INTUSSUSCEPTION - US FINDINGS WITH PATHOLOGICAL CORRELATION - THE CRESCENT-IN-DOUGHNUT SIGN

PURPOSE: To determine the characteristic ultrasound (US) findings of i ntussusception and to explain its different components. MATERIALS AND METHODS: Three intussusceptions were surgically induced in pigs, and i n vitro US scans were compared with the corresponding pathologic slice s. US findings in 44 cases of pediatric intussusception confirmed by m eans of saline enema examination were analyzed. RESULTS: Axial images of intussusception showed a doughnut pattern. The hypoechoic external ring was formed by the everted returning limb of intussusceptum and, t o a lesser degree, by the intussuscipiens. The doughnut's center varie d according to the scan level. Scans obtained at the middle or at the base of the intussusception showed a characteristic hyperechoic cresce nt in all cases. This crescent was formed by the mesentery enclosing t he entering limb of the intussusceptum, which the authors have termed the ''crescent-in-doughnut sign.'' On scans obtained at the apex of th e intussusception, the center was hypoechoic owing to the entering lim b of the intussusceptum and the absence of the mesentery. CONCLUSION: The crescent-in-doughnut sign appears to be a characteristic feature o f intussusception.