Peritonitis: limiting the damage.

Reducing the morbidity associated with peritonitis is one of the major challenges to improve outcomes for patients on peritoneal dialysis (PD). In the short-term, during the actual episode, patients suffer pain, risk of hospitalization and social inconvenience, with extra and often numerous hospital visits. In one series, peritonitis accounted for 25% of hospital admissions for patients on PD [1]. In the long term, peritonitis is a major cause of patients transferring to haemodialysis, accounting for 13–54% of technique failure in longterm continuous ambulatory peritoneal dialysis (CAPD) patients [2] and 43% of patients on automated peritoneal dialysis (APD) [3]. Even in patients who recover from the initial episode, peritonitis causes other long-term sequelae, such as changes in membrane permeability and sclerosing peritonitis, which eventually contribute to technique failure. Severe or repeated episodes of peritonitis are particularly damaging to the peritoneal membrane. Davies et al. [4] showed that in the short term, single episodes had no significant effect on membrane permeability or ultrafiltration, while recurrences or clusters of infection caused an increase in membrane permeability and reductions in ultrafiltration. Interestingly, these changes were more marked with higher cumulative dialysate leukocyte counts, independently of the infecting organisms. Longitudinal studies have not shown that these effects on membrane transport persist for the long term (over years) [4,5]. However, such studies are difficult to interpret. Patients with severe peritonitis will probably not be included either because of poor ultrafiltration, or because of another episode of peritonitis. There is one study, though, that does suggest a subtle long-term ultrafiltration dysfunction after a single episode of peritonitis [6]. In vitro evidence shows that there are pathways from acute inflammation to longer term fibrosis and angiogenesis in the peritoneum that would explain the association between peritonitis and ultrafiltration dysfunction [7]. Sclerosing peritonitis is a rare but devastating complication in patients on PD. Mortality is high, with rates of 37.5% being reported [8]. Although sclerosing peritonitis is a complication predominantly of long-term PD, with most cases occurring after 5 years [8], peritonitis is also an important predisposing factor. A recent large multicentre study from Japan showed that 30% of patients with early-onset sclerosing peritonitis (before 10 years) was associated with peritonitis, though this was not true with onset after 10 years on PD. The Australian data also suggest that around a third of cases are directly associated with an episode of peritonitis [9]. Minimizing the impact of peritonitis in the patient on PD will have a considerable effect on their experience of PD and will also extend their time span on this modality. Several strategies are required to achieve this as shown in Box 1.