Spontaneous bacterial peritonitis (SBP) is a severe infection of ascitic fluid, which accumulates in the abdomen. This condition commonly arises as a complication in individuals with advanced liver disease, particularly cirrhosis. SBP requires immediate medical attention and prompt treatment to prevent severe outcomes. Ascitic fluid creates an environment susceptible to bacterial proliferation.
Diagnosis Confirmation Before Treatment
Confirming the diagnosis of spontaneous bacterial peritonitis is a necessary first step. This involves a procedure called paracentesis, where ascitic fluid is withdrawn from the abdomen. The fluid is then analyzed in a laboratory to identify signs of infection. A polymorphonuclear leukocyte (PMN) count exceeding 250 cells/mm³ in the ascitic fluid is generally considered diagnostic for SBP, even if bacterial cultures are initially negative.
The ascitic fluid is also sent for bacterial culture to identify the specific type of bacteria. While culture results can take several days, treatment for SBP often begins immediately based on the elevated PMN count due to the urgency. This allows for prompt intervention while awaiting more specific bacterial identification. In some cases, transferring ascitic fluid to blood culture media at the bedside can increase culture sensitivity, potentially identifying the pathogen in up to 70% of cases.
Initial Treatment of an Active Infection
Immediate medical interventions for an active SBP infection primarily involve broad-spectrum intravenous (IV) antibiotics. Third-generation cephalosporins, such as cefotaxime or ceftriaxone, are considered standard initial treatment. These antibiotics are typically administered intravenously for a duration of 5 to 7 days, with common doses being 2 grams every 8 hours for cefotaxime or 1-2 grams daily for ceftriaxone. This empiric therapy targets common bacterial culprits, often gram-negative enteric bacteria like E. coli and Klebsiella pneumoniae, which can translocate from the gut into the ascitic fluid.
The second component of initial treatment is the administration of intravenous albumin. Albumin is given to patients with SBP to help prevent hepatorenal syndrome, a severe complication characterized by kidney failure. Studies indicate that albumin infusions can reduce the incidence of renal impairment and mortality in patients with SBP. The recommended dosing typically involves 1.5 grams per kilogram of body weight on the first day, followed by 1 gram per kilogram on the third day. This adjunctive therapy is particularly beneficial for patients who have signs of kidney dysfunction or severe liver disease.
Preventing Recurrence
After an initial SBP episode, long-term strategies prevent future infections. Antibiotic prophylaxis is central to this preventive approach, as SBP has a high recurrence rate; up to 70% of patients experience another episode within a year without it. Prophylaxis involves daily oral antibiotics to suppress bacterial overgrowth and translocation from the gut.
Secondary prophylaxis is prescribed for patients who have experienced an SBP episode. Common antibiotics include norfloxacin (400 mg once daily), ciprofloxacin (500 mg orally once daily), or trimethoprim-sulfamethoxazole (one double-strength tablet daily). Norfloxacin is often recommended as a first-line agent, with ciprofloxacin as an alternative, especially where norfloxacin is unavailable.
Primary prophylaxis is for high-risk patients who have not had SBP, such as those with low ascitic fluid protein levels (less than 1.5 g/dL) or acute gastrointestinal bleeding. For patients with gastrointestinal bleeding, a short course of intravenous ceftriaxone (about 7 days) is often preferred. Continuous use of these antibiotics reduces recurrence, improving patient outcomes and survival.
Addressing the Underlying Cause
Since spontaneous bacterial peritonitis is a complication of advanced liver disease, long-term management involves addressing the underlying cirrhosis. Managing the progression of liver damage is important for reducing the risk of future SBP episodes. This often includes lifestyle adjustments, such as avoiding alcohol, and adherence to prescribed medications that manage cirrhosis-related complications.
For eligible patients, a liver transplant is the only definitive treatment, effectively eliminating SBP risk by replacing the diseased liver. Liver transplantation should be considered for suitable SBP survivors, given the high mortality rates associated with recurrent infections. This procedure can improve long-term prognosis and quality of life for individuals with end-stage liver disease. While waiting for a transplant, or if not eligible, ongoing management of cirrhosis symptoms and complications remains the focus of care.