Renal sonography in the intensive care unit: when is it necessary?

OBJECTIVE: To evaluate the efficacy of renal sonography performed in intensive care units on patients with the diagnosis of acute or acute-on-chronic renal failure.
METHODS: We reviewed all renal sonograms performed in our institution during 1 year on critically ill patients for evaluation of renal failure. Renal failure was defined as a serum creatinine level greater than 1.5 mg/dL or an increase of greater than 20% from the baseline creatinine level. Exclusion criteria included patient age younger than 18 years and signs or symptoms of obstructive uropathy. Using the electronic medical record, we recorded patient age, sex, blood urea nitrogen level, serum creatinine level, blood urea nitrogen-creatinine ratio, and clinical indication for intensive care unit admission. Sonographic reports were reviewed for the presence or absence of hydronephrosis. The total cost of these examinations was estimated with the use of Medicare reimbursement rates for 2000.
RESULTS: One hundred five renal sonographic examinations were performed on 104 patients meeting all inclusion criteria. Only 1 study had positive results for hydronephrosis, which was graded as mild. Incidental findings not immediately affecting patient care and including ascites and simple renal cysts were identified in 91 patients. The estimated total cost of the examinations was $13,350.75.
CONCLUSIONS: In critically ill patients with acute renal failure and no physical findings suggesting obstructive uropathy, renal sonography to evaluate for hydronephrosis is probably not indicated. This holds true regardless of patient age, sex, medical or surgical disposition, and blood urea nitrogen-creatinine ratio.