Spontaneous Bacterial Peritonitis (SBP) is a severe infection of the ascitic fluid that accumulates in the abdomen of individuals with advanced liver disease, primarily cirrhosis. SBP arises spontaneously, meaning it occurs without an obvious source of infection inside the abdomen, such as a perforated bowel. SBP is a serious complication of liver failure and is considered a medical emergency due to its high mortality risk. Management focuses on rapidly clearing the infection, preventing kidney damage, and establishing long-term measures to prevent recurrence.
Confirming the Diagnosis and Starting Treatment
Prompt diagnosis is paramount because delaying treatment significantly increases the risk of death. The procedure necessary for diagnosis is called paracentesis, where a small needle is used to safely remove a sample of the ascitic fluid for laboratory analysis, including cell count and culture. SBP is definitively diagnosed when the count of polymorphonuclear leukocytes (PMNs)—a type of white blood cell—in the ascitic fluid is 250 cells per cubic millimeter or higher. Because laboratory results can take several hours, treatment often begins empirically, meaning it is started immediately based on clinical suspicion and the high PMN count, before culture results are finalized. Starting therapy immediately upon suspicion is a universally accepted practice that improves outcomes. The ascitic fluid culture remains important, as it helps determine the specific bacteria and their susceptibility to antibiotics, guiding later adjustments to the treatment plan.
Acute Antibiotic Regimens
Initial Therapy
The primary treatment for an acute SBP episode involves the immediate, intravenous administration of broad-spectrum antibiotics. This empirical approach targets the most likely causative organisms, which are typically bacteria from the gut, such as Escherichia coli and Klebsiella species. The standard first-line treatment for community-acquired SBP is a third-generation cephalosporin, such as cefotaxime or ceftriaxone. These drugs are highly effective because they achieve high concentrations in the ascitic fluid and target common gram-negative bacteria responsible for the infection.
Monitoring and Adjustment
The typical duration for this acute antibiotic course is generally short, usually lasting between five and seven days. Treatment success is assessed by clinical improvement, such as resolution of fever and abdominal pain, and sometimes by repeating paracentesis to confirm the PMN count has decreased below the diagnostic threshold. If culture results show resistance or if the patient does not improve within 48 hours, the antibiotic regimen must be adjusted. Patients with healthcare-associated SBP or recent antibiotic exposure may require broader-spectrum agents initially due to the higher likelihood of resistant bacteria. Adjusting therapy based on the specific susceptibility of the cultured organism ensures the most effective treatment.
Supportive Care During Treatment
Supportive care measures are a fundamental part of SBP management, focusing on preventing life-threatening complications, particularly kidney injury. The inflammatory cascade triggered by the infection can lead to profound circulatory dysfunction, significantly increasing the risk of developing hepatorenal syndrome (HRS), a severe form of kidney failure. Intravenous albumin administration alongside antibiotics is the established standard of care for patients with SBP to mitigate this risk. Albumin works by expanding the plasma volume and stabilizing circulation, which in turn helps to preserve kidney function.
The recommended dosing schedule involves administering 1.5 grams per kilogram of body weight within six hours of diagnosis, followed by 1 gram per kilogram on day three of treatment. This precise dosing regimen has been shown to reduce both the incidence of renal impairment and the overall mortality rate in patients with SBP. Throughout the acute treatment phase, patients require close monitoring of their fluid balance, electrolytes, and kidney function tests, such as serum creatinine. Careful attention is paid to urine output and any signs of fluid overload, allowing for rapid intervention if there are signs of worsening kidney function or other complications.
Preventing Recurrence
Secondary Prophylaxis
Once the acute SBP infection has been successfully treated, the focus shifts to preventing future episodes, as the recurrence rate is high, reaching up to 70% within one year. This long-term strategy, known as secondary prophylaxis, is considered necessary for all patients who have survived an SBP episode. Secondary prophylaxis involves the use of long-term, low-dose oral antibiotics, a regimen distinctly different from the acute intravenous treatment. Common prophylactic medications include norfloxacin taken daily or trimethoprim-sulfamethoxazole (TMP-SMX). These antibiotics work by reducing the number of bacteria in the gut, minimizing translocation into the ascitic fluid.
Primary Prophylaxis
Prophylactic antibiotics are typically continued indefinitely until the patient’s underlying liver disease is cured, such as through a liver transplant, or until the ascites resolves. Primary prophylaxis—preventive treatment for patients who have never had SBP—is also recommended for high-risk individuals. This includes patients with low protein levels in their ascitic fluid combined with kidney dysfunction or severe liver impairment.