Emphysematous Pyelonephritis (EPN) Workup
- Author: Sugandh Shetty, MD, FRCS; Chief Editor: Edward David Kim, MD, FACS more...
A high index of suspicion is important when attempting to diagnose emphysematous pyelonephritis (EPN) promptly. Laboratory data reveal leukocytosis with a left shift, pyuria, infected urine, thrombocytopenia, an elevated creatinine level, and positive blood culture results. Patients with urosepsis and shock should undergo cardiac and pulmonary function assessment as needed. As described below, computed tomography (CT) scanning is the definitive imaging test for EPN.[13, 14]
Patients should be stabilized with intravenous fluids and intravenous antibiotics prior to radiologic intervention. Kidneys, ureter, and bladder imaging often reveals gas distribution over the region of the kidneys, as depicted in the images below. In patients with emphysematous pyelitis, the collecting system may be filled with gas. An ileus pattern may be seen, suggesting retroperitoneal inflammation.
Renal ultrasonograms often reveal high echogenic areas with dirty shadowing. Hydronephrosis and perinephric fluid may also be seen. (See the image below.)
As previously mentioned, CT scanning is the definitive test for emphysematous pyelonephritis (EPN). Several patterns have been described, including streaky, streaky and mottled, and streaky and bubbly. Gas can be rimlike or crescent shaped in the perinephric area. Gas can also be seen in the renal vein or inferior vena cava and along the psoas muscle. Perinephric abscess may lead to significant gas accumulation in the perinephric space. A stone may be seen in the collecting system. (See the images below.)
In 1970, Langston and Pfister described 3 main radiographic patterns in emphysematous pyelonephritis (EPN), as follows :
Diffuse mottling of the renal parenchyma
Bubbly renal parenchyma surrounded by crescent-shaped gas in the perinephric space
Extension of gas through the Gerota fascia
In 1984, Michaeli et al suggested 3 stages of EPN, as follows :
Stage I - Gas within the renal parenchyma or the perinephric tissue
Stage II - Presence of gas in the kidney and its surroundings
Stage III - Extension of gas through Gerota fascia or bilateral EPN
In 1996, Wan et al described 2 distinct types of EPN, as follows :
Type I - Characterized by parenchymal destruction, with streaky or mottled parenchymal gas and an absence of fluid collection; has a fulminant course and high risk of mortality
Type II - Characterized by renal or perirenal fluid collection, with bubbly gas collection in the perinephric space or in the collecting system and a mortality rate of 18%; according to Wan et al, the compromised immune state of the host leads to fulminant and dry-type EPN, which is fatal
In 2000, Huang and Tseng modified the staging proposed by Michaeli et al, as follows :
Class 1 - Gas confined to the collecting system
Class 2 - Gas confined to the renal parenchyma alone
Class 3A - Perinephric extension of gas or abscess
Class 3B - Extension of gas beyond the Gerota fascia
Class 4 - Bilateral EPN or EPN in a solitary kidney
Note that the classifications are not comparable.
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