Risk factors for development of spontaneous bacterial peritonitis and subsequent mortality in cirrhotic patients with ascites.

Background: Patients with ascites are at risk for developing spontaneous bacterial peritonitis (SBP) - a severe complication associated with high mortality. We aimed to identify risk factors for SBP development and mortality to optimize stratification for primary prophylaxis and therapeutic strategies to improve survival.

Methods: 575 patients with cirrhosis and ascites undergoing paracentesis at a tertiary care hospital were included in this retrospective cohort study. Demographical, clinical and laboratory parameters were recorded at first paracentesis and during follow-up. Multivariate logistic regression analysis was used to identify independent predictors of SBP development and mortality.

Results: Child-Pugh stage C (OR: 3.323; P = 0.009), ascitic fluid polymorph-nuclear cell (PMN) count (OR: 1.544; P = 0.028) and low serum sodium (OR: 0.917; P = 0.029) emerged as independent risk factors for SBP development. SBP-naïve patients undergoing paracentesis and presenting with PMN-counts ≥100 cells/μl, or hyponatraemia <125 mM were at highest risk for developing SBP. Increases in MELD and CRP levels indicated SBP development, while no changes where observed in a matched control group with sterile ascites at multiple paracenteses. MELD score (OR: 1.565; P = 0.001) and CRP (OR: 1.067; P = 0.037) were identified as independent risk factors for 30-day mortality after SBP diagnosis. In particular SBP patients with MELD≥22, CRP ≥3.5 mg/dl and development of grade III/IV hepatic encephalopathy showed highest mortality.

Conclusions: Low serum sodium levels, Child-Pugh stage C and elevated ascites PMN counts (≥100 cells/μl) indicate a significant risk for SBP development. SBP-related mortality is highest in patients with MELD≥22 and elevated CRP levels.