Gastroenterology & Nutrition

Spontaneous Bacterial Peritonitis

Spontaneous bacterial peritonitis (SBP) is infection of ascitic fluid without a surgically treatable intra-abdominal source, usually in advanced cirrhosis; diagnose it promptly with ascitic neutrophil counting and treat immediately with context-appropriate antibiotics, renal-protective albumin when indicated and specialist follow-up.

In a nutshell

Spontaneous bacterial peritonitis is infection of ascitic fluid without a surgically treatable source, usually in advanced cirrhosis. Perform urgent diagnostic paracentesis in hospitalised people with cirrhosis and ascites or relevant deterioration; an ascitic neutrophil count of 250 cells/mm³ or more is treated as SBP, even if culture-negative. Start context-appropriate antibiotics immediately, give albumin when creatinine is increased or rising, assess for secondary peritonitis and arrange secondary prophylaxis and transplant-pathway review.

Classic presentation

A person with cirrhosis and ascites is admitted with new confusion, mild abdominal discomfort or acute kidney injury, without dramatic peritonism; the ascitic neutrophil count is at or above 250 cells/mm³.

Key points

Perform a diagnostic paracentesis without delay in hospitalised people with cirrhosis and ascites, and when there is GI bleeding, shock, fever, encephalopathy or worsening renal/liver function.
Treat an ascitic neutrophil count of 250 cells/mm³ or more as SBP; do not wait for a positive culture.
Send ascitic culture by bedside inoculation before antibiotics where possible and tailor treatment to community versus healthcare-associated infection and local resistance.
In SBP with increased or rising creatinine, give albumin according to the current BSG/BNF/local protocol and monitor for fluid overload.
Multiple organisms, focal peritonism, atypical biochemistry or poor response suggests secondary peritonitis and needs imaging and source-control review.
NICE does not support routine primary antibiotic prophylaxis for all cirrhotic ascites; reserve it for selected high-risk people and use secondary prophylaxis after SBP through hepatology and microbiology.

First-line investigation

Urgent diagnostic ascitic tap for neutrophil count and bedside culture.

Management

Tap, diagnose and start antibiotics

Perform urgent paracentesis; treat an ascitic neutrophil count of 250 cells/mm³ or more immediately with antibiotics chosen for infection context, severity, local resistance and renal function.^1,5,6

Give albumin when renal risk is present

If creatinine is increased or rising, give IV albumin 1.5 g/kg within 6 hours and 1 g/kg on day 3 under current BSG/local protocol, with monitoring for fluid overload.^1,4

Look for resistance, organ failure or secondary peritonitis

Reassess haemodynamics, renal function and clinical response; consider repeat tap at about 48 hours if response is inadequate and urgently investigate a surgically treatable source or resistant infection when neutrophils fail to fall.^1,2

Prevent recurrence and assess transplant need

After recovery, arrange hepatology-led secondary prophylaxis, cirrhosis complication care and transplant assessment where appropriate; do not prescribe routine primary prophylaxis to all ascitic patients.^3,1,2

Exam traps

Absence of guarding or rigidity does not exclude SBP in cirrhosis.
Culture-negative neutrocytic ascites is treated as SBP.
Do not use an old fixed cefotaxime or ciprofloxacin regimen without checking local resistance, the BNF and healthcare-associated risk.
Albumin is not a substitute for antibiotics; apply the renal-function indication and monitor for fluid overload.
Multiple organisms or poor treatment response should trigger a search for secondary peritonitis, not simply broader antibiotics.
NICE primary-prophylaxis guidance is not the same as secondary prophylaxis after a previous SBP episode.

Illustrations

Ascitic fluid obtained at diagnostic paracentesisA clinical image of yellow ascitic fluid obtained at paracentesis, labelled to emphasise that visual appearance cannot diagnose or exclude SBP and that cell count and culture are required.BozmanDima, Wikimedia Commons · CC-BY-SA-4.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.