Intussusception isn’t what happens when a cornerback picks off a quarterback’s pass; it’s when the bowel acts like a telescope, folding in onitself. Frankly, this hurts like the dickens, and your child will be drawing her legs up to her abdomen. It happens most commonly in kids from three months to six years, and the condition also comes with a side order of fever, vomiting, and the passing of currant-colored, jellylike stool. To treat it, a doc will push an enema (either air- or barium-based) into the anus and up the bowel, to help un-telescope that part of the colon and relieve the pain. If the enema doesn’t work, surgery may be necessary.
Answer excerpted from You Raising Your Child