Spontaneous bacterial peritonitis. A review of pathogenesis, diagnosis, and treatment

Spontaneous bacterial peritonitis (SBP) is an increasingly recognized complication of cirrhosis with ascites. However, the presence of ascites from any cause appears to be a risk factor for this infection. The etiology of SBP is multifactorial, including derangements in the reticuloendothelial system, abnormalities of both the serum and ascitic fluid humoral immune systems, and systemic bacteremia. Gram-negative enteric pathogens are the etiologic agents in 70% of the cases; anaerobes are an uncommon cause. Fever and abdominal pain are the most common presenting symptoms. However, asymptomatic patients are being increasingly recognized. When SBP is suspected, paracentesis is indicated. An absolute polymorphonuclear leukocyte count greater than 500/mm3 is highly suggestive of SBP. Ascitic fluid lactate and pH may offer additional diagnostic assistance when the PMN count is ambiguous. Appropriate antibiotic therapy should be initially based on the centrifuged Gram stain of ascites as well as the patient's renal function. Mortality is substantial and appears to be related to the severity of the underlying liver disease.