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Congenital abnormalities of the gastrointestinal tract 

Congenital abnormalities of the gastrointestinal tract
Chapter:
Congenital abnormalities of the gastrointestinal tract
Author(s):

V.M. Wright

, J.A. Walker-Smith

, and I.R. Sanderson

DOI:
10.1093/med/9780199204854.003.1515_update_001

February 27, 2014: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Small intestinal lymphangiectasia—use of capsule endoscopy in diagnosis.

Meconium ileus—use of water-soluble contrast media other than Gastrografin.

Further reading—substantially updated.

Updated on 28 November 2012. The previous version of this content can be found here.
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Essentials

Congenital abnormalities of the gastrointestinal tract usually manifest shortly after birth, but on occasion symptoms may be delayed for months or even years. Any part of the gut can be affected, with problems including oesophageal atresia and tracheo-oesophageal fistula, anterior abdominal wall defects, congenital pyloric stenosis, atresia and stenosis of the small intestine, duplication of the gastrointestinal tract, small-intestinal malrotation with or without volvulus, small-intestinal lymphangiectasia, Meckel’s diverticulum, meconium ileus, congenital short intestine, colonic atresia, Hirschprung’s disease, and imperforate anus.

The widespread use of ultrasonography to assess the fetus allows many of these abnormalities to be recognized prenatally, and associated anomalies (e.g. cardiac lesions) may indicate a major chromosomal abnormality. This allows parental choice to continue with or terminate the pregnancy.

Presentation of congenital abnormalities of the gastrointestinal tract in adult life is uncommon, but small intestinal lymphangiectasia can present in adults with a picture mimicking coeliac disease, and Meckel’s diverticulum—a vestigial remnant of the vitellointestinal duct on the antimesenteric surface of the distal ileum—can cause rectal bleeding or small-intestinal obstruction in young adults.

Embryology of congenital gastrointestinal tract abnormalities

The primitive gut is initially a simple tube of endoderm, the muscle and connective tissue developing from the splanchnopleuric mesoderm. Cranially, the gut terminates at the buccopharyngeal membrane and caudally at the cloacal membrane. Both membranes disappear; failure of the cloacal membrane to do so results in one of the rarer forms of imperforate anus. The primitive foregut diverticulum gives rise to the respiratory system, oesophagus, stomach, duodenum to the level of the ampulla of Vater, liver, and pancreas. The primitive oesophagus lengthens rapidly, becomes narrow, and frequently the lumen is transiently obliterated. A longitudinal, ventral diverticulum of the foregut forms the trachea with ridges on either side that fuse, initially caudally with progression cranially, until the primitive respiratory system is separated from the oesophagus. Failure of this complex process results in the various forms of oesophageal atresia and tracheo-oesophageal fistula. Dilatation of the foregut distal to the oesophagus produces the stomach, initially slung from the dorsal body wall by the dorsal mesentery and from the septum transversum by the ventral mesentery. Rapid differential growth results in the stomach rotating through 90° on its long axis, the dorsal border becoming the greater curvature and the ventral border the lesser curvature. The dorsal mesentery forms the greater omentum. The ventral mesentery, into which the liver bud grows, forms the falciform ligament and coronary ligaments attaching the liver to the diaphragm, and the lesser omentum. Congenital abnormalities of the stomach are excessively rare. The liver arises as a shallow groove on the ventral aspect of the duodenum. The groove becomes tubular and invades the septum transversum and the ventral mesentery. Bile is secreted from the fifth month, and gives meconium its characteristic dark-green appearance. The mesoderm of the septum transversum forms the fibrous tissue of the liver.

The pancreas develops as two outgrowths of the duodenum. One comes from the dorsal aspect, the other from the ventral. The dorsal bud grows into the dorsal mesentery and the ventral bud is swept around dorsally into the mesentery when the duodenum rotates to the right. These two primordia fuse, the ducts fuse, and the main pancreatic duct joins the bile duct to enter the duodenum at the ampulla of Vater. If the ducts do not fuse, an accessory pancreatic duct persists. Annular pancreas is a congenital anomaly where the pancreas surrounds the duodenum, which may be atretic or intrinsically stenosed. Annular pancreas is not the primary cause of the duodenal obstruction in these cases.

The duodenum is derived partly from foregut and partly from the midgut. The loop of primitive duodenum is fixed at the pyloric end, and by the ligament of Treitz at the duodenojejunal flexure to the left of the first lumbar vertebra. By rotating to the right, the entire duodenum comes to lie retroperitoneally in a curve around the head of the pancreas. Failure of the duodenum to fix in this position is a fundamental reason for the gut failing to rotate correctly. During rapid growth the duodenal lumen is obliterated and partial or total failure of recanalization will result in the anomalies of duodenal atresia or stenosis. The small intestine and colon, suspended on the dorsal mesentery, rapidly lengthen and outgrow the primitive peritoneal cavity, and herniation occurs into the umbilical sac during the fifth week of development. Growth in length continues, the loop of bowel rotating through 90° anticlockwise, the cranial limb lengthening more than the caudal limb. About the tenth week the loops of bowel return to the peritoneal cavity, undergoing a further 180° anticlockwise rotation. The small intestine goes first, the large intestine subsequently. Thus the large intestine lies in front of the small. The caecum is initially subhepatic, the large liver occupying the right side of the abdomen, eventually retreating to the right upper quadrant and allowing growth in the length of the ascending colon. The caecum, ascending colon, and descending colon become fixed to the posterior abdominal wall; thus the small bowel is suspended from a mesentery that runs from the left side of the first lumbar vertebra to the right iliac fossa. Failure of the duodenum to rotate and fix, coupled with a failure of normal rotation of the bowel with consequent lack of normal fixation, gives rise to malrotation of the intestine. Abnormal bands run from the caecum, which lies to the left of the midline, to the region of the gallbladder and may compress the duodenum. The narrow mesentery of the small intestine predisposes to a volvulus of the entire midgut.

At the apex of the midgut loop, the primitive gut is in continuity with the extraembryonic yolk sac via the vitellointestinal duct, which runs in the umbilical cord. Obliteration and disappearance of this duct occurs, allowing the bowel to return from the umbilical sac to the enlarged peritoneal cavity. Failure of the duct to disappear may result in a Meckel’s diverticulum, a band connecting the ileum to the umbilicus, a communication between the lumen of the ileum and the umbilicus, or failure of the gut to return completely to the peritoneal cavity, resulting in a small umbilical hernia.

Persistence of the umbilical sac will result in an exomphalos, with the sac containing a variable amount of gut and much of the liver. The embryology of gastroschisis is disputed. It may be due to early rupture of the umbilical sac allowing the primitive gut to extrude into the extraembryonic coelom, or failure of fusion of the lateral body folds producing a defect in the anterior abdominal wall adjacent to the umbilicus.

The midgut comprises the duodenum distal to the ampulla of Vater, jejunum, ileum, caecum, and colon as far as the left transverse colon. Atresia affecting the midgut may occur at single or multiple sites. The cause is probably intrauterine interference with the blood supply to that part of the gut which is affected, with consequent resorption of the ischaemic bowel.

The hindgut gives origin to the left third of the transverse colon, the descending colon, sigmoid, rectum, and upper part of the anal canal, and a considerable part of the urogenital system. The hindgut terminates in the primitive cloaca, which is separated from the proctodaeum (a shallow ectodermal depression) by the cloacal membrane. The primitive cloaca communicates with the hindgut and the allantois. Early in development the cloaca is joined by the pronephric ducts. A coronal septum (the urorectal septum) arises in the angle between the allantois and hindgut, grows caudally, fuses with the cloacal membrane, and divides the cloaca into a dorsal primitive rectum and a ventral primitive urogenital sinus. The cloacal membrane breaks down, establishing continuity between the endodermal hindgut and the ectodermal part of the anal canal. There are many varieties of imperforate anus. Absence of a variable length of rectum and anal canal, known as the ‘high’ anomaly, is frequently associated with the bowel terminating via a rectourethral or rectovaginal fistula. Ten per cent of babies with an imperforate anus will have oesophageal atresia, with or without a fistula, suggesting that the division of trachea and oesophagus and urogenital system and rectum must be occurring at a similar time in gestation, with possibly a similar mechanism producing the division. Anomalies of the urogenital system occur in a very high proportion of affected infants. Abnormalities of the ectodermal component of the anal canal result in ‘low’ imperforate anus.

The ganglion cells of the gut lie in the submucosa and intermyenteric plane. Ectodermal in origin, they migrate caudally along the length of the gut. Failure of migration down to the internal sphincter of the anal canal results in an aganglionic segment extending for a variable distance proximally, and is the underlying abnormality in Hirschsprung’s disease.

Mucosal differentiation occurs in the early months. The inner circular muscle differentiates earlier than the outer longitudinal. Thus the fetal intestinal tract is prepared for digestion, absorption, and propulsion at a comparatively early stage in development.

Intestinal histology in neonates with congenital gastrointestinal tract abnormalities

Histological architecture of the intestines in neonates with abnormalities of the gastrointestinal tract when compared to normal fetuses, is abnormal. The villi may be blunted, the crypts disorganized, and crypt depth significantly decreased, yet enterocyte height may be increased. These findings may be relevant to malabsorption which may complicate such disorders.

Oesophageal atresia and tracheo-oesophageal fistula

The incidence of this condition is approximately 1 in 3500 live births.

The upper oesophagus ends in a blind pouch. In the majority of cases, the lower oesophagus communicates at its upper end with the trachea, that is there is a tracheo-oesophageal fistula. Although much less common, there are a number of well recognized anatomical variations illustrated in Fig. 15.15.1.

Fig. 15.15.1 Anatomical variations of oesophageal atresia and tracheo-oesophageal fistula, indicating the relative frequency.

Fig. 15.15.1
Anatomical variations of oesophageal atresia and tracheo-oesophageal fistula, indicating the relative frequency.

Clinical features

Frequently the infant with oesophageal atresia is premature or small for gestational age. In 50% there is a history of polyhydramnios. Shortly after birth, because swallowing is impossible, copious amounts of frothy saliva dribble from the mouth, associated with choking, dyspnoea, and cyanotic episodes. Frequent suction is required to keep the airway clear. The infant with a tracheo-oesophageal fistula without associated oesophageal atresia coughs, chokes, and becomes cyanosed during feeds. Because air escapes through the fistula into the oesophagus, gaseous distension of the abdomen is frequently present. Aspiration of feed into the airway results in pulmonary collapse and consolidation.

Over 50% of infants with oesophageal atresia have significant associated anomalies. Of particular importance are cardiac, anorectal, urogenital, and skeletal anomalies. The premature infant or the infant who is small for gestational age is more likely to have multiple anomalies than is the full-term infant.

Survival of infants with oesophageal atresia depends on birth weight and associated abnormalities. All infants with a birth weight greater than 1.8 kg and no associated abnormalities or pneumonia should survive; this is also true of larger infants with a moderately severe associated abnormality or pneumonia. The mortality for infants with birth weight less than 1.5 kg, or with multiple severe congenital abnormalities, remains in the region of 20 to 30%.

Diagnosis

When oesophageal atresia is suspected, a size 10 or 12 FG catheter is passed through the mouth and into the oesophagus. If the oesophagus is obstructed, the catheter meets a resistance 9 to 11 cm from the gum margin. A smaller catheter may curl up in the obstructed oesophagus. Contrast studies of the oesophagus are rarely necessary. A chest and abdominal radiograph will show the position of a radio-opaque tube in the upper oesophagus, and the presence of gas in the bowel if a tracheo-oesophageal fistula is present. Complete absence of gas in the abdomen is diagnostic of an oesophageal atresia without a distal tracheo-oesophageal fistula. The radiograph will also reveal any abnormalities of ribs or vertebrae, signs of pneumonia, and may provide evidence of an associated cardiac abnormality.

In isolated tracheo-oesophageal fistula, very careful contrast studies of the oesophagus are required to demonstrate the fistula. Endoscopic examination of trachea and oesophagus is usually diagnostic.

Management

Early division of the tracheo-oesophageal fistula and anastomosis of the oesophagus are possible in the majority of cases. Postoperatively, mechanical ventilation may be necessary, but usually the full-term infant with no preoperative complications only needs careful suction of the nasopharynx to maintain a clear airway. A gastrostomy or a transanastomotic nasogastric tube is usually used to enable the infant to be fed within 48 h of operation. A primary anastomosis may not be feasible in pure oesophageal atresia, extreme prematurity, or where the infant’s general condition is poor. In such cases a tracheo-oesophageal fistula, if present, would be divided and a feeding gastrostomy established. Subsequently, an oesophageal anastomosis, after a delay of 4 to 6 weeks, having left the upper oesophageal pouch intact and kept empty of saliva by continuous suction, may be feasible. Alternatively, a cervical oesophagostomy is done with the intention, when the infant’s condition permits, of establishing continuity between mouth and stomach, using a length of colon, a tube of stomach, or the whole stomach. The choice depends on the surgeon’s preference.

Anterior abdominal wall defects

The incidence of exomphalos and gastroschisis is approximately 1 in 3000 births. An exomphalos occurs because the abdominal contents herniate through the umbilical ring into the base of the umbilical cord and are covered by a translucent membrane composed of peritoneum and amnion. Exomphalos major indicates that the diameter of the defect is greater than 5 cm, exomphalos minor that the defect is less than 5 cm. The contents of the exomphalos almost always include liver and a variable amount of bowel. On occasion, a very small amount of bowel alone herniates into the base of the cord. The diagnosis is frequently made on a prenatal ultrasonographic scan and prompts a search for associated major abnormalities, particularly anencephaly, chromosomal trisomies, major cardiac anomalies, and the Beckwith–Wiedemann syndrome. Associated abnormalities occur in 40%.

The Beckwith–Wiedemann syndrome, also termed the exomphalos macroglossia gigantism (EMG) syndrome, usually presents as a large-for-dates infant with a small exomphalos. The tongue is strikingly large, there are frequently ridges in the earlobes, and a prominent naevus flammeus on the forehead. Hypoglycaemia as a result of hyperinsulinism produced by islet-cell hyperplasia is a common early problem, which may require steroids, glucagon, and rarely subtotal pancreatectomy to effect control. In the long term, children with this syndrome have an increased incidence of solid tumours, particularly nephroblastoma and hepatoblastoma.

In gastroschisis there is a full-thickness defect in the anterior abdominal wall, usually to the right of the umbilical cord. The defect is small but most of the gastrointestinal tract may be extruded through it. In contrast to exomphalos, other abdominal organs are rarely eviscerated and abnormalities outside the gastrointestinal are unusual. Again, prenatal diagnosis on ultrasound scan is common.

Exomphalos

Clinical features

The lesion will be obvious at birth. Occasionally the membrane will rupture during, or shortly after, delivery. Careful examination for associated defects is essential.

Management

A nasogastric tube is passed to decompress the bowel. The sac can be very satisfactorily covered and supported by wrapping clingfilm around the exomphalos and the baby’s trunk. Plain radiographs of chest and abdomen are taken preoperatively in order to study the cardiac contour and the intestinal gas pattern, and to look for evidence of an associated diaphragmatic hernia. If a diaphragmatic hernia is detected on ultrasound before birth, the lungs are evaluated using fetal MRI. If the contents of the sac can be reduced into the peritoneal cavity, the abdominal wall can be closed in layers. If closure of all layers of the abdominal wall is impossible, skin closure alone may be used, or a synthetic material such as Silastic sheeting or Prolene mesh is used to enclose the sac after suturing it to the margins of the defect. Gradual reduction of the contents into the peritoneal cavity is then possible, with delayed closure of the abdominal wall. An alternative is to paint the sac with an antiseptic solution such as 70% alcohol or one of the iodine-based preparations. This results in the formation of a dry eschar that separates after some weeks, leaving a granulating surface, which gradually epithelializes. Any method that does not achieve muscle closure will leave a ventral hernia, which requires surgery at a later date.

Postoperatively, ventilatory support may be necessary. Antibiotics commenced preoperatively are continued postoperatively, particularly if an artificial material is used. Parenteral nutrition will be necessary if oral feeds cannot be given. Survival is related to the size of the lesion and the severity of any associated abnormalities.

Gastroschisis

Clinical features

Babies with this abnormality are frequently small for gestational age. After delivery, heat loss from the exposed bowel rapidly causes hypothermia. Hypoproteinaemia is very common. The small size of the defect in the anterior abdominal wall and the often narrow pedicle from which the bowel is suspended may impair the blood supply and result in infarction of much of the extruded intestine. Atresia may have occurred because of intrauterine impairment of the blood supply.

Management

A nasogastric tube is passed and the bowel decompressed. The bowel can be enclosed in clingfilm (plastic wrap) wrapped around the baby’s trunk, or the baby can be placed in a large polythene bag taped around the chest. This keeps the bowel moist and prevents excessive heat loss. Antibiotics are commenced preoperatively and colloid is given to counteract the existing hypoproteinaemia and hypovolaemia. At operation the anterior abdominal wall is stretched and any meconium washed out per rectum to reduce bulk. Reduction of the extruded bowel is attempted and abdominal wall closure achieved where possible.

In about 10% of cases, primary closure is not possible and a Silastic sheet or Prolene mesh is used to form an artificial sac to enclose the intestine. The material is sutured to the margins of the defect and the size of the sac gradually reduced over some days, squeezing the bowel back into the peritoneal cavity until closure of the abdominal wall becomes feasible—usually after 10 to 14 days. Ventilatory support postoperatively is often necessary. Parenteral nutrition is essential and may need to continue for many weeks until gastrointestinal motility and absorption are adequate. Sepsis is a considerable hazard. The mortality is now 5 to 10% compared with 80% 20 years ago. Improved postoperative management is largely responsible for this.

Congenital pyloric stenosis

Congenital hypertrophic pyloric stenosis is a disorder characterized by hypertrophy of the circular muscle of the pylorus and so obstruction to the gastric outlet. The incidence is 2 per 1000 live births. The aetiology is unknown. Theories include primary muscle hypertrophy, abnormalities of the maturation of ganglion cells, absence of a certain type of ganglion cell, or a response to abnormally high concentrations of circulating gastrin. Genetic and environmental factors play an important part. There is an increased incidence of pyloric stenosis in siblings of an affected child and in the offspring of a woman who has had the condition. Environmental factors include social class, type of feeding, and a seasonal variation with an increase in the winter months. In any large series the male:female ratio is 3 or 4:1 and half the cases will be first-born children.

Clinical features

The onset of symptoms is usually between 3 and 6 weeks of age, but may present shortly after birth. Vomiting of increasing severity is the cardinal symptom, eventually occurring after most feeds and becoming projectile. The vomitus is milk and mucus, and may contain altered blood suggesting an oesophagitis or gastritis; bile is never present. The baby stops gaining weight and becomes constipated. Characteristically the baby is alert, anxious, and hungry. If diagnosis is delayed, severe malnutrition may develop.

Examination reveals evidence of weight loss and in advanced cases signs of dehydration will be evident. When the stomach is full, waves of peristalsis travelling from left to right in the epigastrium will be seen (visible peristalsis). The thickened pylorus is felt as an olive-sized tumour lying deep to the edge of the right rectus and is often most easily felt when the stomach is empty. The diagnosis of pyloric stenosis is made on clinical grounds in the majority of cases. A plain radiograph of the abdomen may be very helpful in revealing a large stomach with a paucity of distal gas. A barium meal is diagnostic when the ‘string’ sign of the elongated pylorus is demonstrated. The barium study may also reveal gastro-oesophageal reflux, which is commonly associated with pyloric stenosis. Ultrasonography is now widely used—pyloric length more than 1.2 cm and wall width more than 3 mm supporting the diagnosis.

Management

In the child presenting early, electrolyte disturbance and dehydration are minimal. In the later case, dehydration with hypochloraemic alkalosis and marked potassium depletion occurs. Preoperative correction of water and electrolyte deficits is essential. The operation of pyloromyotomy, described by Ramstedt in 1912, splits the hypertrophied muscle longitudinally allowing the mucosa to bulge through the defect, thus enlarging the pyloric canal. Postoperatively, various feeding regimens are advocated; all aim to have the baby on a normal feeds by 48 to 72 h postoperatively. The prognosis is excellent.

Atresia and stenosis of the small intestine

An intrinsic obstruction may produce either complete or partial obliteration of the bowel lumen. Complete obliteration may be due to a gap between the two ends of the small intestine, with or without a connecting band between these ends, or a complete mucosal diaphragm. Such complete obstruction is known as atresia. When obstruction is incomplete it may be due to a narrowing of the lumen—a stenosis—or a mucosal diaphragm with a hole. Small-intestinal atresia is a more common finding than is stenosis. The duodenum is most often affected, followed by jejunum, and least often ileum.

Associated abnormalities of the gastrointestinal tract, including malrotation, oesophageal atresia, imperforate anus, biliary atresia, and annular pancreas are a feature of duodenal atresia/stenosis. Localized volvulus and meconium ileus are associated with jejunoileal atresias.

Intrinsic obstruction of the small intestine of congenital origin presents most often in the neonatal period but when the obstruction is partial it may first present much later, in infancy and childhood.

Congenital intrinsic duodenal obstruction

When duodenal obstruction is complete, vomiting usually occurs within a few hours of birth and is bile stained unless the obstruction is proximal to the ampulla of Vater, when the vomiting is persistent and copious but not bile stained. Meconium may be passed normally and there may be obvious epigastric distension. In view of the association with other abnormalities, these should be sought carefully. In particular, the infant should be examined for evidence of Down’s syndrome. Duodenal lesions are an association of this syndrome and occur in 10% of cases. When obstruction is incomplete the symptoms may be intermittent and the diagnosis delayed.

Congenital intrinsic duodenal obstruction may be accompanied by an annular pancreas; this is a sign of failure of duodenal development rather than an obstructive lesion per se. In infants with duodenal atresia, at operation, it often looks as if there is an annular pancreas because there is interposition of the pancreas between the two ends of the duodenal atresia.

Congenital intrinsic duodenal obstruction is not, in general, associated with multiple atresias in the remainder of the small intestine, but there may be obstruction at two levels in the duodenum.

Jejunoileal obstruction

Symptoms, typically bile-stained vomiting and abdominal distension, usually occur within the first 2 days of life. Meconium may or may not be passed. When obstruction is incomplete the diagnosis may again be long delayed and the child may present with intermittent vomiting, abdominal distension, and even with features of malabsorption—a clinical picture that may resemble coeliac disease.

Diagnosis

Plain radiographs of the abdomen are usually diagnostic in infants who present with a complete obstruction. In duodenal atresia there is the characteristic ‘double bubble’ (Fig. 15.15.2). When duodenal obstruction is incomplete there may be small amounts of air in the lower bowel. A barium meal may be necessary to demonstrate the obstruction and may suggest an associated malrotation. When there is complete jejunoileal obstruction there are usually multiple dilated loops of intestine. A barium enema may reveal an unused microcolon. When obstruction is incomplete a barium follow-through may be needed to establish the diagnosis. Rarely, laparotomy may be the final court of appeal.

Fig. 15.15.2 Plain radiograph of the abdomen of an infant with duodenal atresia showing characteristic ‘double bubble’.

Fig. 15.15.2
Plain radiograph of the abdomen of an infant with duodenal atresia showing characteristic ‘double bubble’.

Management

A nasogastric tube is passed to empty the stomach and allow accurate measurement of gastric losses. Correction of fluid and electrolyte disturbances, if present, should precede surgery, provided that gangrenous or ischaemic bowel is not suspected. At laparotomy, care should be taken to exclude any other gastrointestinal abnormality. In duodenal obstruction, the operation of choice is duodenoduodenostomy. In jejunoileal lesions, adequate resection of the proximal dilated gut reduces the great discrepancy in size between the two blind ends and so facilitates end-to-end anastomosis, although an oblique-to-end anastomosis is sometimes necessary. Leaving the dilated gut immediately proximal to the anastomosis results in ineffective peristalsis and delay in establishing enteral feeds.

Considerable loss of intestinal length may occur as a result of the intrauterine process producing the atresia; surgical correction, particularly of multiple atresias, will result in further loss. Every effort is made to preserve some ileum and the ileocaecal valve. Loss of considerable lengths of jejunum is well tolerated. Loss of ileum, particularly if the ileocaecal valve is also lost, presents management problems throughout childhood because malabsorption of a variety of important nutrients occurs. The enterohepatic circulation may be impaired. Early liver damage is a consequence of prolonged parenteral nutrition and episodes of sepsis.

Duplication of gastrointestinal tract

Definition

Duplications are cystic or tubular structures whose lumen is lined by a mucous membrane, usually supported by smooth muscle. They occur most often within the dorsal mesentery of the gut. They are also sometimes described as enteric cysts, neurenteric cysts, and reduplications. Duplications may occur anywhere along the alimentary tract but they are found most often in relation to the small intestine, particularly the ileum. They may not communicate with the lumen of the gastrointestinal tract. Duplications may be found in association with intestinal atresias. Sometimes those associated with the small intestine are lined by gastric mucosa and peptic ulceration of the adjacent small-intestinal mucosa, with bleeding, may occur. Those associated with the colon never contain ectopic gastric mucosa.

Clinical features

These are congenital malformations that present most often in early infancy. Later presentation, even into adult life, is well recognized. Duplications may present in infancy as a small-bowel obstruction, or a small cystic duplication may form the lead point of an intussusception. A palpable abdominal mass in infancy, as well as rectal bleeding and volvulus, may also be modes of presentation of this disorder. The clinical diagnosis is often difficult and the diagnosis may sometimes be made only at laparotomy. A technetium scan may be helpful by demonstrating ectopic gastric mucosa. Initial presentation may be a posterior mediastinal cystic mass, possibly associated with cervical or upper thoracic vertebral abnormalities. The mass is likely to communicate through the diaphragm with an intestinal duplication.

Management

Excision of a cystic duplication with or without the adjacent intestine is usually straightforward. Any associated thoracic cyst will also need excision. Short tubular duplications can be excised with the adjacent intestine; very extensive tubular duplications can be opened longitudinally and the mucosa stripped out, leaving the common muscle wall.

Small-intestinal malrotation with or without volvulus

Malrotation of the small intestine is due to disordered movement of the intestine around the superior mesenteric artery during the course of development of the embryo.

Two main abnormalities that produce symptoms may occur. First, there is a gross narrowing of the base of the mesentery, which may allow the midgut to twist around and cause a volvulus. This may occur acutely, causing complete obstruction, or it may occur intermittently, producing bouts of partial or complete obstruction that release themselves spontaneously. Secondly, there may be partial duodenal obstruction from extrinsic compression of the small intestine by peritoneal bands (Ladd’s bands) that extend from the caecum to the subhepatic region.

Malrotation may be associated with duodenal atresia or stenosis. It is also found in association with diaphragmatic hernia, omphalocele, and gastroschisis. However, malrotation may be asymptomatic and is sometimes discovered only as an incidental finding on a barium study. The majority of children who develop symptoms related to malrotation do so within the neonatal period, presenting with features of intestinal obstruction, complete or incomplete. When there is a volvulus there may also be obstruction to the blood supply to the bowel, which if complete will lead to extensive gangrene of the small bowel. The passage of bloody stools may be an early sign of this complication.

Those children with malrotation who present later in childhood may do so with features of intermittent obstruction such as episodes of vomiting, often bile stained, and abdominal pain, but sometimes they may manifest with features of malabsorption and many clinical features suggestive of coeliac disease. This is due to intestinal stasis with bacterial overgrowth in the lumen of the small intestine. Steatorrhoea may be accompanied at times by protein-losing enteropathy from obstruction of the mesenteric lymphatics, and chylous ascites may also occur.

Diagnosis

The diagnosis needs to be considered in the differential diagnosis of small-intestinal obstruction in infancy.

Plain radiographs of the abdomen may be very useful, typically revealing an air-filled stomach with some gas scattered through the lower part of the abdomen. However, a malrotation may not be accompanied by any abnormality on the plain radiograph of the abdomen and a barium meal will then be necessary to reveal the presence of malrotation by outlining the failure of the duodenum to cross to the left of the vertebral bodies with the fourth part lying adjacent to the first lumbar vertebra.

Management

Surgical intervention is indicated when a firm diagnosis is established. Ladd’s operation is usually the procedure of choice. This involves, in general, the placement of the colon on the left and the small intestine on the right, having divided any bands and adhesions between the duodenum and large bowel, and, by dissection, broadened the base of the mesentery as much as possible. After a volvulus, total bowel necrosis is untreatable, but severe bowel ischaemia can be reversible and a ‘second look’ laparotomy may be necessary.

Small-intestinal lymphangiectasia

Small-intestinal lymphangiectasia has been described as a primary, i.e. a congenital, abnormality or as a secondary manifestation of some other disease process such as constrictive pericarditis. The primary abnormality may be accompanied by generalized lymphatic abnormalities including lymphoedema, chylous ascites, and hypoplasia of the peripheral lymphatic system, but the lymphatic abnormality may be confined to the small bowel and its mesentery. It is usually, but not invariably, accompanied by hypoproteinaemic oedema. Radioisotope studies have demonstrated that the hypoproteinaemia is due to abnormal protein loss into the gut. The pathogenesis of the hypoproteinaemia has been attributed to the rupture of dilated lymphatic channels or to protein exudation from intestinal capillaries via an intact epithelium, where there is obstruction of lymphatic flow.

Clinical features

It is a rare condition, which may present throughout life but most often in the first 2 years with diarrhoea and failure to thrive and, later, generalized oedema with hypoproteinaemia. The clinical picture may resemble coeliac disease. There is lymphopenia in the presence of a normal bone marrow and reduction of serum albumin, serum IgG, and carrier proteins such as protein-bound iodine. The severe protein loss may be accompanied by enteric calcium loss, leading to hypocalcaemia. Steatorrhoea is often found in this disorder.

Diagnosis

Congenital abnormalities of the gastrointestinal tractDiagnosis is made by showing the characteristic lymphatic abnormality on small intestinal biopsy, that is dilated lacteals, but the lesion is patchy. One negative biopsy does not exclude the diagnosis. Capsule endoscopy allows a comprehensive view of the small intestine, demonstrating oedematous mucosa and pale swollen villi in affected areas.

Pathology

Autopsy studies show that dilated lacteals may occur irregularly along the small bowel and there may be gross dilatation of lymphatics projecting into the lumen. Lymphatic proliferation and dilation may also occur within the mesentery, as well as the serosal, muscular, and submucosal layers of the small-intestinal wall, and extend into the lymph nodes and occupy part of the nodal tissue.

Treatment

This is usually dietetic, as the lymphangiectasia is rarely localized enough to allow surgical excision to effect a permanent cure. The amount of long-chain fat in the diet, which is normally absorbed via the intestinal lymphatics, should be limited. This leads to a reduction in the volume of intestinal lymph and in the pressure in the dilated lymphatics. It is best done by placing the child on a low-fat diet (5–10 g/day) and adding medium-chain triglycerides, instead of the usual long-chain dietary fats, in unrestricted amounts. A milk containing medium-chain triglyceride such as Pregestimil may be used, with medium-chain triglyceride oil for cooking. Some children may be resistant to this therapy when the abnormality is very extensive and, on occasion, death may result despite therapy. Albumin infusions are of little value in management as their benefit is so transitory. Steroids have been advocated but there is little evidence to justify their use. In a follow-up study of children, although there was a continuing chyle leak, as shown by persistent lymphopenia and hypoalbuminaemia, there was a rapid and sustained improvement in dependent oedema following the use of the diet recommended above, although asymmetrical oedema from peripheral lymphatic abnormalities was unaffected. Their growth rate improved on the diet. Clinical relapse occurred quickly when the diet was relaxed. Continued adherence to a strict diet, at least through puberty, is therefore recommended. Indeed it seems probable that this is a lifelong disorder and that some dietetic management may usually need to be permanent.

Meckel’s diverticulum

This diverticulum is the vestigial remnant of the vitellointestinal duct. Although most people who have such a diverticulum are asymptomatic, complications may arise, which may present in a variety of ways. In children, these complications chiefly arise in association with the presence of ectopic gastric mucosa in the diverticulum. Other ectopic tissue, for example pancreatic tissue and colonic mucosa, may be found in some cases.

The diverticulum is located in the distal ileum within 100 cm of the ileocaecal valve. It is always antemesenteric.

Clinical features

Rectal bleeding is the main symptom. This is usually the passage of bright blood rather than tarry melaena stools. Typically the stool is at first dark in colour but later bright red. Bleeding may be acute, with shock requiring urgent blood transfusion, or it may be chronic. From a practical viewpoint any child who has a massive, painless, rectal bleed should be regarded as having a Meckel’s diverticulum until proved otherwise. Most often bleeding from a Meckel’s diverticulum is associated with ulceration of the small bowel adjacent to ectopic gastric or pancreatic mucosa but this is not always the case as bleeding may occur in the absence of ectopic mucosa.

Small-intestinal obstruction may also be a mode of presentation. This may be as a volvulus associated with a band, or an intussusception with the diverticulum as the lead point. Acute diverticulitis occurs and may produce a picture indistinguishable from acute appendicitis.

Diagnosis and management

This depends upon the mode of presentation. When rectal bleeding occurs, other causes need to be excluded. Investigation may include colonoscopy to exclude colonic causes and upper endoscopy to exclude peptic ulceration or oesophagitis.

Barium follow-through is usually an unrewarding investigation. a technetium scan is usually the most important investigation. The radionuclide 99Tcm concentrates in the gastric mucosa. When it is given intravenously, ectopic gastric mucosa appears as an abnormal localization on abdominal imaging with a gamma-camera. In this way a Meckel’s diverticulum with ectopic gastric mucosa or indeed a duplication with such ectopic tissue may be diagnosed. A negative scan may prompt angiography. However, negative investigations in a child with severe bleeding should not deter a surgeon from proceeding with a diagnostic laparotomy, or laparoscopy if appropriately skilled. Indeed, when considering the other modes of presentation of Meckel’s diverticulum it is often only at laparotomy that the role of a Meckel’s diverticulum in the child’s intestinal pathology is appreciated.

Meconium ileus

This is a manifestation of cystic fibrosis, the disorder sometimes known as fibrocystic disease of the pancreas. Meconium ileus is the earliest mode of presentation of this disorder during the neonatal period. A similar syndrome in older children and young adults who have cystic fibrosis may occur—the meconium ileus equivalent. The abnormally viscid consistency of the meconium produces an intraluminal obstruction. It may result from several factors including the lack of pancreatic enzymes during fetal life, which may account for the high protein content of the meconium. There is also evidence of reduced secretion of water and electrolytes in such infants, which may further render the meconium more viscid. The meconium, because of its high viscosity and tendency to adhere to the mucosa, cannot be propelled along the bowel and so small-intestinal obstruction results. This occurs most often in the distal ileum.

Clinical features

The neonate with this disorder usually develops signs of intestinal obstruction within the first 24 to 48 h of life, with the classical signs of bile-stained vomiting, progressive abdominal distension, and failure to pass meconium. In simple meconium ileus, the meconium is the sole source of the obstruction, but meconium ileus may be complicated by perforation of the gut and, when this occurs in utero, intraperitoneal calcification may be observed on a plain radiograph of the abdomen, providing evidence of meconium peritonitis. Perforation may also occur in the neonatal period. Volvulus and atresia may also complicate meconium ileus.

In simple meconium ileus, the plain radiograph of the abdomen may show dilated bowel but few fluid levels. Sometimes there is the appearance of bubbly meconium in the right lower quadrant. Bowel loops may be palpable. If a contrast enema is performed a microcolon, a consequence of disuse, will be demonstrated. Atresia associated with meconium ileus is frequently indistinguishable radiologically from an atresia of ischaemic origin.

Management

Congenital abnormalities of the gastrointestinal tractWhen meconium ileus is complicated by atresia or perforation, gangrene, peritonitis, or associated volvulus, surgical intervention is essential. Surgical options include the formation of a double-barrelled stoma with subsequent irrigation of the meconium from the distal bowel over a week or so, or intraoperative irrigation of the bowel with an immediate end-to-end anastomosis. In both options, an associated atresia or necrotic bowel are resected. The treatment of uncomplicated meconium ileus using enemas containing pancreatic enzymes, mucolytic agents such as acetylcysteine, and the detergent Tween 80 had been advocated for some time: Noblett in Melbourne, in 1969, used a Gastrografin enema to relieve intraluminal obstruction. Gastrografin is a radio-opaque, hyperosmolar solution that is effective because of its hypertonicity. This technique should not be used until a plain radiograph of the abdomen has excluded the possibility of complicated meconium ileus. An initial barium enema should exclude Hirschsprung’s disease and demonstrate a microcolon extending to the proximal colon. The retrograde passage of contrast medium through the ileocaecal valve should demonstrate intraluminal meconium with passage into proximal dilated ileum, thus excluding an ileal atresia. After a successful Gastrografin enema, large amounts of meconium will be passed. Other water-soluble contrast media have replaced Gastrografin in many paediatric radiology departments.

Although there may be no signs clinically or radiologically of pulmonary complications in the neonatal period, physiotherapy should be started and any chest infections treated with antibiotics when they occur (as for older children with cystic fibrosis). A pancreatic enzyme preparation should also be started, at first in small dosage when milk feeds have begun. The diagnosis should be confirmed by sweat electrolyte estimations; concentrations of sweat sodium above 60 mmol/litre are abnormal. In the majority of infants with cystic fibrosis, the finding of the abnormal gene Δ‎F508 or one of the other recognized mutations confirms the diagnosis. In a minority the abnormal gene is not identifiable.

Congenital short intestine

There is a syndrome of congenital short intestine in association with malrotation with clinical features similar to those that follow massive intestinal resection. There is also another syndrome of congenital short intestine in association with pyloric hypertrophy and malrotation. This latter syndrome is due to an absence or diminution of argyrophil ganglion cells in the small-intestinal wall. These cells normally organize peristalsis and ensure that the bolus moves forward at the correct speed. In the absence of such innervation, smooth muscle of the small-intestinal wall contracts spontaneously and rhythmically, but segmentation is not coordinated and the food bolus does not move forward, and there is work hypertrophy of smooth muscle. Both syndromes are rare and often only diagnosed at laparotomy.

Colonic atresia

Atresia of the large intestine is rare. In any series of cases of intestinal atresias, fewer than 10% will have isolated colonic atresia.

Clinical features

The baby presents in the first 24 to 48 h with marked abdominal distension, vomiting, and failure to pass meconium.

Diagnosis

Abdominal radiographs reveal multiple dilated loops of bowel with fluid levels; the position of the loops may suggest a large bowel obstruction. Confirmation of the level of the atresia is obtained by barium enema.

Management

Nasogastric suction and intravenous fluids are commenced preoperatively. At laparotomy the lesion may be an isolated atresia or associated with multiple atresias of small and large bowel. If the atresia is solitary, it may be possible to perform an anastomosis after resection of the atresia and a length of the grossly dilated proximal bowel. Frequently a colostomy is fashioned to allow the dilated proximal bowel to contract before an end-to-end anastomosis some weeks later.

Hirschsprung’s disease

In this condition, ganglion cells are absent in the bowel wall. The distal rectum is always aganglionic and the aganglionosis extends proximally for a variable distance. In 70% the rectosigmoid is involved, in 20% the aganglionosis extends proximal to the sigmoid for a variable distance up the colon, and in 10% the aganglionosis extends into the small intestine. The aganglionic bowel is incapable of coordinated peristalsis and passively constricts, resulting in a mechanical obstruction. The incidence is approximately 1 in 5000 births.

Clinical features

Hirschsprung’s disease is not associated with a high incidence of prematurity, and most of the babies have a birth weight appropriate for gestational age. This contrasts sharply with most of the other congenital obstructions of the alimentary tract. Associated abnormalities are rare. The most important association is with Down’s syndrome.

Symptoms of Hirschsprung’s disease are present in the first few days of life in almost all cases. Exceptionally, a baby will have no symptoms during the early neonatal period. The major symptoms are failure to pass meconium within 36 h of birth, abdominal distension, vomiting, and poor feeding. These may occur singly or in combination. Frequently, a rectal examination will relieve the obstruction by passively dilating the aganglionic segment. Twenty to 50% of patients with Hirschsprung’s disease are not diagnosed in the early weeks of life. Later presentation is with constipation that dates back to the neonatal period. It is not accompanied by soiling and is frequently associated with failure to thrive. Presentation may be delayed for months or years.

Hirschsprung’s enterocolitis may be the mode of presentation in the infant of a few weeks of age. This condition, the precise cause of which is unknown, presents with abdominal distension, profuse diarrhoea, and circulatory collapse. The infant is gravely ill and the mortality is 20%. The child with this complication, successfully treated initially, may have absorptive problems for some time, suffer recurrent episodes of enterocolitis despite successful surgery, and the surgery is attended by a higher rate of complications. The incidence of enterocolitis can be greatly reduced if the diagnosis of Hirschsprung’s disease is made in the first week of life.

Diagnosis

In the neonatal period a plain abdominal radiograph will reveal distension of small and large bowel. A barium enema may show the narrow aganglionic bowel with dilated proximal bowel (Fig. 15.15.3) but a normal barium enema does not exclude Hirschsprung’s disease. A 24-h film showing retained barium in the colon is often more helpful than the actual enema in confirming the clinical suspicion of Hirschsprung’s disease. The definitive diagnostic procedure is a rectal biopsy. Suction biopsy enables the pathologist to look for ganglion cells in the submucosal plexus; full-thickness biopsy provides the intermyenteric plexus as well but this is usually unnecessary. In Hirschsprung’s disease, ganglion cells are absent, hypertrophic nerve trunks are present, and if a histochemical stain for acetylcholinesterase is used, this reveals excessive amounts of this enzyme in the bowel wall. Anorectal manometry in Hirschsprung’s disease typically shows failure of relaxation of the internal sphincter in response to rectal distension but this reflex is frequently absent in normal term babies until after the second week of life. This method of diagnosis is therefore unreliable in the neonatal period, requires considerable expertise to obtain reliable results, and cannot be regarded as suitable for the routine diagnosis of Hirschsprung’s disease.

Fig. 15.15.3 Barium enema in Hirschsprung’s disease illustrating a narrow aganglionic rectum with dilation proximally.

Fig. 15.15.3
Barium enema in Hirschsprung’s disease illustrating a narrow aganglionic rectum with dilation proximally.

Management

Following diagnosis, either definitive surgery is carried out or a colostomy is fashioned in ganglionic bowel and definitive surgery deferred for a period of time. Definitive surgery consists of excision of aganglionic bowel with a ‘pull through’ procedure, enabling an anastomosis to be made between the anus and ganglionic colon. The three operations most often performed are those described by Swenson, Duhamel, and Soave. Provided that the surgery is uncomplicated, the long-term complications, which include faecal and urinary incontinence, and impotence, should be minimal. Bowel control is likely to be imperfect for a number of years, with soiling as a major problem, but good bowel control will be achieved in the majority of patients treated by experienced surgeons.

Imperforate anus

The exact incidence of this abnormality is not known but the usual incidence quoted is 1 in 5000 births. The basic classification differentiates between the high anomalies, where the bowel terminates above the pelvic floor, the bowel narrowing down to communicate with the urethra in the male (a rectourethral fistula) and the vagina or vestibule in the female (a rectovaginal/vestibular fistula) in the majority of cases. In the low anomalies, the bowel passes through the pelvic floor and either opens on to the perineum in an ectopic position, or lies just beneath the skin-covered anus. The high anomaly is more likely to occur in boys, the low in girls. Overall, more boys than girls present with an imperforate anus. Associated anomalies of the urogenital tract, oesophagus, heart, and skeletal system are common.

Clinical features

Early examination of the perineum will establish the presence of an anorectal anomaly. In boys, the presence of meconium on the perineum usually indicates a low anomaly. In girls, careful inspection is necessary to differentiate meconium being passed per vaginum, indicating a high anomaly, from meconium emerging from a perineal site, suggesting a low anomaly. Careful probing of any opening will enable the direction in which the bowel is running to be established. In girls, doubt about the precise anatomy of the anomaly may be resolved by contrast studies. In boys, differentiating a completely covered anus from a high anomaly may be difficult in the early hours after birth. Examination of the urine microscopically may reveal the presence of squamous cells or debris, suggesting a fistula between bowel and urethra. Occasionally, meconium is passed per urethra.

A lateral film of the pelvis taken after the infant has lain ‘bottom up’ over a foam wedge for some minutes will often reveal the level at which the rectum terminates, but this film cannot be reliably interpreted in the first few hours after birth because air may not have reached the distal bowel. In boys, a micturating cystourethrogram will demonstrate a rectourethral fistula in a high proportion of cases, but is rarely necessary as an initial diagnostic procedure. Having defined the nature of the anorectal anomaly, evidence of any associated abnormality should be sought by careful clinical examination and radiographs of chest, abdomen, and the vertebral column.

Management

A low anomaly usually requires a perineal procedure to enlarge the opening. Dilatation alone may suffice, but in the majority of cases a simple anoplasty produces a more satisfactory result. In the long term, the functional results for the low anomalies should be very good. A high anomaly necessitates a defunctioning colostomy in the neonatal period. Definitive surgery involves division of any fistula and positioning the bowel accurately within the pelvic floor and sphincter muscles. Delay in achieving bowel control is common and a number of secondary operations designed to improve control have been advocated. However, if the initial surgery is meticulous, acceptable continence should be achieved in over 80% of children within the first 10 years. A permanent colostomy should rarely be necessary. The high incidence of associated genitourinary abnormalities makes it mandatory to investigate carefully the urinary tract at an early stage. The mortality for anorectal anomalies is largely dictated by the presence of other serious abnormalities.

Further reading

Christison-Lagay ER, et al. (2011). Neonatal abdominal wall defects. Semin Fetal Neonatal Med, 16, 164–72.Find this resource:

Condino AA, et al. (2004). Abnormal intestinal histology in neonates with congenital anomalies of the gastrointestinal tract. Biol Neonate, 85, 145–50.Find this resource:

Dalla Vecchia LK, et al. (1998). Intestinal atresia and stenosis: a 25 year experience with 277 cases. Arch Surg 133, 490–6.Find this resource:

Freeman NV, et al. (eds) (1994). Surgery of the newborn. Churchill Livingstone, London.Find this resource:

    Gupta AK, Cuglani B (2005). Imaging of congenital anomalies of the gastrointestinal tract. Ind J Pediatr, 72, 403–14.Find this resource:

    Khong PL, et al. (2003). Ultrasonography of Intra-abdominal cystic lesions in the newborn. Clin Radiol, 58, 449–54.Find this resource:

    Kotecha M, et al. (2012). Multimodality imaging manifestations of the Meckel diverticulum in children. Pediatr Radiol, 42, 95–103.Find this resource:

    Marcelis C, et al. (2011). Chromosomal anomalies in the etiology of anorectal malformations: a review. Am J Med Genet A, 155, 2692–704.Find this resource:

    Pierro, A et al. (1997). Staged pull-through for rectosigmoid Hirschsprung’s disease is not safer than primary pull-through. J Pediatr Surg, 32, 505–9.Find this resource:

    Roberts HE, et al. (1998). Increased frequency of cystic fibrosis among infants with jejunoileal atresia. Am J Med Genet, 78, 446–9.Find this resource:

    Schoenwolf GC, et al. (eds) (2008). Larsen’s human embyrology. Elsevier/Churchill Livingstone, Philadelphia, PA.Find this resource:

      Shaul DB, Harrison EA (1997). Classification of anorectal malformations—initial approach, diagnostic tests, and colostomy. Semin Pediatr Surg, 6, 187–95.Find this resource:

      Stevenson RE, et al. (eds) (2008). Human malformations and related anomalies. Oxford University Press, Oxford.Find this resource:

        Veereman-Wauters G (1996). Normal gut development and postnatal adaptation. Eur J Pediatr, 155, 627–32.Find this resource:

        Victoria T, et al. (2012). Use of magnetic resonance imaging in prenatal prognosis of the fetus with isolated left congenital diaphragmatic hernia. Prenat Diagn, 32, 715–23.Find this resource:

        Wen J, et al. (2010). Primary intestinal lymphangiectasia: four case reports and a review of the literature. Dig Dis Sci, 55, 3466–72.Find this resource: