What is Spontaneous Bacterial Peritonitis (SBP)?
Spontaneous Bacterial Peritonitis (SBP) is an acute bacterial infection of the ascitic fluid in the peritoneal cavity, often occurring in patients with advanced liver disease, particularly those with cirrhosis. Unlike other forms of peritonitis, SBP arises without an evident intra-abdominal source of infection. The condition is a serious complication of cirrhosis and is associated with significant morbidity and mortality.
What Causes SBP?
SBP is primarily caused by translocation of bacteria from the intestinal tract. The most common pathogens involved are gram-negative bacteria, particularly Escherichia coli and Klebsiella pneumoniae. Gram-positive bacteria like Streptococcus species can also be involved. The exact mechanism involves increased intestinal permeability, immune system dysfunction, and alterations in gut flora, which are common in patients with liver disease.
Patients with cirrhosis and ascites are at the highest risk for developing SBP. Additional risk factors include a low protein concentration in the ascitic fluid, previous episodes of SBP, gastrointestinal bleeding, and severe liver dysfunction. These patients often have compromised immune systems, making them more susceptible to infections.
Symptoms of SBP can be subtle and nonspecific, which makes early diagnosis challenging. Common symptoms include abdominal pain, fever, altered mental status, and worsening liver function. Some patients may present with signs of systemic infection like hypotension or shock. Given the nonspecific nature of these symptoms, a high index of suspicion is necessary for timely diagnosis.
How is SBP Diagnosed?
Diagnosis of SBP is primarily based on the analysis of ascitic fluid obtained via paracentesis. The hallmark diagnostic criterion is an elevated neutrophil count (polymorphonuclear leukocytes, or PMNs) in the ascitic fluid, typically greater than 250 cells/mm³. A positive culture of the ascitic fluid can also support the diagnosis, but cultures can be negative in up to 60% of cases. Blood cultures and other laboratory tests may aid in the diagnosis and management.
What is the Treatment for SBP?
The cornerstone of SBP treatment is the prompt initiation of antibiotics. Empirical therapy usually involves third-generation cephalosporins, such as cefotaxime, due to their broad-spectrum coverage. In patients with a history of β-lactam allergy or resistant organisms, alternative agents like quinolones may be used. Adjunctive therapy with albumin has been shown to reduce renal impairment and mortality in some patients. Once the causative organism is identified, antibiotic therapy can be tailored accordingly.
Can SBP be Prevented?
Prophylactic antibiotics are recommended for patients at high risk of developing SBP, such as those with low protein levels in ascitic fluid or a history of prior SBP. Norfloxacin is commonly used for long-term prophylaxis. Additionally, addressing factors that contribute to cirrhosis and ascites, such as alcohol consumption and viral hepatitis, can reduce the risk of SBP. Regular monitoring and management of ascites can also play a preventive role.
What is the Prognosis for Patients with SBP?
The prognosis of SBP depends on various factors, including the severity of liver disease, the rapidity of diagnosis, and the effectiveness of treatment. Even with treatment, SBP has a high mortality rate, ranging from 20% to 40%. Early recognition and management of the condition are crucial in improving outcomes. Patients who survive an episode of SBP are at high risk for recurrence and require close monitoring and preventive measures.
Conclusion
SBP is a serious and potentially life-threatening infection that primarily affects patients with cirrhosis and ascites. Timely diagnosis and treatment are critical to improve patient outcomes. Understanding the risk factors, clinical presentation, and management strategies is essential for healthcare providers to effectively care for patients at risk of or affected by SBP. Ongoing research and advances in the management of liver disease may further help in reducing the incidence and impact of this condition.
