Intussusception: Trapped peritoneal fluid detected with US - Relationship to reducibility and ischemia

PURPOSE: To determine the frequency and meaning of fluid inside the intussusception at ultrasound (US) and its relationship to irreducibility and ischemia. MATERIALS AND METHODS: US enabled the diagnosis of intussusception in 145 cases. Shape and axial diameters of the area of fluid were determined. US-guided hydrostatic reduction was attempted in 144 cases. RESULTS: Fluid was present in the intussusception in 20 cases (14%) and appeared on axial images as an anechoic crescent between both serosal layers of the enfolded and everted intussusceptum. No cystic structural anomaly was detected at surgery. Rates of reduction were 89% (111 of 125) in cases without fluid and 26% (five of 19) in cases with fluid (P < .001). At surgery, ischemia was absent in all 14 cases without fluid and present in 10 of 20 cases with fluid; necrosis was present in two cases with fluid. Areas of fluid greater than 14 x 5 mm, especially if associated with fluid in the dilated apex of the intussusception, were strongly related to irreducibility and ischemia (odds-likelihood ratio, 67.5). CONCLUSION: Fluid seen inside the intussusception represented trapped peritoneal fluid. Substantial amounts of fluid were associated with irreducibility and ischemia.