A case of asymptomatic pneumatosis intestinalis caused by a non-toxigenic Clostridium difficile in a woman affected by hereditary nonpoliposis colorectal cancer (HNPCC)

Clinical History

67-year-old woman with HNPCC (Lynch Syndrome) with a history of sigmoid cancer surgically removed 4 years before with anterior resection of sigma and end-to-end anastomosis. The woman now presented with alteration of bowel habits and mixorrhoea (mucus in stools). The patient performed a water-enema Computed Tomography for cancer follow-up.

Imaging Findings

Water-enema CT images revealed multiple gaseous cysts filling the walls of the entire descending colon and sigma till the surgical anastomosis (localized at 12 cm from the anus). Cysts reach 18 millimeters in maximum diameter. No cyst was found in the right colon, in the transverse colon and in the rectum. There was not mural thickening and no abnormal enhancement pattern at any level of the colon. Mesenteric fat was normal and changes like oedema or vessel enlargement were not visible. Free fluid in the abdomen was not present. No signs of intestinal obstruction like distention or air-fluid levels were found. No pneumoperitoneum and no gas in the portal system were present. No mesenteric arteries or veins occlusion were detectable. These findings suggested a diagnosis of pneumatosis intestinalis.

Discussion

The presence of gas in the bowel wall can be primary (15%), and predominantly involves the large bowel; secondary (85%) in case of underlying disease and most often involving the small bowel and occurring in various clinical settings, up to being an alarming sign of intestinal ischaemia [1, 2].
Three hypotheses have been proposed to identify the source of the gas within the walls: intraluminal gas, bacterial production of gas, and pulmonary gas with a yet unclear mechanism [2, 3, 4].
Endoluminal gas can reach the intestinal wall as a result of increased intraluminal pressure in the setting of a normal mucosal barrier as occurring in vomit, blunt abdominal trauma [5], intestinal obstruction, endoscopy [2]. Enhanced gut permeability to gas can also be induced by defects in the mucosa or in the gut's immune barrier (intramural lymphoid tissue) as seen in patients with pneumatosis due to immunodeficiency, immunosuppressive or cytotoxic therapy [1, 6] that present a normal intraluminal pressure. A defect in the mucosa or an immune deficiency can also lead to the direct invasion and damage of the wall by the gas-producing bacteria.
In our case we ruled out: intestinal ischaemia: because mesenteric arteries were normal and no changes of bowel wall and mesenteric fat were found; obstruction: because no distention or air-fluid level were present; perforation: because there was no pneumoperitoneum and no free fluid.
Therefore endoscopic biopsies were performed and no lesions or any kind of pathogen were found at the level of the bowel wall at the anatomopathological analysis. A repeated stool culture was positive only for Clostridium difficile but negative for both the Clostridium toxins A and B. Another finding was the melanosis of the colon, more evident on the right side, possibly caused by a previous abuse of laxative drugs. Pneumatosis resolved within two months of metronidazole therapy. Our patient had several conditions that may have caused or at least favoured the onset of pneumatosis. Repeated colonoscopies (for HNPCC screening) may have increased stress on the intestinal wall due to the air pressure generated during endoscopy. Melanosis coli is a sign of damage of the intestinal parietal cells that may have facilitated the air passage across the mucosa [7]. The discovery of C. difficile in stool culture suggested an action of bacteria in the formation of pneumatosis supported by the efficacy of therapy with metronidazole. In particular the absence of the toxin could explain the lack of intestinal symptoms.

Differential Diagnosis List

Final Diagnosis

Pneumatosis intestinalis

URL:	https://www.eurorad.org/case/12637
DOI:	10.1594/EURORAD/CASE.12637
ISSN:	1563-4086