Intussusception

described: ileocolic, colocolic, ileoilealcolic and ileoileal, this latter being the least frequent. The condition typically occurs in infants between approximately 6 months and 2 years with most cases clustered between 6 and 12 months. In most cases no lead point is identified as the cause. Known lead points include Meckels diverticulum, intestinal duplication and polyps. In the idiopathic group it is thought that hypertrophy of the Peyer's patches possibly due to a viral insult is the triggering factor. Intussusception tends to present seasonally with peaks in spring and summer. Clinical presentation is with attacks of colicky abdominal pain, drawing the legs up to the tummy, and paleness, followed by periods of relaxation and return to normal colour. Currant jelly stools are found in about one third of patients. If the intussusception is unrelieved the child develops symptoms of bowel obstruction. Ischaemia of the intussusceptum may cause perforation and subsequent peritonitis. Intussusception may be transitory and reduce spontaneously. Transitory intussusceptions are seen in children with cystic fibrosis and non-specific abdominal pain. Transitory intussusception are usually ileoileal distinguishable on ultrasound by smaller calibre of the bowel.

Imaging

On abdominal radiographs, the classical description of an intussusception is a mass lesion seen indenting the colon with or without signs of bowel obstruction. There is a paucity of right-sided colonic gas. Intussusceptions may present anywhere along the colon and even present in the rectum. The typical location is from the hepatic flexure to mid descending colon. A normal abdominal radiograph does not exclude intussusception. Ultrasound is the most sensitive technique to demonstrate intussusception (Fig.1). The typical appearance is described variously as a "target sign" a doughnut sign, pseudokidney, or a sandwich sign. All terms reflect the presence of multiple layers of hypoechoic bowel wall with more echogenic colonic mucosa and intestinal content centrally. Small amounts of free fluid between the bowel loops is a frequent finding. Colour Doppler has been used to assess bowel viability and as a prognostic sign that reduction will be successful, no colour signal of the intussusception being regarded as having a poor prognosis. This finding is still under debate. One may sometimes see intestinal lymphadenopathy with intussusception.

Reduction

Non-operative reduction of the intussusception is attempted in most children. The only contraindication is a shocked child with signs of peritonism, failure to rapidly resuscitate with intravenous fluids, or the presence of a pneumperitoneum on abdominal radiography. Reduction may be hydrostatic using water soluble contrast or dilute barium, or pneumatic (Fig.2). Success rates of 7080% are achieved by most experienced paediatric radiologists. Most children still have the intussusception reduction monitored by fluoroscopy. Ultrasonic monitoring of hydrostatic reduction is an alternative approach. The use of analgesia for the reduction also varies but in general is recommended.

Successful reduction of an intussusception is confirmed if air or contrast reflux into the small bowel. This may be prevented by oedema of the ileocaecal valve which may persist as a filling defect in the caecum on fluoroscopy (Fig.3). Children are often operated on in the mistaken belief that there is a persistent intussusception. A policy that prevents unnecessary surgery is to repeat the ultrasound, which may be difficult if there is a large amount of residual air from pneumatic reduction but the ileocaecal valve should be visible. If there is no other evidence of an intussusception then a period of observation of the child for the next 10 hours or so is instituted. In 90% of patients signs and symptoms do not recur.

A practice in some units is to repeat the enema after a period in these children but this is not necessary, as it is clinically obvious that the child is either well or has recurrent symptoms.

About 10% of intussusceptions recur after operative or non-operative reduction. Recurrence is not a contra indication to further non-operative reduction.

Intussusception presenting under three months or beyond two years is more likely to have a lead point as causation. A decision for surgical or non-operative management must be made individually. Children with cystic fibrosis  get both transient and fixed intussusception and should be managed if possible non-operatively. Transient intussusceptions require no treatment. Non-operative reduction of intussusception complicating typhlitis haemolytic-uraemic syndrome or Henoch Schonlein purpura is also indicated, if possible. See hydrostatic reduction of intussusception, air reduction of intussusception

HC

HC