Genitourinary Radiology
Genitourinary Radiology
This domain covers renal masses and cystic disease, urinary stones, prostate MRI, adrenal lesions, and bladder/testicular pathology. Expect Bosniak and PI-RADS classification and stone CT interpretation.
Core rules
- Bosniak: I simple cyst; II benign minimally complex; IIF indeterminate, follow-up; III indeterminate, surgery, with thick irregular enhancing septa; IV clearly malignant, with an enhancing solid nodule.
- Renal cell carcinoma subtypes: clear cell is hypervascular with washout; papillary is hypovascular; chromophobe is intermediate. Oncocytoma may have a central scar but cannot be reliably distinguished by imaging alone.
- Noncontrast CT stone protocol: stone size, location, and obstruction (hydronephrosis, perinephric stranding). Uric acid stones are radiolucent on plain film but visible on CT.
- PI-RADS: peripheral-zone score is driven by DWI; transition-zone score is driven by T2. Scores 4–5 prompt targeted biopsy.
Worked example
A 62-year-old has a 3 cm left renal cyst with thick irregular enhancing septa and a mural nodule. This is Bosniak IV, not a simple cyst; surgical excision is advised. A 2.5 cm cyst with a few thin septa and no enhancement would be Bosniak IIF and followed.
Traps
Overcalling pseudoenhancement on CT as a solid renal mass; using Bosniak on noncontrast studies alone; missing an obstructing stone because no stone is seen on radiograph; calling a hypervascular small mass an oncocytoma without pathology; misassigning PI-RADS without adequate DWI.