AKT · Gastroenterology/Liver

Ascites & spontaneous bacterial peritonitis

Peritoneal fluid accumulation (portal hypertension) ± infection (SBP)

Overview

Accumulation of fluid in the peritoneal cavity. In cirrhosis it results from portal hypertension + low albumin (high serum-ascites albumin gradient, SAAG ≥11 g/L). Managed with salt restriction, spironolactone (± furosemide) and drainage for tense ascites. SPONTANEOUS BACTERIAL PERITONITIS — infection of the ascitic fluid (neutrophils ≥250/mm³) without a surgical source — must be excluded by diagnostic tap in any decompensating cirrhotic and treated with antibiotics.

Recognise

Abdominal distension/discomfort, shifting dullness, fluid thrill, weight gain; ± peripheral oedema; dyspnoea if tense
Portal-hypertensive cause: high SAAG (≥11 g/L) — cirrhosis, heart failure, Budd-Chiari; low SAAG (<11) — malignancy, TB, nephrotic, pancreatic
SBP: fever, abdominal pain, worsening encephalopathy/renal function in a cirrhotic — or SILENT; ascitic neutrophils ≥250/mm³

Red flags

SBP (ascitic neutrophils ≥250) → antibiotics + albumin; high mortality and recurrence
Tense ascites with respiratory compromise → therapeutic paracentesis (+ albumin cover)

Differentials & how to tell them apart

Cardiac asciteshigh SAAG but with raised JVP/heart failure — not portal-hypertensive cirrhosis

Malignant ascitesLOW SAAG, positive cytology — peritoneal/ovarian/GI malignancy

Secondary bacterial peritonitisa surgical source (perforation) — multiple organisms, very high neutrophils, needs surgery not just antibiotics

Investigations

DIAGNOSTIC ASCITIC TAP in every new/decompensating ascites: cell count (neutrophils ≥250 = SBP), albumin (SAAG), culture, cytology (malignancy), amylase. U&Es, LFTs, albumin, INR.

Management

Salt restriction + spironolactone (±furosemide); SBP → antibiotics + albumin

1Diagnostic ascitic tap in everyone (cell count + SAAG + culture + cytology). Cirrhotic ascites: salt restriction + spironolactone (± furosemide); therapeutic paracentesis with albumin cover for tense ascites.Gate: Always tap NEW/decompensating ascites to EXCLUDE SBP (neutrophils ≥250) — it is often silent and lethal; SBP is treated with antibiotics + albumin, whereas SECONDARY peritonitis (a surgical source) needs surgery
2Refractory ascites → repeated paracentesis/TIPS/transplant; SBP → IV antibiotics + albumin + long-term prophylaxis; treat the underlying liver disease.

Salt restriction + spironolactone (± furosemide) — first-line for cirrhotic ascites

Therapeutic paracentesis + IV albumin — for tense/refractory ascites (albumin to prevent post-paracentesis circulatory dysfunction)

IV antibiotics (e.g. cefotaxime) + albumin for SBP; secondary prophylaxis — prophylactic antibiotics in high-risk patients

Key points

Ascites → tap it (SAAG splits portal-hypertensive [≥11] from malignant/other [<11]; neutrophils ≥250 = SBP). Cirrhotic ascites: spironolactone-based; tense → drain with albumin. Never miss silent SBP in a decompensating cirrhotic.

Monitor & prognosis

Weight, renal function/sodium; SBP recurrence.

Ascites/SBP mark advanced liver disease.

Source: EASL; BSG; NICE