Frontal view of an inguinal hernia (right). https://en.wikipedia.org/wiki/Inguinal_hernia
- A hernia is a protrusion of normal cavity contents through the fascia and muscular layers designed to contain them.
- In an indirect inguinal hernia, visceral contents herniate through the inguinal canal. The inguinal canal is formed by the aponeurosis of the inguinal canal anteriorly and the transversus abdominus muscle and transversalis fascia posteriorly.
- In a direct inguinal hernia (uncommon in children), the visceral contents protrude through a weakness in the abdominal wall (typically Hesselbach’s triangle, bounded by the inferior epigastric vessles, the inguinal ligament, and the rectus sheath) and exit through the superficial inguinal ring.
- A hydrocele is the result of a patent processus vaginalis that permits peritoneal fluid to travel into the scrotum.
- An incarcerated hernia is one in which the visceral contents cannot be reduced into their normal cavity. A strangulated hernia has compromised blood supply caused by edema.
During the 3rd month of gestation, the testis begins its descent from a retroperitoneal location, following the course of the gubernaculum through the inguinal canal. An extension of the peritoneum called the processus vaginalis in males and the canal of Nuck in females is the remnant of this descent. It is obliterated in 95-98% of term infants.
- The majority of inguinal hernias in infants and children are indirect. They are nine times more common in boys with the majority occurring on the right (60%). 25% occur on the left and 15% are bilateral. Overall, 3-5% of full-term infants and 5-30% of premature infants have an inguinal hernia.
- Increased incidence with prematurity (respiratory disease causes increased abdominal pressure), family history, abdominal wall defects, exstrophy of the bladder or cloaca, GU anomalies, undescended testes, intersex disorders, liver disease with ascites, peritoneal dialysis, V-P shunts, cystic fibrosis, disorders of connective tissue formation, mucopolysaccharidosis.
- The hallmark of an indirect inguinal hernia is a groin bulge at the top of the scrotum or within the scrotum. One must differentiate from retractable testes that may appear as an inguinal bulge.
- The bulge most visible during periods of increased intra-abdominal pressure (crying, straining). It may reduce spontaneously or may be manually reduced. In males, the most common content is bowel, in females, the ovary.
- Physical exam may only reveal a thickened spermatic cord(silk-glove) sign. This results from swelling after a recent herniation and/or cremasteric muscle hypertrophy.
- Communicating hydroceles frequently present with a history of a scrotal mass that changes in size; the scrotal size increases during crying, defecation and decreases after periods of inactivity, e.g. sleeping. They may be differentiated from hernias by the absence of a palpable mass but rather the presence of a fluctuant mass.
- Increased fat in the pubic area may make the diagnosis difficult. A hernia not felt on careful examination is unlikely to incarcerate.
- An incarcerated hernia can present with pain, vomiting, and irreducible mass. This is a surgical emergency. The overall rate of incarceration is 12% and is most common in the first 3-6 months. The incidence of incarceration in premature infants is 31%
- Surgical repair of hernias is offered to prevent incarceration or obstruction or, in females, torsion of the ovary. The high risk of incarceration in the pediatric age group make the presence of an inguinal hernia an indication for surgical repair. Observation is advocated for infants with hydrocele until 12 months.
- Preterm infants are usually operated on before leaving the NICU. Infants under 3 months usually operated on as soon as possible (usu. 24-48 hrs) and older children can be booked electively.
- Surgical options include an open or laparascopic technique. Most surgeons will look for and repair a contralateral patent processus vaginalis (PPV). There is some evidence that looking for a contralateral PPV is more successful with a laparascopic approach, but that recurrent hernia is less frequent with the open approach. Repair of a recurrent hernia is usually attempted with the technique not used on the first approach to avoid scar tissue.
- Complications include injury to the vas deferens (treatment is microsurgical repair), injury to genital femoral nerve resulting in chronic pain, testicular ascent following inguinal tissue contracture, and testicular atrophy. A direct inguinal hernia usually only occurs in children as a result of an indirect inguinal hernia repair.
- Clarke S. Pediatric inguinal hernia and hydrocele: an evidence-based review in the era of minimal access surgery. J Laparoendosc Adv Surg Tech A. 2010 Apr;20(3):305-9.
- Kapur P, Caty MG and Glick PL. Pediatric Hernias and Hydroceles. Pediatric Clinics of North America. 1998: 45(4):773-789.
- Maisonet Lourdes. Inguinal Hernia. Pediatrics in Review. January 2003
- AAP. Assessment and Management of Inguinal Hernia in Infants. Pediatrics October 2012