronal (a) and axial (b) images. Solid tissue in the lumbar ureter (empty arrow in (a)) determines complete occlusion of the urinary tract with hydronephrosis. Note the reduced nephrographic effect and absent excretion of contrast medium in the left kidney.

Figure 5

Flat ureteral UTUC: nephrographic-excretory axial (a) and CPR—curved planar reconstruction—coronal (b) images. An irregular wall thickening (arrows), without lumen narrowing, extends in the upper ureter. Urinary stones are visible in inferior calyces.

Figure 6

Pyelocaliceal infiltrative UTUC: nephrographic-excretory axial (a) and coronal (b) images. Extensive pyelocaliceal wall thickening with lumen narrowing causes diffused attenuation of the renal sinus fat due to tumoral infiltration (empty arrows).

Figure 7

Caliceal infiltrative UTUC: coronal cortico-medullary (a) and nephrographic-excretory (b) images. Solid tissue occupies upper and medium calyces (*); the direct infiltration of kidney parenchyma appears hyper-enhancing compared to medulla in the cortico-medullary phase (arrow in (a)) and shows wash out in the nephrographic phase (arrow in (b)).

Figure 8

Hypertrophied papilla: nephrographic-excretory coronal (a), sagittal (b) and axial (c) images. A filling defect with smooth margins and regular shape is recognizable in the superior calyx (arrows); the forniceal structure is preserved.

Figure 9

Blood clot: nephrographic-excretory axial (a), coronal (b) and sagittal (c) images. A small filling defect in the superior calyx without contact with the caliceal wall.

Figure 10

Suburothelial hemorrhage: axial images. In the unenhanced scan (a) diffuse hyperdense urothelial wall thickening is clearly visible. In the nephrographic (b) and excretory (c) phases wall thickening is hardly differentiable from a UTUC. Complete disease resolution on follow up CTU (d) confirmed the benign nature of previous extensive urothelial thickening.

Figure 11

Renal papillary necrosis: excretory coronal images. The central erosion of a papilla appears as a focal spot of opacified urine inside renal medulla, with a teardrop shape (arrow in (a)) and a ball-on-tee shape (arrow in (b)); in the end stage necrotic papilla creates a filling defect in the excavated calyx, the signet ring sign (arrow in (c)).

Figure 12

Inflammatory disease: CPR cortico-medullary images in corona (a) and sagittal (b) planes. Diffuse urothelial thickening with homogenous enhancement associated to haziness of sinus fat and mild hydronephrosis.

Figure 13

Inflammatory disease. Nephrographic-excretory CPR (a,c) and axial (b,d) images. A short ureteral wall thickening, with smooth margins and symmetric appearance, causes mild lumen stricture (arrows in (a,b)); clinical and laboratory data are indicative of an inflammatory disease. The follow up CTU performed 3 months later (c,d), demonstrates a complete resolution, confirming the benign nature.

Figure 14

Retroperitoneal fibrosis. Nephrographic axial (a) and coronal (b,c) images. Low enhancing solid tissue surround an aneurismatic abdominal aorta, causing encasement and medial deviation with narrowing of both ureters (arrows), already treated with ureteral stents.

Figure 15

Pyeloureteritis cystica: ascending pyelography (a) and CT nephrographic coronal CT (b) images. Multiple small and regular filling defects are recognizable in the renal pelvis and proximal ureter (arrows in (a)), which correspond to tiny hypodense lesions inside a diffuse enhancing urothelial wall thickening (arrows in (b)).

Figure 16

Urogenital tuberculosis: nephrographic-excretory CPR (a), coronal (b) and sagittal (c) images. Widespread enhancing urothelial wall thickening affects renal pelvis and the entire ureter (a). Multiple caliceal erosions with complete expulsion of necrotic papilla are recognizable in the upper and medium part of the kidney (full arrows), the inferior calyx presents a rose-thorn shape (empty arrows), while the lower pole is replaced by a large fluid cavity (*).

Figure 17

Fibroepithelial polyp: nephrographic-excretory axial (a,b) and CPR (c) images. A smooth-margin mass develops inside the ureter without associated wall thickening (arrows). Note complete lumen occlusion with upstream dilation and absent contrast excretion, by comparison with the contralateral normal ureter (empty arrow). When typical aspects are absent, differential diagnosis with UTUC is difficult.

Figure 18

Recurrent RCC: cortico-medullary (a) and excretory (b) coronal images. A polilobulated lesion with inhomogeneous early contrast enhancement (full arrows) develops inside the renal parenchyma and extend in renal pelvis (*). The organ shape is altered and an exophytic mass is recognizable in the site of previous local surgery (empty arrows).

Figure 19

Renal sinus lymphoma: nephrographic-excretory axial (a) and MIP (b) images. Hypovascular and homogenous solid tissue diffusively involves renal sinus fat without distortion of pyelocaliceal system.