Urothelial carcinoma of the renal pelvis is a malignant tumor arising from the urothelial epithelium of the collecting system. It accounts for 5-10% of all renal tumors. Typically occurs in men aged 60-70 years (M:F = 3:1). The most common symptom is painless gross hematuria (70-80%). The tumor grows within the renal pelvis and calyces creating a filling defect, but characteristically preserves the bean-shaped renal contour (bean shape sign). Multifocality is an important feature — 2-4% of patients develop synchronous contralateral upper tract tumors, and 20-50% develop synchronous or metachronous bladder tumors. Smoking and aristolochic acid exposure (Balkan nephropathy) are the most important risk factors. Five-year survival is stage-dependent: superficial (Ta/T1) 60-90%, muscle-invasive (T2+) 15-40%.
Age Range
50-80
Peak Age
65
Gender
Male predominant
Prevalence
Common
Malignant neoplasm arising from the urothelial (transitional) epithelium lining the renal pelvis and calyces. Urothelial carcinogenesis is explained by the 'field effect' concept — the entire urothelial surface (renal pelvis, ureter, bladder) is exposed to the same carcinogens and carries risk for multifocal tumor development. Therefore, 20-50% of patients have concurrent bladder tumors. The tumor typically grows in a papillary or sessile (broad-based) pattern. The papillary type grows exophytically into the collecting system lumen creating a filling defect. The sessile type tends toward infiltrative growth and has a more aggressive course. Characteristically, the tumor spreads within the collecting system rather than infiltrating renal parenchyma — therefore the external renal contour is preserved (bean shape sign). However, in advanced stages, invasion of peripelvic fat and renal parenchyma may be seen. Obstructive growth causes hydronephrosis, and vascular invasion leads to hematuria. Smoking (4-7 fold risk increase), aristolochic acid, phenacetin, cyclophosphamide, and chronic inflammation (stones, infection) are the main risk factors. Lynch syndrome (MSH2 mutation) is important in the hereditary form.
Urothelial carcinoma growing within the renal pelvis preserves the normal bean-shaped external renal contour. While RCC originates from the renal cortex and deforms the contour through exophytic growth, urothelial carcinoma grows within the central collecting system and does not disrupt the peripheral contour. This finding is the strongest morphological clue for distinguishing urothelial carcinoma from RCC in renal pelvis-centered masses. In advanced stage (T3-T4) tumors, this finding may be lost with peripelvic/parenchymal invasion.
Soft tissue attenuation filling defect within the opacified collecting system on excretory phase. The tumor is surrounded by contrast-opacified urine creating a negative silhouette. Papillary type appears as an irregular, polypoid filling defect; sessile type appears as broad-based focal wall thickening. Adequate delay time (>10-15 min) for complete collecting system opacification is critical.
Report Sentence
A filling defect of soft tissue attenuation measuring approximately ___ mm is seen within the renal pelvis/calyx, surrounded by opacified urine on excretory phase, and urothelial carcinoma should be the primary consideration.
The normal bean-shaped renal contour is preserved — the tumor growing within the renal pelvis does not deform the external renal contour. This finding is critically important in differential diagnosis with renal cell carcinoma (RCC), which markedly deforms the renal contour. In advanced stages (T3-T4), contour disruption may occur due to invasion of peripelvic fat and parenchyma.
Report Sentence
A soft tissue mass at the level of the renal pelvis is seen with preserved external renal contour (bean shape sign); this finding is consistent with urothelial carcinoma of collecting system origin.
Moderate enhancement in arterial phase (20-40 HU increase). Significantly less than the markedly hypervascular enhancement of RCC (>80-100 HU increase). Sessile type shows homogeneous enhancement along wall thickening; papillary type shows moderate enhancement of the polypoid mass. Intratumoral necrotic areas do not enhance and may create heterogeneous appearance.
Report Sentence
The renal pelvis mass demonstrates moderate enhancement in arterial phase; this enhancement pattern is consistent with urothelial carcinoma, differing from the markedly hypervascular enhancement of RCC.
Varying degrees of hydronephrosis develop due to tumor obstruction of the renal pelvis or ureteropelvic junction (UPJ). In nephrographic phase, dilated calyces are seen surrounded by opacified renal parenchyma. Cortical thinning may accompany depending on the degree of obstruction. Delayed contrast retention by the kidney (prolonged nephrogram) supports ipsilateral obstruction. Perinephric fluid (stranding) may be seen in acute obstruction.
Report Sentence
Grade ___ hydronephrosis is seen in the left/right kidney suggesting obstructive uropathy associated with the soft tissue mass at the level of the renal pelvis.
Intermediate signal intensity soft tissue mass in the renal pelvis/calyces on T2-weighted images. The tumor surrounded by high-signal urine creates a distinct contrast with low-to-intermediate signal. Papillary type shows intraluminal polypoid mass; sessile type shows focal wall thickening. Signal change in peripelvic fat on T2 is a finding favoring peripelvic invasion.
Report Sentence
An intermediate signal intensity soft tissue mass is seen within the renal pelvis, surrounded by high-signal urine on T2-weighted sequences, consistent with urothelial carcinoma.
The tumor shows markedly high signal on diffusion-weighted imaging (DWI) with low ADC values on the ADC map. The high cellularity of urothelial carcinoma manifests as diffusion restriction. DWI plays a critical role in tumor detection, especially in obstructed kidneys where excretory phase opacification is inadequate. Diffusion restriction is more pronounced in high-grade tumors.
Report Sentence
The renal pelvis mass demonstrates marked diffusion restriction on DWI (ADC: ___ × 10⁻³ mm²/s), consistent with a highly cellular malignant tumor.
Focal or segmental thickening of the ipsilateral ureteral wall on portal venous or delayed phase, additional filling defects along the ureter, and/or intraluminal lesions within the bladder indicate synchronous urothelial involvement. Due to the field effect, evaluation of the entire urothelial tract is mandatory. The ipsilateral distal ureter may terminate with a 'goblet sign' — the dilated ureter abruptly narrows at the tumor level.
Report Sentence
Focal wall thickening along the ipsilateral ureter and additional filling defect within the bladder are seen suggesting multifocal urothelial involvement; systematic evaluation of the entire urothelial tract is recommended.
Intermediate echogenicity (hypoechoic to isoechoic) solid mass within the renal sinus, among highly echogenic sinus fat. The hypoechoic tumor can be distinguished from the surrounding hyperechoic sinus fat. Accompanying caliectasis (hydronephrosis) is commonly seen. Low to moderate vascularity within the mass may be noted on color Doppler. Small tumors can be easily missed on US — US is used for screening, CT urography is required for diagnosis.
Report Sentence
A hypoechoic solid mass measuring approximately ___ mm at the renal sinus level is seen with accompanying caliectasis; CT urography is recommended to exclude urothelial pathology.
Criteria
Exophytic, polypoid growth pattern toward the collecting system lumen. Generally associated with low-grade histology. The tumor surface is irregular with a 'sea anemone'-like frondose architecture.
Distinct Features
Creates typical polypoid filling defect on excretory phase. Moderate enhancement, well-defined base, rarely deep invasion. Better prognosis — 60-90% five-year survival (Ta/T1 stage). Appears red, fragile, papillary on cystoscopy. Frequently multifocal.
Criteria
Broad-based, infiltrative growth pattern spreading along the wall. Generally associated with high-grade histology. Manifests as focal or diffuse wall thickening.
Distinct Features
Appears as focal ureter/pelvic wall thickening rather than filling defect on excretory phase. Tends toward early periurothelial invasion and deep muscle invasion — more aggressive. Poor prognosis — 15-40% five-year survival (T2+ stage). More pronounced diffusion restriction on DWI. Renal sinus fat invasion more common. Peripelvic stranding is prominent.
Criteria
High-grade in situ dysplasia of the urothelial mucosa. Does not form a macroscopic mass — manifests as a flat, erythematous change on the mucosal surface. Diagnosis is usually made by cytology or biopsy.
Distinct Features
Usually invisible on conventional imaging — CT/MR may be normal. Focal ureteral wall thickening may be the only clue. Focal mucosal diffusion restriction on DWI may be the sole finding. Diagnosis is made by selective ureteral cytology or URS biopsy. Risk of progression to invasive urothelial carcinoma is high (50-75%). If urine cytology is positive but imaging shows no findings, CIS should be considered.
Criteria
Rare histological variant. Small papillary tumor cell clusters float in lacunar-like spaces — resembles serous carcinoma morphology. Aggressive biological behavior, early lymphatic invasion, and high-stage presentation.
Distinct Features
Cannot be distinguished from conventional urothelial carcinoma on imaging — diagnosis is histopathological. Early lymph node metastasis (70%+) and poor prognosis. Partial response to chemotherapy. Radical nephroureterectomy is standard treatment. Cystectomy may be needed (bladder involvement frequent).
Distinguishing Feature
Collecting duct carcinoma originates from the renal medulla and shows infiltrative growth — disrupts the renal contour (bean shape sign negative). Shows markedly heterogeneous enhancement (different from the moderate enhancement of urothelial carcinoma). Medullary-centered, presenting as a parenchymal mass rather than creating a renal pelvis filling defect. Younger age (30-40) and more aggressive course.
Distinguishing Feature
Clear cell RCC originates from the renal cortex and deforms the renal contour through exophytic growth (bean shape sign negative). Shows dramatic hypervascular enhancement in arterial phase (>80-100 HU increase) — very different from the moderate enhancement of urothelial carcinoma (20-40 HU). Typically cortical-centered, exophytic mass; urothelial carcinoma is central pelvis-centered filling defect. Marked washout is seen in portal venous phase in RCC.
Distinguishing Feature
Renal abscess is parenchymal-located and shows rim (ring) enhancement — different from the solid enhancement of urothelial carcinoma. The abscess has smooth, thin walls with low-density content (fluid/pus). Clinically, fever, leukocytosis, and elevated CRP are prominent — fever is not expected in urothelial carcinoma. Abscess shows marked restriction on DWI but ADC values differ from tumor (abscess: viscous fluid restriction; tumor: cellular restriction).
Distinguishing Feature
Medullary carcinoma develops in young patients (10-30 years) and in the setting of sickle cell disease/trait — demographic profile very different from urothelial carcinoma (60-70 years). Appears as an infiltrative, poorly defined mass in the renomedullary region. Unlike the collecting system filling defect pattern of urothelial carcinoma, parenchymal destruction is prominent. Retroperitoneal lymphadenopathy and distant metastasis are common at diagnosis. Extremely aggressive — median survival <6 months.
Distinguishing Feature
Blood clot (coagulum) can create a filling defect within the renal pelvis and may be confused with urothelial carcinoma. Differentiation: clot shows no enhancement (avascular in all phases); shape is variable and may change position on follow-up; acute clot shows high attenuation on non-contrast CT (60-80 HU) but density decreases over time. Urothelial carcinoma creates a fixed-position, enhancing filling defect that grows on follow-up. In case of doubt, repeat CT urography or URS confirmation is performed.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralUrothelial carcinoma of the renal pelvis is a malignant tumor requiring urgent urology consultation. Standard treatment is radical nephroureterectomy + bladder cuff excision (including ipsilateral kidney, ureter, and bladder orifice). In low-risk tumors (low-grade, <2 cm, papillary, unifocal), kidney-sparing treatment (URS with laser ablation) may be considered — especially in solitary kidney or bilateral disease. Neoadjuvant cisplatin-based chemotherapy (GC regimen) provides survival benefit in muscle-invasive/advanced disease. Cystoscopy is mandatory after diagnosis — investigation for synchronous bladder tumor. Postoperative follow-up: cystoscopy + upper tract imaging (CT urography) — 3 months, 6 months, then annually. Urine cytology is used in follow-up. Immunotherapy (pembrolizumab) is approved for metastatic disease.
Urothelial carcinoma can be multifocal and metachronous; the entire urothelial system including bladder and ureter must be evaluated. Nephroureterectomy is the standard treatment. Cystoscopic follow-up is required for potential bladder tumor development.