Zonal colonic aganglionosis.

The customary approach to the diagnosis of Hirschsprung's disease is based on the existence of a single distal aganglionic region extending to the anal margin. Segmental aganglionosis, however, may involve only a limited segment of colon which is interposed between lengths of normal bowel. Awareness of this variant aids in the interpretation of the barium enema in children with signs and symptoms of aganglionosis, especially when the rectal biopsy is normal.