The diagnostic accuracy of the rectal biopsy in acute graft-versus-host disease: a prospective study of thirteen patients.

We carried out a coded, prospective analysis of sequential rectal biopsies from 13 patients undergoing allogeneic bone marrow transplantation in order to study the accuracy of these biopsies in the diagnosis of acute graft-versus-host disease (GVHD). We also tested the hypothesis that individual crypt cell degeneration is the initial lesion of intestinal GVHD. Pretransplant biopsies were normal. All biopsies taken 7--10 days after transplantation were diffusely abnormal with nuclear atypia and crypt cell degeneration. These changes were due to the conditioning regimen of total body irradiation and chemotherapy and had resolved by day 20 after transplantation. When acute GVHD was present, rectal biopsies were focally abnormal with crypt cell degeneration, crypt dilation, and crypt abscess. Rectal biopsies were normal after day 20 in those patients who did not have clinical evidence of GVHD. The location of cell degeneration at the base of crypts suggests that an immunologic mechanism is responsible for damage to rectal mucosa in GVHD. The rectal biopsy is an accurate way of detecting intestinal involvement with acute GVHD if done after resolution of radiation/chemotherapy effects.