From the Guidelines
Spontaneous bacterial peritonitis (SBP) is diagnosed when a patient with ascites has an elevated ascitic fluid absolute neutrophil count ≥250 cells/mm³ without an evident intra-abdominal surgically treatable source of infection, as recommended by the most recent guidelines 1. To diagnose SBP, a diagnostic paracentesis should be performed, and the ascitic fluid should be sent for cell count with differential, culture in blood culture bottles (which increases yield), and protein analysis. The diagnosis is primarily based on the neutrophil count rather than culture results, as cultures may be negative in up to 40% of cases, as noted in previous studies 1. Patients typically present with fever, abdominal pain, and altered mental status, though some may be asymptomatic. Once SBP is diagnosed, empiric antibiotic therapy should be started immediately with a third-generation cephalosporin like ceftriaxone 2g IV daily or cefotaxime 2g IV every 8 hours, considering the local resistance profile and the severity of infection 1. For patients with renal dysfunction, albumin administration (1.5 g/kg on day 1 and 1 g/kg on day 3) is recommended to reduce the risk of hepatorenal syndrome, as supported by previous research 1. Treatment typically continues for 5-7 days, and a follow-up paracentesis showing a decrease in neutrophil count by at least 25% after 48 hours indicates response to therapy. After recovery, all patients should receive long-term prophylaxis with norfloxacin 400mg daily or trimethoprim-sulfamethoxazole to prevent recurrence, as SBP has a high mortality rate and recurrence risk. Some key points to consider in the diagnosis and management of SBP include:
- Diagnostic paracentesis should be performed without delay in all cirrhotic patients with ascites on hospital admission to rule out SBP 1.
- Ascitic fluid culture with bedside inoculation of blood culture bottles should be performed to guide the choice of antibiotic treatment when SBP is suspected 1.
- A second diagnostic paracentesis at 48 hours from the start of treatment may be considered to check the efficacy of antibiotic therapy in patients who have an apparently inadequate response 1.
From the Research
SBP Diagnosis
- Spontaneous bacterial peritonitis (SBP) is a common infection in patients with cirrhosis and ascites, associated with significant risk of mortality 2.
- The typical presentation of SBP includes abdominal pain, worsening ascites, fever, or altered mental status in a patient with known liver disease; however, some patients may be asymptomatic or present with only mild symptoms 2, 3.
- Paracentesis is the diagnostic modality of choice and should be performed in any patient with ascites and concern for SBP or upper gastrointestinal bleeding, or in those being admitted for a complication of cirrhosis 2, 3.
- An ascites absolute neutrophil count (ANC) ≥ 250 cells/mm3 is diagnostic of SBP 2, 4.
- Ascitic fluid should be placed in blood culture bottles to improve the culture yield 2, 3.
- Leukocyte esterase reagent strips can be used for rapid diagnosis if available 2.
Diagnostic Considerations
- Patients with severe intrahepatic shunting and those with an ascitic fluid total protein concentration of less than 1 g/dl appear to be particularly susceptible to bacterial infection of their ascites 3.
- Ultrasound should be used to optimize the paracentesis procedure 2.
- Repeating the paracentesis after 48 hours of treatment to reculture the fluid and reassess the ascitic fluid neutrophil count appears to be the best way to assess efficacy of treatment 3.
Bacteriology
- SBP is commonly due to Gram-negative bacteria, but infections due to Gram-positive bacteria and multidrug-resistant bacteria are increasing 2, 4, 5.
- Gram-positive cocci (GPC) such as Staphylococcus, Enterococcus as well as multi-resistant bacteria have become common pathogens and have changed the conventional approach to treatment of SBP 5.