Ultrasound features of intussusception predicting outcome of air enema

To examine features identified on US which predict success or failure of air-enema reduction of intussusception.

A retrospective study of 117 consecutive episodes of intussusception, presenting for US over a 6-year period. The specific features examined were: free fluid within the peritoneum, small-bowel obstruction, colonic wall thickness, and fluid trapped between the colon and the intussusceptum.

The overall reduction rate, irrespective of US features, over the 6-year period was 72 %. Reduction rates were significantly higher with the absence of free fluid, trapped fluid, or small-bowel obstruction (93 %). The presence of trapped fluid predicted an unfavourable outcome, with a significantly lower success rate (25 %). Colonic wall thickness did not predict outcome; in successful reductions, mean wall thickness was 7.2 mm and in failed reductions 7.6 mm.

Where free fluid, small-bowel obstruction, and trapped fluid are absent, almost 100 % success with air-enema reduction should be achievable. Where trapped fluid is present, air enema should be performed cautiously to avoid perforation caused by overvigorous attempts at pneumatic reduction of an incarcerated intussusception.