A form of obstruction of the bowels in which part of the INTESTINE enters within that part immediately beneath it. This can best be understood by observing what takes place in the fingers of a tightly fitting glove, as they turn outside-in when the glove is pulled off the hand. Mostly, the condition affects infants. Often it occurs during the course of a viral infection or a mild attack of gastroenteritis, or it may be that swelling of lymphoid tissue in the gut provokes the event. The point at which it most often occurs is the junction between the small and the large intestines, the former passing within the latter. The symptoms are those of intestinal obstruction in general (see INTESTINE, DISEASES OF – Obstruction), and in addition there is often a discharge of blood-stained mucus from the bowel. Unless the symptoms rapidly subside, when it may be assumed that the bowel has righted itself, treatment consists of either hydrostatic reduction by means of an air or contrast medium ENEMA, or an operation. At operation the intussusception is either reduced or, if this is not possible, the obstructed part is cut out and the ends of the intestine then stitched together. The condition may recur in about 5 per cent of patients.