Clinical and radiological findings in patients with gas forming renal abscess treated conservatively

Purpose: Emphysematous pyelonephritis in diabetics is considered a potentially lethal infection. Mortality rates of patients treated conservatively approaches 80% in some series. These patients often present with signs of sepsis or septic shock. In contrast, gas forming renal abscess is rare, with patients presenting entirely differently from those with emphysematous pyelonephritis. To our knowledge this process has been previously described only in isolated case reports. We describe a series of 5 patients with this distinct process. Materials and Methods: We reviewed the clinical and radiological features of 5 patients with gas forming renal abscesses. Results: Each patient presented with diabetes mellitus with initial blood glucose ranging from 313 to 552 mg./dl., fever (average 101F), flank or abdominal pain and pyuria. No patient had evidence of septic shock at hospitalization. Escherichia coli was the documented organism in each case. Mild renal insufficiency was noted in most patients based on serum creatinine. Radiological evaluation revealed gas filled pockets within the renal parenchyma, which were most effectively shown by computerized tomography (CT) of the abdomen. There was no radiological evidence of pus. Percutaneous drainage of an abscess in 1 case did not produce any purulent material or alter the clinical course. Each patient responded to correction of the underlying metabolic abnormalities with intravenous antibiotics (average 23 days) followed by prolonged oral antibiotic therapy (average 9 weeks). In contrast to the management of emphysematous pyelonephritis, surgical or percutaneous drainage was not necessary. Serial CT revealed complete resolution of gas in the parenchyma within 6 months in patients with long-term followup. Of note, gas was persistent on CT months after infection had clinically resolved. Conclusions: We describe a unique entity within the spectrum of pyelonephritis. The clinical appearance of gas forming abscesses within the renal parenchyma without liquefaction in diabetic patients was remarkably benign compared to the radiographic appearance of the disease process. Conservative management with intravenous and oral antibiotics was successful in each patient, avoiding the need for invasive intervention.