CT urogram in a 58-year-old male shows a 3 cm solid, enhancing renal mass in the upper pole of the left kidney. CT attenuation values of 35 HU on unenhanced and 95 HU on nephrographic phase images. The degree of enhancement is:
- A Non-enhancing (≤10 HU) — likely simple cyst
- B Pseudoenhancement — artefactual change in a simple cyst
- C Indeterminate — requires MRI with diffusion sequences
- D Enhancing (+60 HU) — strongly suggestive of renal cell carcinoma ✓
Explanation
Enhancement in CT urography is defined as an increase in attenuation of ≥20 HU between unenhanced and post-contrast phases. This lesion shows 60 HU enhancement (95 - 35 = 60 HU), which is robust true enhancement strongly suggestive of a solid, vascular renal mass — most likely renal cell carcinoma (clear cell RCC). Pseudoenhancement (artefactual +10–20 HU increase seen in simple cysts due to beam hardening) is typically <20 HU and occurs only in small cysts within a contrast-filled collecting system. Enhancement ≥20 HU in a solid mass effectively confirms vascularity and warrants further workup/surgery.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.