Exomphalos (Fig. 1) 2157 is characterized by herniation of intra-abdominal contents through a full-thickness umbilical defect which is covered by a sac composed of peritoneum internally and umbilical cord amnion externally. The umbilical vessels are usually spread out over the sac. Gastroschisis is characterized by a defect in the abdominal wall, 1 to 5 cm in diameter, usually just to the right of the umbilicus (Fig. 2) 2158. The herniated viscera are not covered by a sac and the bowel is usually non-rotated. The mesentery is thick.

Following formation of the body of the embryo, rapid growth of the midgut results in herniation through the umbilicus to form the ‘physiological hernia’. The intestine returns to the abdominal cavity between the tenth and twelfth week, when normal intestinal rotation takes place. The recti and oblique muscles are seen within the abdominal wall by day 52. Duhamel suggested that exomphalos represents a failure of the lateral folds of the body wall to fuse during formation of the body of the embryo. De Vries proposed that the abnormality is caused by persistence of the body stalk of the germinal disc, associated with arrest of development of the abdominal wall musculature.

According to Duhamel's theory, gastroschisis occurs as a result of a localized teratogenic incident which affects the normal differentiation of the periumbilical mesoderm. De Vries argues that a defect in involution of the right umbilical vein results in local ischaemia, resulting in necrosis of the periumbilical abdominal wall.

Exomphalos occurs in between 1 in 4000 and 1 in 10000 live births. The incidence of gastroschisis seems to be increasing, with a reported incidence of 1 in 17000 in 1952 and an estimated present incidence of about 1 in 5000. The reasons for this apparent increase are unclear. Exomphalos is more common in males than females, with a sex ratio of 3:2, but gastroschisis occurs equally.

Associated congenital malformations are frequently seen in children with exomphalos; such abnormalities will occur in about two-thirds of children with large defects.

Up to 10 per cent of patients have the Beckwith–Wiederman syndrome, with macroglossia and organomegaly. The principal danger in these patients is postnatal hypoglycaemia (due to pancreatic islet hyperplasia) causing cerebral damage. Associated major cardiac anomalies are seen in 25 to 33 per cent and about 25 per cent have gastrointestinal abnormalities. Trisomy (usually 21 or 18) is seen in 15 per cent of patients.

Gastroschisis is rarely associated with abnormalities outside the gastrointestinal system. Atresia, often resulting from local ischaemia at the neck of the sac, is by far the most common abnormality associated with gastroschisis, with an incidence of between 11 and 23 per cent. A significant number of these are colonic (which are otherwise rare).

These major abdominal wall defects present many difficulties in management and should be treated in a paediatric surgical unit. The principal immediate problems are profound heat and fluid loss from the eviscerated bowel and intestinal distension from swallowed air (especially if the baby is ventilated). Prompt postnatal management is therefore of great importance. A large nasogastric tube must be inserted and left on free drainage with regular aspiration. Wrapping up the whole of the baby's trunk in ‘cling film’ minimizes both heat and fluid loss, while an intravenous infusion of plasma will correct the fluid deficit. Every baby with exomphalos must be examined for signs of the Beckwith–Wiederman syndrome since severe hypoglycaemia may occur shortly after birth, resulting in cerebral damage. A thorough clinical cardiac assessment should be performed preoperatively.

In the treatment of exomphalos the umbilical vessels are divided and the sac excised. For both conditions the abdominal cavity is forcibly stretched to allow the herniated viscera to be returned (after division of Ladd's bands, if present). It is normally possible to effect a primary closure, but closure may result in such an increase of intra-abdominal pressure that ventilation or venous return is compromised. If this is the case a prosthetic ‘silo’ may be constructed from silastic sheeting. The gut is then gradually returned to the abdominal cavity by serially reducing the size of the sac over the following week, after which the wound is repaired. Associated atresias are dealt with by primary anastomosis or creation of stomas as appropriate, depending on the condition of the gut.

When operating for gastroschisis a central venous feeding line may be sited, since establishment of normal intestinal activity often takes 2 or more weeks, necessitating total parenteral nutrition. Postoperative ventilation is frequently necessary.

Children with gastroschisis and those with exomphalos uncomplicated by associated abnormalities may lead a completely normal life.

There is no evidence that early delivery or operative delivery by caesarian section reduce the morbidity associated with either condition. If a prenatal diagnosis is made by ultrasound a paediatric surgeon should discuss the nature of the condition and the prognosis with the parents. Gastroschisis in itself should not be an indication for termination of pregnancy since the prognosis is very good; the advice given to parents of a child with exomphalos will depend on the presence of associated syndromes or abnormalities. Delivery should take place in the institution where the paediatric surgical unit is located.

The vitellointestinal duct connects the primitive midgut to the yolk sac. Spontaneous obliteration usually occurs before the sixth week of embryonic life.

The urachus (connecting the bladder to the allantois) develops from the urogenital compartment of the cloaca. It is usually obliterated by the time of birth.

Anatomical abnormalities and discharge are frequent reasons for referral to the paediatric surgeon. Discharge of fluid or mucus is usually due to local infection. Anatomical abnormalities are related either to the gastrointestinal tract or to the urinary tract.

Umbilical granuloma results from incomplete separation of the umbilical cord. Application of a silver nitrate stick is usually effective as a rapid treatment. Umbilical polyps represent failure of complete obliteration of the vitellointestinal duct and require surgical removal. A search should be made for an associated umbilical sinus and, if a sinus is present, a coexistent fibrous intra-abdominal band. Fibrous bands connecting the umbilicus with the intestine may give rise to an internal hernia at any age. Patent vitellointestinal duct is uncommon and may open into a normal umbilicus or an exomphalos. At surgery malrotation must be treated if present. Patent urachus is very rare and is usually suspected following passage of urine via the umbilicus during the first 3 weeks of life. Bladder outflow obstruction also may be present. Cysts may persist in an obliterated urachus, giving rise to abscesses. These present as a tender midline swelling and may point to the bladder or umbilicus.

Umbilical hernia is common in the young child, especially in those with Down's syndrome or hypothyroidism. The majority of paediatric hernias resolve spontaneously within the first 6 years of life, but a hernia that is still present at this age, or one which has a particularly wide opening, should be treated surgically. Non-absorbable sutures should be used to repair the defect. Paraumbilical herniae always require operative repair.

Small defects in the linea alba above the umbilicus allow extraperitoneal fat to herniate through into the subcutaneous tissues. These herniae, whilst usually very small, often cause considerable discomfort. Non-absorbable sutures should be used to repair them.

In this condition of unknown aetiology there is a deficiency of the musculature of the anterior abdominal wall as a result of which the skin is very wrinkled, and resembles a prune. The incidence is between 1 in 29000 and 1 in 40000 live births and 95 per cent of affected children are male. Abnormalities of the urinary tract and cryptorchidism are almost always present. Plication operations designed to treat abdominal wall laxity yield little or no improvement to the function or appearance of the abdomen. Historically the prune-belly syndrome had a very high infant mortality rate, due principally to urinary abnormalities; recent improvements in urological management have reduced this considerably.

In this extremely rare condition (incidence between 1 in 200000 and 1 in 400000 live births) a midline fusion defect affects the cloacal membrane. The condition occurs more frequently in males. The bladder and hindgut are exstrophic and the short small bowel terminates as a stoma.

If untreated, this severe abnormality is usually rapidly fatal due to ileal fluid loss. Even after successful closure of the defect many potential problems remain: major associated abnormalities are found in about 85 per cent of cases, affecting the gut, spine, and urinary tract.

The pentalogy comprises an upper midline exomphalos, an anterior diaphragmatic hernia with an associated sternal cleft, ectopia cordis, and intracardiac defects. It is rare and frequently fatal despite attempts at operative correction. Operation may be avoided in patients with lethal cardiac defects if preoperative echo cardiography is performed.

During the third month of gestation the processus vaginalis is formed at the internal inguinal ring. Following descent of the testis, contraction of the processus normally occurs before 32 weeks of gestation. The factors responsible for obliteration of the processus are unknown.

The condition affects 1 to 2 per cent of children; 90 per cent of patients are boys. Prematurity is associated with an increased incidence.

In the majority the processus is patent throughout its whole length but sometimes a blind ending sac is found.

The diagnosis is often made from the history alone, especially in younger children since the hernia may not be visible. In the presence of an empty sac, the cord is described as thickened. In the acute situation an irreducible hernia may be difficult to differentiate from acute hydrocele, inguinal lymphadenitis, or torsion of an undescended testis.

Irreducibility occurs in 2 to 18 per cent of patients; the incidence rises to 30 per cent or more in the first 8 weeks of life. This poses two dangers—intestinal gangrene and gonadal infarction. The risk of gonadal infarction secondary to irreducibility appears to be much higher (30 per cent) in infants less than 12 weeks of age than in older children.

In infants under 6 months of age herniotomy should be performed as an early elective procedure because of the risk of irreducibility. In the case of very small premature babies in special care units, however, the benefits of waiting for the lungs to mature outweigh the risk of irreducibility.

The inguinal ligament is identified in a groin crease incision and followed medially until the spermatic cord is seen at the external ring. In children less than 18 months old the operation may be performed through the external ring since the inguinal canal is short, but in older children access is best obtained by making a small ‘buttonhole’ incision in the external oblique aponeurosis through which the cord may be delivered. Following separation of the patent processus from the rest of the cord contents, and ensuring that it is empty, the processus is divided and tied off proximally as close as possible to the internal ring, using a slowly absorbable material. The distal end should be left open to avoid the complication of iatrogenic hydrocele. If the external oblique aponeurosis has been opened it is repaired with absorbable sutures.

Providing the child is well with no evidence of intestinal gangrene an attempt should be made to reduce the hernia by taxis. Sedation with morphine considerably aids this procedure and it is essential that an intravenous infusion is sited prior to the attempt. After reduction observations must be made and recorded in case of accidental reduction of gangrenous gut or ‘en masse’ reduction. In this way approximately 70 per cent of acutely irreducible hernias may be reduced: operation should be performed 24 to 48 h later. Failure of manual reduction is an indication for emergency operation. This may be an extremely difficult procedure because the processus is very friable.

Haematoma and sepsis are occasional complications. The hernia may recur at any time postoperatively, and this is much more common following emergency operation.

A hydrocele results when the narrowly patent processus allows peritoneal fluid to accumulate inside. It is seen more often on the right side but the condition is frequently bilateral. Encysted hydroceles are less common. In the majority of infants hydroceles will spontaneously resolve by 1 year of age and operation is therefore delayed until this time unless the collection is very large or symptomatic. The operation is exactly the same as for inguinal hernia.

This extremely rare condition is seen most frequently in 5- to 10-year-old girls. Strangulation is uncommon. Operation is by one of the standard approaches.

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