THE POST-REDUCTION DONUT SIGN

A donut-shaped intestinal structure in the lower right abdomen, observ ed during abdominal ultrasound investigation following nonoperative in tussusception reduction, may create a diagnostic problem concerning di fferentiation from a residual or recurrent intussusception or underlyi ng small bowel disease. In 30 cases of ileocolic intussusception an ab dominal ultrasound examination was performed after reduction, the succ ess of which was proven by radiological and clinical criteria. More th an half of the examinations showed an aperistaltic ''donut'' in the il eocecal region which was similar to the target sign commonly seen in i ntussusception. Differentiation was possible according to the followin g two criteria: first, the diameter of the donut was smaller than that of the original target sign seen in these patients. Second, the donut consisted of a broad hypoechoic rim and an echogenic center, whereas the target was normally composed of multiple concentric rings. One thi rd of the patients showed localized thickening of the walls of the dis tal ileal loops which did not cause diagnostic problems. All of the su spicious intestinal structures disappeared within the first 5 days fol lowing reduction. It is our opinion that the post-reduction donut corr elates with significant edema of the ileocecal valve and does not repr esent a mechanical lead point or persisting residual intussusception.