Your intestine is shaped like a long tube. In intussusception, one part of your intestine — usually the small intestine — slides inside an adjacent part. This is sometimes called telescoping because it's similar to the way a collapsible telescope folds together.
In some cases, the telescoping is caused by an abnormal growth in the intestine, such as a polyp or a tumor (called a lead point). The normal wave-like contractions of the intestine grab this lead point and pull it and the lining of the intestine into the bowel ahead of it. In most cases, however, no cause can be identified for intussusception