A hernia is an abnormal protrusion of a cavity’s contents, through a weakness in the wall of the cavity, taking with it all the linings of the cavity, although these may be markedly attenuated (Fig. 11.2). Hernias of the abdominal wall are common. Multiple factors contribute to the development of hernias. In essence, hernias can be considered design faults, either anatomical or through inherited collagen disorders, although these two factors work together in the majority of patients. Hernias may exploit natural openings such as the inguinal and femoral canals, umbilicus, obturator canal or oesophageal hiatus, or protrude through areas weakened by stretching (e.g. epigastric hernia) or surgical incision. In addition to these ‘weak’ anatomical areas, the collagen make up of the tissues, especially the Type I to III collagen ratio is also important. Type I imparts the strength to the tendon or fascia, Type III provides elastic recoil to the tissue. The Type I/III collagen ratio varies between individuals but is constant in all the fascia of a particular individual. Hernias can be considered as a disease of collagen metabolism.

Fig. 11.2 Hernia.

A Anatomical structure.B Parts of the hernial sac.

The hernia is immediately invested by a peritoneal sac drawn from the lining of the abdominal wall (Fig. 11.2). The sac is covered in turn by those tissues that are stretched in front of it as the hernia enlarges (i.e. the coverings). The neck of the sac is the constriction formed by the orifice in the abdominal wall through which the hernia passes. A hernia may contain any intra-abdominal structure but most commonly contains omentum and/or small bowel. A hernia may involve only part of the circumference of the bowel (Richter’s hernia), a Meckel’s diverticulum (Littré’s hernia) or an incarcerated appendix (Amyand’s hernia). A sliding inguinal hernia is defined as one in which a viscus forms a portion of the wall of the hernia sac. Most commonly, the viscus involved is caecum, sigmoid colon or urinary bladder. In the early stages of a hernia, sometimes the hernial contents are pre-peritoneal fat only, such as a lipoma of the cord which can mimic an inguinal hernia.

Summary Box 11.1 Hernia

• A hernia is an abnormal protrusion of a cavity’s contents through a weakness in the wall of the cavity, but takes with it all the linings of the cavity

• Hernias of the abdominal wall are common and may exploit natural openings or weak areas caused by stretching or surgical incisions in association with a defect in collagen metabolism

• Abdominal hernias have a peritoneal sac, the neck of which is often unyielding and constitutes a potential source of compression of the hernial contents

• Hernia may be classified as reducible or irreducible, and the contents (e.g. bowel) may become obstructed or strangulated

• Strangulation denotes compromise of the blood supply of the contents and its development significantly increases morbidity and mortality. The low-pressure venous drainage is occluded first and then the arterial supply becomes occluded, with the development of gangrene.

Inguinal hernia

Groin hernias account for three-quarters of all abdominal wall hernias, and inguinal herniorrhaphy is one of the most frequently performed general surgical procedures. The most common types of groin hernia are indirect inguinal (60%), direct inguinal (25%) and femoral (15%) (Fig. 11.3). Most (85%) groin hernias occur in males. Inguinal hernias occur in 1–3% of all newborn males. The incidence in premature infants is 30 times that seen at term. In early life, an indirect inguinal hernia is by far the most common variety. After middle age, weakness of the abdominal musculature leads to an increasing incidence of direct inguinal hernias. Femoral hernias are relatively more common in females (possibly because of stretching of ligaments and widening of the femoral ring in pregnancy), but an indirect inguinal hernia is still the most common type of groin hernia in women.

Fig. 11.3 Anatomy of the internal inguinal ring, showing sites of herniation from within.

Surgical anatomy

The inguinal canal is an oblique passage in the lower anterior abdominal wall, through which the spermatic cord passes to the testis in the male, or the round ligament to the labium majus in the female. The processus vaginalis traversing the canal is normally obliterated at birth, but persistence in whole or in part presents an anatomical predisposition to an indirect inguinal hernia (Fig. 11.4). The openings of the canal are formed by the internal and external rings. The internal (deep) inguinal ring is an opening in the transversalis fascia, which lies approximately 1 cm above the mid-inguinal point (midway between the pubic tubercle and the anterior superior iliac spine). The internal inguinal ring is bounded medially by the inferior epigastric artery (Fig. 11.3). The inguinal canal ends at the external (superficial) inguinal ring, which is an opening in the aponeurosis of the external oblique muscle just above and medial to the pubic tubercle. At birth, the internal and external rings lie on top of each other, so that the inguinal canal is short and straight; with growth, the two rings move apart so that the canal becomes longer and oblique.

Fig. 11.4 Processus vaginalis testis.

A Normal obliteration of processus vaginalis.B Persistence of patent processus.

The testis and spermatic cord receive a covering from each of the layers as they pass through the abdominal wall. The innermost layer is derived from the transversalis fascia (the internal spermatic fascia), the middle layer from the internal oblique muscle (the cremasteric muscle and fascia), and the outer layer from the external oblique aponeurosis (the external spermatic fascia). Within the inguinal canal, the spermatic cord is covered only by the cremasteric and internal spermatic fasciae. The spermatic cord consists of the vas deferens, the artery of the vas (branch of the inferior vesical artery), the testicular artery (branch of the aorta on the right and renal artery on the left), the cremasteric artery (branch of the inferior epigastric artery), the pampiniform plexus of veins, the ilio-inguinal nerve, the genital branch of the genitofemoral nerve and lymphatics.

Indirect inguinal hernia

An indirect inguinal hernia enters the internal (deep) inguinal ring and descends within the coverings of the spermatic cord so that it can pass on down into the scrotum, the so-called inguino-scrotal hernia. Very occasionally, it enlarges between the muscle layers of the abdominal wall to form an interstitial hernia.

Clinical features

Inguinal hernias typically develop over months to years. While such hernia may cause no symptoms, there may be a dragging discomfort in the groin, particularly during lifting or straining, or at the end of the day. Following a period of rest, such symptoms may improve until further strenuous activity. It is not unusual for a patient to present with a lump in the groin rather than because of painful symptoms.

The hernia forms a swelling in the inguinal canal, which may extend into the scrotum. It is often readily visible when the patient stands or is asked to cough. However, as the population becomes fatter, and patients tend to present earlier with symptoms or a small swelling, the diagnosis may not be so obvious on inspection of the groin. However, look for signs of asymmetry between the two groins. While bilateral inguinal hernias are not unusual, it is unusual for both hernias to be of similar size (Fig. 11.5). An inguinal hernia, which passes into the scrotum, passes above and medial to the pubic tubercle, in contrast to a femoral hernia, which bulges below and lateral to the tubercle (Fig. 11.6). Again, in more obese patients, such landmarks can be difficult to palpate with confidence. A cough impulse is normally palpable, and bowel sounds can often be heard within the hernia on auscultation. If there is no visible swelling, a cough impulse is sought with the patient standing.

Fig. 11.5 Clinical photograph of bilateral inguinal hernia.

Fig. 11.6 Exit of femoral and inguinal hernias.

The hernia often reduces spontaneously when the patient lies down, or it may be reduced by gentle pressure applied in an upward and lateral direction. It may be possible to control the hernia, once reduced, by placing a finger over the internal (deep) inguinal ring.

Direct inguinal hernia

Direct hernias are due to weakness of the abdominal wall and may be precipitated by increases in intra-abdominal pressure (e.g. obstructive airways disease, prostatism or chronic constipation). The hernia protrudes through the transversalis fascia in the posterior wall of the inguinal canal. The defect is bounded above by the conjoint tendon, below by the inguinal ligament, and laterally by the inferior epigastric vessels (Fig. 11.3). These boundaries mark the area known as Hesselbach’s triangle. The hernia occasionally bulges through the external (superficial) inguinal ring, but the transversalis fascia cannot stretch sufficiently to allow it to descend down into the scrotum. The sac has a wide neck, so that the hernia seldom becomes irreducible, obstructs or strangulates. As shown in Figure 11.3, the neck of the sac of a direct inguinal hernia lies medial to the inferior epigastric vessels, whereas that of an indirect hernia lies lateral to them. A combined indirect and direct hernia may occur on the same side (pantaloon or saddle-bag hernia), with sacs straddling the inferior epigastric vessels.

Clinical features

The hernia forms a diffuse bulge in the region of the medial part of the inguinal canal. It is usually readily reduced by backward pressure, and the edges of the defect may then be palpable. Clinically, it is frequently impossible to determine whether a hernia confined to the inguinal canal is of the direct or the indirect variety.

Management of uncomplicated inguinal hernia

The identification of an inguinal hernia in any child is nearly always an indication to operate. Elective surgery is usually undertaken on a day-case basis, with liberal use of local anaesthetic blocks for postoperative pain relief.

Adults with a symptomatic inguinal hernia should be offered surgery. Open mesh repair or laparoscopic mesh repair aims to reduce postoperative pain to a minimum, enabling most procedures to be undertaken as day cases EBM 11.1. Inguinal hernias can be controlled by a truss, but this is uncomfortable and is now seldom indicated, as repair using local or regional anaesthestic techniques can be employed in higher-risk patients.

11.1 Laparoscopic inguinal hernia repair

‘Laparoscopic inguinal hernia repair is associated with less acute and chronic pain, less nerve injuries such as numbness, quicker return to normal activity and work, and significantly fewer postoperative complications such as infection and haematoma formation than open inguinal hernia repair. Hospital costs are higher for laparoscopic repair and it requires the use of general anaesthetic.’

www.nice.org.uk/TA083guidance,2010

Indirect inguinal hernia

The first step in the open approach is to open the inguinal canal, free the hernial sac from the spermatic cord (Fig. 11.7) and excise it after transfixing and ligating its neck. Simple excision of the sac (herniotomy) is all that is needed in young children. In older children and adults, the internal ring is usually stretched and widened, and therefore after herniotomy it is necessary to tighten the deep ring and/or strengthen the posterior wall with a mesh (herniorrhaphy or hernioplasty). Suture repair alone is rare in developed countries in adults, but still has a place in the repair of groin hernias in adolescents (a rare age for presentation of groin hernias).

Fig. 11.7 Principle of dissection in the repair of a right inguinal hernia.

Direct hernia

In a direct hernia, the sac, following mobilization from the spermatic cord, is not normally excised and it is simply invaginated by sutures placed in the transversalis fascia. Insertion of a synthetic mesh is currently used to reinforce the posterior wall of the inguinal canal EBM 11.2.

11.2 Use of mesh in hernia repair

‘Mesh reduces the risk of hernia recurrence.’

Flum et al, Ann Surg 2003;237:129.

In all hernia repairs, it is important to avoid constricting the spermatic cord by making the deep inguinal ring too tight. This may compromise the blood supply to the testis, particularly in large or recurrent hernias. In older patients, removal of the testis may be considered so that the inguinal canal can be completely obliterated in recurrent hernias.

The most common surgical procedure now performed is the Lichtenstein open tension-free repair, which involves the insertion of a synthetic mesh underneath the spermatic cord (Fig. 11.8). The mesh is secured to the aponeurotic tissue overlying the pubic bone medially, the inguinal ligament inferiorly, and the internal oblique aponeurosis and conjoint tendon superiorly. Laterally, the mesh is divided and its two sides wrapped around the spermatic cord and sutured in place.

Fig. 11.8 Lichtenstein open mesh repair – right sided hernia.

A The lower border of the mesh is secured in place with a continuous suture to the inguinal ligament.B Interrupted sutures are placed between the upper edge of the mesh and the underlying aponeurosis.C A suture is placed laterally to close the two tails around the internal ring.

Laparoscopic hernia repair, using a transperitoneal or pre-peritoneal approach, is increasing in popularity. The technique involves reducing the hernial sac and inserting a mesh. Proponents of these techniques emphasize minimal pain, both acute and chronic, a more rapid return to normal activities and work, improved cosmesis and fewer infective complications; however, critics emphasize the necessity for a general anaesthetic, the violation of the peritoneal cavity (with the transperitoneal approach), increased hospital costs and the technical difficulty of the surgery. An additional benefit of laparoscopic surgery is that the mesh is larger than that used at open surgery, and covers the direct, indirect and femoral hernial orifices. It is generally accepted that the laparoscopic approach is particularly useful for patients with recurrent inguinal hernias or bilateral inguinal hernias, or exploration of the groin when a symptomatic hernia is suspected from the history but is not obvious on clinical examination.

The asymptomatic inguinal hernia does not always require repair. However, the majority of such hernias become symptomatic within several years, at which time they can be repaired.

Approximately 5% of hernias will recur. Early recurrence within 2 years is usually a result of an inadequate primary operation, whereas late recurrence reflects progression of the underlying muscular weakness. Recurrent hernias can be difficult to repair and the laparoscopic approach may be of particular benefit to these patients.

Sportsman’s hernia

Groin injury leading to chronic groin pain is often referred to as the sportsman’s hernia. However, the definition, investigation and treatment of this condition remain controversial. The differential diagnosis includes musculotendinous injuries, osteitis pubis, nerve entrapment, urological pathology or bone and joint disease. In many cases, clinical signs are lacking, despite the patient’s symptoms. Herniography studies have demonstrated a significant incidence of symptomatic impalpable hernia in patients presenting with obscure groin pain. Dynamic ultrasound (ultrasound examination of the groin with the patient at rest and when straining) is replacing herniography as it is non-invasive. MRI scanning is also used, more to exclude other pathology that might be causing the groin pain rather than to diagnose a sportsman’s hernia.

A deficiency of the posterior inguinal wall is the most common operative finding in patients with chronic groin pain. Some authors have described a tear in the conjoint tendon as the cause of the pain, whereas in Gilmore’s description, a tear in the external oblique aponeurosis, causing dilatation of the external (superficial) inguinal ring, was implicated. Surgical intervention is recommended only when conservative management has failed. Appropriate repair of the posterior wall of the inguinal canal has proved to be of therapeutic benefit in selected patients.

Femoral hernia

A femoral hernia projects through the femoral ring and passes down the femoral canal. The ring is bounded laterally by the femoral vein, superiorly by the inguinal ligament, medially by the lacunar ligament, and inferiorly by the superior ramus of the pubis and the reflected part of the inguinal ligament (pectineal ligament of Astley Cooper) (Fig. 11.9). As the hernia enlarges, it passes through the saphenous opening in the deep fascia of the thigh (the site of penetration of the long saphenous vein to join the femoral vein) and then turns upwards to lie in front of the inguinal ligament. The hernia has many coverings and may be deceptively small, sometimes escaping detection. It frequently contains omentum or small bowel, but the urinary bladder can ‘slide’ into the medial wall of the sac.

Fig. 11.9 Anatomy of the femoral ring.

Clinical features

The hernia forms a bulge in the upper inner aspect of the thigh. While a lump or swelling may be the presenting symptom, groin pain related to exercise is also a common presentation. It can sometimes be difficult to differentiate between an inguinal and a femoral hernia, but as indicated earlier, the former passes above and medial to the pubic tubercle as it enters the groin, whereas the latter passes below and lateral to it. Tracing the tendon of adductor longus upwards to its insertion can be a useful guide to the position of the pubic tubercle.

A femoral hernia is frequently difficult or impossible to reduce because of its J-shaped course and the tight neck of the sac. As well as needing to be differentiated from inguinal hernia, it can be confused with an inguinal lymph node (no cough impulse, irreducible), saphenous varix (positive cough impulse or ‘saphenous thrill’, which is prominent on standing but disappears on elevating the leg), ectopic testis, psoas abscess, hydrocoele of the spermatic cord or a lipoma.

Surgical repair of femoral hernia

A femoral hernia is particularly likely to obstruct and strangulate (indeed 40% of such hernias present this way), and therefore surgical intervention is indicated EBM 11.3. As with inguinal hernia, repair can be carried out under local or general anaesthesia.

11.3 Emergency hernia surgey

‘Infarcted bowel is the main risk factor for death in hernia surgery.’

Derici et al, Hernia 2007;11:341.

The aim of operation is to reduce the sac and obliterate the femoral ring by suturing the inguinal ligament to the pectineal ligament. The femoral canal can be approached from below the inguinal ligament, through the inguinal canal, or from above by entering the rectus sheath and displacing the rectus abdominis medially. The approach from above (McEvedy approach) gives the best access, and is particularly useful if the hernia contains strangulated bowel and intestinal resection is required. The laparoscopic approach is an alternative ‘high’ approach.

Summary Box 11.2 Groin hernias

• Indirect inguinal hernias comprise 60% of all groin hernias and commence at the deep inguinal ring, lateral to the inferior epigastric vessels

• Direct inguinal hernias account for 25% of all groin hernias and bulge through a weakness in the back wall of the inguinal canal, medial to the inferior epigastric vessels. They rarely obstruct or strangulate

• Indirect inguinal hernias may pass down within the coverings of the spermatic cord to the scrotum; direct hernias do not descend into the scrotum

• Asymptomatic inguinal hernias do not have to be repaired, especially in the elderly

• Femoral hernias account for 15% of all groin hernias and pass through the femoral canal, emerging below and lateral to the pubic tubercle (in contrast to inguinal hernias, which pass medially to the tubercle and may descend to the scrotum)

• Femoral hernias are often small and easy to miss on clinical examination, but are prone to obstruct and strangulate.

Ventral hernia

Ventral hernias occur through areas of weakness in the anterior abdominal wall (Fig. 11.10): namely, the linea alba (epigastric hernia), the umbilicus (umbilical and paraumbilical hernia), the lateral border of the rectus sheath (Spigelian hernia), and the scar tissue of surgical incisions (incisional hernia). Such incisions include scars from laparoscopic surgery, the so-called port-site hernia.

Fig. 11.10 Types of ventral hernia.

A Epigastric: through the linea alba. B Umbilical: through an umbilical scar. C Para-umbilical: above or below the umbilicus. D Spigelian: lateral edge of rectus muscle. E Incisional: anywhere.

Epigastric hernia

Epigastric hernias protrude through the linea alba above the level of the umbilicus. The herniation may consist of extraperitoneal fat or may be a protrusion of peritoneum containing omentum. The hernia is common in thin individuals and can cause local discomfort. Unless large, epigastric hernias are rarely visible on inspection, but are palpable as a firm midline lump. It is repaired by closing the defect with non-absorbable sutures, or by inserting a small mesh, or by laparoscopic intraperitoneal mesh repair.

Umbilical hernia

True umbilical hernias occur in infants. The small sac protrudes through the umbilicus, particularly as the child cries, but is easily reduced. Over 95% of these hernias close spontaneously in the first 3 years of life. Persistence after the third birthday is an indication for elective repair. Surgery involves excision of the hernial sac and closure of the defect in the fascia of the abdominal wall.

Para-umbilical hernia

This hernia is caused by gradual weakening of the tissues around the umbilicus (Fig. 11.11). It most often affects obese multiparous women, and passes through the attenuated linea alba just above or below the umbilicus. The peritoneal sac is often preceded by the extrusion of a small knuckle of extraperitoneal fat through the linea alba. The hernia gradually enlarges, the covering tissues become stretched and thin, and eventually loops of bowel may become visible under parchment-like skin. The sac is often multilocular and may be irreducible because of adhesions that form between omentum and loops of bowel. The skin may become reddened, excoriated and ulcerated, and rarely an intestinal fistula may even develop.

Fig. 11.11 Clinical photograph of a para-umbilical hernia – note the appendicectomy scar.

Operation is advised because of the risk of obstruction and strangulation. Unless there is a large protrusion of the umbilicus itself, most surgical repairs can be performed preserving the umbilicus. Through a transverse subumbilical incision, the anterior layer of the rectus sheath is exposed. The sac is opened and the contents are reduced. The classic Mayo repair involves the development of a flap of rectus sheath and linea alba above and below the hernial defect. The defect is closed by overlapping the layers, using mattress sutures of non-absorbable material in a ‘double-breasted’ fashion. Alternatively, the defect can be closed using non-absorbable transverse sutures or the insertion of a mesh. Like epigastric hernias, there is increasing use of laparoscopic mesh repair, especially for a large hernia or a small hernia in a fat patient.

Incisional hernia

Incisional hernias occur after 5% of all abdominal operations. Over half of incisional hernias occur in the first 5 years after the original surgery. Midline vertical incisions are most often affected, and poor surgical technique, wound infection, obesity and chest infection are important predisposing factors, in addition to the collagen metabolism status of the patient. The diffuse bulge in the wound is best seen when the patient coughs or raises the head and shoulders from a pillow, thereby contracting the abdominal muscles (Fig. 11.12). Strangulation is rare, but surgical repair is usually advised.

Fig. 11.12 Clinical photograph of a midline incisional hernia.

Again, open or laparoscopic mesh repair is possible. At open surgery, the mesh can be inserted as an onlay, inlay, sublay or intraperitoneal position (Fig. 11.13). The sublay operation is associated with the lowest incidence of wound complications and recurrence of the hernia. Many incisional hernia wounds are cosmetically poor, so laparoscopic surgery for cosmesis is not so clear cut. However, laparoscopic surgery is associated with less pain, shorter hospital stay and more rapid return to activities. However, it is difficult to restore the normal anatomy by bringing the muscles together again at laparoscopic surgery, and thus such an approach is mainly used for smaller incisional hernias.

Fig. 11.13 Position of mesh at open incisional hernia repair.

A Onlay – mesh anterior to the muscles in the subcutaneous space. B Inlay – mesh bridges the gap in the muscles. C Sublay – mesh within the muscle layers and/or the pre-peritoneal space. D Intra-peritoneal onlay mesh (IPOM).

Parastomal hernia

These occur after the formation of an abdominal wall stoma. The majority of patients with a stoma will develop a parastomal hernia with time. The best way to treat such a hernia includes reversing the stoma, if possible. Otherwise, the techniques for incisional hernia are relevant here including repositioning of the stoma. There is evidence to support the use of mesh reinforcement at the time of creation of the stoma to minimize the risk of parastomal hernia development. Such prophylactic use of mesh is also considered in other high risk groups, such as midline incisions in the obese.

Rare external hernia

• A Spigelian hernia occurs through the linea semilunaris at the outer border of the rectus abdominis muscle. Treatment is surgical, as the hernia is liable to strangulate

• A lumbar hernia forms a diffuse bulge above the iliac crest between the posterior borders of the external oblique and latissimus dorsi muscles. It seldom requires treatment

• An obturator hernia is a rare hernia that is more common in women and passes through the obturator canal. Patients may present with knee pain owing to pressure on the obturator nerve; however, the diagnosis is frequently made only when the hernia has strangulated and is discovered at laparotomy.

Internal hernia

Herniation of the stomach through the oesophageal hiatus in the diaphragm (hiatus hernia) is a common cause of internal herniation and is considered in Chapter 13. A variety of cul-de-sacs and peritoneal defects resulting from rotation of the bowel and other abnormalities of development may be responsible for the entrapment of bowel and acute intestinal obstruction. For example, herniation may occur through the foramen of Winslow (opening of the lesser sac) and through various openings in the diaphragm, including the oesophageal hiatus (Fig. 11.14). In addition, bowel operations, such as the development of a Roux loop can lead to ‘iatrogenic’ sites for internal hernia formation.