eMedicine Specialties > Pediatrics: General Medicine > Gastroenterology

Pediatric Hernias

Author: Andre Hebra, MD, Chief, Division of Pediatric Surgery, Medical University of South Carolina; Professor of Surgery and Pediatrics, Medical University of South Carolina
Contributor Information and Disclosures

Updated: Nov 24, 2008

Introduction

Background

Approximately 400 years ago, a French surgeon named Ambroise Pare described the reduction of an incarcerated pediatric hernia and the application of trusses. He recognized that inguinal hernias in children were probably congenital in nature and that they could be cured. Unfortunately, despite the many historical descriptions of conservative medical management of inguinal hernias, no effective nonsurgical means of treating this condition is recognized. All pediatric inguinal hernias require operative treatment to prevent the development of complications, such as inguinal hernia incarceration or strangulation.

Today, inguinal hernia repair is one of the most common pediatric operations performed. Inguinal hernia is a type of ventral hernia that occurs when an intra-abdominal structure, such as bowel or omentum, protrudes through a defect in the abdominal wall. Most hernias that are present at birth or in childhood are indirect inguinal hernias. Other less common types of ventral hernias include umbilical, epigastric, and incisional hernias.

In this article, the embryology, clinical presentation, and management of inguinal hernias are discussed in relation to the pediatric population. Because inguinal hernias are common, every clinician must be well versed in the subject and able to provide optimal care to patients and their families, especially because hernias can be organ-threatening or life-threatening if not expeditiously managed.

Pathophysiology

The processus vaginalis is an outpouching of peritoneum attached to the testicle that trails behind as it descends retroperitoneally into the scrotum. When obliteration of the processus vaginalis fails to occur, inguinal hernia results.¹ A review of embryonic development of the inguinal region is important to understanding the pathophysiology and surgical management of inguinal hernias.

Although the sex of the embryo is determined at fertilization, the gonads do not begin to differentiate until 7 weeks' gestation. Primordial germ cells migrate along the dorsal mesentery of the gut. They arrive at the primitive gonads early in the fifth week of development and, during the sixth week, invade the genital ridges, which lie on the medial aspect of the mesonephros. The coelomic epithelium proliferates, and the underlying mesenchyme condenses, forming the primitive sex cords.

Under the influence of the Y chromosome, the cords in the male embryo proliferate to form the testes. Near the end of the second month, the testis and mesonephros are attached by the urogenital mesentery to the posterior abdominal wall. As the mesonephros degenerates, only the testis remains suspended. At its caudal end, the attachment is ligamentous and is known as the caudal genital ligament. The gubernaculum, a mesenchymal structure rich in extracellular matrices, also extends from the caudal pole of the testis. This structure attaches in the inguinal region between the differentiating internal and external oblique muscles prior to descent of the testes. As the testes begin to descend at about 28 weeks' gestation, an outgrowth of gubernaculum from the inguinal region grows toward the scrotal area, and as the testis passes through the inguinal canal, this portion of the gubernaculum comes in contact with the scrotal floor.

During this time, the peritoneum of the coelomic cavity is forming an evagination on each side of the midline into the ventral abdominal wall. This evagination, known as the processus vaginalis, follows the path of the gubernaculum testis into the scrotal swellings and forms, along with the muscle and fascia, the inguinal canal. The descent of the testes through the inguinal canal is thought to be regulated by both androgenic hormones produced by the fetal testis and mechanical factors resulting from increased abdominal pressure.

As each testis descends, the layers of the abdominal wall contribute to the layers of the spermatic cord. The internal spermatic fascia is a reflection of the transversalis fascia, the internal oblique muscle helps form the cremaster muscle, and the external spermatic fascia results from the external oblique aponeurosis. In addition, a reflected fold of the processus vaginalis covers each testis and becomes known as the visceral and parietal layers of the tunica vaginalis.

In the female embryo, the ovaries descend into the pelvis but do not leave the abdominal cavity. The upper portion of the gubernaculum becomes the ovarian ligament, and the lower portion becomes the round ligament, which travels through the inguinal ring into the labium majus. If the processus vaginalis remains patent, it extends into the labium majus and is known as the canal of Nuck.

Before birth, the layers of the processus vaginalis normally fuse, closing off the entrance into the inguinal canal from the abdominal cavity. In some individuals, the processus vaginalis remains patent through infancy, into childhood, and possibly even into adulthood. The precise cause of the obliteration of the processus vaginalis is unknown, but some studies indicate that calcitonin gene-related peptide (CGRP), released from the genitofemoral nerve, may have a role in the fusion.

When luminal obliteration fails to occur, a ready-made sac is present where abdominal contents may herniate. Even when the processus vaginalis is patent, the entrance may be adequately covered by the internal oblique and transverse abdominal muscles, preventing escape of abdominal contents for many years. Failure of fusion can result not only in an inguinal hernia, but also in a communicating or noncommunicating hydrocele.

In infants, the most common type of hydrocele is the communicating type. A communicating hydrocele results when the proximal portion of the processus vaginalis remains patent, allowing fluid from the abdominal cavity to freely enter the scrotal sac. When closure is present proximally but fluid remains trapped within the tunica distally, a noncommunicating hydrocele results.

Frequency

United States

Although the exact incidence of indirect inguinal hernia in infants and children is unknown, the reported incidence ranges from 1-5%. Sixty percent of hernias occur on the right side. Premature infants are at increased risk for inguinal hernia, with incidence rates of 2% in females and 7-30% in males. Approximately 5% of all males develop a hernia during their lifetime.

International

International incidence rates are similar to those in the United States.

Mortality/Morbidity

An incarcerated or strangulated inguinal hernia can result in severe complications and even death. An incarcerated or strangulated inguinal and/or femoral hernia may also result in significant sequela, depending on which visceral structure is involved in the hernia sac. Such sequela can range from life-threatening complications to gonadal dysfunction, including intestinal necrosis and perforation, intestinal obstruction, intestinal stricture, testicular necrosis, testicular atrophy, ovarian necrosis, ovarian atrophy, and tubal stricture.

Race

Inguinal hernia appears to occur equally among races. Umbilical hernias, on the other hand, appear to be more common in blacks than in other races.

Sex

Inguinal hernias are much more common in males than in females. The male-to-female ratio is estimated to be 4-8:1.

Age

Premature infants are at an increased risk for inguinal hernia, with the incidence ranging from 7-30%. Moreover, the associated risk of incarceration is more than 60% in this population. Most pediatric ventral and inguinal hernias are detected in the first year of life. Occasionally, hernias may remain asymptomatic and unnoticed by the parents until later in life. Finding an adult patient with an indirect inguinal hernia that has been present since birth is not unusual.

Clinical

History

• The infant or child with an inguinal hernia generally presents with an obvious bulge at the internal or external ring or within the scrotum. The parents typically provide the history of a visible swelling or bulge, commonly intermittent, in the inguinoscrotal region in boys and inguinolabial region in girls. Media file 1 depicts a 4-month-old baby boy with a large right-sided inguinal hernia.
• The swelling may or may not be associated with any pain or discomfort. More commonly, no pain is associated with a simple inguinal hernia in an infant. The parents may perceive the bulge as being painful when, in truth, it causes no discomfort to the patient.
• The bulge commonly occurs after crying or straining and often resolves during the night while the baby is sleeping.
• Indirect hernias are more common on the right side because of delayed descent of the right testicle. Hernias are present on the right side in 60% of patients, on the left in 30%, and bilaterally in 10% of patients.
• If the patient or the family provides a history of a painful bulge in the inguinal region, one must suspect the presence of an incarcerated inguinal hernia. Patients with an incarcerated hernia generally present with a tender firm mass in the inguinal canal or scrotum. The child may be fussy, unwilling to feed, and inconsolably crying. The skin overlying the bulge may be edematous, erythematous, and discolored.

Physical

Examine the patient in both supine and standing positions. Physical examination of a child with an inguinal hernia typically reveals a palpable smooth mass originating from the external ring lateral to the pubic tubercle. The mass may only be noticeable after coughing or performing a Valsalva maneuver, and it should be reduced easily. Occasionally, the examining physician may feel the loops of intestine within the hernia sac. In girls, feeling the ovary in the hernia sac is not unusual; it is not infrequently confused with a lymph node in the groin region. In boys, palpation of both testicles is important to rule out an undescended or retractile testicle.

• Inguinal hernia incarceration: The bowel can become swollen, edematous, engorged, and trapped outside of the abdominal cavity, a process known as incarceration. Incarceration is the most common cause of bowel obstruction in infants and children and the second most common cause of intestinal obstruction in North America (second only to intra-abdominal adhesions from previous surgeries). If entrapment becomes so severe that the vascular supply is compromised, inguinal hernia strangulation results. In cases of incarceration, ischemic necrosis develops, and intestinal perforation may result, representing a true medical emergency. When an incarceration is encountered, an attempt should be made to reduce it manually if the patient has no signs of systemic toxicity (eg, leukocytosis, severe tachycardia, abdominal distention, bilious vomiting, discoloration of the entrapped viscera). If the patient appears toxic, emergent surgical exploration after appropriate resuscitation is necessary.
• Hernia and hydrocele: In boys, differentiating between a hernia and a hydrocele is not always easy. Transillumination has been advocated as a means of distinguishing between the presence of a sac filled with fluid in the scrotum (hydrocele) and the presence of bowel in the scrotal sac. However, in cases of inguinal hernia incarceration, transillumination may not be beneficial because any viscera that is distended and fluid-filled in the scrotum of a young infant may also transilluminate. A rectal examination may be helpful if intestine can be felt descending through the internal ring.
• Silk sign: When the hernia sac is palpated over the cord structures, the sensation may be similar to that of rubbing 2 layers of silk together. This finding is known as the silk sign and is highly suggestive of an inguinal hernia. The silk sign is particularly important in young children and infants, in whom palpation of the external inguinal ring and inguinal canal is difficult because the patients' small size.
• Spontaneously reducing hernia: Inguinal hernias that spontaneously reduce (ie, they are only noticed by the parents or caregivers and elude the examining physician) are not unusual. In such cases, maneuvers to increase the patient's intra-abdominal pressure may be attempted. Lifting the infant's or the child's arms above the head may provoke crying or a struggle to get free and thus increased intra-abdominal pressure. Older children can be asked to cough or blow up a balloon.
• Femoral hernia: A femoral hernia can be very difficult to differentiate from an indirect inguinal hernia. Its location is below the inguinal canal, through the femoral canal. The differentiation is often made only at the time of operative repair, once the anatomy and relationship to the inguinal ligament is clearly visualized. The signs and symptoms for femoral hernias are essentially the same as those described for indirect inguinal hernias.

Causes

The cause of inguinal hernia in children can be termed an abnormality of embryologic development of the fetus. However, some children may present with an acquired form of inguinal hernia, also called a direct inguinal hernia. In this type of hernia, weakness of the inguinal floor is present, which allows for protrusion of viscera from the abdominal cavity. The hernia sac is composed of the peritoneal fold that contains the hernia.

Anatomically speaking, indirect and direct inguinal hernias differ in that the direct hernia bulges through the inguinal floor medial to the inferior epigastric vessels and the indirect hernia arises lateral to the inferior epigastric vessels. Either hernia may cause fullness or a palpable bulge in the inguinal region, and distinguishing between the two types on the basis of physical examination findings may be difficult. The clinician may assume, until proven otherwise, that the pediatric patient with an inguinal hernia has indirect inguinal hernia.

• The following are associated with an increased risk of inguinal hernia:
  • Prematurity and low birth weight (Incidence approaches 50%.)
  • Urologic conditions
    • Cryptorchidism
    • Hypospadias
    • Epispadias
    • Exstrophy of the bladder
    • Ambiguous genitalia
  • Patent processus vaginalis, which may be present because of increased abdominal pressure due to ventriculoperitoneal shunts, peritoneal dialysis, or ascites
  • Abdominal wall defects
    • Gastroschisis
    • Omphalocele
  • Family history
    • Meconium peritonitis
    • Cystic fibrosis
    • Connective tissue disease
    • Mucopolysaccharidosis
    • Congenital dislocation of the hip
    • Ehlers-Danlos syndrome
    • Marfan syndrome
    • Cloacal exstrophy
    • Fetal hydrops
    • Liver disease with ascites
    • Ventriculoperitoneal shunting for hydrocephalus
• Figures regarding inguinal hernia incarceration indicate the following risk patterns:
  • Incarceration occurs in 17% of right-sided hernias and 7% of left-sided hernias.
  • More than 50% of cases of incarceration occur within the first 6 months of life; the risk gradually decreases after age 1 year.
  • Premature infants have twice the risk of incarceration than the general pediatric population.
  • More than two thirds of all incarcerations occur in children younger than 1 year.
  • Girls are more likely to develop incarceration of an inguinal hernia; the incidence in girls is 17.2%, whereas the incidence in boys is 12%.

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