COMPLICATED PYELONEPHRITIS

Emphysematous pyelonephritis (EPN) is an uncommon but life-threatening necrotizing infection that causes gas formation in the collecting system and renal parenchyma. It is most common in diabetic patients with poor glycemic control.

EPN can occur secondary to E. coli or Klebsiella spp. Less commonly, Proteus, Pseudomonas, and Clostridium species may be responsible. Gas accumulation occurs in tissues with rapid catabolism where efficient transport of the end products is not present. In diabetes, heavy glycosylation of peripheral vessel walls can produce this effect because of poor circulation.

In addition to the typical symptoms of pyelonephritis described above, patients with EPN can have shock, altered sensorium, thrombocytopenia, and dyspnea. X-ray and CT scans may be notable for the presence of extraluminal gas in the renal tissue and perirenal space.

Nephrectomy is generally the treatment of choice; however, it may not be possible in the setting of decreased renal function, thrombocytopenia, hemodynamic instability, or altered mental status. In these situations, a conservative approach may be pursued, including percutaneous drainage and antibiotic therapy.

Xanthogranulomatous pyelonephritis is another rare form of complicated pyelonephritis, in which the kidney undergoes wide destruction, with the damaged parenchyma replaced by lipid-laden macrophages in granulomatous tissue.