Rectal biopsy in patients with Crohn's disease. Normal mucosa on sigmoidoscopic examination.

Of 99 patients with Crohn's disease whose rectal segment appeared normal on sigmoidoscopy, there was histologic inflammation in 45% and features characteristic of Crohn's disease in 30% of rectal biopsy specimens. Granulomas were found in 18% of patients, including 13% of those with ileitis, 13% of those with ileocolitis, and 37% of those with colitis. Eleven of the 17 granulomas were small undermarcated microgranulomas. Rectal biopsy specimens are of value to confirm the diagnosis in Crohn's disease and to determine the state of clinical activity even when the sigmoidoscopic appearance is normal.