Medical imaging of renal diseases-suggested indication for different modalities

The diagnostic work-up of the urologic patient must be tailored to the presenting symptom complex, carefully selecting from the many modilities available, those most likely to establish the diagnosis and extent of the suspected lesions. Intravenous urography is the most rewarding initial procedure for many presenting symptoms, including suspected masses, pyuria, hematuria, and flank pain. Nuclear imaging is particularly effective in differentiating renal lobulations from true masses, in demonstrating parenchymal scarring in chronic pyelonephritis when the IVP is equivocal, and in assessing the decrease in perfusion and function in obstructive nephropathy when the IVP is indeterminate. It is the preferred procedure for acute renal infarction and acute tubular necrosis and has a greater sensitivity of detection for renal trauma than the IVP. Gallium-67 renal imaging appear helpful in the detection of occult pyelonephritis or interstitial nephritis. However, it cannot differentiate focal acute pyelonephritis from abscess or abscess from neoplasm. Ultrasoneography is the initial procedure of choice in the differentiation of cystic from solid renal masses and in anuria or oliguria. When a kidney fails to visualize by IVP or nuclear imaging, it can confirm or rule out obstruction. In upper tract infections, it may demonstrate renal or perirenal abscess. Although retrograde pyelography is performed less frequently in recent years, it remains extremely useful in confirming and relieving obstructive uropathy and in delineating tumors of the collecting system. Computed tomography effectively demonstrates hydronephrosis, renal abscess, tumors, and cysts and retroperitoneal involvement. More experience is needed to judge the efficiency of "dynamic" CT for the quantification of renal function. Renal angiography remains invaluable as a secondary procedure (as opposed to initial screening) in renal trauma, vascular anomalies, and in renal tumors to delineate the anatomy of the arterial supply and possible renal vein involvement.