CT urogram (CTU) in a 60-year-old male with painless haematuria and a right ureteric filling defect shows an eccentric hyperdense filling defect in the proximal ureter on nephrographic phase with upstream hydronephrosis. The finding is stable in appearance on delayed phase. The most important CT feature differentiating ureteric transitional cell carcinoma (TCC) from a ureteric calculus is:

• A TCC causes more proximal hydronephrosis than stones
• B TCC is always in the distal ureter
• C Stones enhance with contrast, TCC does not
• D Ureteric calculus shows periureteric soft tissue 'rim sign' and CT attenuation > 200 HU, whereas TCC shows soft tissue attenuation (20–80 HU) without a calcium rim ✓

Explanation

CT differentiates ureteric calculus from TCC by Hounsfield Unit (HU) density: calculi measure > 200 HU (often > 500 HU), do not enhance, and show a 'rim sign' (halo of soft tissue periureteric inflammation). TCC has soft tissue density (20–80 HU) on non-contrast CT, enhances with contrast on the nephrographic phase, and causes proximal hydronephrosis without the calcium attenuation. Stones never enhance; TCC does.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.