Emphysematous Pyelonephritis

Authors: Erin Solis and Cary Huang

Edited by Christopher Parker, DO and Molly Hartrich, MD

46-year-old male status post renal transplant with new onset dysuria

Vital signs on arrival:

T 37.4ºC HR 111 BP 68/40 RR 20

SpO2 98% on RA


A 46-year-old male with DM who received a kidney transplant approximately 2 months ago presents with chills, weakness, dizziness, and new onset dysuria. Symptoms started yesterday. He is currently taking tacrolimus and mycophenolate. Physical exam is notable for bruising over the abdomen without tenderness to palpation. Exam is otherwise unremarkable. Labs show Cr 7.6 from a baseline of 1.99, BUN 87, HCO3 18, anion gap 18, beta-hydroxy 2.4, Glucose 522, Hgb 7.6, with WBC and lactate within normal limits. Chest x-ray is unremarkable. The following ultrasound images of the transplanted kidney were obtained in the ED. What abnormal findings can you identify on the following clips? What is the diagnosis?

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Figure 1

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FINDINGS: Mild hydronephrosis and air in the renal collecting system
DIAGNOSIS: Emphysematous Pyelonephritis

This patient has hyperechogenicity, subtle ring-down reverberation, and dirty shadowing of the renal pelvis suggesting air in the renal collecting system. He was started on IVF, imipenem, and an insulin drip for sepsis in the setting of AKI and DKA.

The diagnosis of emphysematous pyelonephritis and emphysematous cystitis were confirmed by both technician-performed renal ultrasound (Figure 1) and CT (Figure 2), which is considered the gold standard for diagnosis [1,3]. Ultrasound is not consistently effective at demonstrating gas in the renal parenchyma, being only accurate in 50% of cases per one report [2]. Two signs to look for include dirty shadowing and ring-down reverberation artifact.

The finding of hydronephrosis is common in transplanted kidneys and can be seen in this patient's ultrasound (Figure 3). Typically, hydronephrosis slowly resolves after transplant, but mild dilation can be permanent due to a denervated collecting system or bladder dysfunction. However, hydronephrosis may be the result of renal calculi, pyonephrosis, clot, ureteral strictures, or urothelial neoplasm [4]. Ultrasound has up to 94% specificity for identifying moderate to severe hydronephrosis and can help direct initial management [5].

Emphysematous pyelonephritis presents similarly to severe pyelonephritis, but patients are often very ill, and imaging demonstrates the presence of gas in the renal parenchyma, collecting system, or perinephric tissue [1]. Up to 95% of patients have a history of uncontrolled DM [3]. DKA is also an important predictor of increased mortality for these patients [2]. A transplanted kidney is at higher risk of infection spreading due to lack of investing fascia [1].

Emphysematous pyelonephritis in a renal allograft with concurrent emphysematous cystitis is a rarely reported condition. However, evidence suggests benefit of additional interventions, such as percutaneous drainage of abscesses compared to treatment with antibiotics alone [2,6,7]. It is important to evaluate for findings suggesting air in the collecting system in high-risk patients and know the next steps in management.

Figure 1. CT abdomen pelvis demonstrating emphysematous pyelonephritis (arrow) and emphysematous cystitis.

Figure 2. Ultrasound of transplanted kidney showing hyperechogenicity of collecting system (arrows) with ring-down reverberation artifact (star).

Figure 3. Ultrasound of transplanted kidney showing mild dilation of renal pelvis (arrowhead).


References


  1. Narcisse D, Agarwal M, Hancock M, Wells D, Sands C. A rare case of emphysematous pyelonephritis in a renal transplant patient. Ther Adv Infect Dis. 2016 Dec;3(6):141-144. doi:10.1177/2049936116678122. Epub 2016 Nov 17. PMID: 28386406; PMCID: PMC5375091.

  2. Wang, J. M., Lim, H. K., & Pang, K. K. (2007). Emphysematous pyelonephritis: Twelve years’ experience at a medical center. Scandinavian journal of urology and nephrology, 41(3), 223-229.

  3. Ubee SS, McGlynn L, Fordham M. Emphysematous pyelonephritis. BJU Int. 2011 May;107(9):1474-8. doi: 10.1111/j.1464-410X.2010.09660.x. Epub 2010 Sep 14. PMID: 20840327.

  4. Elsayes KM, Menias CO, Willatt J, Azar S, Harvin HJ, Platt JF. Imaging of renal transplant: Utility and spectrum of diagnostic findings. Current problems in diagnostic radiology. 2011 May 1;40(3):127-39. Doi:10.1053/ajkd.2002.31978.

  5. Wong C, Teitge B, Ross M, Young P, Robertson HL, Lang E. The accuracy and prognostic value of point‐of‐care ultrasound for nephrolithiasis in the emergency department: A systematic review and meta‐analysis. Academic Emergency Medicine. 2018 Jun;25(6):684-98. doi:10.1111/acem.13388. PMID: 29427476.

  6. Li S, Wang J, Hu J, He L, Wang C. Emphysematous pyelonephritis and cystitis: A case report and literature review. J Int Med Res. 2018 Jul;46(7):2954-2960. doi: 10.1177/0300060518770341. Epub 2018 Jun 19. PMID: 29916283; PMCID: PMC6124253.

  7. Song Y, Shen X. Diabetic ketoacidosis complicated by emphysematous pyelonephritis: A case report and literature review. BMC Urol. 2020;20(1):6. Published 2020 Jan 29. doi:10.1186/s12894-020-0575-0.