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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.
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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%).
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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.
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