Intussusception is a condition in which one part of the intestine folds or "telescopes" into the part of the intestine immediately downstream. This causes obstruction of the intestine at the point where it telescoped, and is a surgical emergency (although nowadays intussusception is most often treated during the X-ray procedure used for diagnosis). Intussusception occurs in adults, but is much more common in children, especially those between age 6 months and age 3 years (4 out of 5 children with intussusception are 2 years old or younger).
The telescoping may happen when a lead (as in "leader") point -- a mass in the intestinal wall such as swollen lymph nodes, or a mass in the intestine such as a mass of hard stool (which can occur in cystic fibrosis) -- is pulled into and down the intestine just as if it were something to be digested. The pulling of the lead point also pulls down on the intestinal tissue above the lead point. However, a lead point is identified with certainty in only 1 out of 4 children with intussusception. Infections with adenovirus may make a child more susceptible to intussusception, possibly by causing lymph nodes to swell, and i seems to happen more often at times of the year when we see a lot of gastroenteritis (which may also cause swollen intestinal lymph nodes). Other infections, including ear infections, the flu, and even colds, may also make a child more susceptible to intussusception, although only a tiny fraction of children with infections develop intussusceptions. Children who received the first oral vaccine for rotavirus in the late 1990's were over 20 times as likely to have intussusception as children who did not receive the vaccine -- one reason why that vaccine was taken off the market. There have been some cases of intussusception with the new rotavirus vaccine, but the frequency of intussusception with the new vaccine is the same as for children who aren't vaccinated. Intussusceptions are also seen, although not very often, in children who have had recent abdominal surgery.
An intussusception can occur anywhere in the intestine from the jejunum (the part of the small intestine just after where the liver, bile ducts, and pancreas connect) to the colon (the large intestine). The terms we use to describe where an intussusception is located include:
The problem with an intussusception is that the telescoped intestine's inside diameter is much less than that of normal intestine. Also, and perhaps more important, the mesentery (the sheet of tissue that runs from the outside of the intestine to the back of the abdomen, and that contains all of the blood vessels and nerves supplying the intestine) is also pulled into the telescoping intestine. The compression pinches the blood vessels, and the lack of blood to that section of intestine causes the section to swell, making the compression worse. If left untreated, the "intussuscepted" intestinal tissue will die and become infected, and possibly perforate, spilling intestinal contents into the abdominal cavity.
A child with an intussusception usually develops intermittent crampy abdominal pain, which is severe and progressively worsens. Initially the pains come every 15-20 minutes, but become more frequent and more severe with time. The child may cry inconsolably and may pull her legs up toward her abdomen to try and reduce the pain. She may vomit after a pain episode; as the intussusception continues, the vomited material may become green with bile staining. She may also be relatively comfortable between pain cycles. In almost 3/4 of cases there may be blood in the stool; often the stool contains both blood and intestinal mucus, and looks like currant jelly (currant jelly stool is a classic sign of intussusception). Infants with intussusception may not have any obvious signs of pain; conversely, older children with intussusception may have no symptoms except pain. Sometimes a child (usually a baby) with intussusception has no symptoms except lethargy, and no physical signs of abdominal problems, and may be diagnosed initially with sepsis or meningitis.
We usually diagnose intussusception by X-ray or ultrasound images. The best way to confirm an intussusception is to give the patient an enema, using air or a water-soluble liquid that blocks X-rays, at low pressure. The air or the contrast medium helps us see the swollen tissue. Even better, the pressure often pushes the telescoped part of the intestine upwards and reduces the intussusception -- and usually that's all the treatment the child needs. There is a small risk that the swollen, sick part of the intestine will perforate with the enema: the air or liquid enema may be safer than an enema with other X-ray contrast media such as barium. Often we will give antibiotics before the enema to fight any bacteria that may end up in the abdominal cavity if there actually is a perforation. Intussusceptions that cannot be reduced with an enema need to be reduced by a surgeon.