Inguinal hernias are among the most common congenital conditions in children. They have a reported incidence of 0.74% to 6.62% in children to 15 years of age¹ and 3.5% to 5% in full-term newborns,² with a tenfold increase in males versus females.³ Premature infants of less than 36 weeks gestational age have a rate approaching 7%,⁴ with the highest rate seen in infants less than 28 weeks of gestational age or with a birth weight less than 1000 g.² Ten percent of these may become incarcerated before 1 year of age,⁵ with the greatest risk occurring during the first 6 months of life.⁶

Hernias in the groin can be divided into three types: direct, indirect, and femoral. An indirect inguinal hernia occurs when abdominal contents pass through the internal ring and then traverse the inguinal canal into the scrotum. Congenital inguinal hernias, by far the most common, are indirect by definition⁷ due to a processus vaginalis that fails to fully close. Direct inguinal hernias are rare in children and occur when there is a weakness in the abdominal musculature allowing intestine to protrude into the inguinal canal. Femoral hernias pass into the femoral canal and not into the scrotum or labia.

There is an outpouching of the peritoneum into the inguinal canal by the processus vaginalis about the third month of gestation. In males, the testes descend into the scrotum during the seventh month of gestation, the left usually preceding the right. The processus vaginalis will remain partially patent in approximately 70% of term male infants in the first 2 weeks after birth but will be virtually obliterated by the third week, again the left before the right.⁸ This probably explains why a majority of inguinal hernias are found on the right side (60%) compared with 30% on the left and 10% bilaterally.⁹

The processus vaginalis does not become as deep in females since ovarian descent is restricted by the ovarian ligament. The extension of the processus vaginalis past the inguinal canal is referred to as the canal of Nuck in females. An indirect hernia can occur if it remains patent.

As opposed to a hernia where intestine enters the inguinal canal, a hydrocele may occur when the processus vaginalis narrows to the point that only fluid can pass (communicating). The hydrocele is noncommunicating when fluid is trapped after the processus closes.

In the first year of life, inguinal hernias most often present as a bulge in the groin, scrotum, or labia. The bulge may come and go and be exacerbated with crying, cough, or dyschezia. Although usually asymptomatic at times, the parent may report that the child is fussier when the bulge is present. Children may note a bulge along with a feeling of fullness in the affected area.

The hernia may be an incidental finding during a physical examination. The examiner may note a swelling in the groin, scrotum, or labia that has a smooth consistency and may withdraw through the inguinal ring when the child relaxes or with the application of gentle pressure. The “silk glove sign” involves palpating the spermatic cord in males or the processus vaginalis in females over the pubic tubercle. It is a highly accurate way (sensitivity of 91% and a specificity of 97.3%) of demonstrating a patent processus vaginalis.¹⁰ Examination in the male should include signs of a retractile testicle and in the female a protruding fallopian tube or ovary.