We compared the postoperative course in children and teenagers who underwent subtotal colectomy, mucosal proctectomy, and either straight ileoanal anastomosis (group 1, n = 8) or ileal pouch-anal anastomosis (group 2, n = 10) for the surgical treatment of idiopathic ulcerative colitis (n = 15) and familial polyposis coli (n = 3). Two of eight children in group 1 developed intractable diarrhea that persisted despite revision of the anastomosis to include an ileal pouch; therefore, ileostomies were necessary in both cases. One patient in group 2 had a diverting ileostomy as a result of abscess formation at the site of the ileoanal anastomosis. Despite a longer period of postoperative follow-up (48.9 +/- 11.8 months), the remaining six patients in group 1 had a significantly greater number of bowel movements each day (7.8 +/- 6.5) as compared with the nine patients in group 2 who had 4.8 +/- 2.6 stools each day (p less than 0.05) at a mean follow-up of 15.7 +/- 9.0 months. A proportion of children in both groups had a poor postoperative functional outcome as determined by fecal incontinence (2 of 6 in group 1, 6 of 9 in group 2), perianal dermatitis (2 of 6, 4 of 9), and therapy with the antidiarrheal agent loperamide (4 of 6, 2 of 9). Increased school attendance (5 of 6, 7 of 7) and improvement in level of participation in social activities (5 of 6, 7 of 7) as compared with the 6-month period prior to surgery occurred, however, for most of the children with ulcerative colitis in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)