Pneumatosis coli: a proposed pathogenesis based on study of 25 cases and review of the literature.

Pneumatosis coli is a rare condition characterised by multiple gas-filled cysts within the bowel wall. We present 25 cases treated over the past 30 years. The patients' mean age was 59 years: 15 were female. Presenting symptoms included diarrhoea (n = 17), mucus discharge (n = 17), rectal bleeding (n = 15) and constipation (n = 12). Pneumatosis usually affected the left colon (96%), and diagnosis was by sigmoidoscopy and biopsy in 18 cases (72%). Pneumatosis coli was associated with psychiatric disorders (36%), chronic lung disease (20%) and colitis (12%). A redundant sigmoid colon was observed in 80% of cases on contrast radiology. Five patients had mucosal pseudolipomatosis on histological examination. Histological and immunohistochemical review indicated that the cysts were lined by cells of macrophage/monocyte phenotype and that many similar mononuclear cells were present in the adjacent submucosa and overlying mucosa. Treatment with antidiarrhoeals and anti-inflammatory drugs in 14 patients resulted in improvement in 9 cases (64%). Oxygen therapy (n = 9) always alleviated symptoms. There was a high recurrence rate (50-78%), but with further courses of therapy lasting remission was achieved in five patients. Two patients underwent colectomy. The associations of pneumatosis coli with psychiatric disorders and mucosal pseudolipomatosis are new and of possible pathogenetic significance. A novel pathogenetic mechanism is suggested to explain the association of pneumatosis coli and chronic respiratory disorders. A model of pneumatosis coli linking some of the apparently disparate pathogenetic theories is proposed.