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Emphysematous Pyelonephritis (EPN) Workup

  • Author: Sugandh Shetty, MD, FRCS; Chief Editor: Edward David Kim, MD, FACS  more...
 
Updated: Dec 30, 2015
 

Approach Considerations

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]

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Imaging Studies

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.

Kidneys, ureter, and bladder imaging showing a str Kidneys, ureter, and bladder imaging showing a streaky gas pattern over the entire right kidney in a patient with emphysematous pyelonephritis.
Emphysematous pyelonephritis. Kidneys, ureter, and Emphysematous pyelonephritis. Kidneys, ureter, and bladder imaging showing gas over the region of the right kidney. White arrows outline the area. The faint outline of a staghorn calculus can be seen in the right kidney.

Renal ultrasonograms often reveal high echogenic areas with dirty shadowing. Hydronephrosis and perinephric fluid may also be seen. (See the image below.)

Emphysematous pyelonephritis. Renal sonogram showi Emphysematous pyelonephritis. Renal sonogram showing hyperechoic shadows suggestive of gas along the lower pole of the kidney.

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.)

CT scan showing right renal and perinephric gas in CT scan showing right renal and perinephric gas in a patient with emphysematous pyelonephritis.
CT scan showing gas in both kidneys and the inferi CT scan showing gas in both kidneys and the inferior vena cava in a patient with bilateral emphysematous pyelonephritis.
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Radiologic Classification

In 1970, Langston and Pfister described 3 main radiographic patterns in emphysematous pyelonephritis (EPN), as follows[15] :

  • 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[16] :

  • 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[17] :

  • 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[2] :

  • 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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Contributor Information and Disclosures
Author

Sugandh Shetty, MD, FRCS Associate Professor of Urology, Oakland University William Beaumont School of Medicine; Attending Physician, Department of Urology, William Beaumont Hospital

Sugandh Shetty, MD, FRCS is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Ajay K Singh, MB, MRCP, MBA Associate Professor of Medicine, Harvard Medical School; Director of Dialysis, Renal Division, Brigham and Women's Hospital; Director, Brigham/Falkner Dialysis Unit, Faulkner Hospital

Disclosure: Nothing to disclose.

Chief Editor

Edward David Kim, MD, FACS Professor of Surgery, Division of Urology, University of Tennessee Graduate School of Medicine; Consulting Staff, University of Tennessee Medical Center

Edward David Kim, MD, FACS is a member of the following medical societies: American College of Surgeons, Tennessee Medical Association, Sexual Medicine Society of North America, American Society for Reproductive Medicine, American Society of Andrology, American Urological Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Repros.

References
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  2. Huang JJ, Tseng CC. Emphysematous pyelonephritis: clinicoradiological classification, management, prognosis, and pathogenesis. Arch Intern Med. 2000 Mar 27. 160(6):797-805. [Medline].

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  10. Yang WH, Shen NC. Gas-forming infection of the urinary tract: an investigation of fermentation as a mechanism. J Urol. 1990 May. 143(5):960-4. [Medline].

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  12. Wang YC, Wang JM, Chow YC, Chiu AW, Yang S. Pneumomediastinum and subcutaneous emphysema as the manifestation of emphysematous pyelonephritis. Int J Urol. 2004 Oct. 11(10):909-11. [Medline].

  13. Tsu JH, Chan CK, Chu RW, Law IC, Kong CK, Liu PL, et al. Emphysematous pyelonephritis: an 8-year retrospective review across four acute hospitals. Asian J Surg. 2013 Jul. 36(3):121-5. [Medline].

  14. Fatima R, Jha R, Muthukrishnan J, Gude D, Nath V, Shekhar S, et al. Emphysematous pyelonephritis: A single center study. Indian J Nephrol. 2013 Mar. 23(2):119-24. [Medline]. [Full Text].

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  18. Uruc F, Yuksel OH, Sahin A, Urkmez A, Yildirim C, Verit A. Emphysematous pyelonephritis: Our experience in managing these cases. Can Urol Assoc J. 2015 Jul-Aug. 9 (7-8):E480-3. [Medline].

  19. Aboumarzouk OM, Hughes O, Narahari K, Coulthard R, Kynaston H, Chlosta P, et al. Emphysematous pyelonephritis: Time for a management plan with an evidence-based approach. Arab J Urol. 2014 Jun. 12 (2):106-15. [Medline].

  20. Nana GR, Brodie A, Akhter W, Karim O, Motiwala H. Nephroureterectomy for emphysematous pyelonephritis: An aggressive approach is sometimes necessary. A case report and literature review. Int J Surg Case Rep. 2015. 10:179-82. [Medline].

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Kidneys, ureter, and bladder imaging showing a streaky gas pattern over the entire right kidney in a patient with emphysematous pyelonephritis.
Emphysematous pyelonephritis. Kidneys, ureter, and bladder imaging showing gas over the region of the right kidney. White arrows outline the area. The faint outline of a staghorn calculus can be seen in the right kidney.
Emphysematous pyelonephritis. Renal sonogram showing hyperechoic shadows suggestive of gas along the lower pole of the kidney.
Emphysematous pyelonephritis. CT scan showing gas in the left kidney, with stones and xanthogranulomatous pyelonephritis.
CT scan showing right renal and perinephric gas in a patient with emphysematous pyelonephritis.
CT scan showing gas in both kidneys and the inferior vena cava in a patient with bilateral emphysematous pyelonephritis.
Algorithm for the management of emphysematous pyelonephritis.
 
 
 
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