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113 Hernias

Hernias—defined as a protrusion of a structure or part of a structure through tissues normally containing it—are encountered frequently in pediatric clinical practice. In children, external hernias represent the vast majority and are typically in, but not limited to, the inguinal and umbilical regions. Umbilical hernias are very common, most notably in premature infants, infants of African and African American descent, and infants with certain diseases or genetic syndromes. It is estimated that inguinal hernias occur in roughly 1% to 5% of all children, with an increased incidence in specific populations such as those with a family history of inguinal hernia and premature infants, who can have an incidence near 30% in those with birth weights less than 1000 g. Inguinal hernias can cause significant morbidity because of incarceration and strangulation, making it essential that general practitioners and subspecialists alike understand how to approach the condition and recognize when emergent therapy is required.

Congenital diaphragmatic hernia (CDH) and hiatal hernia are the two most common internal hernia types among children. CDH is a neonatal surgical emergency that presents with a scaphoid abdomen, cyanosis, and respiratory distress within minutes of birth as a result of the herniation of abdominal contents into the thoracic cavity (Figure 113-1 see Chapter 102). Hiatal hernias, in which intraabdominal portions of the esophagus, the stomach, or both pass into the thorax, are less common in children than adults but remain an important consideration in certain clinical circumstances. Other internal hernias, including paraduodenal and mesenteric hernias, occur within the abdominal cavity. These are largely the result of congenital abnormalities and in rare circumstances become clinically relevant in childhood.

Etiology and Pathogenesis

External Hernias

Inguinal Hernia

Indirect inguinal hernias are congenital in origin, arising from incomplete embryogenesis. In boys, the testes are initially in a retroperitoneal position. A portion of peritoneum called the processus vaginalis attaches to the testes and precedes the testicular descent through the internal inguinal ring into the scrotal sac. The testes are located at the internal inguinal ring by 28 weeks of gestation and reach their final destination by 36 weeks with the left side completing its descent slightly earlier than the right. The processus vaginalis creates a patent conduit between the abdomen and the scrotum via the inguinal canal and typically obliterates between 36 and 40 weeks of gestation or in the postnatal period. If the processus vaginalis remains patent, abdominal contents may escape through the internal inguinal ring into the inguinal canal and the scrotum (Figure 113-2).

In girls, the ovaries also start in a retroperitoneal position; however, their descent is modified, and they do not leave the abdominal cavity. The processus vaginalis extends through the inguinal canal with the round ligament to the labia majoris and usually obliterates between 32 and 36 weeks of gestation. This embryologic difference is likely why indirect inguinal hernias occur six times more commonly in boys than girls.

Patients with cryptorchidism (failure of one or both testicles to descend into the scrotum), urogenital malformations, and increased intraabdominal pressure are at increased risk for developing indirect inguinal hernias. Direct inguinal hernias are rare in children, entering the inguinal canal through a defect in the posterior wall of the canal medial to the inferior epigastric vessels. Femoral hernias, also rare in children, penetrate an acquired muscular defect in the abdominal wall posterior to the inguinal ligament. Patients with connective tissue disorders and those who have had previous surgery to correct an inguinal hernia have greater risk for femoral or direct inguinal hernias.

Internal Hernias

Hiatal Hernia

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