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In continuous ambulatory peritoneal dialysis (CAPD) the CAPD tube provides a portal of entry for both microorganisms and air into the peritoneal cavity. Bacterial/fungal colonization of the fluid, with abdominal symptoms and systemic upset, will usually settle with conservative measures1 but the presence of a pneumoperitoneum may or may not signify gastrointestinal perforation.
A woman aged 88 with end-stage renal failure (ESRF) of unknown origin had been using CAPD for a year when she experienced abdominal pain and noted cloudiness of the CAPD bags. She had generalized abdominal tenderness but was afebrile. On microscopy the peritoneal dialysis fluid contained > 100 leucocytes/mL and an erect chest X-ray revealed bilateral pneumoperitoneum. She was treated with intraperitoneal vancomycin and gentamicin and made steady clinical improvement. No organisms were cultured. She continues to use CAPD.
A man of 20 with ESRF from posterior urethral valves and with a history of two failed renal transplants reported abdominal pain and cloudy CAPD bags. He was pyrexial (39°C) and tachycardic, with generalized abdominal tenderness. An erect chest X-ray showed a small rim of free air under the right hemidiaphragm. The dialysis fluid contained > 100 leucocytes/mL and gram-positive cocci were isolated. After four days of intraperitoneal vancomycin and gentamicin he was discharged much improved. When fluid cultures grew coagulase-negative staphylococci he was prescribed a further eight days of intraperitoneal vancomycin.
A man of 66 with ESRF from renovascular disease had had a CAPD tube inserted two months after a laparotomy for omental patching of a perforated jejunal diverticulum. Vascular access difficulties had been an obstacle to haemodialysis. Five months later he was admitted with abdominal pain and cloudy CAPD bags. On admission he was afebrile but tachycardic with generalized abdominal tenderness. An erect chest X-ray revealed a small right pneumoperitoneum and the CAPD fluid contained > 100 leucocytes/mL. In view of the history, an urgent laparotomy was performed but there was no sign of a perforated viscus. The CAPD tube was removed, with extensive intra-abdominal lavage. A coagulase-negative staphylococcus was cultured from the CAPD fluid. This patient required intensive care postoperatively and his recovery was delayed by sepsis, angina, antibiotic-induced diarrhoea and a haematemesis. He awaits a definitive vascular access procedure.
Pneumoperitoneum has been reported in 11–34% of patients undertaking CAPD, usually in the absence of symptoms.2–4 It is only the small minority with abdominal symptoms who create a diagnostic dilemma. Among general surgical patients with gastrointestinal perforation 60–80% have free subdiaphragmatic air on an erect chest X-ray.5 In CAPD patients the specificity of this sign is much lower. Some workers have suggested that a large pneumoperitoneum is indicative of visceral perforation3–4 but this is not always so.6 Furthermore, peritoneal dialysis fluid may dilute the initial intraperitoneal contamination that follows gastrointestinal perforation and, together with intraperitoneal antibiotics, mask clinical signs.7 Regular assessment is essential in those treated conservatively. In addition, the content of the CAPD effluent can be revealing: it may contain faeces, food or bile. If it does not, microscopy and Gram stain can be done quickly. Mixed Gram-negative or anaerobic organisms suggest perforation; a single organism, particularly if a staphylococcus, is more consistent with CAPD peritonitis (as in cases 1 and 2). Individuals with ESRF are often elderly, with co-morbidity,8 and laparotomy presents a substantial risk.9 Also it may necessitate termination of this mode of dialysis, as in case 3. The decision to operate should be based on microbiological evidence and the clinical judgment of the surgeon.