Chapter 64: The Abdominal Wall, Hernia and Umbilicus

Inguinal Hernia

Inguinal hernia, often referred to as a ‘rupture’ by patients, is the most common hernia in men and is around 10 times more common in men than in women. There are two basic types that are fundamentally different in anatomy, causation and complications. However, they are anatomically very close to each other, the surgical repair techniques are very similar and ultimate reinforcement of the weakened anatomy is identical, so they are often referred to together as inguinal hernia.

Congenital inguinal hernias are of the indirect type, whereas the acquired hernias may be either indirect or direct.

Anatomy of the inguinal canal

As the testis descends from the abdominal cavity to the scrotum it passes through a defect in the transversalis fascia called the deep inguinal ring, just deep to the abdominal muscles. This ring lies midway between the anterior superior iliac spine and the pubic tubercle, approximately 2–3 cm above and marginally lateral to the femoral artery pulse in the groin. The inferior epigastric vessels lie just medial to the deep inguinal ring, passing from the iliac vessels to rectus abdominis. Muscle fibres from the innermost two layers of the lateral abdominal wall, the transversus muscle and the internal oblique muscle, arch over the deep inguinal ring from lateral to medial before descending to become attached to the pubic tubercle. These two muscles fuse and become tendinous, forming the conjoint tendon. Below this arch there is no muscle but only transversalis fascia and external oblique aponeurosis, resulting in an area of weakness (Figure 64.10).

The testis proceeds medially and downwards along the inguinal canal. Anterior to the canal is the aponeurosis of the external oblique muscle, the fibres of which run downwards and medially. The testis finally emerges through an inverted V-shaped defect in the aponeurosis, the superficial inguinal ring, and descends into the scrotum.

The inguinal canal is roofed by the conjoint tendon; its posterior wall is transversalis fascia, the anterior wall is the external oblique aponeurosis and the floor is the free inferior edge of the external oblique aponeurosis, rolled inwards thickened to become the inguinal (Poupart’s) ligament. The inguinal canal in males contains the testicular artery, veins, lymphatics and the vas deferens all covered in cremasteric muscle. In females, the round ligament descends through the canal to end in the labia majora. Three important nerves, the ilioinguinal, the iliohypogastric and the genital branch of the genitofemoral nerve, also pass through the canal.

As the testis descends, a tube of peritoneum is pulled with the testis and wraps around it ultimately to form the tunica vaginalis. This peritoneal tube should obliterate, possibly under hormonal control, but it commonly fails to do so completely. As a result, bowel within the peritoneal cavity can pass inside the tube towards the scrotum. Inguinal hernias in neonates and children are always of this congenital type. However, in other patients, the muscles around the deep inguinal ring can prevent a hernia from developing until later in life, when, under the constant positive abdominal pressure, the deep inguinal ring and muscles are stretched and a hernia becomes apparent. As the hernia increases in size, the contents are directed down into the scrotum. These hernias can become massive and may be referred to as a scrotal hernia (Figure S64.1). An indirect hernia is lateral because its origin is lateral to the inferior epigastric vessels. It is also oblique as the hernia passes obliquely from lateral to medial through the abdominal muscle layers. An indirect hernia can pass all the way down to the scrotum, following the line of the processus vaginalis, while this is not possible with a direct hernia.

The second type of inguinal hernia, referred to as direct or medial, is always acquired. It is a result of stretching and weakening of the abdominal wall just medial to the inferior epigastric vessels, an area known as Hesselbach’s triangle, the three sides of which are the inferior epigastric vessels laterally, the lateral edge of rectus abdominis muscle medially and the inguinal ligament below (the iliopubic tract) (Figure 64.11). This area is weak because the abdominal wall at this point consists of only transversalis fascia covered by the external oblique aponeurosis.

A direct medial hernia is more likely in elderly patients. It is broadly based and therefore unlikely to strangulate. The bladder can be pulled into a direct hernia (Figure 64.12).

Inguinal hernias are sometimes referred to as ‘sliding’ in type. These are acquired indirect hernias arising at the deep inguinal ring lateral to the inferior epigastric vessels. Retroperitoneal fatty tissue is pushed downwards along the inguinal canal. As more tissue enters the hernia, peritoneum is pulled with it, thus creating a sac. However, the sac has formed secondarily, distinguishing it from a classic indirect hernia. On the left side, sigmoid colon may descend into a sliding hernia and the caecum may do so on the left. Surgeons need extra caution during repair because the bowel may form part of the sac itself and can be damaged during the dissection.

Figure S64.1

A very large right-sided indirect inguinal hernia that has descended into the scrotum. Note the penile retraction, which can cause problems with micturition (courtesy of Dr A de Beaux, Edinburgh, UK).

Occasionally, both lateral and medial hernias are present in the same patient (pantaloon hernia).

Figure 64.12

A cystogram showing that part of the urinary bladder has descended into a left direct inguinal hernia (arrows).

Classification

Many ways to classify inguinal (and femoral) hernias have been described. The European Hernia Society has recently suggested a simplified system of:

• primary or recurrent (P or R);
• lateral, medial or femoral (L, M or F);
• defect size in fingerbreadths (assumed to be 1.5 cm), with three sizes of one fingerbreadth or less, between one and three fingerbreadths and three or more fingerbreadths.

A primary indirect inguinal hernia with a 3-cm defect size would be PL2.

Diagnosis of an inguinal hernia

In most cases, the diagnosis of an inguinal hernia is simple. Often the hernia will reduce on lying and reappear on standing. With the patient lying down, the patient is asked to reduce the hernia if it has not spontaneously reduced. If the patient cannot then the surgeon gently attempts to reduce the hernia. Once reduced, the surgeon identifies the bony landmarks of the anterosuperior iliac spine and pubic tubercle, from which the location of the deep inguinal ring can be found just above the midpoint of the inguinal ligament. Gentle pressure is applied at this point and the patient asked to cough. If the hernia is controlled with pressure on the deep inguinal ring then it is likely to be indirect/lateral; if the hernia appears medial to this point despite local pressure, then it is direct/medial. Other examination techniques have been suggested but even experienced surgeons find it difficult to distinguish lateral and medial hernias with certainty (Figure 64.13).

Diagnostic difficulties

Confirmation of the diagnosis may not be possible when the patient describes an intermittent swelling but nothing is found on examination. Surgeons will often accept the diagnosis on history alone but re-examination at a later date or investigation by ultrasound scan may be requested.

Figure 64.13

Oblique left inguinal hernia that became apparent when the patient coughed and persisted until it was reduced when he lay down.

If an inguinal hernia becomes irreducible and tense there may be no cough impulse. Differential diagnosis would include a groin lymph node mass, psoas abscess, subcutaneous soft tissue mass (e.g. lipoma) or an abdominal mass (Figures S64.2 and S64.3). Such cases may require investigation by either ultrasonography or CT.

Large scrotal hernias may be misdiagnosed as a hydrocele or other testicular swelling. The surgeon should be able to identify the upper limit of a swelling that arises from within the scrotum, but a large scrotal hernia has no upper limit because it extends back along the inguinal canal to the peritoneal cavity. In cases of doubt, ultrasonography or CT should establish the diagnosis.

As inguinal hernia is so common, less experienced clinicians might suggest this diagnosis when referring cases of femoral hernia or Spigelian hernia. A saphena varix may present as a groin swelling that increases in size on standing and with a definite cough impulse and be misdiagnosed as a hernia, particularly in pregnant women.

It is essential in men to examine the scrotal contents to exclude other pathologies and to check that the patient has both testes. It is also important to examine the opposite side because contralateral hernia is common. A patient with a single hernia has a 50% lifetime risk of developing a hernia on the other side. Some surgeons have suggested that patients should be offered bilateral repair, especially if laparoscopic surgery is planned, but this is not widespread practice at present.

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Umbilical Hernia in Adults

Conditions that cause stretching and thinning of the midline raphe (linea alba), such as pregnancy, obesity and liver disease with cirrhosis and ascites, predispose to reopening of the umbilical defect. In adults, the defect can be not only through the umbilicus but also in the median raphe (linea alba) immediately adjacent to (most often above) the true umbilicus. The latter are commonly called ‘paraumbilical’ hernias; however, under current guidelines, any hernia in the immediate vicinity of the umbilicus can now be called ‘umbilical’. Small umbilical hernias often contain extraperitoneal fat or omentum. Larger hernias can contain small or large bowel. Because the hernia neck is relatively narrow in relation to the size of the sac, they are prone to become irreducible, obstructed and strangulated.

Clinical features

Umbilical hernias are commonly seen in overweight men with a thinned and attenuated midline raphe or in postpartum women with a weakened abdominal wall. The bulge is typically slightly to one side of the umbilical depression, creating a crescent-shaped appearance to the umbilicus (Figure 64.18). Women are affected more than men. Most patients complain of pain due to tissue tension or symptoms of intermittent bowel obstruction. In large hernias, the overlying skin may become very thin; while overlying skin irritation and ulceration may be seen, spontaneous rupture is extremely rare.

Figure 64.18

A small adult umbilical hernia.

Treatment

As a result of the high risk of strangulation, surgery should be advised in cases where the hernia contains bowel. Small hernias may be left alone if they are asymptomatic, but they may enlarge and require surgery at a later date. Surgery may be performed open or laparoscopically.

Open umbilical hernia repair

Very small defects less than 1 cm in size may be closed with a simple suture repair as long as the fascia is not closed under tension. An alternative technique utilises a darn suture where a non-absorbable, monofilament suture is criss-crossed across the defect and anchored firmly to the fascia all around. For defects up to 2 cm in diameter a transverse incision is made and the hernia sac dissected, opened and its contents reduced. The peritoneum is closed. The defect in the linea alba is extended in a transverse direction and the fascial edges are closed in an overlapping style with the superior flap on top (‘waistcoat over trousers’) (Mayo). Non-absorbable sutures are used and the skin is closed in a routine manner, but redundant skin may need to be excised to achieve a better cosmetic result. The Mayo repair remains popular for defects up to 2 cm, but the larger the defect the more tissue tension. Current evidence advises the use of mesh even in small defects, and certainly for all defects larger than 2 cm, owing to the high likelihood of recurrence (Figure 64.19).

Figure 64.19

A massive umbilical hernia, intraoperative view.

Mesh may be placed in one of several anatomical planes:

• In the retromuscular space. The linea alba is opened vertically and both left and right posterior rectus sheaths are incised to expose the rectus muscle. The posterior sheaths are sutured together and the muscles elevated away from the sheath to develop the retromuscular space, into which a sheet of mesh is placed and fixed by sutures. The mesh should overlap the zone of repair by at least 5 cm in all directions. This is a very secure repair, ideal for larger hernias, but requires extensive dissection.
• In the extraperitoneal/preperitoneal space. After dealing with the hernia sac, the avascular plane immediately deep to the posterior rectus sheaths and linea alba, just outside the peritoneum, is developed with primarily blunt dissection. Care must be taken to avoid ‘buttonholing’ the peritoneum because it is thin and fragile. Mesh can then be tucked into this space, ensuring a good overlap as before. Ideally, the linea alba is closed over the mesh. This plane is difficult to establish beyond the lateral extent of the falciform ligament and median umbilical fold as the peritoneum becomes firmly attached to the posterior rectus sheath, so this technique, although very reliable in terms of recurrence rate, is best suited to small- to moderate-sized umbilical hernias.
• In the subcutaneous plane. This is the simplest technique, the so-called ‘onlay’ mesh. The peritoneal sac and contents are dealt with as above. The defect in the linea alba is closed; doing so in a transverse direction is thought to involve less strain on the tissues than a vertical closure. Skin flaps are elevated bilaterally to expose enough of the anterior rectus sheaths to fix a disc of mesh with sufficient overlap. The subcutaneous dissection risks seroma formation and damage to the perforating nerves and vessels while the mesh is prone to infection in the event of overlying wound breakdown.
• Within the peritoneal cavity. The sac is dealt with and a tissue-separating mesh is introduced onto the undersurface of the abdominal wall and fixed to one side of the incision with sufficient overlap. The amount of overlap required relates to the size of the initial defect. Transfascial sutures are then placed to allow fixation of the other side of the mesh to the abdominal wall after the hernia defect has been closed. This repair is awkward to perform, requires the use of expensive mesh and carries the risk of intraperitoneal adhesions/erosion into bowel as well as bowel herniation between the mesh and the abdominal wall if fixation is not precise. This repair is discouraged in the recent primary ventral hernia guidelines.

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Incisional Hernia

These arise through a defect in the musculofascial layers of the abdominal wall at the site of a postoperative scar. Thus, they may appear anywhere where a laparotomy has been made.

Incidence and aetiology

Incisional hernias have been reported in 10–50% of laparotomy incisions and 1–5% of laparoscopic port-site incisions. Factors predisposing to their development include patient factors (genetic collagen disorders, obesity, general poor healing due to malnutrition, immunosuppression or steroid therapy, chronic cough, cancer), wound factors (poor quality tissues, wound tension, wound infection) and surgical factors (inappropriate suture material, poor closure technique).

An incisional hernia usually starts as disruption of the musculofascial layers of a wound in the early postoperative period. This may progress rapidly to full thickness wound dehiscence, usually heralded by a serosanguineous discharge around the sixth postoperative day, but more commonly the event passes unnoticed if the overlying skin wound has healed securely. A visible swelling may take weeks, months or years to appear. Many incisional hernias may be preventable by ensuring healthy wound edges, minimal wound tension and good surgical technique as described by the European Hernia Society abdominal wall closure guidelines. The small-stitch, small-bite technique is recommended, and the role of prophylactic mesh in high-risk patients is also a current area of research.

Clinical features

Incisional hernias commonly appear as a localised swelling involving part of a surgical scar but may present as a diffuse bulging of the whole length of the incision (Figure 64.25). Alternatively there may be several discrete hernias along the length of the incision, but even with apparently singular hernias unsuspected defects are frequently found at operation (Figure 64.26). Incisional hernias tend to increase steadily in size with time, and the overlying skin may become thin and atrophic. Local trauma and microvascular damage to skin may lead to ulceration. Episodes of intestinal obstruction are common because there are usually coexisting internal adhesions, but strangulation is less frequent because most incisional hernias are shallow and wide-necked. As with any hernia type, strangulation is most likely when the fibrous defect is small and the sac is large.

Treatment

Asymptomatic incisional hernias may not require treatment. The wearing of an abdominal binder or belt often provides symptomatic relief and may prevent the hernia from increasing in size. Many patients with an incisional hernia have other comorbidities and discussion around the balance of benefits and risks of surgery is important. The decision to operate and choice of technique should always be agreed between the patient and the surgeon and patients’ preferences need to be respected. Repair of large and/or complex incisional hernias can be extremely challenging; in such cases advice from, or referral to, a colleague with a special interest in abdominal wall reconstruction should be considered.

Each patient undergoing an elective incisional hernia repair should be optimised for surgery. In many centres, patients undergo formal multidisciplinary team assessment and this is likely to become the standard of care in the coming years. So-called ‘prehabilitation’ includes weight loss if the patient is obese, smoking cessation, fitness improvement and core strength exercising. Loss of 7% of total bodyweight achieves a significant improvement in metabolic state, and 5 kg of body weight is said to create about one extra litre of space inside the adult male abdomen (0.5 litres in women).

Management of the very large incisional hernia

Very large incisional hernias require careful thought before treatment begins. If the volume of the sac is more than 25% of the volume of the abdominal cavity (and this can be calculated from CT images), then there are likely to be issues of loss of abdominal domain when the hernia is repaired. Loss of abdominal domain describes the situation where either the fascial edges cannot be brought back together without undue tension or the sac is so large that the contents of the hernia cannot be reduced back inside the abdomen. Even if they can, the resulting high intra-abdominal pressure can lead to visceral compression and pulmonary complications as a result of impaired diaphragmatic movement and the inevitable wound tension can lead to wound breakdown and failure of the repair. In such cases, preoperative strategies include injection of botulinum toxin A into the lateral muscle groups or progressive preoperative pneumoperitoneum, while intraoperative strategies include resection of omentum or bowel and/or the use of musculofascial flaps to effectively expand the abdominal wall. Even if loss of domain is not a concern, large defects can still be very difficult to close and the same special techniques may need to be used to avoid producing excessive tension in the repair. In addition, patients with poor quality or redundant skin may benefit from a wedge excision of skin and fat (lipectomy) to improve the abdominal contour postoperatively.

The need for these adjunctive techniques must be anticipated and planned for in advance, and for this reason such cases are generally best managed in a centre with specialist hernia interest.

Prevention of incisional hernia

The risk of incisional hernia may be reduced by improving the patient’s general condition preoperatively where possible, e.g. smoking cessation, weight loss for obesity or improving nutritional status in undernourished individuals. Closing the fascial layers with good technique and materials is important. For years it has been advised that sutures should be 1 cm back from the wound edge and 1 cm apart, but recent work has shown that lower incisional hernia rates and reduced infection rates are gained when smaller and closer bites are used: 5 mm apart and 5–8 mm back from the wound edge, with care taken to incorporate fascia only in the suture bites (no muscle) and to minimise excessive suture tension. A 2/0 slowly resorbable suture is also recommended rather than traditional heavier and/or non-absorbable materials (see Chapter 7).

There is no evidence that interrupted sutures are better or worse than continuous. However, if continuous suturing is used, the tissue bites must not be too near the fascial edge or pulled too tight because they may cut out. The optimal ratio of suture length to wound length is 4:1. If a ratio of less than this is achieved, the suture bites are likely to be too far apart and/ or too tight (and vice versa).

Drains should be brought out through separate incisions and not through the wound itself because this prevents fascial apposition and increases the risk of hernia formation.

Studies in obese patients undergoing bariatric surgery have suggested that placement of a prophylactic mesh in patients at high risk of incisional hernia formation will substantially reduce that risk. Use of prophylactic mesh may reduce the risk of parastomal herniation, which occurs in up to 50% of patients.

Principles of surgical repair

For repair of most incisional hernias, both open and laparoscopic options are available. A number of principles apply, irrespective of the technique used. First, the repair should cover the whole length of the previous incision. Second, approximation of the musculofascial layers should be done with minimal tension; third, prosthetic mesh should be used to reduce the risk of recurrence. Mesh may be contraindicated in a contaminated field, e.g. in the event of perforation of strangulated bowel, but mesh may still be used in a clean-contaminated field, such as after an elective bowel resection, if strict hygiene measures are observed and appropriate prophylactic antibiotics are given.

Open repair

The previous incision is opened along its full length to reveal any clinically unsuspected defects. The hernial sac, its neck and the margins of the defect are fully exposed. The sac can be opened, contents reduced, local adhesions divided and any redundant sac excised to allow safe fascial closure.

Simple suture techniques without the use of prosthetic mesh for reinforcement, even with the overlapping repair of Mayo or the layered closure of da Silva, are not recommended because of the unacceptable risk of recurrence. However, they may be the only option in the presence of gross contamination, where mesh is contraindicated. Mesh should ideally be used in a tension-free manner to augment primary fascial closure and not used to ‘bridge’ a gap between fascial edges as the unsupported mesh centrally will inevitably bulge outwards postoperatively, giving the appearance of recurrence. However, if the mesh-to-defect area ratio is sufficiently large, i.e. there is sufficient circumferential overlap of mesh in relation to the size of the defect, then a bridging repair is generally secure. Mesh can be placed in one of several planes, as for primary ventral hernia repair. The simplest approach is an onlay mesh but this carries the risk of mesh exposure and contamination in the event of wound infection or wound breakdown. Furthermore, placement of a large onlay mesh requires elevation of large skin flaps, which increases the risk of wound seroma and overlying skin ischaemia. Intraperitoneal mesh placement is difficult at open surgery and mesh in direct contact with the intra-abdominal organs is prone to complications such as adhesive bowel obstruction, erosion into adjacent organs and bowel fistulation. The retromuscular plane is preferred by many surgeons.

Retromuscular mesh repair

Once the old scar has been excised, the sac exposed fully and the fascial edges displayed all around the hernia defect, the sac is opened in the line of the wound. Multiple defects are joined into one so that the entire old incision has been reopened. For a midline incisional hernia, both posterior rectus sheaths are then incised, close to the midline and over the full length of the incision, to enter the avascular plane between the rectus abdominis muscle and the posterior sheath on each side. This plane is opened up widely. Below the arcuate line the space extends extraperitoneally into the retropubic space, and superiorly the dissection can continue beyond the xiphisternum and the costal margin if necessary. Once the dissection is complete, the two posterior rectus sheath edges are sutured together and a sheet of large-pore mesh is then laid across them, deep to the rectus muscle bellies, and may be fixed to the posterior sheath by interrupted sutures or glue. The mesh must be large enough to ensure a sufficient overlap of the underlying suture line. Careful haemostasis and meticulous asepsis are essential during this operation. The anterior rectus sheaths are then sutured together over the mesh so that the mesh is completely covered by muscle and fascia and is not in communication with the subcutaneous plane. Redundant skin may need to be excised to improve the cosmetic result.

When the defect is large and/or there is significant loss of abdominal domain, primary closure of the posterior rectus sheath may not be achievable without undue tension. In such cases, one of several types of component separation techniques can be utilised. The anterior components separation technique divides the external oblique aponeurosis just lateral to its insertion into the anterior rectus sheath, thus allowing the rectus muscle complex to move medially and enable midline closure with retromuscular mesh placement. The posterior components separation technique, also known as the TAR (transverse abdominis release), involves dividing the posterior rectus sheath and transversus abdominis muscle and continuing the dissection laterally in the extraperitoneal plane in order to mobilise the rectus muscle complex as above and allow placement of a large mesh to strengthen the lateral abdominal wall.

Both components separation techniques facilitate midline closure by incising the lateral musculofascial layers. A third technique, a modification of the standard retromuscular mesh repair called the peritoneal flap repair, utilises redundant sac as an extension of the rectus sheaths in the midline to allow closure prior to mesh placement. The lateral musculofascial layers are not disturbed.

Laparoscopic repair

Great advances have been made in applying laparoscopic tech- niques to incisional hernia repair. Laparoscopy and division of adhesions is initially performed, hernia contents are reduced and the fibrous margins of the hernia defect(s) are exposed. Often the falciform ligament and median umbilical fold need to be taken down. Some surgeons prefer to close the fascial defect(s) with sutures before reinforcing with mesh, while others simply ‘bridge’ the defect with no attempt at closure. Larger defects are more difficult to close, but bridging large defects is associated with bulging of the mesh postoperatively, often referred to as ‘pseudo-recurrence’ (Figure 64.27). Only small hernias can be safely fixed without closing the defect, as the large mesh to defect area ratio will help to minimise mesh bulging and recurrence.

The mesh is placed directly onto the peritoneum deep to the abdominal wall muscles, fixed in place with tissue glue, sutures or staple/tacks and is known as an IPOM repair. Special meshes with anti-adhesion coatings must be used, so-called ‘tissue separating’ meshes, and these are generally expensive.

Laparoscopic IPOM repair is losing some popularity because mesh within the abdominal cavity is prone to complications such as adhesive bowel obstruction, erosion and fistulation. It also makes future laparoscopy and laparotomy more difficult. To overcome this, more complex laparoscopic operations are being developed, placing mesh in the retromuscular or preperitoneal spaces. Furthermore, the application of laparoscopic posterior components separation techniques has allowed even large defects to be repaired this way, including closure of the defect and avoidance of mesh within the abdominal cavity. The utilisation of robot-assisted platforms has facilitated this and demonstrated benefit to patients in the case of large incisional hernias, especially in frail patients, as the operative morbidity and time to resumption of physical activity are significantly reduced.

In the presence of dense peritoneal adhesions, the laparoscopic surgeon needs to take great care because injury to the bowel is possible and may not be recognised. If occult bowel injury does occur it can lead to postoperative peritonitis.

Figure 64.27

Abdominal computed tomography scan showing mesh bulge (pseudo-recurrence) 2 years after a laparoscopic repair of incisional hernia. The two white dots are metal tacks still in place, fixing the mesh to the underside of the abdominal wall.