PATHOGENESIS AND EPIDEMIOLOGY
There are 2 types of inguinal hernias: direct and indirect. Occasionally, femoral hernias are grouped with inguinal hernias, but anatomically, they are in a distinct area. The overwhelming majority (99%) of hernias in infants and children are of the indirect type, which occur secondary to a patent processus vaginalis. The processus vaginalis accompanies the testis on its descent from the retroperitoneum into the scrotum, and normally obliterates by term. In girls, the processus vaginalis accompanies the round ligament into the labia majora. If it remains patent, it can result in a communicating hydrocele if the opening is so small that only fluid can pass through. If the opening allows egress of intra-abdominal organs, it is an indirect hernia (Fig. 400-1). Conceptually, the primary difference between a communicating hydrocele and an indirect inguinal hernia is the width of the patent processus.
Anatomy of indirect inguinal hernia in boys.
A direct inguinal hernia is much rarer and represents 0.5% to 1% of inguinal hernias in children. It results from muscle weakness in the floor of the inguinal canal (internal oblique and transversus abdominis muscles). Classically, the diagnosis is based on where the inguinal bulge is identified. In a direct hernia, the protrusion or bulge is found medial to the epigastric vessels. Conversely, indirect hernias are found lateral to the epigastric vessels.
A femoral hernia is not a true inguinal hernia, as it is not in the inguinal canal. Nevertheless, it is often noted as a groin mass. It is the least common, representing less than 0.5% of groin hernias. The defect is in the femoral canal.
The incidence of inguinal hernia in children is 3% to 5%. It is 5 to 10 times more common in boys. Most inguinal hernias present in the first year of life, and one-third of patients are less than 6 months of age. Location is on the right side in 60%, on the left side in 30%, and bilateral in 10%. It is more common in premature infants, with up to 25% affected. Conditions that increase intra-abdominal pressure (eg, repair of abdominal wall defect), increase the amount of peritoneal fluid (eg, ascites, peritoneal dialysis, ventriculoperitoneal shunt), and delay closure of the processus vaginalis (eg, undescended testis), and connective tissue disorders increase the risk of inguinal hernia.
Inguinal hernia presents as a bulge in the groin. It is located at the external inguinal ring and can extend along the spermatic cord into the scrotum. A reducible hernia is soft, and can be pushed back into the abdomen. It can cause discomfort, but not exquisite pain and tenderness. It most commonly contains intestine. A communicating hydrocele presents similar to an inguinal hernia but ...