Definition

A hernia is an outpouching of the parietal peritoneum through a preformed or secondarily established hiatus. If the hernia extends beyond the abdominal cavity and is thus visible on the surface of the body, it is defined as an external hernia. If the outpouching is limited to peritoneal pockets, it is known as an internal hernia. An intermediate position is taken by the interparietal hernias of the abdominal wall. Hernias may include intra- and retroperitoneal organs, either permanently or intermittently. Depending on the size of the outpouching, we speak of complete (total) or incomplete (partial) hernias. Based on their formation, we distinguish between congenital (e.g., umbilical hernias and indirect inguinal hernias, if the processus vaginalis is open) and acquired hernias (e.g., direct, femoral, and incisional hernias) (1).

History

The first description of an inguinal hernia appears in the Ebers papyrus (1555 B.C.). Hippocrates (460–375 B.C.) mentions hernias of the pubic and umbilical regions. The first anatomical studies of the inguinal region date back to Galen (131–210 A.D.).

Disregarding the historical precursors of inguinal hernia management by barbers, rupture cutters, and bathing masters, the real history of inguinal hernia surgery begins at the end of the nineteenth century. The first attempts to reduce the hernial orifice were made by Marcy (1871), Steele (1874), and Czerny (1887). It was Bassini in 1890 who introduced and established tactical surgical principles with excellent results by repairing the posterior wall of the inguinal canal and reducing of the internal inguinal ring. It was only in the middle of the twentieth century that Bassini's concept was improved by Shouldice (1945) and McVay and Anson (1942), showing the importance of the fascia transversalis.

The use of fascia grafts to close large hernial orifices and recurrent hernias dates back to Halsted (1903), Kirschner (1908), Rehn (1914), and Koontz (1926). The use of alloplastic material was introduced by Stock (1954) and Usher (1962). Preperitoneal mesh-implantation was first described by Rives (1965) for unilateral hernias and by Stoppa (1968) for bilateral inguinal hernias. In 1970, it was Lichtenstein who advocated and used mesh to bolster the repair of both direct and recurrent hernias.

The first laparoscopic hernia repair was performed by Ger (1982), by simply closing the peritoneal opening with staples without dissection, ligation, or reduction of the sac. In 1989, it was Bogojavalensky to revived this procedure by introducing the mesh-plug technique. The first series of laparoscopic herniorrhaphies were published by Schultz in 1990. Since that time, three laparoscopic procedures have been established: intra-abdominal onlay mesh- (IPOM, Fitzgibbons and Toy 1990), the transabdominal preperitoneal mesh- (TAPP, Arregui 1991), and total extraperitoneal mesh- (TEP, Dulucq 1991) implants (2).

Pathogenesis

The pathogenesis of hernias is multifactorial. Congenital hernias are preformed hernial openings caused by incomplete closure of the abdominal wall (e.g., persistent processus vaginalis), while, in acquired hernias, the cause is increasing dehiscence of fascial structure with accompanying loss of abdominal wall strength. The develop typically in locations where larger blood vessels or the spermatic cord lie, or where previous incisions were made.

Different etiological factors, such as increased intra-abdominal pressure (in pregnancy, intra-abdominal tumors, chronic obstructive lung disease, ascites, chronic intestinal obstruction, and adiposity), or pathological changes in connective tissue of the abdominal wall, are blamed, without conclusive significance. New material for understanding the pathogenetics has been provided by recent studies on collagen metabolism disorder, in which an increase of collagen III war proven in patients with hernia.

Epidemiology

The incidence of inguinal hernia in the population varies between 2% and 4%, increasing with age up to 20%. In 95% of cases, hernias are external, and in 5% they are internal. Of all hernias, 75% are inguinal (two thirds indirect and one third direct); 10% are incisional, and 5–7% are umbilical, femoral, or in other, rare locations. Whereas about 80–90% of inguinal hernias occur in males, 75% of all femoral hernias are found in females. With over 750,000 inguinal hernia operations per year in the USA, inguinal hernia repair is the most common operation for general surgeons (6).

Diagnosis

History, local examination with inspection and palpation of the hernial opening, auscultation, and diaphanoscopy are employed for hernia diagnosis. In case of uncertain clinical findings, sonography is the best means for confirming the hernial opening and content. Radiographic diagnosis of hernias is rarely required. The imaging techniques that can be used are plain abdominal film, upper gastrointestinal series and/or contrast enema, intravenous pyelography and cystography, herniography, and CT-scan or MRT. Differential diagnosis include: lymphadenitis, lipoma, varicose nodules of the saphenous vein, hydrocele, tumors, abscesses, cysts, endometriosis, and inguinal testis.

Classification

Until now, a general classification system that includes all kinds of hernias is not available. For inguinal hernias, several classifications take into consideration hernia-size and/or anatomical position, for example, the Aachen Hernia Classification (Table Ia) or the Nyhus Classification from 1993 (Table Ib).

Table Ia

Aachen hernia classification.

Table Ib

Nyhus hernia classification.

Symptoms and Complications

To what extent a hernia represents a disease entity rarely depends on the fact of the hernia itself, but rather on the fate of hernial contents. Giant hernias may cause significant bodily discomfort by weight alone; Hernias may cause complaints from restriction of physical activity develop surface ulceration, or be displeasing on aesthetic and cosmetic grounds alone. But changes in the contents lead more commonly to the hernia's becoming a true disease entity. These include nutritional (perfusion) problems of the mesentery, bowel, and omentum or/and interference in propulsion and incarceration of intestinal contents (partial or complete intestinal obstruction).

Surgical Procedures

Since the first Bassini procedure at the end of the last century, many different operative techniques have been introduced, most recently laparoscopic procedures. At present, two different major principles of repair are established: mesh-free hernia repair and tension-free hernia repair with mesh (Table II). These can be performed using an open approach or laparoscopically with an anterior or posterior approach.

Table II

Methods of hernia repair.

Today, there is a great variety of surgical procedures available for the repair of inguinal hernia. Each procedures has its own advantages and complications. As an open anterior procedure, the Shouldice repair with local anesthesia is the standard mesh-free procedure for uncomplicated primary, unilateral hernias.

In centers specializing in hernioplasty, the incidence of recurrence in a follow-up over 10 years could be reduced to 2%, although the overall recurrence rate remains at approximately 10–15% in general hospitals.

The development of different laparoscopic techniques (TAPP/IPOM, and TEP) adds another new field of hernia repair. Although limited by small study size with short follow-up periods, the preliminary results published are quite promising, with an incidence of recurrence between 0,1–3,6%. Variations in the laparoscopic approach to the preperitoneal space and differences in dissection and fixation techniques reflect that the procedure is still evolving, and there is still no consensus on the best laparoscopic herniorrhaphy. Besides the routine use of general anesthesia and procedure-related increased costs, the cumulating long-term mesh complications as shrinkage, erosion of neighboring structures such as blood vessels, spermatic cord, or bladder, adhesion- and fistula-formation, and a possible reduction of the abdominal wall mobility, make final evaluation of these surgical procedures impossible for the time being.

All tension-free hernia repair techniques with mesh have shown excellent results without statistical proof of the superiority of any single method. But, aside from low recurrence rates, long-term consequences of the mesh-related risks, such as mesh migration, and persistent chronic inflammation at the interface still remain open. Further long follow-up as well as larger studies comparing the results of open and laparoscopic repairs are needed (4, 8).

Inguinal Hernia in Adults

Inguinal hernia in the adult is the most common type of hernia (75%) and occurs mainly in males. Indirect herniation occurs through a persistent processus vaginalis (60–70%) and direct herniation through the fossa inguinalis medialis (30–40%). In up to 15% of patients, they occur bilaterally.

Inguinal Hernia in Children

Inguinal hernia is the most common surgical disease in children, with an incidence of 1–2%. Hernias occur five times more often in boys than in girls. Sixty percent of cases occur on the right side, and 10% bilaterally. In almost every case, inguinal hernias in children result from an abnormally persistent processus vaginalis, that remains open in 80–90% of neonates and is still present in 50% at the end of the first year. This persistence does not imply the presence of a hernia, but means simply a potential for hernia formation. Because of a high risk of incarcerational, especially testis or ovar, particularly at premature age or under 3 months (14–30%), an operation should not be delayed.

The main management procedure is high ligation of the hernial sac. In girls, the hernial sac should be sutured under the obliquus internus muscle for fixation of the rotundum ligament.

Femoral Hernia

Five to seven percent of all hernias are femoral hernias. They occur predominantly in females, where they make up to 75% of cases, with coincidence of inguinal hernia in 9% in females and 50% in males. Here, the herniation passes under the inguinal ligament through the lacuna vasorum medially of the v. femoralis. Management involves operative therapy by crural, inguinal, or preperitoneal approach for direct fixation of the inguinal ligament to the fascia pectinea of the pubic bone. Of late, reinforcement with mesh is advised.

Epigastric Hernia

This type of hernia presents herniation into preformed defects of the linea alba between xiphoid and umbilicus. First description was made by Arnaud de Villeneuve in 1285, but it was not until 1812 that the term epigastric hernia was introduced by Leveille. It represents 0,5–5% of all hernias. Usually, the hernia sac content is preperitoneal fatty tissue. There is a male predominance with a male to female ration of at least 3:1, diagnosis usually made in the third to fifth decade. Defects of the fascia may vary in diameter from several centimeters to only a few millimeters. The larger ones usually readily reducible, whereas the smaller ones often became in-carcerated. Multiple fascial defects are present in between 20 to 25% of individuals. Clinically, the majority of epigastric hernias (75%) are asymptomatic. Vague upper abdominal pain and nausea associated with epigastric tenderness may be present. Incarceration is common, especially in smaller hernias, but strangulation is unusual.

Operative management aims at reposition of the hernia sac contents and direct closure of the hernial opening with a continuous suture. Due to high recurrence rates, tension-free hernia repair with mesh is becoming more common.

Umbilical Hernia

The umbilicus is a natural hernial opening in the abdominal wall. It can develop a hernia at any age. In children, umbilical hernias are the third most common disorder after hydroceles and inguinal hernias. The hernia is present in about one to every five birth, the incidence in black infants being up to eight times higher than in white infants. Predisposing factors are a low birth weight and prematurity. A familial predisposition appears in 9 to 12%, but no genetic pattern of inheritance has been identified. In children most umbilical hernias are asymptomatic beside the obvious cosmetic defect. Infantile umbilical hernias rarely enlarge over time and will disappear in 90% of children by the age of 2 years. The spontaneous resolution appears to be directly influenced by the size of the umbilical ring. Defects with an umbilical ring larger than 1.5 cm are unlikely to resolve spontaneously. Complications such as strangulation of omentum or intestine and evisceration are seldom and occur approximately in 4% of cases. Indication for surgical repair are occurrence of complaints and complications or a persistence of the hernia beyond the age of 2 years. If the fascial defect is less then 1.5 cm in diameter or is asymptomatic a herniorrhaphy may be delayed until the child is 5 years old.

Umbilical hernias in adults are indirect herniations through the umbilical canal, and there have a high tendency to incarce-rate and strangulate and do not resolve spontaneously. Most of these patients are women.

Because the risk of incarceration rises to 30%, operation is advised. Management includes operative therapy with repositioning of the hernial content and continuous suture, using local anesthesia in elective repair in adults or general anesthesia in children or in an emergency situation.

An exception are acquired umbilical hernias, that may occur in patients with acute abdominal distension. Reasons for an acute elevation of the intra-abdominal pressure include ascites from cirrhosis, congestive heart failure or nephrosis. Patients undergoing peritoneal dialysis also have a high incidence of these hernias. As the majority of these patients have serious underlying problems, a surgical repair is not indicated unless complications, such as incarceration or spontaneous rupture, occur.

Spieghelian Hernia

Hernias of the linea semilunaris occur usually at the intersection with the linea semicircularis (arcuata). The first description was made by Henry-Francois Lu Dran in 1742, and named after the Belgian anatomist, Adriaan van den Spieghel. They are always acquired, occurring between the fourth and seventh decade, with a female to male ratio of 4:3. The majority of hernias (95%) are located below the umbilicus. With equal frequency on the left and right side of the body and bilateral in about 10% of the cases. The symptoms vary considerably, including abdominal pain, a mass in the anterior abdominal wall or signs of incarceration with or without intestinal obstruction. Today there are approximately 1000 cases are reported in the literature. The therapy is always surgical.

Obturator Hernia

Obturator hernias are internal herniations through the obturator foramen, bordered by the obturator vessels and nerve. It was first described by Roland Arnaud de Ronsil in 1772. They are acquired, occurring predominantly in females (female to male ratio of 6:1) in the seventh to eighth decades, never externally visible and rarely palpable. Typical symptoms are intestinal obstruction and the Howship-Romberg sign (pain extending down the inner surface of a thigh to the knee relieved by flexion of the thigh) and a history of previous attacks. When they case symptoms, they are almost always incarcerated, usually on the right side and often combined with a femoral hernial. Management includes a transperitoneal or preperitoneal approach and hernia orifice closure with direct suture or mesh.

Perineal Hernia

Perineal hernias are primary or secondary herniations of the pelvic floor that appear para- or retrorectally between the levator ani and coccygeal muscles. Primary hernias occur mostly in females, secondary hernias in both females and males and rarely with an incarceration. Management includes transperitoneal or combined abdominal and perineal approaches and direct suture or mesh.

Incisional or Recurrent Hernia

Any recurrent hernia, either inguinal, epigastric, umbilical, or at any other location, must be understood as an incisional hernia. Primary incisional herniation after laparotomy develops in up to 15% of cases, depending on the time of follow-up, and is the most common postoperative complication.

Ethiology: Any factor that impairs normal wound healing may contribute to the development of incisional hernia. Postoperative wound infection is considered to be one of the most important risk factor. Depending on the patients condition, there are some typical patient-related risk factors, such as arteriosclerosis and diabetes mellitus, that may lead to a local reduction of blood supply, causing a reduction of wound oxygenation and nutrition. Metabolic disorders such as obesity, renal insufficiency, diabetes and deficiency of protein, coagulation factor VIII or vitamin C have also an impairment on the wound healing, smoking as well as certain medications, such as steroids and chemotherapeutic agents. The assumption that an increased intra-abdominal pressure caused by postoperative chronic cough, constipation and bowel distention, or by a repair under tension is associated with a higher incidence of incisional hernia is suspected but could not be proven until now. Hesselink et al., who investigated the influence of different risk factors, found the size of the hernial defect to be a significant parameter. Incisional hernias smaller than 4 cm had a lower risk of recurrence than larger hernias. In recent studies, a defect in collagen metabolism could be proven as well, indicating the key role of the development of a mechanically strong scar tissue. The presence of a systematic collagen defect might explain the high coincidence with aortic aneurysm and the high incidence in patients with known collagen diseases.

The influence of the surgeon and this technique of primary closure after laparotomy was shown by Israelsson, who proved a suture-wound length ration of 4:1 to be of significant importance to prevent the development of a incisional hernia.

Techniques of repair: Correlating with the repair of inguinal hernias, many different operative techniques for incisional hernia have been introduced, most recently laparoscopic procedures. At present, two different major principles of repair are established: mesh-free hernia repair (conventional methods) and tension-free hernia repair with mesh. Depending of the position of the mesh-placement the sublay-, inlay- and onlay technique are differentiated.

Conventional repair of incisional hernia are performed with continuous or single stitch suture, or fascia doubling in a Mayo's operation with absorbable or nonabsorbable suture material. The results especially for large primary or recurrent hernias have shown a recurrence rates of up to 50%. The disappointing results after repetition of the primary failing techniques recommends a change of technique.

In case of properly performed primary operation that means usually the reinforcement with alloplastic material, in regard to no mesh-free alternative.

In case of small hernias with a size of four or less centimeters an attempt to try nonabsorbable continuous sutures, if absorbable materials has been used before, can be undertaken. Unfortunately there are no studies comparing mesh-repair with nonabsorbable suture up to now.

The mesh repair was first introduced by Usher who published his results with mesh made from nonresorbable polypropylene in 1959. In the following decades until today many modifications concerning material and other textile structure have been introduced. Today the surgeon has a great variety of different biomaterials to choose of (Table III).

Table III

Biomaterials for abdominal wall augmentation.

A first classification has been undertaken by Amid in 1997. Based on their pore size, he grouped the most frequently-used materials in hernia surgery into 4 types:

Type I: totally macroporous prostheses with a pore size larger than 75 microns, allowing admission of macrophages, fibroblasts, blood vessels and collagen fibers into the pores (Marlex®, Prolene®, Atrium®, Trelex®).

Type II: totally microporous prostheses, with a pore size less than 10 microns in at least one of their three dimensions (ePTFE → Goretex®, Surgical Membrane®, Dualmesh®).

Type III: macroporous protheses with multifilamentous or microporous components (PTFE mesh = Teflon®, braided Dacron mesh = Mersilene®, braided polypropylene mesh = Surgipro®, perforated PTFE patch = MaxcroMesh®).

Type IV: biomaterials with submicronic pore size (silastic, Cellgard®, Preclude Pericardial membrane, Preclude Dura-substitue).

With the recent development of new meshes an additional group should be added: low weight biomaterials with extended pore size > 4 mm (e.g. Vypro®).

The meshes are usually implanted in the sublay-technique, covered by muscle and fascia from one side, and peritoneum from the other side. This position, in the midline behind the rectus muscle on the post rectus sheath, the intraabdominal pressure prevents dislocation with a minimum requirement to scar fixation. Due to wound and mesh shrinkage an overlap of minimum 6 cm over the fascial margin is essential. To prevent intestinal fistula formation, direct contact between bowel and mesh has to be avoided.

With the implantation of alloplastic nonabsorbable materials in the sublay-technique the recurrence rate could be reduced below 5%.

The reduction of recurrence rate though is achieved by an increase of local complications. The need of an extended preparation of the subfacial space lead to a higher rate of postoperative bleeding and hematomas. The use of alloplastic material leads to an increase of seroma formation, requiring placement of several drainages. In most studies an increase of the infection rate was not shown, but recently the development of late abscesses are reported. Long-term mesh migration with arrosion of neighboring structures (e.g. urine-bladder, intestine, ductus deferrens) due to an improper mesh-fixation are observed as well. Whether late complications due to the foreign body reaction can occur is rather doubtful.

In large hernias with implantation of heavyweight meshes more than 200 cm² in size, the formation of a scar plate with its rigidity is responsible for the consecutive subjective complaints, that can occur in up to 50% of patients.

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