Acute intestinal obstruction of the newborn

Neonatal intestinal obstruction has an approximate incidence of 1:2000 live births. Congenital atresia and stenosis are the commonest causes. Volvulus neonatorum, meconium ileus and Hirschsprung's disease may also be responsible.

Congenital atresia

The incidence of atresia varies with anatomical site:

duodenum — 35 per cent;

jejunum — 15 per cent;

ileum — 25 per cent;

ascending colon — 10 per cent;

  multiple sites — 15 per cent.

The high incidence of multiple sites makes peroperative assessment of the whole small and large bowel mandatory. Except in the case of duodenal atresia there are frequently associated abnormalities of the heart and great vessels.

Atresia/stenosis of the duodenum

Atresia and stenosis occur with equal frequency. In most cases, except for the oesophagus, duodenum and rectum, the atresia is a result of an intrauterine vascular accident occurring late in pregnancy such as volvulus, intussusception or strangulation at the umbilical ring. As the foetus is germ-free the ischaemic portion is absorbed and disappears. In the presence of complete obstruction, persistent vomiting occurs from birth. The presence or absence of bile is dependent on the relationship of the septum to the duodenal papilla. Bile-stained vomiting is nearly always organic in origin. Distension is often absent but visible peristalsis may be seen in the left upper quadrant. Atresia of the duodenum occurs at the level of the ampulla of Vater. Thirty per cent of babies have associated Down’s syndrome. Radiography reveals a classic so-called double stomach due to gross distention of the stomach and upper part of the duodenum with two air—fluid levels (Fig. 58.21).In cases of partial obstruction the location of the lesion may be confirmed by installation, via a nasogastric tube, of a small volume of gastrograffin. Once the lesion is confirmed the medium must be aspirated. Suprapapillary duodenal atresia may be distinguished from oesophageal atresia by the absence of dribbling saliva, and from infantile pyloric stenosis by the absence of a lump.

Duodenal obstruction in infancy may also be due to midgut volvulus, a band obstruction or an annular pancreas.

Treatment

Surgery is required as soon as resuscitation is complete. Duodeno­jejunostomy is the operation of choice. A silastic catheter is introduced through a stab incision in the antrum and guided through the anastomosis. A Witzel gastrostomy is constructed around the proximal tube which is brought out through a stab incision. Early enteral feeding through this tube is recommended.

Atresia/stenosis of the jejunum/ileum

There are four main types:

type 1 — diaphragm with continuity of the bowel wall;

type 2 — gap between the two ends (may be connected by fibrous cord) plus a mesenteric defect;

type 3 — multiple atresias;

type 4 — apple peel atresia with loss of dorsal mesentery.

The vital importance of a diagnosis lies in the fact that proximal distention of the bowel may be so great that the vascular integrity of the bowel wall is compromised leading to gangrene and perforation (Fig. 58.22).

In ileal atresia the child is born with abdominal distension or it presents within 24 hours of birth. In jejunal atresia early distention is lacking but vomiting occurs early. In both conditions the vomit contains bile and some meconium is likely to be evacuated.

Radiography

Plain radiographs are only diagnostic when air—fluid levels are seen. When they are present the obstruction is usually well advanced.

Surgery

If the stenosis is ileal and the discrepancy in bowel diameter above and below the obstruction is marked the two limbs may he brought out in a manner similar to the Paul—Mikulicz procedure. The proximal limb will need to he proud of the abdominal wall (usually by eversion) in order to prevent skin excoriation. Secondary closure by circumstomal mobilization and anastomosis, rather than use of crushing clamps, is recommended. When the stenosis is jejunal, the impact of the high jejunostomy output can make subsequent management difficult and wherever possible an end-to-end anastomosis is recommended.

Arrested rotation

Up to 10 weeks of gestation the gut lies outside the abdominal cavity. The orderly return may he arrested at any stage resulting in four major types of arrest.

The whole bowel may remain free as a narrow-based mesentery. The caecum may he displaced with transduodenal bands. The intestine may return in a clockwise direction producing a reversed intestinal rotation or a failure of rotation altogether, with the small bowel on the right and the large bowel on the left.

The most common anomaly is where the caecum remains in the left hypochondrium and a peritoneal band is found running from the caecum to the right side of the abdomen and then across the second part of the duodenum — the transduodenal hand of Ladd. The symptoms of repeated vomiting, due to pressure on the duodenum, and the radiographic appearances are identical to those of duodenal stenosis. Treatment consists of early laparotomy after appropriate resuscitation. The band is divided near its attachment to the parietal peritoneum. Often there is a second band which must also be divided, extending from the midline to the commencement of the caecum. The caecum and the colon are centred on the left of the abdominal cavity with the small bowel on the right (Nixon).

Meconium ileus

This is the neonatal manifestation of cystic fibrosis. Meconium is normally kept fluid by the action of pancreatic enzymes. The terminal ileum becomes filled with meconium and viscid mucus resulting in progressive inspissation in utero and neonatal obstruction. Inspissated meconium may be palpated as a rubbery swelling. Abdominal radiography may reveal a distended small intestine, with mottling. Fluid levels are generally not seen. Unlike ileal atresia there is no abrupt termination of the gas-filled intestine. As the condition is due to an autosomal recessive genetic defect a family history may he present. Further assessment includes absence of trypsin from stool or bile and a concentration of sodium chloride in sweat greater than 80 mmol/litre, or a negative immunoreactive blood trypsin estimation.

Forty per cent of cases are associated with complications such as volvulus neonatorum, atresia or meconium peritonitis (Dickson). Any evidence to suggest an acute intra-abdominal process due to twisting of the grossly distended proximal bowel indicates the need for urgent laparotomy. When this is not so, a gastrografin or mypaque enema may be given to confirm the diagnosis. The radio-opaque fluid will pass easily to the ileum where it may disperse the obstructing meconium and relieve the condition owing to its high osmolarity and detergent action. As the instilled solution is markedly hypertonic, the rapid loss of fluid into the bowel lumen must be corrected by replacement. If conservative management fails, laporotomy is indicated. The only condition with which meconium ileus may be confused is Hirschsprung’s disease affecting the whole colon. The standard treatment is resection of the most dilated segment with an end-to-side anastomosis of the colon to the ileum. The distal ileal opening is formed into an ileostomy, through which the meconium may he irrigated postoperatively (the Bishop—Koop operation). The ilesotomy becomes a mucus flstula which usually requires subsequent closure (Fig. 58.23).

Necrotising enterocolitis

This is a common phenomenon amongst sick premature neonates. The risk is inversely proportional to birth weight and may be associated with hypoxia, hypothermia, hypotension and umbilical artery cannulation. The ileum, caecum, distal colon and total colon are affected with a complete spectrum from mucosal to transmural necrosis.

The usual presentation is bilious vomiting, abdominal distension, colour change and lethargy in a high-risk neonate. The abdomen is usually soft. Abdominal radiographs may show pneumatosis intestinalis or free intraperitoneal air. Management consists of aggressive resuscitation with intravenous feeding. The optimal time for surgery is not in the acute phase as the baby can withstand the pressure of necrosis better than an adult but not the stress of laparotomy. At laparotomy excision of all necrotic bowel with primary anastomosis is usual. The overall mortality is 25 per cent with 10—30 per cent of neonates developing a colonic stricture.