Introduction

The surgical history of inguinal hernias is a long way to today's mesh-based open and laparoscopic repairs, helpful in studying the evolution in anatomical understanding, development and application of the techniques of general surgery. Inguinal hernia repair is one of the most commonly performed surgeries in the world. While numerous surgical approaches exist to treat inguinal hernias, the use of mesh was associated with a reduced rate of recurrence.

Anatomy:

A useful learning tool in gaining a working knowledge of the inguinal region is visualizing it as it is surgically approached in the open technique.

1. The inguinal region is part of the anterolateral abdominal wall, which is made up of 9 layers. These layers, from superficial to deep, are the skin, the Camper and Scarpa fascia, the external oblique aponeurosis, the internal oblique and transversus muscles, the transversalis fascia, the preperitoneal fat, and the peritoneum.
   1. The first layers encountered upon dissection through the subcutaneous tissues are the Camper and Scarpa fascia. Contained in this space are the superficial branches of the femoral vessels, namely, the superficial circumflex and the epigastric and external pudendal arteries, which can be safely ligated and divided when encountered.
   2. The inguinal canal can be visualized as a tunnel traveling from lateral to medial in an oblique fashion. It has a roof facing anteriorly, a floor facing posteriorly, a superior (cranial) wall and an inferior (caudal) wall. The canal contents (cord structures in men or the round ligament in women) are the traffic that traverses the tunnel.
2. The external oblique aponeurosis serves as the roof of the inguinal canal and opens just lateral to and above the pubic tubercle. This is the superficial inguinal ring, which allows the cord structures egress.
3. The floor of the canal is composed of the transversus abdominus muscle and the transversalis fascia. The entrance to the inguinal canal is through these layers, and this entrance comprises the internal or deep ring.
4. The inferior wall is the inguinal ligament. The inguinal ligament is formed by the lower edge of the external oblique aponeurosis and extends from the anterior superior iliac spine to its attachments at the pubic tubercle and fans out to form the Lacunar ligament. The inguinal ligament folds over itself to form the shelving edge. This folded-over sling of external oblique aponeurosis is the true lower wall of the inguinal canal.
5. The superior wall consists of a union of the internal oblique and transversus muscles aponeurosis, which arches from its attachment at the lateral segment of the inguinal ligament over the internal inguinal ring, ending medially at the rectus sheath and coming together inferomedially to insert on the pubic tubercle, thus forming the conjoined tendon.
6. The cord structures include the vas deferens, testicular artery, artery of the ductus deferens, cremasteric artery, pampiniform plexus, and genital branch of the genitofemoral nerve, parasympathetic and sympathetic nerves, and lymph vessels.

Nerves of the groin

Acceptance of meshed-based repairs has increased and the significant reduction of inguinal hernia recurrence, the most worrisome complication of herniorrhaphy is chronic groin pain. Causalgia syndromes of each of the 3 nerves of the groin are well described. Current recommendations are nerve identification and preservation.

1. Ilioinguinal nerve: The ilioinguinal nerve runs medially through the inguinal canal along with the cord structures traveling from the internal ring to the external ring. It innervates the upper and medial parts of the thigh, the anterior scrotum, and the base of the penis.
2. Iliohypogastric nerve: The iliohypogastric nerve runs below the external oblique aponeurosis but cranial to the spermatic cord, then perforates the external oblique cranial to the superficial ring. It innervates the skin above the pubis.
3. Genital branch of the genitofemoral nerve: This branch travels with the cremasteric vessels through the inguinal canal. It innervates the cremaster muscle and provides sensory innervation to the scrotum.
4. In the anatomical distribution of these nerves some variations remain, e.g., the occasional absence of an ilioinguinal nerve.

Definitions:

1. An indirect hernia is defined as a defect protruding through the internal or deep inguinal ring, while a direct hernia is a defect protruding through the external/superficial ring. A more anatomic way to look at this is that an indirect hernia is lateral to the inferior epigastric artery and vein, while a direct hernia is medial to these vessels. The Hesselbach triangle is the zone of the inguinal floor through which direct hernias protrude, and its boundaries are the epigastric vessels laterally, the rectus sheath medially, and the inguinal ligament inferiorly.
2. A sliding inguinal hernia is one in which a portion of the wall of the hernia sac is made up of an intra-abdominal organ. As the peritoneum is stretched and pushed through the hernia defect and becomes the hernia sac, retroperitoneal structures such as the colon or bladder are dragged along with it and, thus, come to comprise one of its walls.
3. Bilateral and pediatric hernias are most commonly indirect hernias and arise because of the patency of the processus vaginalis. Unlike pediatric hernias, surgical treatment of indirect hernias in the adult population requires more than simple ligation of the hernia sac. This is because the patent processus is only part of the story. With time, the internal ring dilates, leaving an adult with what can be a sizable defect in the floor of the inguinal canal; this must be closed in addition to division/reduction of the indirect hernia sac.
4. A hydrocele is a commonly encountered pathology related to hernias.

Indications

1. Classically, the existence of an inguinal hernia has been reason enough for operative intervention.
2. Symptomatic patients (with pain or discomfort) should undergo repair; however, up to one third of patients with inguinal hernias are asymptomatic.
3. In one study, the substantial patient crossover from the observation group to the surgery arm led the authors to conclude that observation may delay but not prevent surgery. This reasoning holds particularly true in the younger patient population. Thus, even an asymptomatic patient, if medically fit, should be offered surgical repair.
4. Recurrence rates were higher in women and that recurrence in women was more likely to be of the femoral variety than in men.

Contraindications

1. Inguinal hernia repair has no absolute contraindications. As in any other elective surgical procedure, the patient must be medically optimized. Any medical issues, whether acute (e.g., upper respiratory tract or skin infection) or exacerbations of underlying medical conditions (e.g., poorly controlled diabetes mellitus), should be fully addressed and the surgery delayed accordingly.
2. Patients with high operative risk should undergo a full preoperative workup and determination of the risk-to-benefit ratio.