Peritonitis is one of the major complications of peritoneal dialysis (PD) and, despite reductions in overall peritonitis rates, remains the primary reason why patients switch from PD to hemodialysis (HD) [1,2]. Observational data from a national cohort of incident PD patients starting dialysis in 2000 suggested that 5 percent of patients transferred to HD because of peritonitis during the first year (versus 4.2 for catheter related problems, 3.9 for adequacy issues, and 2.6 for psychosocial issues). Percentages were similar for year two . These authors also noted that the rate of transfer to HD because of peritonitis during year one showed a progressive decline from 1999 to 2001.
The overwhelming majority of peritonitis cases are caused by pathogenic bacteria, with a small number of cases being caused by fungi, mostly Candida species. The role of viral infection is uncertain. Although anecdotal cases of viral peritonitis have been reported , viruses are more likely to predispose patients to bacterial peritonitis [5,6].
Peritonitis is not only a cause of morbidity but can also result in mortality. In one retrospective Spanish study of 565 patients, 41 of 693 episodes of peritonitis resulted in death (6 percent) . The highest mortality was associated with specific organisms, particularly fungus (28 percent of deaths), enteric organisms (19 percent) and Staphylococcus aureus (15 percent). Data from the United States similarly suggest that mortality is related to the specific infectious pathogen; it was less than 5 percent overall in one study  and 3.5 percent overall in another .
Peritonitis is also associated with increased risk of death from non-infectious causes. In a study of 1316 PD patients who died while being treated with PD or within 30 days of transfer to hemodialysis, there was a much greater risk of having had peritonitis within the four months prior to death compared with the rest of the year, even though the immediate cause of death was not attributed to peritonitis in the majority of cases . In particular, there was a marked increase in the risk of having had peritonitis in the 30 days prior to death among patients who died of cardiovascular, cerebrovascular or peripheral vascular disease (odds ratio 3.4, 95% CI 2.4-4.6).
The microbiology and therapy of peritonitis in patients treated with CAPD will be reviewed here. The approach to the diagnosis of peritonitis, including exclusion of predisposing intraabdominal diseases (such as pancreatitis), is discussed separately. (See "Clinical manifestations and diagnosis of peritonitis in peritoneal dialysis".)