Intussusception 

Key points

• The diagnosis of intussusception requires a high index of suspicion. Consider intussusception in infants and children with intermittent distress, vomiting or isolated unexplained lethargy
• Delayed presentation of intussusception can manifest as small bowel obstruction, bowel perforation, peritonitis and/or shock 
• Ultrasound is the initial study of choice 

Background

• Intussusception is the invagination (telescoping) of a proximal segment of bowel into the distal bowel lumen. 
• The commonest site is a segment of ileum moving into the colon through the ileo-caecal valve. This process leads to bowel obstruction, venous congestion and bowel wall ischaemia. 
• Perforation can occur and lead to peritonitis and shock
• The triad of
  • intermittent abdominal pain
  • palpable abdominal mass
  • red currant jelly stools
    • occurs in only 1/3 of children 

• May occur at any age, but most commonly between 2 months and 2 years of age 
• Most cases are idiopathic (90%) 
• In older children, a pathological lead point may be the cause 

Assessment

• History
  • Intermittent pain or distress
  • Episodes can recur within minutes to hours and may increase in frequency over the next 12–24 hours
  • The child may appear very well between episodes
  • Pallor, especially during episodes
  • Lethargy may be the only presenting symptom. It may be profound, episodic or persistent
  • Vomiting is usually a prominent feature (but bile stained vomiting is a late sign and indicates a bowel obstruction)
  • Diarrhoea is quite common initially and can lead to a misdiagnosis of gastroenteritis. Rectal bleeding or the classic “red currant jelly” stool are late signs suggesting bowel ischemia and infarction

• Additional risk factors
  • Recent intussusception (may present with more subtle symptoms)
  • Potential lead point
    • Meckel’s diverticulum
    • Henoch Schonlein Purpura
    • Lymphoma
    • luminal polyps (eg Peutz Jegher Syndrome) 
  • Recent bowel surgery
  • Recent rotavirus vaccination

Examination

• Abdominal mass may be felt – typically a sausage shaped mass in the right abdomen, crossing the midline in the epigastrium or behind umbilicus (in 2/3 of children). The abdominal mass may be subtle and examination is best performed when the child is settled in between episodes
• Abdominal distension suggests bowel obstruction
• Tenderness or guarding may suggest perforation and peritonitis
• Inspection of the nappy and perianal region should be done. A rectal examination is rarely indicated
• Infants may present with Hypovolaemic shock

Investigations

• Ultrasound scan
  • High sensitivity (>98%) and specificity (>98%) when performed by an experienced paediatric ultrasonographer
  • Point of Care Ultrasound can be used to confirm the diagnosis of intussusception by appropriately trained clinicians. It should not be used to exclude the diagnosis
• Abdominal X-Ray
  • Perform AXR only if there are signs of obstruction or perforation
  • A normal AXR does not exclude intussusception (sensitivity <50%)
  • Signs suggesting intussusception on an abdominal x-ray include:
    • an abnormal gas pattern, with an empty right lower quadrant and visible soft tissue mass in the upper abdomen
    • a soft tissue mass surrounded by a crescent lucency of bowel gas (crescent sign)
    • lack of faecal material in the large bowel
    • signs of small bowel obstruction
    • pneumoperitoneum indicating bowel perforation
• Contrast / gas enema
  • The enema may be used diagnostically and therapeutically in consultation with a surgical team
  • There is a small risk of bowel perforation and bacteraemia during the gas enema. Therefore, the enema is performed where paediatric surgery is available in case of the need for laparotomy. Usually, a surgical doctor, as well as a suitably trained nurse, will accompany the child with appropriate resuscitation equipment
  • Contraindicated if peritonitis, shock, perforation, or an unstable clinical condition is present
• Blood tests
  • Blood glucose
  • Venous Gas, FBE and UEC if the child looks unwell
  • Blood group and hold prior to theatre

Management

• Analgesia and resuscitation should precede investigation (see flowchart below)
• Secure IV access for all children suspected to have intussusception before diagnostic imaging
• Treat hypovolaemic shock with IV boluses of 20 mL/kg normal saline
• Give adequate analgesia (usually intranasal fentanyl or IV morphine).