Atypical rectosigmoid histology in children with newly diagnosed ulcerative colitis.

BACKGROUND: In the untreated patient with inflammatory colitis, rectal sparing or patchy rectal inflammation is generally considered a sign of Crohn's disease (CD), rather than ulcerative colitis (UC).
METHODS: The initial endoscopic rectosigmoid mucosal biopsies obtained at disease onset from 12 untreated children with UC who ultimately required surgery were blindly reviewed (randomly mixed with another 62 specimens obtained from children with CD or treated UC). Biopsies were classified as typical UC if there was diffuse, active inflammation and severe crypt destruction or distortion. Those with patchy, active inflammation and only mild crypt changes were classified as CD. Because all 12 subjects had ultimately been proven to have UC by examination of a subtotal colectomy specimen, for the purposes of this report biopsies read as either normal or CD were both considered evidence of atypical UC with rectal sparing.
RESULTS: Five of 12 subjects (seven biopsies) had atypical histology. Mild, patchy inflammation was seen in six rectal or sigmoid biopsies, whereas one rectal biopsy was normal. The remaining seven subjects (10 biopsies) had diffuse inflammation. Two of five subjects with atypical biopsies had an endoscopically normal rectosigmoid, one had patchy inflammation, and the remaining two had diffuse endoscopic changes. All seven subjects with typical UC histology had diffuse endoscopic changes. Subjects with atypical findings could not be differentiated by age, duration, or types of symptoms at presentation, years of disease at colectomy, or indications for colectomy.
CONCLUSIONS: Patchy or absent inflammation of the rectum and sigmoid can be present in untreated children with UC at disease onset. Because such children may be mistakenly diagnosed as having CD, these data must be considered when treatments or clinical research protocols are designed to include children with colitis.