Inguinal hernia

Inguinal hernias are protrusions of abdominal cavity contents through the inguinal canal. They are very common (it is estimated that 7% of the population will develop an abdominal wall hernia)[ and their repair is one of the most frequently performed surgical operations.

There are two types of inguinal hernia, direct and indirect. Direct inguinal hernias occur when abdominal contents herniate through a weak point in the fascia of the abdominal wall and into the inguinal canal. Indirect inguinal hernias occur when abdominal contents protrude through the deep inguinal ring; this is ultimately caused by failure of embryonic closure of the processus vaginalis.

Origin

In men, indirect hernias follow the same route as the descending testes, which migrates from the abdomen into the scrotum during the development of the urinary and reproductive organs. The larger size of their inguinal canal, which transmitted the testicle and accommodates the structures of the spermatic cord, might be one reason why men are 25 times more likely to have an inguinal hernia than women. Although several mechanisms such as strength of the posterior wall of the inguinal canal and shutter mechanisms compensating for raised intra-abdominal pressure prevent hernia formation in normal individuals, the exact importance of each factor is still under debate.

Clinical presentation

Hernias present as bulges in the groin area that can become more prominent when coughing, straining, or standing up. They are often painful, and the bulge commonly disappears on lying down. The inability to "reduce", or place the bulge back into the abdomen usually means the hernia is "incarcerated," often necessitating emergency surgery.

As the hernia progresses, contents of the abdominal cavity, such as the intestines, can descend into the hernia and run the risk of being pinched within the hernia, causing an intestinal obstruction. If the blood supply of the portion of the intestine caught in the hernia is compromised, the hernia is deemed "strangulated," and gut ischemia and gangrene can result, with potentially fatal consequences. The timing of complications is not predictable; some hernias remain static for years, others progress rapidly from the time of onset. Provided there are no serious co-existing medical problems, patients are advised to get the hernia repaired surgically at the earliest convenience after a diagnosis is made. Emergency surgery for complications such as incarceration and strangulation carry much higher risk than planned, "elective" procedures.

Diagnosis

The diagnosis of inguinal hernia rests on the history given by the patient and the physician's examination of the groin. Further tests are rarely needed to confirm the diagnosis. However, in unclear cases an ultrasound scan or a CT scan might be of help, especially to rule out a hydrocele.

Surgical treatment

(Surgical incision in groin after inguinal hernia operation.)

Surgical correction of inguinal hernias, called a herniorrhaphy or hernioplasty, is now often performed as an ambulatory, or "day surgery," procedure. There are various surgical strategies which may be considered in the planning of inguinal hernia repair. These include the consideration of mesh use, type of open repair, use of laparoscopy, type of anesthesia, appropriateness of bilateral repair, etc. During surgery conducted under local anaesthesia, the patient will be asked to cough and strain during the procedure to help in demonstrating that the repair is "tension free" and sound.

Subtypes

Type	Description	Relationship to inferior epigastric vessels	Covered by internal spermatic fascia?	Usual onset
indirect inguinal hernia	protrudes through the inguinal ring and is ultimately the result of the failure of embryonic closure of the internal inguinal ring after the testicle passes through it	Lateral	Yes	Congenital
direct inguinal hernia	enters through a weak point in the fascia of the abdominal wall (Hesselbach triangle)	Medial	No	Adult

Inguinal hernias, in turn, belongs to groin hernias, which also includes femoral hernias. A femoral hernia is not via the inguinal canal, but via the femoral canal, which normally allows passage of the common femoral artery and vein from the pelvis to the leg.

In Amyand's hernia, the content of the inguinal hernia is the appendix.

Additional images

Different types of inguinal hernias.

Inguinal fossae