B-mode sonography in acute renal failure

B-mode sonography is an extremely useful and cost-effective method to eliminate urinary obstruction as a cause of acute renal failure and should be performed on all patients in whom obstruction is likely or in whom the cause of renal failure is not apparent. The threshold should be reduced in patients with solitary kidneys and sonography is probably indicated in all transplant patients. Sonography has very little utility in the management of other patients with acute renal failure. Although sonographic changes do occur in acute tubular necrosis, they are difficult to detect in the absence of baseline studies and are nonspecific.