Introduction

Intussusception is a common cause of paediatric bowel obstruction, particularly in children less than 2 years of age. Intussusception occurs when a bowel segment (usually the small intestine) invaginates into the lumen of a more distal lumen of bowel. The invaginated segment, known as the intussusceptum, is carried distally by peristalsis while the mesentery and vessels are squeezed within the engulfing segment (intussuscipiens). The resulting venous congestion is the cause of the blood and mucous in the stool, the classic ‘redcurrant jelly’ stool that may result in some cases. Intussusception occurs most commonly at the terminal ileum when the terminal ileum is carried through the ileocaecal valve into the colon (ileocolic ~90%) and in some instances the telescoping small bowel may even reach the rectum.

Aetiology

Most cases of intussusceptions are idiopathic without any mass lesion acting as a lead point or an apex of the intussusceptum. In non-idiopathic intussusception, the following may act as lead points:

Meckel’s diverticulum or polyp related.

Haemolytic–uraemic syndrome.

Cystic fibrosis with inspissated bowel content.

Henoch–Schönlein purpura (HSP) with intramural haemorrhage.

Lymphoma and leukaemia involving the bowel wall.

Epidemiology

Most of the children are younger than 1 year of age, and the peak incidence occurs in infants between 5 and 10 months of age. Intussusception is the most common cause of intestinal obstruction in patients between 3 months and 3 years. Patients under 3 years of age with intussusception usually do not have a mass lesion as the lead point, the telescoping is idiopathic and they are usually responsive to non-operative reduction. Older children may have a surgical lead point to the intussusception and require operative reduction.

The estimated incidence is 1 to 4 per 1000 live births. There is an overall male preponderance, with a male-to-female ratio of approximately 3 to 1. Mortality with treatment is rare. Morbidity is increased by a delay in diagnosis and is likely to be due to bowel wall necrosis and perforation. Delay will cause prolonged intestinal obstruction with persistent vomiting, causing resultant dehydration and electrolyte imbalance.

Clinical

Clinically, the four classic symptoms and signs of vomiting, abdominal pain, abdominal mass and bloody stool described in patients with intussusception are present in less than one half of patients with the disease.^1,2 Intestinal obstruction is often the presenting sign.

The patient is usually in the infant age group and is previously healthy and well nourished, with acute onset of symptoms. The presentation is one of sudden onset of intermittent colicky abdominal pain, manifesting as episodic bouts (1–10 minutes) of crying. One of the descriptions sometimes given by the caregivers is the drawing up of the legs to the child’s abdomen and then kicking the legs in the air. The child is often inconsolable during an episode of distress. Often the child will appear pale due to increased vagal tone caused by the telescoping bowel. Between the episodes, the child may be flat, lethargic or fall asleep exhausted, whereas some children will resume normal activity until another bout of distress occurs.

There is poor feeding, vomiting, and there may be passage of loose or watery stools. The child may have one or more episodes of loose stool which may be followed by blood or mucus per rectum within 12–24 hours. The mixture of mucus and shed blood described as ‘redcurrant jelly’ is a late sign. The diarrhoea, which occurs early, may lead to a misdiagnosis of gastroenteritis, so intussusception should be considered in any young child having episodic distress in the setting of a diarrhoeal illness. Initially the vomiting is non-bilious but it becomes bilious when intestinal obstruction occurs. There may be a preceding upper respiratory tract infection, which can sometimes distract from the true cause of the child’s distress. This condition is unusual in children who are malnourished. The child usually appears chubby and in good health. The child when observed will be seen to have paroxysmal crying spells which represent episodes of abdominal pain between periods of lethargy. In late presentations, the child may be floridly shocked and minimally reactive from collapse.

One must be mindful of the small subset of ‘encephalopathic’ intussusceptions that present without symptoms to suggest a gastrointestinal problem (‘painless presentation’). These children will present with lethargy, sweating and pallor which may be episodic.

Most children appear pale, but with pink conjunctivae. On examination, a right hypochondrium or mid-abdominal sausage-shaped mass may be palpated and this is best felt when the child is quiet between spasms of colic. Abdominal palpation may be soft and appear non-tender in some cases, whereas some children will elicit non-specific guarding. If obstruction has occurred distension and tenderness will be present. The nappy should be checked for any blood, and in suspicious cases a gentle rectal swab may reveal otherwise occult blood. Rarely, the bowel can progress to present rectally and prolapse. The presence of fever and leukocytosis are late signs and may indicate transmural gangrene and infarction. The occurrence of intestinal gangrene and infarction can be suggested by the presence of peritonitis, with the physical signs of rigidity and involuntary guarding.

Often patients with intussusception do not present with classic signs and symptoms, which may lead to an unfortunate delay in diagnosis, with disastrous consequences. Therefore it is essential to maintain a high index of suspicion for intussusception when evaluating a child presenting with abdominal pain, especially those less than 5 years of age or those who have HSP and episodic severe pain.

Investigations

All children should be resuscitated and stabilised prior to any imaging.

Management

The treatment in the emergency department is to initially provide stabilisation depending on the child’s clinical condition and consult with a paediatric surgeon. Intravenous fluids should be started for resuscitation (normal saline bolus) and subsequent rehydration as required. The stomach should be decompressed by use of a nasogastric tube, if there is a bowel obstruction.

Non-operative reduction by air enema (hydrostatic reduction) is now generally accepted as the modality of treatment for most patients. Absolute contraindications include peritonitis, perforation or profound shock.¹⁸

Outcome

Various authors have reported reduction rates of between 80 and 90% using air enema.^{19–20,26–28} The perforation rate is quoted to be less than 1%.^18,19 Factors that are associated with lower reduction and higher perforation rate, especially if more than one of the following are present: (a) patient’s age: younger than 3 months or older than 5 years; (b) long duration of symptoms, especially if more than 48 hours; (c) passage of blood per rectum; (d) significant dehydration; (e) small bowel obstruction and (f) the presence of dissection sign on contrast study.^20–25

Surgical reduction is now performed after failure to achieve reduction or when it is contraindicated to perform non-operative reduction.

The overall mortality rate of intussusception is less than 1%.¹⁸ Mortality rates observed among children in industrialised countries are lower than those in developing countries.^1,28–33 Some of these deaths are preventable and may be related to reduced access to or delays in seeking health care, factors known to be associated with mortality in children with intussusception.^31–33 Therefore, early diagnosis and management play an important role in the reduction of mortality.