some centers utilize prone films or left lateral decubitus radiographs to enhance air movement into the cecum In the patient with symptoms longer than to 12 hours, flat and upright films often show signs of intestinal obstruction, including distended bowel with air–fluid levels ( Fig 116.5 ) A characteristic “target” sign may be seen, or more commonly a paucity of gas in the right lower quadrant Occasionally, the actual head of the intussusception can be seen on a plain film as a soft tissue mass ( Fig 116.8A ) US can be used diagnostically with reported sensitivity of 98% to 100%, demonstrating the “target sign” on the transverse view and the “pseudokidney sign” on the longitudinal view ( Figs 116.8B and 116.8C ) Whether all patients should have plain films prior to US is debatable If signs of intestinal obstruction or peritonitis, plain films may demonstrate pneumatosis or free air and thereby expedite operative care Oftentimes, the radiologist may request a plain film prior to enema reduction but not necessarily before US Plain films may be useful in settings where US is not immediately available, in order to exclude a diagnosis of intussusception when the pretest suspicion is low Hydrostatically controlled contrast enema or air insufflation enema has been a successful therapy in up to 70% to 95% of cases with higher success rates reported with air reduction Strict reduction guidelines must be followed to avoid perforation The full reduction of the intussusception is confirmed only when there has been adequate reflux of barium or air into the ileum Patients with peritonitis or free air on plain radiograph should not have an enema study or reduction attempt In the seriously ill infant with signs of peritonitis or a frank small bowel obstruction, the diagnosis of intussusception can be made with isotonic water-soluble contrast media with no attempt at reduction The reduction in such infants should be performed surgically Perforation rates with enema reduction have been reported in up to 3% Risk factors for failed reduction and perforation include: patient age younger than months or older than years; long duration of symptoms, especially if greater than 48 hours; hematochezia; significant dehydration; and evidence of small bowel obstruction on plain radiograph