Jason D. Fraser and Charles L. Snyder

History

The term hernia comes from the Greek ‘hernios’, meaning offshoot or bud. Inguinal hernias were described in the Ebers Papyrus in 1552 BC,¹ and were found in Egyptian mummies. Celsus is thought to have performed hernia repairs in 50 AD. Galen (b. 129 AD) described the processus vaginalis, defined hernias as a rupture of the peritoneum, and advised surgical repair.² Ambrose Paré advocated repair of inguinal hernias in childhood in the 16th century, and condemned concomitant castration.¹ In 1807, Cooper identified the transversalis fascia and the ligament associated with his name. In 1817, Cloquet observed that the processus vaginalis is often patent at birth and described femoral hernias.^3,4 Marcy reported high ligation of the hernia sac in 1871.⁵ In 1877, von Czerny first described narrowing the inguinal canal and tightening the external inguinal ring,^6,7 followed by Bassini’s description of internal inguinal ring tightening and reinforcement of the posterior canal in 1887.⁸ Gross reported a 0.45% recurrence rate in a large series of inguinal hernia repairs (3,874 children) in 1953.⁹

Incidence

Approximately 1–5% of all children will develop an inguinal hernia and a positive family history is found in about 10%.¹⁰ There is an increased incidence in twins, more frequently in male twins.¹¹ In a series of 6,361 pediatric herniorrhaphies performed by a single surgeon, the male-to-female ratio was 5 to 1, and right-sided hernias were twice as common as those on the left.¹² The mean age at diagnosis was 3.3 years.

The incidence of an inguinal hernia varies directly with the degree of prematurity. The overall incidence of inguinal hernia in premature infants is estimated to be 10–30%, whereas term newborns have a rate of 3–5%.13–15 The incidence by gender is closer to 1 : 1 in premature infants. Comorbidities such as chronic lung disease associated with prematurity may play a role in the development of an inguinal hernia.

Associations

Embryology and Anatomy

The inguinal canal is a six-sided cylinder. The cephalad opening is the internal inguinal ring and the caudal border is the external inguinal ring. The cephalad aspect is bordered by the internal oblique, transversus abdominis, and medial external oblique fibers. The floor is formed by the transversalis fascia and the ‘conjoint tendon.’ The anterior roof is created primarily by the aponeurosis of the external oblique. The inferior wall is composed by the inguinal ligament, lacunar ligament (medial third), and iliopubic tract (lateral third). Contents include the ilioinguinal nerve (exiting through the external inguinal ring) and in males, the spermatic cord. In females, it also contains the round ligament.²¹

The processus vaginalis is a peritoneal diverticulum extending through the internal inguinal ring into the inguinal canal. It can be seen by 3 months of fetal life.²² The somatic base of this diverticulum is the transversalis portion of the endoabdominal fascia. The gonads form on the anteromedial nephrogenic ridges in the retroperitoneum during the 5th week of gestation. The gonads are attached to the scrotum by the gubernaculum in the male and to the labia via the round ligament in the female. Gonadal descent begins by 3 months’ gestation, and the testis reaches the internal inguinal ring by about 7 months. Descent of the testis is thought to be directed in the abdominal phase by insulin-like 3 protein, a product of the Leydig cells, and directed in the second phase by androgens and release of calcitonin gene-related peptide (CGRP) from the genitofemoral nerve (via fetal androgen release).^23,24 CGRP appears to mediate closure of the patent processus vaginalis (PPV), although this process is not completely understood.²⁴

The testis begins to descend down the canal by the seventh month of fetal life preceded and guided by the processus vaginalis.22,24,25 The processus, which is located anterior and medial to the cord structures, gradually obliterates, and the scrotal portion forms the tunica vaginalis. The female anlage of the processus vaginalis is the canal of Nuck, a structure that leads to the labia majora. This also closes by about 7 months of fetal life, and ovarian descent is arrested in the pelvis.²² The precise incidence of PPV in newborns is unknown and depends on gender and gestational age. It is estimated to be 40–60%, but may be lower or higher.²⁶ However, at autopsy, only 5% of adults have a PPV.²² PPVs can still close after birth, but this is felt less likely to occur with increasing age. It is failure of the PPV to close that results in an indirect inguinal hernia. As mentioned, the factors driving PPV closure are incompletely understood. Intra-abdominal pressure probably plays a role because disorders with increased abdominal pressure/fluid (e.g., ascites, VPS) are associated with an increased incidence of indirect inguinal hernias and an increased incidence of bilaterality.¹⁷ Indirect inguinal hernias are more common on the right. The various clinical findings related to the processus vaginalis are illustrated in Figure 50-1.

The layers of the abdominal wall contribute to the layers of the testis and spermatic cord as the gonad descends. The internal spermatic fascia is a continuation of the transversalis fascia, the cremaster muscle derives from the internal oblique, and the external spermatic fascia originates from the external oblique aponeurosis. The processus vaginalis envelops the testis as the visceral and parietal layers of the tunica vaginalis.²²

Clinical Presentation

Most hernias are asymptomatic except for inguinal bulging with straining. They are often found by the parents or pediatrician on routine physical examination. The diagnosis is clinical and rests squarely on the history and physical examination. Maneuvers such as having the child raise the head while supine or ‘blowing up a balloon’ with a thumb in the mouth may be helpful in small children. Standing the child upright may also help demonstrate the hernia. The differential diagnosis includes a retractile testis, lymphadenopathy, hydrocele, and prepubertal fat.

A common occurrence is a normal examination in combination with a suggestive history. Cell phone picture documentation by the parents has become commonplace. A good history is acceptable as an indication for operation. False-negative explorations are rare. In the previously mentioned series of 6,361 hernia repairs by a single surgeon (definitive inguinal hernia on examination was the indication for operation), there was only one false-negative exploration (0.02%).¹²

Children are often referred for inguinal pain in the absence of any history of bulging or swelling, often with a normal physical examination. Other sources such as musculoskeletal strain, gastrointestinal, or genitourinary abnormalities should be excluded before operative intervention. Diagnostic transumbilical laparoscopy is useful in a small subset with equivocal examinations or persistent symptoms and no other apparent cause.

Ancillary findings such as a ‘silk glove sign’ (feeling the thickened peritoneum of the patent processus as the cord is palpated) or examination under anesthesia are of variable reliability.27,28 Radiologic diagnostic aids are not generally necessary or helpful. Ultrasonography (US) can be used to identify a PPV indirectly via widening of the internal inguinal ring (more than 4–5 mm is positive), but the technique is highly operator dependent and not widely used in children.^29,30 It is not generally necessary to restrict an asymptomatic child’s activities until repair is scheduled, but prompt repair may decrease interim incarceration, particularly in the very young.

Sometimes an incidental PPV is discovered in a child undergoing operation for an unrelated problem. A common scenario is finding a unilateral or bilateral PPV during the course of a laparoscopic appendectomy, or other operation. It is probably best not to perform a PPV repair in that setting as the patient is not symptomatic. The child and the family should be informed of the findings and instructed to watch for symptoms.

Management