Virtual Hospital: Radiology Resident Case of the Week: Emphysematous Pyelonephritis

Radiology Resident Case of the Week

Emphysematous Pyelonephritis

December 26, 1996

Carl Raboi
Peer Review Status: Not reviewed

Clinical Sx:
Emphysematous Pyelonephritis is a fulminant infection of the renal parenchyma (pyelonephritis) and perirenal tissues with gas formation in the non functioning kidney. The organism causing this disease is a Gram Negative pathogen, usually E. coli (in 70%), and less likely Klebsiella, Aerobacter, and Proteus. Patients are usually immunocompromised, primarily diabetics (in 90%). This disease is more likely to occur in the left than the right and is bilateral in 5-10% of cases. They usually present with fever, flank pain, chills, nausea, vomiting, and malaise. Even with prompt nephrectomy, mortality is still 30-50%.

Etiology/Pathophysiology
This disorder is most likely due to ischemia in the infected tissue and low oxygen tension occurring with anaerobic metabolism. The gas present within the kidney is carbon dioxide and hydrogen released by the facultative anaerobic organisms and nitrogen released during tissue necrosis

Pathology:

Miscellaneous

Imaging

On CT: Radiographic changes can be divided into three stages:
1. Mottled lucency extending radially along the renal parenchyma
2. Air in bubbled pattern in parenchyma and air in Gerotta's fascia
3. Air infiltrates parenchyma, extends beyond Gerotta's fascia within the retroperitoneum

On US: Dense echoes and "dirty shadowing" in the parenchyma may be seen or perinephric gas will reflect all sound so that the kidney will not be visualized

DDX
1. Emphysematous Pyelitis - gas in renal pelvis only
2. Pelvis gas due to penetrating trauma, instrumentation, ureteroenteric anastomoses, or fistula
3. Renal infarction with parenchymal gas

Key references
Dunnick, N. Reed: Textbook of Radiology, Williams and Wilkins, 1991.

RSNA Syllabus: A Categorical Course in Genitourinary Radiology. Nov 27 - Dec 2, 1994.

ACR Code

Keywords:

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