Evolutionary changes in the pathologic diagnosis after the ileoanal pouch procedure

Inadequate initial differentiation between ulcerative colitis and Crohn's disease may lead to a diagnosis of indeterminate colitis. Construction of an ileoanal pouch in these patients may result in significant morbidity and pouch failure when the ultimate diagnosis is Crohn's disease.

We prospectively studied 543 patients with idiopathic inflammatory bowel disease to determine whether a patient's pathologic diagnosis changed with time and how it affected outcome.

Preoperative diagnosis was ulcerative colitis in 499 patients, indeterminate colitis in 42 patients, and Crohn's disease in 2 patients. Prior colectomy was performed in 58 percent of patients with ulcerative colitis and in all patients with indeterminate colitis and Crohn's disease. Postoperatively, the diagnosis changed in 20 patients with ulcerative colitis (13 to indeterminate colitis, 7 to Crohn's disease). Another two patients with indeterminate colitis showed evidence of Crohn's disease in the resected rectal specimen. As patients were followed up, an additional 13 patients were found to have Crohn's disease (5 indeterminate colitis, 8 ulcerative colitis). With the current diagnosis, perineal complications and pouch failure occurred, respectively, in 23 and in 2 percent of patients with ulcerative colitis, in 44 and in 12 percent of patients with indeterminate colitis, and in 63 and in 37 percent of patients with Crohn's disease. Pathologic diagnosis was altered in 35 patients (6 percent) overall, with a 12-fold increase in the diagnosis of Crohn's disease. Only 3 percent of patients with ulcerative colitis compared with 13 percent of patients with indeterminate colitis had a change in diagnosis to Crohn's disease (P = 0.006; Fisher's exact test).

Pouch-related complications, eventual pouch failure, and discovery of underlying Crohn's disease occurred in a significant number of patients with a diagnosis of indeterminate colitis. Until more accurate diagnostic differentiation is available, caution is advised in recommending the ileoanal pouch procedure to patients with indeterminate colitis.