Intussusception of the intestines. intussusception (upper centre) of the small intestine. Intussusception is a condition in which part of the intestines telescopes into an adjacent part. It causes abdominal pain, nausea and bleeding from the rectum, and the condition is fatal if not corrected. In most cases, introducing a barium enema, a solution of barium salts that is opaque to X-rays, can both diagnose and treat the condition. However it can recur, and surgical correction is then required.