Closed loop onstruction represent a surgical emergency, because this lesion leads to small boweel infarction, perforation, and peritonitis if not treated in time. We analyzed the CT and ultrasonographic findings of 4 patients prospectively and 2 patients retrospectively with surgically proven closed loop obstruction of the small boweel to evaluate the characteristic findings, the cause of the closed loop obstruction and predictive criteria for the viablity of the involved bowel loop. The characteristic CT and sonographic features of the closed loop obstruction of the small bowel included; dilated fluid-filled bowel loops, the thickened bowel wall, absence of peristalsis, and ascites. In one case, closed loop obstructio originating from umbilical hernia was documented by CT and sonography. The possible criteria for the gangrenous changes could be the maximal thickness of bowel more than 7mm, and infiltration in the mesentery/omentum.