Renal abscess: an illustrative case and review of the literature.

A patient had pyleonephritis with fever and pain that did not resolve, which prompted an abdominal ultrasound examination that showed an abscess within the renal cortex. Renal abscesses are particularly dangerous because of their location and potential spread to adjacent tissues. Although ultrasound is the best modality for imaging a renal abscess, computed tomography provides better tissue contrast, especially in obese patients. The pathophysiology of renal abscesses has changed during the past 25 years. Most cases are now caused by gram negative enteric organisms that are similarly pathogenic in uncomplicated cystitis and pyelonephritis. Successful treatment of a renal abscess requires long-term intravenous and oral antibiotics; surgical or percutaneous drainage is reserved for nonresponders.