Toxic megacolon

Case contributed by Dr Vu Tran

Presentation

3 days of worsening abdominal pain, diarrhea and vomitting. Tachycardic, febrile with raised inflammatory markers.

Patient Data

Age: 20 years
Gender: Male
CT

Large amount of fecal material in the rectum and distal sigmoid, with the remainder of the colon back to the hepatic flexure demonstrating gaseous distension and measuring up to 8 cm in diameter. Further fecal material is seen in the cecum and ascending colon. No distension of the small bowel, likely reflecting a competent ileocecal valve.
Small amount of free fluid. No organized collection. No extraluminal gas or pneumatosis.

Circumferential wall thickening of the colon is demonstrated from the splenic flexure to the rectum. Engorgement of the paracolic veins and engorgement of the inferior mesenteric vein. Reactive prominence of the draining mesenteric nodes. An indwelling catheter balloon is present in the urinary bladder.

Conclusion:
Long segment colitis from the rectum to the splenic flexure, with marked gaseous distension. The possibilities include infective and inflammatory colitides. In that context the dilated appearance may be in keeping with toxic megacolon.
Another possibility is stercoral colitis, with a migrating fecal bolus currently in the rectum.

He met the clinical criteria of toxic megacolon 1, 2. There was colonic distension of the transverse colon measuring 8.5cm. He was febrile at 38ºC, tachycardia at HR >148 and anaemic at Hb 105 g/L. He also had hypotension of SBP 92 and severe electrolytes disturbances with serum magnesium of 0.51mmol/L and phosphate 0.44 mol/L on admission.

He had an emergency operation.

A flexible sigmoidoscopy was performed first. It demonstrated diffuse severe inflammation in the descending colon (Figure 1 and 2). The colitis was associated with ulcerations and pustules. It endoscopically resembled pseudomembranous colitis. Large amount of gas and diarrhoea was evacuated from the colon to facilitate laparoscopic surgery.

He then proceeded to have a laparoscopic hand assisted total colectomy and ileostomy. Findings included a very distended upper rectum measuring 14cm.

Photo

Flexible sigmoidoscopy. Figure 1) Diffuse severe inflammation in the descending colon with ulcerations and pustules. Figure 2) Patchy erythema of sigmoid colon. 

Case Discussion

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.

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Case information

rID: 79504
Published: 5th Jul 2020
Last edited: 5th Jul 2020
Inclusion in quiz mode: Included

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