RADIOLOGY: KIDNEY: Case# 32916: EMPHYSEMATOUS PYELONEPHRITIS. This is a 48-year-old female with sickle cell disease who presents with sickle cell crisis. The examination is being requested to rule out perinephric abscess. Strandy inflammatory changes are seen around a swollen right kidney. Intraparenchymal gas is identified which also extends out of the kidney into the retroperitoneum and crosses the midline. The left kidney is normal in appearance. mphysematous pyelonephritis is a form of acute pyelonephritis with air in the renal parenchyma. It is most commonly a mixed flora infections with Gram negative organisms. CT shows gas collections within the renal parenchyma. The presence of residual gas on CT can be used as an indicator of the effectiveness of antibiotic therapy. This is because the CO2 generated by the bacteria is quickly resorbed.