Free air on CT and the risk of peritonitis in peritoneal dialysis patients: a retrospective study

Background: Intra-abdominal free air is found frequently in patients undergoing peritoneal dialysis (PD). Some studies have investigated an association between intra-abdominal free air and peritonitis in PD patients. However, most used chest X-rays, which are of limited sensitivity, and the association was not made clear. We conducted a retrospective study of the association between peritonitis and intra-abdominal free air using computed tomography. Methods: The presence and volume of free air, and its relationship with other variables, were assessed on review of routine examinations in 108 patients. Correlations between the presence of free air and age, duration of PD, continuous ambulatory versus automated PD, presence or absence of a person who assisted in bag changes, exit-site infection, tunnel infection and peritonitis were assessed. Results: Free air was detected in 29 patients (27.1%). The prevalence of peritonitis was higher in the free air (+) group than in the free air (?) group: 1/40.2 patient-months for free air (+) versus 1/96.9 patient-months for free air (?). The risk ratio of free air for peritonitis was 2.41 (95% confidence interval: 2.28–2.55) and was similar when corrected for age, gender, albumin, diabetes mellitus and body mass index. Conclusion: Free air is an independent risk factor for peritonitis in PD patients. This suggests that bag change procedures should be re-evaluated, and patients re-educated, when necessary.