Uroradiology and Imaging
Core concepts
Know modality selection: ultrasound for screening/hydronephrosis and testis; CT urography for hematuria and stone/upper tract evaluation; MRI for staging and renal mass characterization; nuclear medicine (DMSA, MAG3) for function and obstruction. Understand contrast phases (noncontrast, corticomedullary, nephrographic, excretory) and radiation stewardship. Recognize classic appearances: staghorn calculus, hydronephrosis, renal mass enhancement, and testicular torsion (absent flow).
Traps
Do not use intravenous contrast in a patient with severe renal impairment without weighing benefit; avoid gadolinium in severe renal failure due to nephrogenic systemic fibrosis risk. CT is preferred for acute flank pain and stones; ultrasound is preferred in pregnancy and children. A nonenhancing renal cyst is Bosniak I and needs no follow-up; complex cysts need surveillance or surgery.
Worked rule of thumb
Acute flank pain in a nonpregnant adult: noncontrast CT for stones. Suspected upper-tract urothelial carcinoma or painless hematuria: CT urography. Testicular pain with absent Doppler flow: torsion - surgical emergency.
Exam strategy
Match modality to clinical question, patient safety, and acuity.