The incidence of inguinal herniae in children has been reported to be between 0.8% and 4.4%,¹ rising to 18.9% to 30% of preterm infants.^2,³ Inguinal herniae are six times more common in boys and are more common in twins.^1,⁴ Around 1 in 10 inguinal hernias are non-reducible at presentation, although a careful history from the parents will often elucidate earlier signs and symptoms. In this group, over two-thirds are under 1 year of age.

In children, inguinal herniae are almost always indirect.⁵ The hernia exits the peritoneal cavity via the internal inguinal ring to enter the inguinal canal, leaving the canal via the external inguinal ring. The sac is intimately related to the contents of the spermatic cord. It is compression of the testicular vessels by hernial contents that may render the testis ischaemic. In contrast, in females the risk of ischaemia to the ovary and adnexae usually occurs as a result of torsion of these structures within the hernial sac.

Rarely, direct inguinal herniae may occur, with some series reporting an incidence of up to 5%.⁶ Typically, these children have either had previous inguinal surgery, a connective tissue disorder or were delivered at less than 30 weeks’ gestation. The clinical management and surgical approach remains similar to indirect inguinal herniae.

Inguinal herniae usually present as a swelling in the inguinal region first noticed by the carer when changing or bathing the child, especially if crying or straining.⁷ The swelling may extend into the scrotum in boys or the labia majora in girls. Persistent tachycardia, overlying erythema and marked tenderness suggest an irreducible hernia complicated by ischaemia.⁸ Occasionally, an irreducible hernia may present with vomiting and abdominal distension as a result of intestinal obstruction.

A hernia can be differentiated from a hydrocele as the latter transilluminates and does not usually extend into the inguinal region. In neonates, these differences may be less obvious and a hernia may appear to transilluminate. Encysted hydroceles of the cord and, rarely, testicular torsion may also cause diagnostic confusion. Where there is any doubt regarding the diagnosis, a paediatric surgeon should be consulted.

Femoral

Femoral herniae are rare in children, accounting for between 0.4 and 1.1% of all groin hernias.^1,⁹ They are often not diagnosed prior to surgery and are one cause of recurrent ‘inguinal’ herniae in children. Typically, most present between 4 and 10 years of age and there is an equal sex incidence. Clinically, the hernia presents as a swelling that is inferior and lateral to the pubic tubercle. As in adults, femoral herniae are associated with a high incidence of complications, so prompt surgical intervention is required.

Umbilical and paraumbilical herniae

A true umbilical hernia occurs through the umbilical ring as opposed to a paraumbilical hernia that results from a defect adjacent to the umbilical ring.

Umbilical herniae are very common, occurring in up to 18.5% of infants under 6 months of age.⁵ They are more common in Afro-Caribbean children and in premature infants, when the incidence rises to between 41.6 and 75%.^10,¹¹ The vast majority of umbilical defects appear to close spontaneously with increasing age, largely irrespective of the size of the defect. Given the very low risk of the hernia becoming non-reducible, surgical repair is only indicated for those herniae that persist beyond 3 and 5 years of age, or in the very few that present with symptoms.¹²

Paraumbilical defects do not close with increasing age and should be referred for elective repair on diagnosis.