Ref: Bailey & Love's Short Practice of Surgery 25th Edition Chapter 66 Intestinal Obstruction Pages 1191-12 & Donald A, Antonio!i, " Gastrointestinal Autonomic Nerve Tumors, expanding the spectrum of gastrointestinal stromal tumors," Arch Pathol Lab Med: 1989: 113: 831-833.Explanation:IntussusceptionInvagination of an intestinal segment (the intussusception) into the next distal part of the intestine forms a sheath around it (the intussuscipiens) producing a form of intestinal obstruction called 'intussusception'.The most common cause is hypertrophy of the Peyer's patches in the terminal ileum from an antecedent viral infection.The hypertrophied lymphatic patch becomes drawn into the lumen of the terminal ileum and is moved progressively into the ascending and transverse colon.Other predisposing factors includePolypsMeckel's diverticulumBenign tumors like lipomaLeiomyomaMalignant tumors such as lymphoma which may act as lead points for intussusception.GI lipomas, most common in the ileum, are single intramural lesion, submucosal in location and usually small.One portion of the gut becomes invaginated within an immediately adjacent segment: almost invariably, it is the proximal into the distal.The condition is encountered most commonly in children, with a peak incidence between 5 and 10 months of age.About 90% of cases are idiopathic but an associated upper respiratory tract infection or gastroenteritis may precede the condition.It is believed that hyperplasia of Peyer's patches in the terminal ileum.Weaning, loss of passively acquired maternal immunity and common viral pathogens have all been implicated in the pathogenesis of intussusception in infancy.Children Pathological lead pointsMeckel's diverticulumPolypduplication,Henoch-Schonlein purpuraAppendixAdult cases lead pointA polyp (e.g. Peutz-Jeghers syndrome)A submucosal lipomaother tumoursPathologyAn intussusception is composed of three parts:The entering or inner tube (intussusceptum)The returning or middle tube:The sheath or outer tube (intussuscipiens).The part that advances is the apex, the mass is the intussusception and the neck is the junction of the entering layer with the mass.An intussusception is an example of a strangulating obstruction as the blood supply of the inner layer is usually impaired.The degree of ischaemia is dependent on the tightness of the invagination, which is usually greatest as it passes through the ileocaecal valve.Intussusception may be anatomically defined according to the site and extent of invagination.In most children, the intussusception is ileocolicIn adults, colocolic intussusception is commonIntussusceptionMost common in childrenPrimary or secondary to intestinal pathology, e.g. polypMeckel's diverticulumIleocolic is the commonest varietyCan lead to an ischaemic segmentRadiological reduction is indicated in most casesThe remainder require surgery