INFLAMMATORY BOWEL-DISEASE - THE PATHOLOGY OF RECURRENCE

Current knowledge of the pathology of recurrent Crohn's disease is derived from study of endoscopic biopsies of recurrent lesions and surgical re-excision specimens. The main site of recurrence is the neoterminal ileum. The first lesions identified endoscopically are aphthous ulcers. Later lesions are serpiginous ulcers separating nodular mucosal remnants. Finally stenosis of the neoterminal ileum or anastomosis develops. Even though the terminal ileum looks normal endoscopically there may be focal inflammation on biopsy indicating that inflammation precedes ulceration. Granulomas are also early lesions. Mucosal regeneration, gastric metaplasia, submucosal lymphoid follicular aggregates and transmural inflammation follow ulceration in time. Strictures and sinuses are late complications. In re-excision specimens sinuses and fistulae may arise at the anastomosis. The absence of disease at resection margins does not prevent recurrence and there is no indication for frozen section of the margins at surgery. Disease at a resection margin does not affect postoperative anastomotic integrity. These facts emphasize that the principle in the surgical management of Crohn's disease should be conservation of tissue. Crohn's disease confined to the appendix is not followed by development of Crohn's disease of the bowel in the vast majority of instances. Ulcerative colitis does not recur following colectomy and ileostomy. Chronic ileal pouchitis refractory to antibiotic therapy may have a histological appearance resembling either ulcerative colitis or Crohn's disease. The former may represent a recurrence of ulcerative colitis and the latter a misdiagnosis of Crohn's disease, but the biology and natural history of the various forms of pouchitis are not yet elucidated.