Chapter 405. Inguinal and Other Hernias

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.

Epidemiology

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.

Pathophysiology

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

Treatment

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

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%.

Umbilical hernias are common in infants and result from persistence of a gap in the abdominal muscular wall where the umbilical vessels entered the umbilical cord. Umbilical hernias occur in 1 of every 6 children and affect boys and girls equally. Umbilical hernias are more common among African American children than children of European ancestry. In addition, low-birth-weight and premature infants are more likely to have umbilical hernias. The hernia is evident as a bulge occurring with straining. Umbilical hernias can be associated with conditions such as mucopolysaccharide storage diseases, Beckwith-Wiedemann syndrome, and Down syndrome.

Umbilical hernias of less than 1.5 to 2 cm usually close by age 3 or 4, such that surgery is rarely indicated.14 Larger hernias are less likely to close. Practices such as taping a coin or bandage over the umbilicus are not recommended since there is a small risk of trapping a loop of bowel so that it cannot reduce into the abdominal cavity, causing ischemia. An umbilical hernia should be differentiated from a paraumbilical hernia that is due to a muscular defect in the midline near the umbilicus. It also must be differentiated from a small omphalocele.

Obstruction and strangulation of an umbilical hernia is rare because the underlying defect in the abdominal wall is comparatively larger and the length shorter than for an inguinal hernia. Those hernias with a very narrow base are more likely to cause incarceration of viscera. If an umbilical hernia is not causing symptoms and is reducible, observation is recommended. Symptoms that prompt evaluation and possible surgery include umbilical pain, vomiting, and apparent bowel obstruction.15 Although incarceration can occur at any age, it is most common around age 3 years when the abdominal wall defect is small in size. Findings of a painful, irreducible umbilical mass should lead to prompt surgical consultation and intervention.

Surgical repair of an umbilical hernia depends upon the size of the hernia. Small hernias are usually repaired by stitching the muscular wall together; large hernias may be reinforced with mesh over the opening in the abdominal wall. An alternative approach for closure of umbilical hernias less than 1.5 cm in diameter using a minimally invasive approach of injecting biodegradable dextranomer microspheres in hyaluronic acid has recently been reported, but routine use will require further study.16