Acute renal and urinary tract disease.

Patients with acute urinary tract disorders often present with acute abdominal symptoms. Sonography and CT are often the first investigations performed when the clinical nature of the symptoms is unclear. However, excretory urography and cystography, scintigraphy, and angiography all play useful roles in evaluating patients with acute urinary tract disorders. Patients with suspected acute renal obstruction due to ureteric calculi are best assessed by excretory urography. If the latter study is contraindicated, sonography with duplex Doppler analysis of small intra-renal arteries may suggest the diagnosis by showing a dilated collecting system and an elevated resistive index. Patients with acute renal trauma are best imaged by CT, although excretory urography is an appropriate alternative if a mild exclusively renal injury is suspected. Patients with refractory acute renal infections require imaging to identify either pyonephrosis or large renal or perinephric abscesses that require immediate intervention. CT and sonography are most useful for identifying these complications. Acute renal vascular disorders, including renal hemorrhage, renal infarction, and renal vein thrombosis are readily diagnosed by contrast-enhanced CT. Both sonography and MR imaging help in the diagnosis of acute renal vein thrombosis. Most acute bladder disorders are diagnosed clinically. Cystography, however, is essential for the diagnosis of traumatic bladder rupture. Pelvic CT is a useful alternative to cystography for diagnosing bladder rupture in patients who undergo CT as their first imaging study because of suspected head or abdominal injuries.