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There has been recent controversy regarding the clinical significance of pneumoperitoneum in patients undergoing peritoneal dialysis. The incidence of pneumoperitoneum has been estimated to be 21.2% to 33.7% in prior studies of peritoneal dialysis patients. Of the peritoneal dialysis patients with pneumoperitoneum, only a small percentage (5.9% to 14.3%) had documented visceral perforations. The controversy arises in that anywhere from 20% to 100% of peritoneal dialysis patients with pneumoperitoneum and peritonitis had visceral perforation, and 32.4% to 57.1% of chronic ambulatory peritoneal dialysis patients had asymptomatic pneumoperitoneum of unknown etiology. These disparate incidences made clinical interpretation of pneumoperitoneum difficult. In addition, prior study result disagreed as to the usefulness of the extent of pneumoperitoneum in predicting visceral perforation. We retrospectively reviewed 694 chest x-ray film and acute abdominal series reports from 1982 to 1993 in 75 peritoneal dialysis patients, with 9.3 +/- 1.3 (mean +/- SEM) x-ray films per patient. The reports were confirmed by reviewing 363 x-ray films (52%). Eight patients (10.7%) had 10 episodes of pneumoperitoneum. Six of these eight patients had asymptomatic pneumoperitoneum from a known etiology: four had undergone abdominal surgery for catheter placement the prior week and two had catheter manipulation immediately preceding the x-ray. One patient had three episodes of pneumoperitoneum: one after catheter placement and two not associated with a known etiology for pneumoperitoneum while on the cycler. One patient had a surgically confirmed colonic perforation with a large pneumoperitoneum and peritonitis.(ABSTRACT TRUNCATED AT 250 WORDS)

In a retrospective study we reviewed upright chest x-ray films of 101 continuous ambulatory peritoneal dialysis (CAPD) patients to determine the incidence and significance of free subdiaphragmal air. A pneumoperitoneum (PP) was diagnosed if a minimal shadow of free air was detected under the diaphragm. The amount of free air was determined by measuring the height and width of the subdiaphragmal air shadow. Of all CAPD patients, 33.6% (34 of 101) had at least one occurrence of PP. Thirteen of these 34 patients (38.2%) were diagnosed within 30 days after catheter implantation, 10 patients (29.5%) acquired a PP during an episode of peritonitis, and in 11 patients (32.4%) no additional risk factor could be determined. Patients radiographed within 30 days after catheter implantation showed a statistically significant higher incidence of PP compared with the same patients radiographed later (22% v 10%; P < 0.05). The incidence of PP in CAPD patients suffering from peritonitis (33%) was significantly higher than in patients without peritonitis (10%; P < 0.001). The amount of free air did not differ statistically significantly between the investigated groups. Only two patients with PP and peritonitis had surgically confirmed visceral perforation. Therefore, the main reason for PP seemed to be handling faults during CAPD bag exchange. There was no correlation between the organisms causing peritonitis and PP or the CAPD connector system and PP. In conclusion, a PP occurs in approximately one third of all CAPD patients and a visceral perforation cannot be diagnosed by the occurrence and amount of free subdiaphragmal air.