Chapter 47: Inguinal Hernia

• Most inguinal hernias are asymptomatic and are managed by referral to a pediatric surgeon for elective management.

• Incarcerated hernias are best reduced by the taxis method.

• Inability to reduce an inguinal hernia requires emergent referral to a surgeon.

Inguinal hernias are among the most common congenital conditions in children. They have a reported incidence of 0.8% to 4.4% in children¹ and 3.5% to 5% in full-term newborns² with a 10-fold 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 in to 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 gentile 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.

In differentiating between a hernia and a hydrocele, the hydrocele will transilluminate whereas a hernia will not. In addition, the examiner should be able to get their fingers above the hydrocele and not with a hernia since the hernia communicates with the abdominal cavity.¹¹ Ultrasound can be helpful in the differentiating a hernia from a hydrocele.^12,13

Incarceration of a hernia occurs when the abdominal contents become trapped within the patent process vaginalis and do not retract above the inguinal ring (Fig. 47-1). Although most often it is small bowel that becomes incarcerated, any abdominal contents are at risk. In females, this can include the ovary and fallopian tube. A hernia becomes strangulated when the blood supply becomes compromised. Initially, the flow to the lymphatics and veins is affected leading to engorgement of the trapped viscera and eventually reducing or stopping the arterial flow. This can ultimately lead to ischemia, gangrene, and perforation of the affected viscera. Blood flow to the testis can also be reduced leading to ischemic damage. Incarceration is most frequent in the first 6 months of life and is comparatively rare after 5 years of age.¹⁴

With an incarcerated hernia, the child may develop fussiness, poor feeding, abdominal pain, or vomiting. A tender, nonfluctuant, palpable mass will be present in the inguinal area and may extend into the scrotum or labia. As strangulation ensues, bilious emesis from obstruction, blood in the stool, and fever along with signs of peritonitis and sepsis may occur. Strangulation can arise within 2 hours from the onset of incarceration.

Most hernias will spontaneously retract or with the placement of the patient in Trendelenburg with mild pressure applied to the hernia sac. Incinerated hernias in the emergency department should be reduced, unless there are signs of obstruction or peritonitis. The manual reduction method called taxis (Fig. 47-2) has been shown to have a success rate of 75% to 85%.¹⁵ Prior to reduction, the child should be adequately sedated. In addition to providing analgesia for this painful procedure, it also decreases the child's resistance that could raise intra-abdominal pressure making reduction more difficult or unsuccessful.

The taxis method has the practitioner gently applying downward traction along the hernia sac with one hand while applying slight pressure at the inguinal ring. The elongated hernia is then guided back through the ring into the abdominal cavity. Merely pressing on the hernia to force in back through the ring may cause the hernia sac to bulge and actually obstruct the path back preventing reduction.

All children with inguinal hernias, especially infants, should be referred to a pediatric surgeon. Those who require reduction of an incarcerated hernia should see the surgeon within 24 to 48 hours after discharge because of the risk of reoccurrence. Strangulated hernias are surgical emergencies requiring immediate referral to a pediatric surgeon.