7.5 Bilious vomiting

Introduction

Any child presenting to the emergency department (ED) with bilious vomiting has a surgical cause of intestinal obstruction until proven otherwise. Bilious vomiting occurs when the vomitus contains bile. Typically this is indicated by its bright green colour, although the discolouration may vary from a pale yellow to a dark greenish brown. Often the carer is aware of the importance of this sign and will have preserved a towel or item of clothing stained with the vomitus for inspection. For practical purposes, bilious vomiting indicates an intestinal obstruction. Some indication of the likely aetiology and level of the obstruction may be determined from the age of the child, the past medical history and length of illness prior to onset of vomiting. Rapid onset of bilious vomiting and a non-distended abdomen suggest a proximal obstruction, whereas, late onset of bilious vomiting and abdominal distension, a distal obstruction. Immediate referral to a paediatric surgeon is indicated, as urgent surgical intervention may be required.

Causes

The possible causes of bilious vomiting are as shown in Table 7.5.1 and are discussed below:

Table 7.5.1 Causes of bilious vomiting
Intestinal atresia
Anorectal anomalies
Meconium ileus
Hirschsprung’s disease
Malrotation with volvulus
Irreducible inguinal hernia
Intussusception
Inflammatory
Meckel’s diverticulum
Adhesions
Non-surgical

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.

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

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