Inguinal hernia

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 the inferior epigastric vessels. Direct inguinal hernias may occur in males or females, but males are ten times more likely to get a direct inguinal hernia.[15]

A direct inguinal hernia protrudes through a weakened area in the transversalis fascia near the medial inguinal fossa within an anatomic region known as the inguinal or Hesselbach's triangle, an area defined by the edge of the rectus abdominis muscle, the inguinal ligament and the inferior epigastric artery. These hernias are capable of exiting via the superficial inguinal ring and are unable to extend into 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.

Since the abdominal walls weaken with age, direct hernias tend to occur in the middle-aged and elderly. This is in contrast to indirect hernias which can occur at any age including the young, since their etiology includes a congenital component where the inguinal canal is left more patent (compared to individuals less susceptible to indirect hernias).[16][17] Additional risk factors include chronic constipation, overweight/obesity, chronic cough, family history and prior episodes of direct inguinal hernias.[15]

Ultrasound of an indirect hernia containing fat, with testicle seen at right.

T2 weighted MRI of the same case (done for another purpose), also demonstrating fat content.

An indirect inguinal hernia results from the failure of embryonic closure of the deep inguinal ring after the testicle has passed through it. It is the most common cause of groin hernia.

In the male 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 deep inguinal ring, which is the beginning of the inguinal canal, remains as an opening in the fascia transversalis, which forms the fascial inner wall of 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.

In an indirect inguinal hernia, the protrusion passes through the deep inguinal ring and is located lateral to the inferior epigastric artery. Hence, the conjoint tendon is not weakened.

There are three main types

• Bubonocele: in this case the hernia is limited in inguinal canal.
• Funicular: here the processus vaginalis is closed at its lower end just above the epididymis. The content of the hernial sac can be felt separately from the testis which lies below the hernia.
• Complete (or scrotal): here the processus vaginalis is patent throughout. The hernial sac is continuous with the tunica vaginalis of the testis. The hernia descends down to the bottom of the scrotum and it is difficult to differentiate the testis from hernia.

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 labium majus on the same side, and hernias can enlarge one labium dramatically if they are allowed to progress.

A physician may diagnose an inguinal hernia, as well as the type, from medical history and physical examination.[20] For confirmation or in uncertain cases, medical ultrasonography is the first choice of imaging, because it can both detect the hernia and evaluate its changes with for example pressure, standing and Valsalva maneuver.[21]

When assessed by ultrasound or cross sectional imaging with CT or MRI, the major differential in diagnosing indirect inguinal hernias is differentiation from spermatic cord lipomas, as both can contain only fat and extend along the inguinal canal into the scrotum.[22]

On axial CT, lipomas originate posterolateral to the cord, and are located inside the cremaster muscle, while inguinal hernias lie anteromedial to the cord and are not intramuscular. Large lipomas may appear nearly indistinguishable as the fat engulfs anatomic boundaries, but they do not change position with coughing or straining.[22]

Differential diagnosis of the symptoms of inguinal hernia mainly includes the following potential conditions:[23]

• Femoral hernia
• Epididymitis
• Testicular torsion
• Lipomas
• Inguinal adenopathy (Lymph node Swelling)
• Groin abscess
• Saphenous vein dilation, called Saphena varix
• Vascular aneurysm or pseudoaneurysm
• Hydrocele
• Varicocele
• Cryptorchidism (Undescended testes)

There is currently no medical recommendation about how to manage an inguinal hernia condition in adults, due to the fact that, until recently,[24][25] elective surgery used to be recommended. The hernia truss is intended to contain a reducible inguinal hernia within the abdomen. It is not considered to provide a cure, and if the pads are hard and intrude into the hernia aperture they may cause scarring and enlargement of the aperture. In addition, most trusses with older designs are not able effectively to contain the hernia at all times, because their pads do not remain permanently in contact with the hernia. The more modern variety of truss is made with non-intrusive flat pads and comes with a guarantee to hold the hernia securely during all activities. Although there is as yet no proof that such devices can prevent an inguinal hernia from progressing, they have been described by users as providing greater confidence and comfort when carrying out physically demanding tasks. A truss also increases the probability of complications, which include strangulation of the hernia, atrophy of the spermatic cord, and atrophy of the fascial margins. This allows the defect to enlarge and makes subsequent repair more difficult.[26] Their popularity is likely to increase, as many individuals with small, painless hernias are now delaying hernia surgery due to the risk of post-herniorrhaphy pain syndrome.[27] The elasticised pants used by athletes also provide useful support for the smaller hernia.

Surgical incision in groin after inguinal hernia operation

Surgical correction of inguinal hernias is called a hernia repair. It is not recommended in minimally symptomatic hernias, for which watchful waiting is advised, due to the risk of post herniorraphy pain syndrome. Surgery is commonly performed as outpatient surgery. There are various surgical strategies which may be considered in the planning of inguinal hernia repair. These include the consideration of mesh use (e.g. synthetic or biologic), open repair, use of laparoscopy, type of anesthesia (general or local), appropriateness of bilateral repair, etc. Laparoscopy is most commonly used for non-emergency cases, however, a minimally invasive open repair may have a lower incidence of post-operative nausea and mesh associated pain. 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 without tension and sound.[28]

Constipation after hernia repair results in strain to evacuate the bowel causing pain, and fear that the sutures may rupture. Opioid analgesia makes constipation worse. Promoting an easy bowel motion is important post-operatively.

Surgical correction is always recommended for inguinal hernias in children.[29]

Emergency surgery for incarceration and strangulation carry much higher risk than planned, "elective" procedures. However, the risk of incarceration is low, evaluated at 0.2% per year.[30] On the other hand, surgery has a risk of inguinodynia (10-12%), and this is why males with minimal symptoms are advised to watchful waiting.[30][31] However, if they experience discomfort while doing physical activities or they routinely avoid them for fear of pain, they should seek surgical evaluation.[32] For female patients, surgery is recommended even for asymptomatic patients.[33]