Intestinal atresia

The term atresia implies maldevelopment of a lumen or opening that is normally patent. If there is just a narrowing of the lumen, this is termed a stenosis. Atresia of the intestinal tract can occur at any level, but in the context of bilious vomiting the level of obstruction is distal to the ampulla of Vater in the second part of the duodenum.

As the lesion is congenital, the child will present in the neonatal period, although increasingly, some of these infants are diagnosed on antenatal ultrasound scans.¹ Proximal lesions, such as duodenal or jejunal atresia, will usually present in the first 24 hours of life whereas more distal lesions, such as ileal or colonic atresias, can present later. Duodenal atresia may be associated with Down’s syndrome and cardiac anomalies in up to 30% of cases.²

Anorectal anomalies

Typically the anus is imperforate and the rectum communicates with the urinary tract or perineum via a fistula. It may occur as part of the VACTERL association of anomalies (vertebral, anorectal, cardiac, tracheo-oesophageal, renal and limb).³ The diagnosis should normally be made as part of the routine assessment of a neonate following delivery, but is occasionally missed, leading to a complete or partial distal obstruction and late onset bilious vomiting. Infrequently, the anomaly may present outside the neonatal period once the child commences solids.

Meconium ileus

This condition occurs in about 10–20% of neonates with cystic fibrosis (CF), although uncommonly it may occur in the absence of CF.⁴ There may be a family history of CF. The condition results from the occlusion of the bowel lumen by abnormally viscous enteric secretions in the small bowel and may be complicated by an atresia.

Hirschsprung’s disease

In this condition the enteric nervous system is abnormal, leading to a distal physiological obstruction. The condition is more common in males by a ratio of 4:1.⁵ In 75% of cases, so called ‘classical’ Hirschsprung’s disease (HD), a variable extent of the rectum and sigmoid colon is involved, leading to a distal colonic obstruction.⁶ In the remaining 25% of cases, bowel proximal to the sigmoid colon will also be aganglionic. About 10% of children with HD will also have Down’s syndrome.⁷ The cardinal feature of HD is the failure to first pass meconium within 24 hours of birth in a term infant, with the later development of bilious vomiting in the first few days of life.

Malrotation with volvulus

The mid-gut normally develops within a physiological hernia in utero. As this reduces towards the end of the first trimester, the mid-gut undergoes an anticlockwise rotation around the axis of the superior mesenteric vessels.⁸ Failure of this process to occur results in malrotation. The onset of bilious vomiting usually indicates that the malrotated small bowel has obstructed as a result of twisting around its pedicle, although occasionally, this may occur as a result of associated congenital bands. There is a high risk of intestinal ischaemia, so urgent surgical intervention is required once the diagnosis has been confirmed.⁹ Although malrotation most commonly presents in the first month of life, it can present at any time and even in adult life.¹⁰

Irreducible inguinal hernia

An irreducible inguinal hernia, particularly in a male, often contains bowel. The resultant obstruction of the bowel at the level of the external inguinal ring may produce bilious vomiting. Untreated, the irreducible hernia is at risk of producing intestinal ischaemia.

Intussusception

In intussusception the proximal bowel (the ‘intussusceptum’) invaginates or telescopes into the distal, receiving bowel (the ‘intussuscipiens’). Initially this involves the ileum invaginating into itself, but then progresses to involve the colon. Most commonly, it presents in infants or toddlers with episodic colicky abdominal pain, which may be associated with vomiting or pallor. As the disease progresses, vomiting may become bilious, resulting from intestinal obstruction. The ‘classical’ redcurrant jelly stool of intussusception is a late phenomenon but occult blood can often be detected earlier.¹¹

In older children above 3 years of age, intussusception is usually associated with a pathological lead point such as a Meckel’s diverticulum (MD) or small bowel polyp.¹² It may also complicate CF and Henoch–Schönlein purpura.

Inflammatory

Complicated acute appendicitis, Meckel’s diverticulitis or inflammatory bowel disease leading to the development of an inflammatory mass may result in intestinal obstruction. This presentation usually occurs when there has been a diagnostic delay of the primary pathology, often in children under 5 years of age.

Meckel’s diverticulum

This represents a remnant of the omphalomesenteric duct and is present in about 2% of the population.¹³ For reasons that are unclear, complications of a MD are more common in males.¹³ MD may lead to a bowel obstruction either as a result of acting as the lead point for an intussusception, due to an associated band adhesion with volvulus or an internal hernia, or rarely an inflammatory mass due to Meckel’s diverticulitis.

Adhesions

Bowel obstruction due to adhesions is uncommon in children following abdominal surgery.⁹ This is fortunate as, unlike adults, the obstruction rarely settles with non-operative intervention.

Non-surgical

A wide variety of medical conditions may occasionally present with bilious vomiting, together with a variable degree of abdominal distension. Severe gastroenteritis with prolonged vomiting, sepsis, pyloric stenosis, hypothyroidism, meconium plug syndrome and the cyclical vomiting syndrome may all lead to a clinical picture similar to intestinal obstruction.¹⁴ Any child presenting with bilious vomiting, however, requires paediatric surgical consultation to exclude a surgical cause.