Imaging in Emphysematous Pyelonephritis

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Imaging is essential to managing emphysematous pyelonephritis —a life-threatening, fulminant, necrotizing upper urinary tract infection associated with gas within the kidney—if an early diagnosis is to be made and a potentially devastating outcome is to be avoided. ^{[1, 2, 3, 4, 5]}

Some confusion exists regarding terminology for conditions involving renal gas. The term emphysematous pyelonephritis should be reserved for renal tract infections with intraparenchymal renal gas. Gas confined to the renal pelvis should be called emphysematous pyelitis, and gas confined to the perinephric space should be called perinephric emphysema. ^{[6, 7, 2, 8, 9, 10, 11]}

Emphysematous pyelonephritis is rare, but the frequency is higher in patients who are immunocompromised, especially patients with diabetes, who account for 87-97% of patients (see the images below). ^[12]

Lu and associates conducted a study to determine the clinical characteristics and prognostic factors of patients with emphysematous pyelonephritis. The study concluded that (1) low albumin levels, (2) an initial presentation of shock, (3) bacteremia, (4) indications for hemodialysis, or (5) polymicrobial infection represent prognostic factors for mortality in patients with emphysematous pyelonephritis. Any 2 or more of these of these prognostic factors carried a high risk of mortality, and these patients should be considered for more aggressive management. ^[3]

Plain abdominal radiography is the initial examination of choice in emphysematous pyelonephritis because this modality better depicts air in the renal collecting system and it is much more specific than ultrasonography. In practice, however, ultrasonography may be the initial examination performed. (See the image below.) ^{[13, 14, 15, 16, 17, 18]}

CT scan findings are diagnostic of the presence of air within the renal tract, and CT images also elegantly depict the renal and perirenal anatomy and the spread of infection to the perinephric tissues. ^{[15, 4]}

Renal function is depressed or even absent on the affected side in emphysematous pyelonephritis, and radionuclide study is an excellent modality for assessing differential function when nephrectomy is contemplated. Scintigraphy has been used to evaluate responses to antimicrobial therapy. Intravenous urography may be necessary if renal intervention is contemplated.

Plain radiographs are good for depicting air within the renal collecting system, but nonspecificity is a problem because of the superimposition of gas from the bowel. Moreover, gas in the retroperitoneum and gas within a renal or perinephric abscess may mimic emphysematous pyelonephritis.

Similarly, ultrasonography is limited because gas within the kidney and/or renal pelvis mimics renal calculi and produces artifact due to reverberation echoes and shadowing.

CT scans do not always depict other causes of intrarenal air, such as reflux of air from the bladder and bronchorenal, enterorenal, or cutaneorenal fistulae. These may occur with xanthogranulomatous pyelonephritis and focal renal abscesses. ^[19]

Radionuclide studies are nonspecific; therefore, they have a limited role in the evaluation of emphysematous pyelonephritis. In addition, radionuclide imaging suffers from a lack of availability. However, it does not result in false-positive or false-negative diagnoses.

Magnetic resonance imaging (MRI) is not the modality of choice in the diagnosis of emphysematous pyelonephritis. MRI findings are a signal void on T1- and T2-weighted images. However, signal voids on MRI scans may occur with renal calculi or rapidly flowing blood, creating false-positive results. Perinephric and intraparenchymal fluid collections are demonstrated well on MRI. ^{[15, 16]}

Emphysema is part of the differential diagnosis of emphysematous pyelonephritis. Other conditions to be considered include the following:

Retroperitoneal perforation of an abdominal viscus

Psoas abscess secondary to gas-forming organisms

Reflux of air from the bladder

Bronchorenal, enterorenal, or cutaneorenal fistulae – As may occur with xanthogranulomatous pyelonephritis

Air in a focal renal abscess – Not life threatening

Gas in the renal parenchyma may be seen in conditions other than emphysematous pyelonephritis on CT scanning. Intraparenchymal renal gas may be seen following urologic intervention such as that for a nephrostomy insertion or may result from a fistulous communication between the gastrointestinal tract and the renal collecting system. These situations do not represent clinical emergencies and are not life-threatening, as in emphysematous pyelonephritis. With the increasing use of abdominal CT scanning, radiologists, especially in the emergency setting, should be aware of this comparatively rare finding and should be familiar with its differential diagnosis.

Emphysematous pyelonephritis has been described as a presenting feature of a urinary bladder adenocarcinoma in a middle-aged, nondiabetic patient. ^[20]

Plain radiographs in patients with emphysematous pyelonephritis may show bubbles of gas within the region of the renal bed and in the upper renal collecting system. These may be diagnostic in the appropriate clinical setting. ^[16] Gas within the collecting system without evidence of renal parenchymal gas may be seen in patients with diabetes and does not have the same ominous prognosis (see the images below). Acute renal edema with obliteration of the renal pelvis can be seen.

Intravenous urography shows significant renal enlargement associated with delayed or absent excretion, and retrograde pyelography can be used to establish the presence of ureteral obstruction.

Plain radiographic findings may be diagnostic in ill patients with diabetes who have signs of acute pyelonephritis.

Renal fossa gas may be confused with gastrointestinal gas. A false-positive diagnosis of emphysematous pyelonephritis may occur with retroperitoneal gas and a psoas abscess secondary to gas-forming organisms. Reflux of air from the bladder and bronchorenal, enterorenal, or cutaneorenal fistulae (as may occur with xanthogranulomatous pyelonephritis ^[19] ) may also lead to false-positive findings. Air can be seen in focal renal abscesses.

CT scanning is the most reliable and sensitive modality in diagnosing emphysematous pyelonephritis. ^{[15, 4, 21]} Intraparenchymal, intracalyceal, and intrapelvic gas and extension into the perinephric space are readily identified on nonenhanced CT scans; ^[21] mottled areas of low attenuation extend radially along the pyramids, and pus may occasionally be seen extending into the renal veins. ^{[22, 23, 24]}

Two subtypes of emphysematous pyelonephritis based on CT scan appearances have been described. ^[12] Type I (33% of patients) is characterized by parenchymal destruction with either absence of fluid collection or presence of streaky or mottled gas radiating from the medulla to the cortex. A crescent of subcapsular or perinephric gas may be present. The absence of fluid collection implies a poor immune response. The mortality rate is high, at 69%. ^{[12, 13]}

Type II (66% of patients) typically has a confined, bubbly, intrarenal gas pattern—probably within abscesses associated with renal and perinephric fluid collection—and gas within the renal pelvis. The mortality rate in type II is 18%. ^{[12, 13]}

Conversion from type I to type II emphysematous pyelonephritis has been described. ^[25] Wan et al correlated imaging findings of types I and II disease with clinical course and prognosis and showed that the radiologic differentiation between the 2 types is important due to the prognostic difference. ^[13] That is, the mortality rate for type I disease was higher than that for type II (69% vs 18%, respectively, as stated above), with type I emphysematous pyelonephritis tending to have a more fulminant course and a significantly shorter interval from clinical onset to death. (See the images below.)

Emphysematous pyelonephritis should be differentiated from reflux of air from the bladder and bronchorenal, enterorenal, or cutaneorenal fistulae (as may occur with xanthogranulomatous pyelonephritis ^[19] ). Air also can be seen in focal renal abscesses, but it is not life threatening.

Ultrasonography is usually the first imaging modality for assessing renal pathology. The ultrasonographic findings often guide clinicians in choosing the next modality, such as CT scanning, to achieve a more specific diagnosis. ^{[15, 18]}

Intrarenal gas causes high-amplitude echoes within the renal sinus/renal parenchyma associated with dirty acoustic shadowing, and ring-down artifacts may result from air bubbles trapped in fluid. In addition, shadowing from gas bubbles in the perinephric space may be seen, making visualization of the kidney difficult (see the following image). Perinephric fluid, if any, tends to be obscured by gas.

Gas within the kidney and/or renal pelvis mimics renal calculi. In select patients, particularly those with diabetes in whom ultrasonograms suggest renal calculi, obtaining a coned radiograph of the renal area is worthwhile to preclude missing the diagnosis of emphysematous pyelonephritis.

Ronald A, Ludwig E. Urinary tract infections in adults with diabetes. Int J Antimicrob Agents. 2001 Apr. 17(4):287-92. [Medline].

Roy C, Pfleger DD, Tuchmann CM, et al. Emphysematous pyelitis: findings in five patients. Radiology. 2001 Mar. 218(3):647-50. [Medline].

Lu YC, Chiang BJ, Pong YH, Chen CH, Pu YS, Hsueh PR. Emphysematous pyelonephritis: Clinical characteristics and prognostic factors. Int J Urol. 2013 Aug 22. [Medline].

Craig WD, Wagner BJ, Travis MD. Pyelonephritis: radiologic-pathologic review. Radiographics. 2008 Jan-Feb. 28(1):255-77; quiz 327-8. [Medline].

Chen CY, Chen CJ. Images in clinical medicine. Emphysematous pyelonephritis. N Engl J Med. 2014 Nov 27. 371 (22):e34. [Medline].

Hui L, Tokeshi J. Emphysematous pyelonephritis. Hawaii Med J. 2000 Aug. 59(8):336-7. [Medline].

Jain SK, Agarwal N, Chaturvedi SK. Emphysematous pyelonephritis: a rare presentation. J Postgrad Med. 2000 Jan-Mar. 46(1):31-2. [Medline].

Sathyanathan VP, Gomathy S, Potty RN, et al. Emphysematous pyelonephritis. J Assoc Physicians India. 1998 Jun. 46(6):562-3. [Medline].

Shokeir AA, El-Azab M, Mohsen T, El-Diasty T. Emphysematous pyelonephritis: a 15-year experience with 20 cases. Urology. 1997 Mar. 49(3):343-6. [Medline].

Falagas ME, Alexiou VG, Giannopoulou KP, Siempos II. Risk factors for mortality in patients with emphysematous pyelonephritis: a meta-analysis. J Urol. 2007 Sep. 178(3 Pt 1):880-5; quiz 1129. [Medline].

Sun JN, Zhang BL, Yu HY, Wang B. Severe emphysematous pyelonephritis mimicking intestinal obstruction. Am J Emerg Med. 2015 Dec. 33 (12):1846.e3-6. [Medline].

Dahnart W. Radiology Review Manual. 6th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2007.

Wan YL, Lee TY, Bullard MJ, Tsai CC. Acute gas-producing bacterial renal infection: correlation between imaging findings and clinical outcome. Radiology. 1996 Feb. 198(2):433-8. [Medline].

Best CD, Terris MK, Tacker JR, Reese JH. Clinical and radiological findings in patients with gas forming renal abscess treated conservatively. J Urol. 1999 Oct. 162(4):1273-6. [Medline].

Grozel F, Berthezene Y, Guerin C, et al. Bilateral emphysematous pyelonephritis resolving to medical therapy: demonstration by US and CT. Eur Radiol. 1997. 7(6):844-6. [Medline].

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

Kuo YT, Chen MT, Liu GC, et al. Emphysematous pyelonephritis: imaging diagnosis and follow-up. Kaohsiung J Med Sci. 1999 Mar. 15(3):159-70. [Medline].

Chen KC, Hung SW, Seow VK, et al. The role of emergency ultrasound for evaluating acute pyelonephritis in the ED. Am J Emerg Med. 2011 Sep. 29(7):721-4. [Medline].

Punekar SV, Kinne JS, Rao SR, et al. Xanthogranulomatous pyelonephritis presenting as emphysematous pyelonephritis: a rare association. J Postgrad Med. 1999 Oct-Dec. 45(4):125. [Medline].

Singh I, Pachisia SS, Kumar S, Arora VK, Kumar P. Emphysematous pyelonephritis: a consequence of adenocarcinoma of urinary bladder in a nondiabetic patient. J Postgrad Med. 2005 Oct-Dec. 51(4):324-5. [Medline].

Portnoy O, Apter S, Koukoui O, Konen E, Amitai MM, Sella T. Gas in the kidney: CT findings. Emerg Radiol. 2007 Jun. 14(2):83-7. [Medline].

Ünlüer EE, Karagöz A. Computed tomography in emphysematous pyelonephritis. Pan Afr Med J. 2015. 22:186. [Medline].

Kangjam SM, Irom KS, Khumallambam IS, Sinam RS. Role of Conservative Management in Emphysematous Pyelonephritis – A Retrospective Study. J Clin Diagn Res. 2015 Nov. 9 (11):PC09-11. [Medline].

Tasleem AM, Murray P, Anjum F, Sriprasad S. CT imaging is invaluable in diagnosing emphysematous pyelonephritis (EPN): a rare urological emergency. BMJ Case Rep. 2014 Apr 4. 2014:[Medline].

Komura S, Shindoh N, Minowa O, et al. Emphysematous pyelonephritis- conversion of type i to type II appearance on serial CT studies. Clin Imaging. 1999 Nov-Dec. 23(6):386-8. [Medline].

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR is a member of the following medical societies: American Association for the Advancement of Science, American Institute of Ultrasound in Medicine, British Medical Association, Royal College of Physicians and Surgeons of the United States, British Society of Interventional Radiology, Royal College of Physicians, Royal College of Radiologists, Royal College of Surgeons of England

Disclosure: Nothing to disclose.

Colm Boylan, MBBCh, MRCP, FRCR Assistant Professor of Radiology, McMaster University School of Medicine; Staff Radiologist, St Joseph’s Hospital, Canada

Colm Boylan, MBBCh, MRCP, FRCR is a member of the following medical societies: Royal College of Radiologists

Disclosure: Nothing to disclose.

Brendan Costello, MD, MBBCh, FRCS(Ed), FRCS(Eng) Clinical Director, Department of Urology, North Manchester General Hospital, UK

Brendan Costello, MD, MBBCh, FRCS(Ed), FRCS(Eng) is a member of the following medical societies: British Medical Association

Disclosure: Nothing to disclose.

Khalid Mahmood, MBBS Locum Appointment Training Specialist Registrar, Department of Radiology-Paediatric, Royal Liverpool (Alder Hey) Children’s Hospital, UK

Disclosure: Nothing to disclose.

Eugene C Lin, MD Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, Society of Nuclear Medicine and Molecular Imaging

Disclosure: Nothing to disclose.

Ramesh Chandra Raja, MBBCh Consulting Staff, Department of Radiology, Rochdale Healthcare NHS Trust, UK

Disclosure: Nothing to disclose.

Arnold C Friedman, MD FACR, Professor, Department of Radiology, Arizona Health Science Center at the University of Arizona.

Arnold C Friedman, MD is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America

Disclosure: Nothing to disclose.

Sumaira MacDonald, MBChB, PhD, MRCP, FRCR Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute

Sumaira MacDonald, MBChB, PhD, MRCP, FRCR is a member of the following medical societies: British Medical Association, Royal College of Physicians, and Royal College of Radiologists

Disclosure: Nothing to disclose.

Steven Perlmutter, MD, FACR Associate Professor of Clinical Radiology, The School of Medicine at Stony Brook University; Medical Director of Radiology, Peconic Bay Medical Center

Steven Perlmutter, MD, FACR is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of Program Directors in Radiology, Association of University Radiologists, Medical Society of the State of New York, Radiological Society of North America, Society of Breast Imaging, Society of Nuclear Medicine, andSociety of Uroradiology

Disclosure: Nothing to disclose.

Philip Wiles, MD Honorary Visiting Professor, Division of Healthcare Professionals, University of Slaford; Honorary Clinical Lecturer, Department of Medicine, University of Manchester; Principal Medical Officer, Co-Operative Insurance Society, UK

Disclosure: Nothing to disclose.

Imaging in Emphysematous Pyelonephritis

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