++
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.
++
++
The incidence of incarceration of an inguinal hernia is between
12% and 17%. The majority (60% to 70%)
of incarcerated hernias occur in the first year of life, with reported
incidences of between 25% and 35% for infants
less than 6 months of age. The incidence of incarceration is slightly
less in premature infants, although the reasons are unclear.
++
The development of an indirect or congenital hernia is preceded
by a lack of closure of the processus vaginalis, which normally
follows descent of the testis through the internal ring and into
the scrotum late in gestation (Fig. 405-1).
The gonads develop near the kidney as a result of migration of primitive
germ cells from the yolk sac to the urogenital ridge, and differentiation
into testis and ovary occurs by 7 or 8 weeks gestation under hormonal
influences. The testis and ovary migrate to the region of the internal
ring in the inguinal region by 28 weeks gestation. The processus
vaginalis develops around the 12th week as an outpouching of the
peritoneum in conjunction with the chorda gubernaculum that eventually
extends from the internal ring into the scrotum.
++
In males, the testis, spermatic cord vessels, and vas deferens
attach to the processus vaginalis and accompany the processus as
it exits the abdomen and descends into the scrotum. Testicular descent
is not complete until late gestation and may continue after birth,
and this explains the increased association between prematurity
and undescended testis. Complete descent of the testis is influenced
by androgenic hormones, adequate end-organ receptors, and mechanical factors
such as increased intra-abdominal pressure. The genito-femoral nerve
also plays an important role through its production of calcitonin,
which facilitates both testicular descent and closure of the processus
vaginalis. Experimental division or injury to both nerves in the
fetus prevents testicular descent. The testis may occasionally pass
to ectopic locations (perineum or femoral region). When testicular
descent is complete, the patent processus vaginalis normally undergoes
obliteration, closing the communication between the peritoneal cavity
and the inguinal canal. In females, the round ligament accompanies
the processus through the inguinal region and attaches to the labia
majora, whereas the ovary arrests at the pelvic brim. The processus
vaginalis obliterates earlier, at about 7 months gestation.
++
Not all patients with a patent processus vaginalis develop an
indirect inguinal hernia since the actual inguinal hernia is
characterized by passage of intra-abdominal viscera into the inguinal
region. Structures within the hernia sac can include small bowel,
appendix, intestines, colon, or rarely, Meckel diverticulum, uterus,
or a portion of the bladder. Generally, herniation is associated with
episodes of increased intra-abdominal pressure and may occur intermittently,
with spontaneous return into the abdominal cavity. Depending on
the extent of patency of the processus vaginalis, hernia contents
may be confined to the inguinal region, or may extend into the scrotum
and may herniate and reduce, or may progress to incarceration. A
hydrocele occurs when only fluid from the peritoneal cavity enters
the patent processus vaginalis such that swelling may exist only
in the scrotum (scrotal hydrocele), along the spermatic cord in
the inguinal region (hydrocele of the spermatic cord), or extend
from the scrotum through the inguinal canal and even into the abdomen
(abdominal-scrotal hydrocele). A hydrocele is termed a communicating hydrocele
if it demonstrates fluctuation in size, typically increasing in
size after activity and decreasing in size when the hydrocele fluid
decompresses into the peritoneal cavity. Occasionally, hydroceles
in older children develop following trauma, inflammation, or tumors
affecting the testes.
++
Direct inguinal hernias occur when abdominal contents herniate
through a defect in the fascia of the abdominal wall, usually in
the region of the inguinal triangle (also known by the eponym Hesselbach
triangle), defined by the space between the rectus abdominis muscle,
the inguinal ligament, and the inferior epigastric vessels.
++
Femoral hernias are also rare in children.5 Femoral
hernias represent protrusion of abdominal viscera through the femoral
canal, and the bulge is located below the inguinal ligament on the
medial aspect of the thigh. They are more common in girls than boys,
with a ratio of 2:1.
+++
Clinical Features
and Differential Diagnosis
++
The hallmark signs of an inguinal hernia on physical examination
are a smooth, firm mass in the inguinal region or scrotum that enlarges with
increased intra-abdominal pressure. The hernia typically reduces
spontaneously or can be reduced by gentle, manual pressure along the
inguinal canal. In girls, the mass typically appears in the upper
region of the labia majora. The bulge or mass is most visible at
times of increased intra-abdominal pressure (crying, straining)
and is often first observed by a parent or on routine examination
by a primary care physician. It may be present at birth or may not appear
until weeks, months, or years later.
++
The physical examination used to demonstrate an inguinal hernia
depends upon the age of the child. In infants, positioning with
the arms stretched straight above the head and legs extended usually
causes them to struggle, increasing intra-abdominal pressure and “pushing out” the
hernia. In older patients performance of a Valsalva maneuver while
standing will increase hernia size, or the hernia can be palpated
with an examining finger invaginating the scrotum to palpate the
external ring (Fig. 405-2). In the female
infant, the ovary and fallopian tube can be contained within the
hernia sac, presenting as a firm, discrete, nontender mass in the
labia majora. If an inguinal hernia is suspected, but
no mass is obvious, one may feel the layers of the hernia sac (processus
vaginalis) when sliding the index finger over the pubic tubercle
(the “silk glove” sign). It is important on examination
to note the position of the testes because retractile testes are
common in infants and young children and can mimic an inguinal hernia
as a mass in the upper scrotum or inguinal region.
++
++
An incarcerated hernia generally presents with symptoms of irritability,
pain in the groin and abdomen, abdominal distension, and vomiting.
A somewhat tense, nonfluctuant mass is present in the inguinal region
and may extend into the scrotum or labia majora. The mass is usually
well defined, typically tender, and does not reduce. With the
onset of ischemic changes, the pain intensifies, and the vomiting becomes
bilious or feculent. Blood may be noted in the stools. There is often
edema and erythema of the overlying skin, with fever and signs of
intestinal obstruction. The testes may be normal, but also may be swollen
and hard on the affected side due to venous congestion of the spermatic
veins and lymphatic vessels in the inguinal canal by the tightly
strangulated hernia mass. Abdominal radiographs demonstrate features
of partial or complete intestinal obstruction, and gas within the
incarcerated bowel segments may be seen below the inguinal ligament
or within the scrotum.
++
In the infant or child with an inguinal mass, the differential
diagnosis includes incarcerated inguinal hernia, acute hydrocele,
torsion of an undescended testis, and suppurative inguinal lymphadenitis.
The infant or child with an incarcerated inguinal hernia is likely
to have associated findings suggestive of intestinal obstruction,
such as colicky abdominal pain, abdominal distension, vomiting,
cessation of stool, and may appear ill, whereas the infant with
an acute hydrocele may have discomfort but is consolable and tolerates
feedings without signs or symptoms suggestive of intestinal obstruction.
On examination of the child with an acute hydrocele, the mass is
typically somewhat mobile, whereas with an incarcerated inguinal
hernia the mass lacks mobility. In addition, the inguinal hernia
always extends through the inguinal region into the abdomen, whereas
the acute hydrocele may be confined to the scrotum or inguinal region
but not extend into the abdominal cavity. Suppurative lymphadenopathy
in the inguinal region can be confused with an incarcerated inguinal
hernia. Examination of the watershed area of the inguinal lymph
node may reveal a superficial infected or crusted lesion. In addition,
the swelling associated with inguinal lymphadenopathy is typically
located more inferiorly and laterally than the mass of an inguinal
hernia, and there may be other affected nodes in the area. Torsion
of an undescended testis may present as a tender, erythematous mass
in the groin, with absence of a gonad in the scrotum of the ipsilateral
side.
++
Infants with intersex problems represent a special case.6 They
frequently present with inguinal hernias, often containing a gonad.
Female infants with inguinal hernias, particularly if the presentation
is bilateral inguinal masses, should be suspected of having testicular
feminization syndrome because 50% of patients with testicular
feminization have an inguinal hernia. Testicular feminization, also
referred to as androgen insensitivity syndrome, is a condition in
which a genotypic male (XY) has reduced or hypofunctional androgen
receptors. In phenotypic females, if the diagnosis of testicular
feminization is suspected, the child should be screened with a buccal
smear for Barr bodies and appropriate genetic evaluation before
proceeding with the hernia repair.
+++
Diagnostic Evaluation
++
An incarcerated hernia is one in which the contents of the hernia
sac cannot be reduced into the abdominal cavity. A strangulated
hernia is one that is tightly constricted in its passage through
the inguinal canal, and as a result, the hernia contents have become
ischemic or gangrenous. The physical exam generally suggests a diagnosis
of inguinal hernia as described above. Transillumination can discriminate
a solid versus cystic mass but is not useful to differentiate a
hydrocele from a hernia. Aspiration of a groin mass is discouraged
because one may enter a hernia sac. Ultrasonography can differentiate
hernia, hydrocele, and lymphadenitis. In cases of potential incarceration,
expeditious diagnosis is important to avoid the potential complications
of an strangulated hernia. Diagnostic laparoscopy has emerged as
an effective and reliable tool in this setting, but requires general
anesthesia.7
++
If an inguinal hernia is identified in the pediatric age range,
operative repair by an experienced pediatric surgeon is recommended.1,7 An
inguinal hernia is not likely to resolve spontaneously, and early repair
eliminates the risk of incarceration and the associated potential
complications, particularly in the first 6 to 12 months of life when
the risk of incarceration is greatest. The timing of repair depends
on several factors, including age, general condition of the patient,
and comorbid conditions. In infants less than 1 year of age diagnosed
with an inguinal hernia, referral to a pediatric surgeon and repair
should proceed promptly because as many as 70% of incarcerated
inguinal hernias requiring emergency operation occur in the first
year of life. In addition, the incidence of testicular atrophy following
incarceration in infants less than 3 months of age has been reported
to be as high as 30%. In children older than 1 year, the
risk of incarceration is less, and the repair can be scheduled with
less urgency. In the routine reducible hernia, referral and repair
should be carried out electively shortly after diagnosis. In patients
with marked prematurity, repair is typically performed before discharge home
from the neonatal intensive care unit.
++
Elective inguinal hernia repair can be safely performed in an
outpatient setting with an expectation for full recovery within
48 hours. The operation should be performed at a facility with the
ability to admit the patient to an inpatient unit as needed. Certain
conditions may dictate postponement of repair, such as marked prematurity, intercurrent
pneumonia (especially respiratory syncytial virus), other infections,
or complex congenital heart disease. Preterm infants mandate special
consideration because of their high risk of apnea and bradycardia
after general anesthesia. Infants less than 44 weeks postconceptual
age and full-term infants less than 3 months of age and with comorbid conditions
should be observed overnight with appropriate apnea and cardiorespiratory
monitors.
++
Unless treated, an incarcerated hernia often progresses rapidly
to strangulation with potential infarction of the hernia contents. The testis
is also at risk of ischemia because of compression of the spermatic
cord structures by the incarcerated or strangulated mass. In females,
the ovary and fallopian tube most commonly protrudes in the hernia,
placing it at risk for torsion, incarceration, strangulation, and
infarction. An incarcerated hernia, without evidence of strangulation,
should initially be managed nonoperatively. Reduction by gentle
compression of the hernia can be attempted. The attempt should not
be continued if the infant is crying and resisting the pressure
on the hernia. The use of sedation or analgesia before attempting
reduction can be helpful; this reduces intra-abdominal pressure
and relieves pressure on the hernia. Other techniques advocated
to assist in the nonoperative reduction of an incarcerated inguinal hernia
include elevation of the lower torso and legs and brief exposure
to an ice pack. Many practitioners do not favor the use of an ice
pack in infants because of the risk of hypothermia.
++
Manual reduction is performed first with traction caudad and
posterior to free the mass from the external inguinal ring and then upward
to reduce the contents back into the peritoneal cavity. If reduction
is successful but difficult, the patient should be observed to ensure
that feedings are tolerated and there is no concern that necrotic
intestine was reduced. Elective repair should be performed within
24 to 48 hours, by which time there is less edema, handling of the
sac is easier, and the risk of surgical complications is reduced.
For any patient who presents with a prolonged history of incarceration
(> 12 hours), signs of peritonitis, or small bowel obstruction,
no attempt at manual reduction should be performed and surgical
consultation should be obtained.
++
A common presentation in female infants is the presence of an
irreducible ovary in the hernia in an otherwise asymptomatic patient. The
inguinal mass is soft, nontender to gentle exam, and swelling and
edema are absent; thus, although incarcerated, there are no findings
suggestive of strangulation. This represents a sliding hernia with
the ovary and fallopian tube fused within the hernia sac. Overzealous
attempts to reduce the hernia are unwarranted and potentially harmful
to the tube and ovary. The risk that incarceration of the ovary
in this setting will lead to strangulation is not known. Most pediatric
surgeons recommend elective repair within 48 to 72 hours.
++
Operative management consists of high ligation of the hernia
sac (processus vaginalis) at the level of the internal inguinal
ring, thus preventing protrusion of abdominal contents into the
inguinal canal. Contralateral groin exploration was routine, but
in patients followed after unilateral inguinal hernia repair only
8% to 31% develop a metachronous hernia; therefore,
routine contralateral groin exploration is no longer widely practiced.8,9 Laparoscopic
repair offers an alternative approach that is increasingly accepted.10 Alternatives
now include ultrasound, which has been demonstrated to be more than
95% accurate and is noninvasive.11 Diagnostic
laparoscopy is highly reliable (> 99%) for assessment of the
contralateral side without risk of injury to the spermatic cord structures
or testis. If patency of the contralateral side is demonstrated,
the surgeon can proceed with bilateral inguinal hernia repair, and
if the contralateral side is properly obliterated, exploration and
potential complications are avoided (Fig 405-3).
However, some even question the need for contralateral side evaluation.12
++
++
Operative repair of a direct inguinal hernia involves repair of
the muscular weakness, and many standard techniques have been described.
In children, the repair can be performed through a single, limited
incision, and therefore laparoscopic repair does not confer any
significant advantage. Recurrence after repair, in contrast to that
in adults, is extraordinarily rare. The use of synthetic material
for repair and other approaches, such as preperitoneal repair, is
rarely required in the pediatric age group. The older child with a
direct inguinal hernia and associated connective tissue disorder
may be the exception, and a laparoscopic approach and use of prosthetic material
may be needed. Repair of a femoral hernia involves closure of the
defect at the femoral canal.
++
Complications after elective inguinal hernia repair are uncommon
(1.5%), but significantly higher in association with incarceration
(10%).13 Wound infection occurs in less than
1% of elective hernia repairs in infants and children,
but the incidence increases to 5% to 7% in association
with incarceration and emergent repair. Wound infections typically
present 3 to 5 days after the surgery, and the incision demonstrates
warmth, erythema, and fluctuance. Most common organisms are gram-positive Staphylococcus and Streptococcus species,
and antibiotic management should cover methicillin-resistant Staphylococcus
aureus.
++
The recurrence rate of elective inguinal hernia repair is generally reported
as 0.5% to 1.0%, with rates as high as 3% to
6% after emergency repair of an incarcerated hernia. The
recurrence rate is also higher after repair in premature infants,
patients with connective tissue disorders (collagen deficiency),
or conditions that cause increased intra-abdominal pressure (ventriculoperitoneal shunts,
ascites, peritoneal catheter for dialysis).
++
Testicular infarction and subsequent testicular atrophy has been
reported to be as high as 30% following incarceration of
an inguinal hernia in infants less than 2 to 3 months of age. There
is no reliable data regarding injury to the vas deferens as a consequence
of compression from an incarcerated hernia or during operative repair,
but the reported incidence is 0.5% to 1.0%.