A 33 y.o. woman with diabetes, sp kidney pancreas transplant in 2022 who presents with abdominal and flank pain

what do you see on her CT?

Our patient had emphysematous pyelonephritis.   This is an acute  necrotizing infection of the renal parenchyma that causes gas formation. Patients present with fever and flank pain; 29% are in septic shock at the time of presentation.

gas in the collecting system

Gas can be confined to the collecting system or spread to the renal parenchyma or beyond Gerota’s fascia to other organs.  The treatment of choice is IV antibiotics.  The most common organism is E. Coli. 

emphysematous pyelo with gas extending to the retroperitoneum

In contrast to emphysematous pyelonephritis,  xanthogranulomatous pyelonephritis is due to a chronic infection and not an acute process. It is usually associated with a staghorn calculus.  Because it distorts the kidney architecture it can be confused with renal cell carcinoma.  The treatment is nephrectomy since the kidney is non functioning. This condition was named for the Greek word “xantho” meaning yellow because the kidney is filled with lipid laden macrophages. Similar to emphysematous pyelonephritis, adjacent organs can be involved.

The bearpaw sign with xanthogranulomatous pyelonephritis in the setting of a staghorn calculus.

Our patient grew E coli. She was treated with IV antibiotics. Unfortunately, her transplanted kidney failed and she is on dialysis. She was readmitted for seizures and a focus was found in the L parietal area. She was started on Keppra. Her MRI did not show PRES although tacrolimus can cause PRES. She remains in the hospital.

Lee G, Moon S, You M, Lim J. A case of xanthogranulomatous pyelonephritis with nephroleural fistula. Formation: role of MRI in diagnosis and treatment. J Korean soc of Radiology 2021;8(2):475-804x

Schubert R. Xanthogranulomatous pyelonephritis Case study. . Radiopedia https://radiopaedia.org/cases/14172

Oliveira e Castro M, Bearpaw sign. Radiology Department, Centro Hospitalar do Algarve-Algarve/PT.

Stoica I, O’Kelly F, McDermott M, Quinn F. Xanthogranulomatous pyelonephritis in a paediatric cohort 1963-2016):outcomes from a large single-center series. Journal of Pediatric Urology (2018).14e1=169e7