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Three distinct anatomic types of inguinal hernias are observed in children: congenital or indirect (99%), direct (0.5%), and femoral (< 0.5%).1 The classic congenital indirect inguinal hernia results from a patent processus vaginalis, which represents an opening from the peritoneum into the inguinal region (Fig. 405-1). Other hernias that occur in children include incisional hernia, which occurs when abdominal viscera protrude through a previous surgical incision, and umbilical hernia, which is discussed below. Diaphragmatic hernia is discussed in Chapter 50. Epigastric hernia are rare in children. They protrude through the linea alba above the level of the umbilicus and appear to develop through one of the foramina of egress of the small paramidline nerves and vessels or through an area of congenital weakness in the linea alba. About 3% to 5% of the population have epigastric hernias. They are more common in men than in women and most common between the ages of 20 and 50. About 20% of epigastric hernias are multiple, and about 80% occur just off the midline.

Figure 405-1.

Indirect inguinal hernia.


The incidence of congenital indirect inguinal hernia is 3.5% to 5.0% in full-term newborn infants, higher in preterm and low-birth-weight infants (10%), and approaches 30% in very-low-birth-weight infants (< 1000 g) and infants less than 28 weeks gestational age.1 Inguinal hernia is much more common in boys than girls, with a male-to-female ratio of 6:1. Sixty percent of inguinal hernias occur on the right side (presumably due to the later descent of the right testis), 30% are on the left side, and 10% are bilateral.2 The incidence of bilateral hernias is higher in premature infants and females (20–40%).

Risk factors for congenital inguinal hernia are listed in Table 405-1. An increased incidence of congenital inguinal hernia has been reported in twins and in individuals who have a family member with an inguinal hernia. Most of the other risk factors result from those conditions that predispose to failure of obliteration of the processus vaginalis. Patients with cystic fibrosis have approximately a 15% incidence of inguinal hernia and absence of the vas deferens in males, believed to be related to an altered embryogenesis of the Wolffian duct structures.3 There is also an increased incidence of inguinal hernia in patients with testicular feminization syndrome and other forms of ambiguous genitalia. Patients with connective tissue disorders, such as Ehlers-Danlos syndrome4 and Marfan syndrome, are not only at risk for hernia but are subject to a high recurrence rate (50%) after repair of an inguinal hernia and are also at greater risk for a direct hernia later in life. Recurrent inguinal hernia in children should prompt consideration of the possible diagnosis of a connective tissue disorder.

Table 405-1. Risk Factors for Hernias

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