Radiology of the Urinary Tract
Imaging is how the urinary tract becomes visible. The art is not knowing every machine — it is choosing the right modality for the clinical question.
The big picture
Imaging is how the urinary tract becomes visible. The art is not knowing every machine — it is choosing the right modality for the clinical question, because each one answers a different kind of question and carries a different cost in radiation, contrast, or money. Ultrasound, CT and MRI give far better soft-tissue detail and multiplanar views than plain films, which is why they have displaced the old intravenous urogram for most problems — but the older studies still have their niches. The goal of this chapter is to build a mental menu: for this patient, what should I order and why?
The framework: group the studies into radiographs and contrast studies (KUB, IVU, cystourethrogram, urethrogram, angiogram), ultrasound, CT, and MRI — then learn the one or two clinical questions each answers best, and the safety issues of the contrast agents.
Mechanism pathway
Tap any step to see why it happens.
Diagnostic algorithm
Each step answers one question. Tap to expand.
Board traps
Non-contrast CT, not IVU, is the modern test for stones; CT urography is the modern workup for haematuria.
Ultrasound first for hydronephrosis, cysts and the scrotum — no radiation, and Doppler answers the torsion question.
Iodinated contrast → nephrotoxicity + allergic reactions; gadolinium → nephrogenic systemic fibrosis in renal impairment. Check renal function before either.
MRI's urologic niche is bladder-tumour staging and telling benign wall thickening from invasion.
The IVU is largely historical — replaced by CT/US/MRI, with narrow remaining uses.
DTPA = glomerular, MAG3 = tubular (drainage + split function); DMSA = cortical (scarring, functional recovery).
The diuretic renogram (furosemide) distinguishes true obstruction from a baggy non-obstructed system.
Bone scan (Tc-99m MDP) detects skeletal mets — used for higher-risk prostate cancer, not everyone.
PSMA PET/CT is the sensitive newer modality for prostate staging and recurrence.
DMSA finds renal cortical scars (key in paediatric UTI/VUR follow-up).