eMedicine Specialties > Urology > Infections and Related Inflammatory Conditions

Emphysematous Pyelonephritis

Author: Sugandh Shetty, MD, Consulting Staff, Department of Urology, William Beaumont Hospital
Contributor Information and Disclosures

Updated: May 1, 2008

Introduction

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 Procedure

Kelly 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.

Frequency

EPN is a rare condition. Only 1-2 cases per year are encountered in a typical busy urological department in the United States. However, the frequency of reports from developing nations suggests that this may be a reflection of access to health care and health education. Because the condition preferentially affects persons with diabetes, the reported frequency reflects how poorly diabetes is controlled in these geographical areas. Renal stones is another predisposing condition and therefore affects the frequency of EPN.

Etiology

Among 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

Pathophysiology

EPN 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.

Presentation

Epidemiology

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.

Indications

Patients with emphysematous pyelonephritis (EPN) should be treated with aggressive medical management and, possibly, prompt surgical intervention.

• Conservative treatment - Percutaneous drainage with antibiotics
  • Those with compromised renal function
  • Early cases associated with gas in the collecting system alone and patient is in otherwise in stable condition
  • Class 1 and class 2 EPN
  • Class 3 and class 4 EPN - In the presence of fewer than 2 risk factors (eg, thrombocytopenia, elevated serum creatinine levels, altered sensorium, shock)
• Surgical treatment - Nephrectomy
  • Treatment of choice for most patients
  • No access to percutaneous drainage or internal stenting (after patient is stabilized)
  • Gas in the renal parenchyma or "dry-type" EPN
  • Possibly bilateral nephrectomy in patients with bilateral EPN
  • Class 3 and class 4 EPN - In the presence of more than 2 risk factors (eg, thrombocytopenia, elevated serum creatinine, altered sensorium, shock)

Contraindications

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.

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