Introduction
Emphysematous pyelonephritis is an infection in the renal parenchyma leading to gas accumulation in the tissues. It is commonly seen in individuals with diabetes mellitus. It has a female predilection. Emphysematous pyelonephritis has signs and symptoms similar to acute pyelonephritis. Emphysematous pyelonephritis, if not recognized and treated promptly, can be fatal.
What Is the Pathophysiology of Emphysematous Pyelonephritis?
Emphysematous pyelonephritis causes extensive infection of the renal parenchyma leading to gas accumulation. It develops suddenly and severely and can be fatal. Urinary tract infections are common in individuals with diabetes, but not all infections lead to emphysematous pyelonephritis. Predisposing factors for emphysematous pyelonephritis in individuals with diabetes include:
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Uncontrolled diabetes.
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High levels of glycosylated hemoglobin.
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Impaired host immune mechanisms.
The pathophysiology of gas accumulation is said to be the fermentation of glucose with carbon dioxide. The pathogens produce carbon dioxide. Schainuck et al. stated that the fermentation produced due to tissue necrosis leads to gas accumulation. The major components in the gas accumulated in emphysematous pyelonephritis involved:
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Nitrogen (60%).
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Hydrogen (15%).
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Carbon dioxide (5%).
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Oxygen (8%).
Huang et al. stated that mixed acid fermentation is the mechanism for gas accumulation because of the presence of hydrogen. The tissue equilibrium of the gas bubbles and tissues helps determine the final carbon dioxide content. Diabetic microangiopathy contributes to the transport of catabolic products, which leads to gas accumulation.
What Is the Etiology of Emphysematous Pyelonephritis?
Enteric gram-negative facultative anaerobes cause emphysematous pyelonephritis. 66 % of the cases have isolated Escherichia coli and Klebsiella species. Blood culture results show similarity with positive urine culture results. Fungi and protozoa are rare in emphysematous pyelonephritis.
What Is the Epidemiology of Emphysematous Pyelonephritis?
Emphysematous pyelonephritis is rare, and only one to two cases have been reported in a year in the United States urologic department. Emphysematous pyelonephritis has an age preference of around 55 years with an age interval of 19 to 81. Emphysematous pyelonephritis is six times more common in women. Most of these individuals have uncontrolled diabetes with high levels of glycosylated hemoglobin. It is also common in individuals having renal stones as it is a predisposing factor. In uncommon cases where the individual does not have diabetes but is seen with renal failure and immunosuppression as a contributing factor. Of these cases, 4% have polycystic kidneys, 22% have obstructed kidney disease, and 4% have end-stage renal disease. Obstruction is one of the major causes of emphysematous pyelonephritis in individuals without diabetes. Emphysematous pyelonephritis has also been associated with kidney transplant cases.
What Is the Prognosis for Emphysematous Pyelonephritis?
Emphysematous pyelonephritis, if left untreated, is fatal. The mortality rate of emphysematous pyelonephritis used to be high before the emergence of antibiotics. However, advancements in imaging techniques, resuscitative management, diabetes control, and minimally invasive techniques have improved case outcomes. Huang and Tseng reported a mortality rate of 19 % for emphysematous pyelonephritis. There was treatment success seen in percutaneous drainage, nephrectomy, and antibiotics. Risk factors for poor diagnosis include:
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Altered level of consciousness.
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Multiple organ failure.
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Hyperglycemia.
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Leukocytosis.
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Thrombocytopenia.
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Acute renal impairment.
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Hypoalbuminemia.
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Septic shock.
The mortality risk is higher in individuals who have undergone antibiotic therapy alone than in individuals who receive percutaneous drainage. Complications of emphysematous pyelonephritis involve perinephric abscess and renal failure.
What Are the Signs and Symptoms of Emphysematous Pyelonephritis?
The signs and symptoms of emphysematous pyelonephritis involve:
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Fever.
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Abdominal pain or flank pain.
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Nausea and vomiting.
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Acute renal impairment.
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Altered sensorium.
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Shock.
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Thrombocytopenia.
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Crepitus is seen in advanced cases.
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Pneumaturia.
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Pneumomediastinum.
Comorbidities involve malnourishment, alcoholism, renal calculi, and diabetic ketoacidosis.
Diagnostic Considerations:
Acute pyelonephritis has a similar presentation as that of emphysematous pyelonephritis. It also has a similar display to xanthogranulomatous pyelonephritis. Xanthogranulomatous pyelonephritis is a condition of renal stone formation in a nonfunctional kidney with a gram-negative infection. Xanthogranulomatous pyelonephritis produces gas in the renal parenchyma and perinephric space, but the degree observed is less than emphysematous pyelonephritis. The treatment for xanthogranulomatous pyelonephritis is surgery. Early nephrectomy may be a choice as the kidney is nonfunctional. The gas produced is confined to the renal pelvis in emphysematous pyelonephritis and helps differentiate it from emphysematous pyelitis.
What Are the Investigations for Emphysematous Pyelonephritis?
Recommended investigations include:
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Urinalysis - Pyuria, infected urine.
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Complete blood count with differential leukocytosis with a left shift and thrombocytopenia.
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Renal function test shows increased creatinine levels.
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Blood cultures show positive results.
Individuals with shock and urosepsis should undergo cardiac and pulmonary function assessments. Imaging studies findings include odd shadowing of the renal pelvis due to gas accumulation in emphysematous pyelonephritis. In ultrasonography, there is the presence of intrarenal gas. Therefore, computed tomography is a test of choice for diagnosing emphysematous pyelonephritis. The radiologic classification is given by Huang and Tseng which involves:
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Class 1: Gas is confined in the collecting system.
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Class 2: Gas is confined to renal parenchyma.
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Class 3A: Perinephric extension of gas or abscess.
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Class 3B: Extension of gas beyond the gerota fascia.
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Class 4: Bilateral emphysematous pyelonephritis or emphysematous pyelonephritis in a solitary kidney.
What Is the Treatment and Management of Emphysematous Pyelonephritis?
Individuals with emphysematous pyelonephritis require resuscitation measures such as:
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Oxygen.
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Intravenous fluid.
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Correction of acid-base imbalances.
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Glycemic control.
Surgery is performed only after the cardiorespiratory status is stable. Conservative treatment with antibiotic therapy is suggested in the following ways:
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Individuals with compromised renal function.
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Individuals who are stable and have gas in the collecting system alone.
Nephrectomy is indicated in the following cases:
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Limited or no access for percutaneous drainage or internal stenting.
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Dry-type emphysematous pyelonephritis or gas in the renal parenchyma.
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In bilateral emphysematous pyelonephritis, possible bilateral nephrectomy.
Antibiotic therapy, as given by Lu et al., based on Huang and Tseng classification:
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Class 1 - Third generation cephalosporins and percutaneous catheter drainage in individuals with uropathy (with or without Amikacin).
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Class 2, 3, and 4 Without Risk Factors - Third-generation cephalosporins with percutaneous catheter drainage.
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Class 2, 3, and 4 With Risk Factors - Carbapenem with or without Vancomycin and percutaneous catheter drainage.
Conclusion
Emphysematous pyelonephritis is an infection in the renal parenchyma leading to gas accumulation in the tissues. It is common in individuals with diabetes mellitus. E.coli is the most common causative agent. Treatment involves antibiotic therapy and surgical intervention.
