Article: Inguinal hernia

Inguinal hernias are protrusions of abdominal cavity contents through an area of the abdominal wall commonly referred to as the groin, and known in anatomic language as the inguinal area or the myopectineal orifice. They are very common and their repair is one of the most frequently performed surgical operations. There are two types of inguinal hernia, direct and indirect. (Femoral hernias occur within the same "myopectineal orifice," but are usually classed as separate from the "inguinal" hernias.)

Origin

Inguinal hernias usually arise as a consequence of the descent of the testis from the abdomen into the scrotum during early fetal life. They are more commonly seen in men due to larger size of their inguinal canal, which transmitted the testicle and accommodates the structures of the spermatic cord. Men are 25 times more likely to have a groin hernia than women, but since this is such a common problem in the general population (it is estimated that 5% of the population will develop an abdominal wall hernia), inguinal hernia is not extremely uncommon in women. Direct hernias however are very uncommon in women.

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" 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. Recent data questions the routine elective repair of all inguinal hernias. Some studies indicate that inguinal hernias can be left to their own devices with no greater risk than prompt elective treatment. Nevertheless, the bias remains toward surgical repair. 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

Despite the profusion of medical technology, 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

See main article at herniorraphy.

Surgical correction of inguinal hernias, called a herniorraphy or hernioplasty, is now often performed as an ambulatory, or "day surgery," procedure.

Subtypes of inguinal hernias

Indirect inguinal hernia

The most common groin hernia, the 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. In the fetus, the peritoneum gives a coat to the testicle as it passes through this ring, forming a temporary connection called the processus vaginalis. In normal development, the processus is obliterated once the testicle is completely descended. The permanent coat of peritoneum that remains around the testicle is called the tunica vaginalis. The testicle remains connected to its blood vessels and the vas deferens, which make up the spermatic cord and descend through the inguinal canal to the scrotum.

The internal inguinal ring, which is the beginning of the inguinal canal, remains as an opening in the internal oblique muscle, which forms the muscular outer wall for the spermatic cord. When the opening is larger than necessary for passage of the spermatic cord, the stage is set for an indirect inguinal hernia. The protrusion of peritoneum through the internal inguinal ring can be considered an incomplete obliteration of the processus. A hernia occurs when intra-abdominal contents, commonly including preperitoneal fatty tissues, the peritoneum itself, and eventually omentum and intestines, traverse the ring to enter the inguinal canal. As time passes, the hernia contents may enlarge, extend the length of the canal, and even exit the canal through the external inguinal ring, an opening in the external oblique fascia, into the scrotum.

A second means of indirect inguinal hernia formation in the spermatic cord is a failure of the processus vaginalis to close properly. This second situation is very common in infants; in many cases the only abdominal contents found in the hernia are fluid. This situation can sometimes be confused with a hydrocele, a collection of fluid around the testicle. The difference is simple to determine; if there is communication between the peritoneum and the fluid, which defines the presence of a hernia, the fluid collection will change in size from time to time. A hydrocoele, on the other hand, remains the same size.

In the female, groin hernias are only 4% as common as in males. Indirect inguinal hernia is still the most common groin hernia for females. If a woman has an indirect inguinal hernia, her internal inguinal ring is patent, which is abnormal for females. The protrusion of peritoneum is not called "processus vaginalis" in women, as this structure is related to the migration of the testicle to the scrotum. It is simply a hernia sac. The eventual destination of the hernia contents for a woman is the vulva majoris on the same side, and hernias can enlarge one vulva dramatically if they are allowed to progress.

During herniorraphy, the surgeon recognizes the "indirect" hernia by noting that the hernia sac begins lateral to the inferior epigastric vessels, indicating that it arose at the top of the inguinal canal.

Direct inguinal hernia

Conversely, the "direct" inguinal hernia enters through a weak point in the fascia of the abdominal wall, and its sac is noted to be medial to these vessels. Direct inguinal hernias are the same in men and women.

A direct inguinal hernia protrudes through a weakened area in the transversalis fascia within an anatomic region known as the medial or Hesselbach's triangle, an area defined by the edge of the rectus abdominis muscle, the inguimedial to the internal ring, and are also capable of exiting via the external ring and moving on to the scrotum. When a patient suffers a simultaneous direct and indirect hernia on the same side, the result is called a "pantaloon" hernia (because it looks like a pair of pants, with the epigastric vessels in the crotch), and the defects can be repaired separately or together.

Femoral hernia

A third type of groin hernia, the "femoral hernia," is rare in men (but still #3, even in women). This hernia exits 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. The most common repair for this type of hernia is the McVay repair, which approximates Cooper's ligament to the inguinal ligament to narrow the femoral canal. Mesh is used less often, partly because the femoral hernia repair is more often emergent, and due to an incarcerated hernia, in which case the risk of mesh infection is unacceptably high.

Theories of hernia formation

It was previously thought that hernias arose as the result of abnormal stress on the abdominal wall; this theory persists in the belief that hernias are caused by coughing too much or lifting heavy objects.

Most researchers still point to a patent processus vaginalis or a failure of the abdominal wall "shutter" (an involuntary movement of the abdominal muscles that closes off the inguinal canal during increased intra-abdominal pressure) as the root cause of indirect hernias.

Current research indicates that patients with direct inguinal hernias are heavily predisposed to herniate elsewhere, and that both direct and indirect hernias tend to run in families. As a result of these and other findings, a few researchers now believe that all direct hernias and many indirect hernias are a symptom of a congenital deficiency of collagen, the major structural fiber in connective tissue. Lack of collagen, according to this theory, results in weakened, attenuated connective tissue that cannot withstand the stresses of normal activity, and hence a hernia forms at the area of greatest weakness.