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Ascites and spontaneous bacterial peritonitis

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Every patient with cirrhosis and ascites admitted urgently to hospital needs prompt diagnostic paracentesis, especially with pain, fever, hypotension, confusion, gastrointestinal bleeding or kidney injury. An ascitic neutrophil count at or above 250 cells/mm³ is treated as SBP without awaiting culture. Start context-appropriate intravenous antibacterials, assess organ failure and give albumin when indicated; repeat evaluation if response is poor. Marked abdominal tenderness, free air, multiple organisms, very high inflammatory burden or failure on treatment raises secondary peritonitis and demands urgent CT and surgical review.

Synopsis

Diagnose new ascites with prompt paracentesis, treat portal fluid retention safely and recognise spontaneous bacterial peritonitis before renal failure develops.

  • Ascites in cirrhosis results from portal hypertension, splanchnic vasodilatation, neurohumoral sodium retention and impaired free-water handling rather than low albumin alone.
  • New-onset ascites requires diagnostic paracentesis to confirm portal aetiology and exclude malignancy, infection, cardiac disease, pancreatic disease or tuberculosis.
  • A serum-ascites albumin gradient of at least 11 g/L supports portal hypertension but does not identify the exact hepatic or cardiac cause.

Key red flags

Tense symptomatic ascites

Marked abdominal pressure causes pain, dyspnoea, poor intake, reflux or an umbilical hernia and usually needs therapeutic paracentesis.

Investigation priorities

01
Diagnostic paracentesis cell count and differentialFirst step

Identify neutrocytic ascites and establish the SBP treatment threshold.

Management branches

New ascitesTap before assuming the cause

Ascites is newly detected or a cirrhotic patient with fluid is admitted.

  1. Assess haemodynamics, respiratory compromise, pain, encephalopathy, bleeding and kidney function and identify a safe paracentesis site with ultrasound when needed.
  2. Send cell count and differential, albumin and protein, inoculate culture bottles at the bedside and pair with same-day serum albumin.

Key medicines

Spironolactone with or without furosemideFor suitable moderate first ascites, BSG guidance starts spironolactone 100 mg daily; recurrent or severe fluid may start spironolactone 100 mg with furosemide 40 mg daily, titrated stepwise only under weight, renal and electrolyte monitoring.
Empiric intravenous antibacterial for SBPStart the current local cirrhosis-sepsis regimen immediately, choosing the agent and dose from community versus nosocomial acquisition, recent prophylaxis or cultures, allergy, kidney function and local resistance patterns.
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Sources and review status6 sources · checked 27 Aug 2026 · clinical review pending
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom