To describe the clinical and microbiological aspects of high-risk peritonitis and to analyze their impact on its outcome.

This was a retrospective review of all culture-positive peritonitis between October 1, 2005 and September 30, 2009. In accordance with recent Infectious Diseases Society of America (IDSA) guidelines, a group of high-risk peritonitis patients was selected based on age, severity of illness, underlying diseases, and acquisition of the infection.

Ninety-three patients with high-risk peritonitis were studied; these patients were divided into subgroups of those with community-associated disease (14%) and those with healthcare-associated disease (86%). The median age of patients was 66 (interquartile range (IQR) 22–95) years. The 30-day mortality rate was 25%. Subgroups differed in age (p=0.011), degree of comorbidity (p=0.023), severity of peritonitis (p=0.036), admission to the intensive care unit (ICU) (p=0.002), length of ICU stay (p<0.001), length of hospital stay (p<0.001), cure at day 30 (p=0.001), and adequate treatment (p=0.042). The microbiological etiology and resistance profiles were similar between the patient groups. Adequate empirical treatment was not related to a better outcome. Severity of disease (p=0.005) and the presence of enterococci (p=0.044) were independently associated with mortality.

The mode of acquisition influences severity and certain parameters of outcome in high-risk peritonitis, but not its microbiological etiology. The outcome seems to depend primarily on severity of peritonitis and much less on the adequacy of treatment.