Patients with chronic liver disease (CLD) can become sick. Really sick. They are high risk of developing bacterial infections. When a bacterial infection occurs within ascites (fluid within the peritoneal cavity), we call it SBP.
The actual pathogenesis of SBP is highly debated. Theories suggest direct bacterial translocation across the bowel wall or haematogenous spread of bacteria in the context of an immunosuppressed state. Liver disease is well known to cause immune dysfunction.
SBP may present in a number of ways including peritonitis (i.e. abdominal pain), hepatic encephalopathy, as an upper gastrointestinal bleed, acute kidney injury or overt sepsis. It complicates ~10% of inpatient admissions with decompensated CLD and requires early recognition and treatment - this is because of the high morbidity and mortality associated with SBP; one year survival after SBP is only 30-50%!
So what do we do when suspect SBP? The key is an ascitic TAP -trans-abdominal paracentesis.
An ascitic TAP involves inserting a small green needle into the abdomen and taking a sample of ascitic fluid. This can be sent for urgent analysis in the lab. SBP is defined as an ascitic fluid white cell count >250/mm3 that is predominantly neutrophilic (i.e. the majority of the white cells seen are neutrophils).
Treatment for SBP is broad-spectrum antibiotics (e.g. third-generation cephalosporin) unless sensitivities for a particular bug are available. They are often given on suspicion (i.e. before the ascitic TAP) to prevent any delay in treatment. Following an episode of SBP, patients require prophylactic oral antibiotics to reduce the risk of it developing again!