You are in: eMedicine Specialties > Urology > Infections and Related Inflammatory Conditions Emphysematous PyelonephritisArticle Last Updated: May 1, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Sugandh Shetty, MD, Consulting Staff, Department of Urology, William Beaumont Hospital Sugandh Shetty is a member of the following medical societies: American Urological Association Editors: Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Ajay K Singh, MB, MRCP, MBA, Associate Professor of Medicine, Director of Dialysis, Department of Medicine, Harvard Medical School; Clinical Chief of Renal Division, Brigham and Women's Hospital; J Stuart Wolf, Jr, MD, FACS, David A Bloom Professor of Urology, Director, Division of Minimally Invasive Urology, Department of Urology, University of Michigan Medical Center; 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 Author and Editor Disclosure Synonyms and related keywords: emphysematous pyelonephritis, emphysematous pyelitis, gas-forming infection of the urinary tract, EPN, renal parenchyma infection, urinary tract infection, UTI, pneumaturia, renal emphysema, pneumo-nephritis, pneumonephritis, diabetes, xanthogranulomatous pyelonephritis INTRODUCTIONSection 2 of 11
  Emphysematous pyelonephritis (EPN) is a severe necrotizing infection of the renal parenchyma; it causes gas formation within the collecting system, renal parenchyma, and/or perirenal tissues. Gas in the renal pelvis alone, without parenchymal gas, is often referred to as emphysematous pyelitis. EPN is common in persons with diabetes, and the presentation of EPN is similar to that of acute pyelonephritis. However, the clinical course of EPN can be severe and life-threatening if not recognized and treated promptly. The first case of pneumaturia was reported in 1898; since then, approximately 200 cases of EPN have been reported. Although most information has been from case reports, a few large series have also been reported. This article describes the pathogenesis, classification, complications, and management of EPN based on a review of 5 large series of 149 patients.1, 2, 3, 4, 5 History of the ProcedureKelly and MacCullum reported the first case of pneumaturia from a gas-forming renal infection in 1898.6 Since then, several terms have been used to describe the condition, such as renal emphysema, pneumonephritis, and emphysematous pyelonephritis. The mortality rate associated with the condition was high before the advent of antibiotics; however, advances in imaging technology, control of diabetes, resuscitative management, and minimally invasive treatment have improved the outcome in patients with EPN. Although nephrectomy may be the quickest way of treating the infection source, renal function is compromised in many patients; therefore, a strategy to save nephrons may be very desirable. The above-mentioned series highlight such an approach, reserving nephrectomy for patients in whom conservative treatment does not elicit a response. FrequencyEPN is a rare condition. Only 1-2 cases per year are encountered in a typical busy urological department in the EtiologyAmong the bacteria associated with EPN, Escherichia coli is isolated in 66% of patients and Klebsiella species are reported in 26%. Proteus, Pseudomonas, and Streptococcus species are other organisms found in patients with EPN. Mixed organisms are observed in 10%. Positive blood culture results are identical to urine culture results in 54% of patients. Rare organisms such as Clostridium and Candida species have also been isolated in patients with EPN. Recently, Entamoeba histolytica and Aspergillus fumigatus have been reported as causes of EPN. Transplanted kidneys may be susceptible to EPN because of associated high-risk factors in the recipient such as diabetes and immunosuppression.7 PathophysiologyEPN is a severe infection of the renal parenchyma that causes gas accumulation in the tissues. The infection often has a fulminating course and can be fatal if left untreated. However, urinary tract infections are common in persons with diabetes, and not all of these infections lead to EPN. The factors that predispose to EPN in persons with diabetes may include uncontrolled diabetes, high levels of glycosylated hemoglobin, and impaired host immune mechanisms. In 1993, Guiard proposed alcoholic fermentation of glucose with carbon dioxide production by the organisms as the cause of gas in the tissues. In 1889, Muller first identified nitrogen, hydrogen, and carbon dioxide in a patient with pneumaturia. Schainuck et al proposed that fermentation products from tissue necrosis produced carbon dioxide.8 Three investigators analyzed the gas content, and all 3 demonstrated that the major components of the gas in EPN include nitrogen (60%), hydrogen (15%), carbon dioxide (5%), and oxygen (8%). Huang et al concluded that mixed acid fermentation is the mechanism of gas production based on the presence of hydrogen.9 Yang and Shen indicated that gas-forming infections depend on rapid tissue catabolism and impaired transport of the end products at the inflammatory site.10 Although carbon dioxide is released by the bacteria, the final tissue equilibrium achieved by tissues and gas bubbles determines the final carbon dioxide content. Diabetic microangiopathy may also contribute to the slow transport of catabolic products and may lead to accumulation of gas. Xanthogranulomatous pyelonephritis, which is usually associated with stones in a nonfunctioning kidney with a severe gram-negative infection, is another septic condition very similar in presentation to EPN. Xanthogranulomatous pyelonephritis may also produce gas in the renal parenchyma and perinephric space, but generally not to the degree observed with EPN. The treatment of xanthogranulomatous pyelonephritis is strictly surgical, requiring early nephrectomy because the kidney is already nonfunctional and is not worth saving. ClinicalEpidemiology The mean age of patients with EPN is reported as 55 years, with a range of 19-81 years. The condition is 6 times more common in women. Ninety-five percent of patients have diabetes. In most patients, the diabetes is uncontrolled, with high levels of glycosylated hemoglobin (72%) or high levels of blood sugar. Rare cases have been reported in persons who do not have diabetes, with renal failure and immunosuppression as contributing factors. Of these patients, 22% have obstructed upper tracts, 4% have polycystic kidneys, and 4% have end-stage renal disease. Obstruction is the main cause of EPN in persons without diabetes. The left kidney is affected more commonly than the right. Bilateral cases have also been reported. Physical Patients typically present with fever (79%), abdominal or flank pain (71%), nausea and vomiting (17%), dyspnea (13%), acute renal impairment (35%), altered sensorium (19%), shock (29%), and thrombocytopenia (46%). Crepitus over the flank area may occur in advanced cases of EPN. Pneumaturia is uncommon unless emphysematous cystitis is present. Subcutaneous emphysema and pneumomediastinum have recently been reported in a case of EPN.11 Pregnancy can also be complicated by EPN.12 Bilateral EPN has also been reported. Coexisting comorbidities include alcoholism, malnourishment, renal calculi, and diabetic ketoacidosis. INDICATIONSSection 3 of 11
Patients with emphysematous pyelonephritis (EPN) should be treated with aggressive medical management and, possibly, prompt surgical intervention.
CONTRAINDICATIONSSection 4 of 11
No contraindications exist for the treatment of emphysematous pyelonephritis (EPN). The infection often has a fulminating course and can be fatal if left untreated. However, surgical intervention should be performed only after stabilization of the cardiorespiratory status. WORKUPSection 5 of 11
Lab Studies
Imaging Studies
StagingSee Imaging Studies. TREATMENTSection 6 of 11
Medical therapyPrompt hydration, fluid resuscitation, and treatment with systemic antibiotics are the mainstays of management. A monitored-care facility may be needed for patients in shock. Control of diabetes and maintenance of adequate fluid balance should be achieved quickly. Initial antibiotic therapy consists of intravenous ampicillin, gentamicin, and metronidazole and is administered until the culture sensitivities are available. In patients with penicillin allergies, vancomycin is used in place of ampicillin. In patients with renal compromise, doses must be adjusted according to creatinine clearance. Start imaging studies immediately. Any obstruction found should be relieved with either percutaneous drainage or stent placement. The decision regarding the percutaneous drainage versus a double-J stent probably depends on the patient's condition (see Surgical Therapy). Placement of a stent requires mild sedation or general anesthesia, whereas a percutaneous procedure can be performed with only a local anesthetic. In cases of bilateral emphysematous pyelonephritis (EPN) or in cases of EPN in a solitary kidney, percutaneous drainage has been useful. EPN with gas in the collecting system alone or gas and fluid in the perinephric space may respond well to percutaneous drainage. Patients with EPN are extremely ill and need resuscitative measures in the intensive care unit. Surgical intervention should be performed only after stabilization of the cardiorespiratory status. Patients with stones and EPN deserve special mention. The presence of a stone often leads to obstruction, which must be urgently relieved with percutaneous drainage or stenting. Definitive treatment for stones should be deferred until later. Huang et al reported an overall EPN mortality rate of 19%.1 They reported significant success with percutaneous drainage and antibiotics (66%). Wan et al reported a mortality rate of 40%.3 Furthermore, Wan et al reported a high risk of death in patients with serum creatinine levels greater than 1.4 mg/dL and platelet count of less than 60,000/μL. Huang et al analyzed 46 cases and concluded that class 1 and class 2 EPN could be managed with percutaneous drainage and antibiotics.1 In class 3 and class 4 EPN, the presence of fewer than 2 risk factors (eg, thrombocytopenia, elevated serum creatinine levels, altered sensorium, shock) indicated that percutaneous drainage and antibiotics could also be used. However, in the presence of more than 2 risk factors, nephrectomy yielded better results.Surgical therapyNephrectomy is the treatment of choice in most patients with EPN. A retroperitoneal flank incision is the preferred approach to avoid peritoneal contamination. Nephrectomy may be associated with significant bleeding and injury to surrounding structures. The initial procedure should often be conservative with care to drain the abscess. Patients may require intensive-care management. In a series in which nephrectomy was the exclusive treatment after stabilization, the mortality rate was low, suggesting that an aggressive surgical option should be chosen. However, less-invasive options, such as percutaneous drainage, have also been used with success.16 Surgical intervention should be performed only after stabilization of the cardiorespiratory status. Gas in the renal parenchyma or dry-type EPN should be treated immediately with nephrectomy. Bilateral nephrectomy may be necessary in patients with bilateral EPN. Mortality rates were 15-20% in 2 series in which nephrectomy was the treatment of choice.5, 4 Follow-upFor excellent patient education resources, visit eMedicine's Kidneys and Urinary System Center. Also, see eMedicine's patient education article Urinary Tract Infections. COMPLICATIONSSection 7 of 11
Untreated cases of emphysematous pyelonephritis (EPN) result in death. Medical treatment of EPN may lead to uncontrollable sepsis that requires surgical intervention. Perinephric abscess and renal failure are other complications. Nephrectomy complications include injury to the colon, duodenum, and great vessels. Postoperative wound infection is common because wound healing in these patients is compromised. OUTCOME AND PROGNOSISSection 8 of 11
Patients with emphysematous pyelonephritis (EPN) should be treated with aggressive medical management and prompt surgical intervention. Conservative treatment, such as percutaneous drainage with antibiotics, should be reserved only for patients with unilateral EPN or bilateral EPN or those with compromised renal function. Early cases of patients with EPN who have gas in the collecting system alone and who are otherwise in stable condition may be treated with antibiotics and drainage. Although nephrectomy offers the best outcome, a trial of conservative treatment with drainage should be offered. However, if access to percutaneous drainage or internal stenting is not available, nephrectomy should be considered after stabilization is achieved. Management is based on the clinical and laboratory findings. If the patient is stable, conservative treatment with antibiotics and drainage should be tried. If the patient has gas in the renal parenchyma and perinephric tissues along with significant exudate, initial percutaneous drainage should be given a chance. Saving nephrons and the patient's life should be weighed based on the clinical situation, response to treatment, and available facilities. FURTHER READINGSection 9 of 11
For additional information, visit Medscape’s Diabetic Microvascular Complications Resource Center and Stone Disease Resource Center. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Emphysematous Pyelonephritis excerpt Article Last Updated: May 1, 2008 | |||||||||||||||||||||||||||||||||||||||||||||||||
