Pre-operative fecal pathogen multiplex PCR did not detect fecal pathogens and was negative for Clostridium difficile.

Histopathology report:
Macroscopic description:
Total colectomy: A colectomy specimen consisting of two segments of bowel. Larger segment consists of small bowel 30 x 20mm. Appendix 40 x 8mm and colon and cecum 270mm with a diameter of up to 120mm. The serosal surface is diffusely congested. Bowel wall is thinned in some areas up to a thickness of 2mm. The mucosal surface is diffusely tan brown and ulcerated with no focal lesions. The appendix is unremarkable. Second segment measures 440mm in length with a diameter of up to 85mm. The serosal surface is also congested. Bowel wall thickness measures between 1mm and 5mm. The mucosal surface is ulcerated with a brown tan appearance. There are no focal lesions. Four lymph nodes identified measuring between 6mm and 13mm in diameter.

Microscopic description:
Sections of the colon show widespread mucosal hemorrhage, focal erosion covered by fibrinopurulent exudate. There is no severe crypt distortion to indicate chronic colitis. The lamina propria is infiltrated by numerous pigment laden macrophages, consistent with melanosis coli. There is no prominent diffuse active chronic inflammation and lymphoid aggregates are mainly mucosal. No granulomas are found. The submucosa shows massive edema, severe congestion and focally hemorrhage. The muscularis propria is preserved in most places and no necrosis or degeneration of muscle fibers are seen. The bowel is markedly attenuated in places and there is mucosal ulceration and infiltration by neutrophils extending to the submucosa. No perforation is seen. Proximal ileal and distal colonic margins shows relatively normal viable bowel. There is no dysplasia or malignancy. The appendix shows focal mucosal acute inflammation. All the lymph nodes sampled show mild reactive changes only. Features are consistent with toxic megacolon. There is no evidence of chronic inflammatory bowel disease as a predisposing cause. Acute infectious colitis could be a possibility.
Diagnosis: total colectomy: toxic megacolon.

His post-op recovery was complicated by ileus and small bowel obstruction. He was discharged home 26 days post-operation.

The cause of toxic megacolon was not identified on histopathology. It was unlikely to be caused by inflammatory bowel disease or ischemia. It is favored to be infectious in origin even though the fecal pathogen PCR was inconclusive. A retrospective study of 70 patients between 1985 to 2004 for toxic megacolon treated surgically demonstrated: 46% of cases were caused by ulcerative colitis, 34% infectious colitis and 11% was due to ischemic colitis ³.