What is emphysematous pyelonephritis, and what are its CT and MR imaging features?
Emphysematous pyelonephritis is a severe, life-threatening infection of the renal parenchyma by gas-forming bacteria. This condition most often occurs in diabetic patients and is often seen when there is obstruction of the collecting system. Rapid progression to septic shock may occur, and the overall mortality rate is as high as 50%.
On CT and MRI, the major imaging finding is very low attenuation/signal intensity gas within the renal parenchyma, often with a radial orientation within the renal pyramids, sometimes extending into the perinephric space, perinephric fascial planes, or collecting system. Associated findings of acute pyelonephritis, as previously described, are also commonly present. Treatment is typically with nephrectomy and antimicrobial therapy.
