The typical emphysematous pyelonephritis patient has diabetes (95% of cases) and a urinary tract obstruction. The clinical presentation can be the same as severe pyelonephritis and physical findings can be absent. Nearly all patients will present with fever, vomiting, and flank pain. Pneumaturia can be seen when the collecting system is involved (pay attention to gas in nephrostomy tubes). Bilateral involvement is seen in up to 10% of cases.
E. coli is the bacteria in approximately 70% of cases with Pseudomonas aeruginosa, Klebsiella pneumoniae and Proteus mirabilis reported less frequency. The pathogenesis is unknown, although high-tissue concentration of glucose, defective tissue perfusion, impaired immunity, and a hypoxic environment of the renal medulla, are thought to predispose to tissue ischemia and necrosis, potentiating the growth of the gas-forming organisms.
Ultrasound is a good imaging modality. It will show the presence of gas which appears as high-amplitude echoes within the renal parenchyma, often with low-level posterior dirty acoustic shadowing (multiple small stones can look the same). In addition it will reveal urinary tract obstruction/hydronephrosis. The gold standard for imaging is computed tomography of the abdomen. Treatment should include fluid resuscitation, antibiotics, tight glucose control, surgical or percutaneous drainage, and potential nephrectomy. Classically, all patients recieved a nephrectomy although more recently there have been good outcomes with percutaneous drainage and medical management. Mortality is 30% to 40%.
Srinivas Vourganti, et al. Ultrasonographic Evaluation of Renal Infections. Radiologic Clinics of North America – Volume 44, Issue 6 (November 2006)
Emphysematous Pyelonephritis: A Case Report Series of Four Patients with Review of Literature. Renal Failure, 31:597–601, 2009
Ubee SS, McGlynn L, Fordham M. Emphysematous pyelonephritis. BJU Int. 2011 May;107(9):1474-8.