An 80-year-old woman was brought to our hospital in an ambulance because of signs of peritoneal irritation. Computed tomography revealed volvulus, sigmoid colon dilation, and free air and pneumatosis within the colonic and bowel wall. An emergency laparotomy was performed after the diagnosis of colonic perforation associated with volvulus or pneumatosis. Numerous gas-filled cysts, up to 10mm in diameter, were located in the resected bowel wall. The cells at the inner lining of the cysts tested positive for D2-40 immunoreactivity, seemingly originating from the lymphatic vessels. In many cysts, KP-1 positive small mononuclear cells and/or foreign-body-type giant cells adhered to the D2-40 positive cells were observed. Fibrosis and lymphoplasmacytic infiltration was observed around the cysts. Contrary to the influential mechanical cause theory, in the present case, pneumatosis may have preceded volvulus, occurring as an idiopathic disease. Therefore, the lymphatic vessels were hypothesized to be associated with the pathogenesis of PCI.