Heterotopic mesenteric ossification after total colectomy for bleeding diverticulosis of the colon--a rare case report.

Heterotopic bone formation within an abdominal incision is a rare sequela of abdominal surgery. Only a few previous reports have noted heterotopic ossification in the mesentery of the small intestine and peri-ileostomy. Here, we report the case of a 60-year-old man who underwent emergent laparotomy and total colectomy with end ileostomy and developed this condition 1 month postoperatively. Heterotopic ossification in the peri-ileostomy tissue caused stenosis of the ileostoma. Laparotomy for re-anastomosis due to a large bone formation at an abdominal midline scar is very difficult and results in a massive abdominal wall defect. Therefore, we used a lower transverse incision to avoid the site of bone formation and resected the terminal ileum with its ossified mesentery. Then, we successfully carried out an anastomosis between the ileum and the rectum. The possible pathogenesis is a metaplastic mechanism of differentiation of immature multipotent mesenchymal cells. Our case provides the experience of treatment and new perspective on currently held hypotheses of heterotopic bone formation.