FREQUENCY OF SPONTANEOUS BACTERIAL PERITONITIS IN PATIENTS PRESENTING WITH ASCITES

Abstract

Background: Spontaneous bacterial peritonitis (SBP) represents a potentially fatal complication in patients with ascites, traditionally considered predominant in cirrhotic patients due to bacterial translocation facilitated by portal hypertension, intestinal bacterial overgrowth, and immune dysfunction. However, the frequency and risk factors of SBP in non-cirrhotic ascites such as congestive heart failure, nephrotic syndrome, and Budd-Chiari syndrome remain inadequately characterized, particularly in resource-limited settings where diagnostic paracentesis is often restricted to patients with suspected liver disease. This knowledge gap may lead to underdiagnosis and delayed treatment, contributing to preventable morbidity and mortality. Furthermore, existing literature from Pakistan and South Asia has predominantly focused on cirrhotic populations, leaving a significant evidence vacuum regarding SBP epidemiology in diverse ascites etiologies.

Methods: This descriptive cross-sectional study was conducted at the Department of Medicine, Mufti Mehmood Memorial Teaching Hospital, Dera Ismail Khan, from 21^st April 2025 to 21^st July 2025. A total of 97 patients aged 18–75 years presenting with ascites of any etiology were enrolled using consecutive non-probability sampling. The sample size was calculated using the WHO sample size calculator assuming an anticipated SBP prevalence of 20.4%, 8% margin of error, and 95% confidence level. Patients with secondary peritonitis, prior abdominal surgery, or recent antibiotic exposure were excluded to minimize confounding. All participants underwent comprehensive clinical assessment and diagnostic paracentesis with ascitic fluid analysis including polymorphonuclear (PMN) neutrophil count, Gram staining, and aerobic/anaerobic cultures. SBP was diagnosed according to standard international criteria (ascitic fluid PMN count >250 cells/mm3 with exclusion of secondary causes). Data were analyzed using SPSS version 25.0 with appropriate parametric and non-parametric tests, binary logistic regression for multivariable analysis, and ROC curve analysis for diagnostic performance evaluation. Statistical significance was set at p<0.05.

Results: Among 97 patients, the mean age was 46.48±16.49 years (range: 18–75 years), with 56.7% (n=55) males and 43.3% (n=42) females. Cirrhosis accounted for 40.2% (n=39) of cases, followed by heart failure (29.9%, n=29), nephrotic syndrome (26.8%, n=26), and Budd-Chiari syndrome (3.1%, n=3). The overall frequency of SBP was 20.6% (n=20; 95% CI: 13.4%–28.9%). Notably, SBP occurred in 15.4% (6/39) of cirrhotic patients compared to 24.1% (14/58) of non-cirrhotic patients, though this difference was not statistically significant (p=0.321, Fisher's exact test). By specific etiology, SBP frequencies were: nephrotic syndrome 26.9% (7/26), heart failure 24.1% (7/29), cirrhosis 15.4% (6/39), and Budd-Chiari syndrome 0% (0/3) (χ2=2.283, df=3, p=0.516; Cramér's V=0.153). Gender showed no association with SBP (20.0% males vs. 21.4% females; χ2<0.001, p=1.000; OR=0.917, 95% CI: 0.336–2.503). Mean age was comparable between SBP (49.70±16.62 years) and non-SBP groups (45.65±16.46 years; t=1.000, df=95, p=0.320). Ascitic fluid PMN count demonstrated excellent discriminatory performance (AUC=0.994, 95% CI: 0.984–1.000, p<0.001), with SBP patients showing significantly elevated counts (mean: 1018.7±303.9 vs. 108.0±72.8 cells/mm3; Mann-Whitney U=195.0, Z=-5.089, p<0.001, effect size r=-0.517). At the standard 250 cells/mm3 threshold, sensitivity was 100% and specificity 77.9%. Culture-positive SBP occurred in 45.0% (9/20) and culture-negative neutrocytic ascites in 55.0% (11/20). Binary logistic regression identified no independent predictors of SBP (age: adjusted OR=1.020, p=0.270; male gender: OR=0.828, p=0.753; heart failure vs. cirrhosis: OR=1.749, p=0.456; nephrotic syndrome vs. cirrhosis: OR=2.082, p=0.343), though the overall model was significant (χ2=28.847, df=4, p<0.001, Nagelkerke R2=0.365).

Conclusions: Spontaneous bacterial peritonitis affects approximately one in five patients presenting with ascites, with comparable frequency across cirrhotic and non-cirrhotic etiologies in this population. The absence of significant demographic or etiological predictors underscores the necessity of routine diagnostic paracentesis in all patients with ascites, regardless of underlying cause or clinical presentation. Ascitic fluid PMN count remains a highly reliable diagnostic biomarker. These findings challenge conventional paradigms that restrict SBP screening to cirrhotic patients and support universal screening strategies to reduce SBP-related morbidity and mortality in resource-limited healthcare settings.