The abdominal wall

Burst abdomen (syn. abdominal dehiscence) and incisional hernia (syn. ventral hernia)

In 1—2 per cent of cases, mostly between the 6th and 8th day after operation, an abdominal wound bursts open and viscera are extruded. The disruption of the wound tends to occur a few days beforehand when the sutures apposing the deep layers (peritoneum, posterior rectus sheath) tear through or even become untied. An incisional hernia usually starts as a symptomless partial disruption of the deeper layers during the immediate or early postoperative period, the event passing unnoticed if the skin wound remains intact after the skin sutures have been removed.

Factors relating to the incidence of burst abdomen and incisional hernia.

Technique of wound closure.

  Choice of suture material catgut leads to a higher incidence of bursts than the use of nonabsorbable monofilament polypropylene, polyamide or wire, and should never be used;

  method of closure interrupted suturing has a low incidence. Through and through suturing is good for the obstructed case. A one-layer closure has a low incidence, but it is higher than that following a two-layered closure. Interrupted ‘far and near’ sutures are a recommended technique for single-layer mass closures. When continuous suturing of layers (one or two) is performed a particular fault is the use of a short length of material, pulled tightly, for in an anaesthetised relaxed patient the incision is shortened thereby, and made taut so that the material will act as if it were a cheese wire cutter when the patient is conscious and coughing. The golden rule is to insert a length of suture at least four times the length of the incision but less than five times the length of the incision. This ensures that the layers are gently apposed;

  drainage directly through a wound leads to a higher incidence of ‘bursts’ than employing drainage through a separate (stab) incision.

Factors relating to incisions. Midline and vertical incisions have a tendency to burst which is higher than those which are transverse. Since the widespread use of nonabsorbable suture materials even midline vertical incisions have a very low incidence of disruption.

Reasons for operation. Infected case; deep wound infection has a notorious reputation for causing burst abdomen and/or late incisional hernias. Operations on the pancreas, with leakage of enzymes, and on obstructed cases are other reasons for disruption.

Coughing; vomiting; distension. At the completion of an operation any violent coughing set off by the removal of an endotracheal tube and suction of the laryngopharynx strains the sutures; likewise cough, vomiting and distension (e.g. due to ileus) in the early postoperative period. Over-vigorous postoperative ventilation in sedated patients can lead to wound disruption.

General condition of the patient. Obesity, jaundice, malignant disease, hypoproteinaemia and anaemia are all factors conducive to disruption of a laparotomy wound (Chapter 1); abdominal wounds in pregnancy are notorious for a high risk of disruption; steroids delay wound healing.

Burst abdomen (syn. abdominal dehiscence)

Clinical features

A serosanguinous (pink) discharge from the wound is a forerunner of disruption in fully 50 per cent of cases. It is the most pathognomonic sign of impending wound disruption and it signifies that intraperitoneal contents are lying extraperitoneally. Patients often volunteer the information that they ‘felt something give way’. If skin sutures have been removed, omentum or coils of intestine may be forced through the wound and will be found lying on the skin. Pain and shock are often absent. It is important to note that there may be symptoms and signs of intestinal obstruction.

Treatment

An emergency operation is required to replace the bowel, relieve any obstruction and to resuture the wound. While awaiting operation, reassure the patient and cover the wound with a sterile towel. The stomach should be emptied using a nasogastric tube and intravenous fluid therapy commenced.

operation. Each protruding coil of intestine is washed gently with saline solution and returned to the abdominal cavity. Then protruding greater omentum is treated similarly and spread over the intestine. The abdominal wall having been cleaned, all layers are approximated by through and through sutures of monofilament nylon, each passed through a soft rubber or plastic tuber collar. The abdominal wall may be supported by strips of adhesive plaster encircling the anterior two-thirds of the circumference of the trunk. Antibiotic therapy should be started.

Contrary to what might be thought, peritonitis rarely supervenes and, although the skin wound may become infected, healing is satisfactory. A second dehiscence rarely occurs. There is biochemical evidence that healing after disruption produces a stronger wound. This is due to the improvement in collagen metabolism under these circumstances. An incisional hernia is often a later sequel (see below).

Incisional hernia (syn. ventral hernia; postoperative hernia)

Aetiology

Incisional hernia occurs most often in obese individuals, and a persistent postoperative cough and postoperative abdomi­nal distension are its precursors. There is a high incidence of incisional hernia following operations for peritonitis because, as a rule, the wound becomes infected. The placing of a drainage tube through a separate stab incision, as opposed to bringing such a tube through the laparotomy wound, reduces the frequency (see also the section ‘General features common to all hernias’).

An incisional hernia usually starts as a symptomless partial disruption of the deeper layers of a laparotomy wound dur­ing the immediate or very early postoperative period. Often the event passes unnoticed if the skin wound remains intact after the stitches have been removed (or because subcuticular stitches have been used which remain in place). A serosanguinous discharge is often the signal of dehiscence, and resuture of the deeper layers of the incision obviates the more difficult repair of an established and much larger hernia later on.

Clinical features

There are great variations in the degree of herniation. The hernia may occur through a small portion of the scar, often the lower end. More frequently, there is a diffuse bulging of the whole length of the incision. A postoperative hernia, especially one through a lower abdominal scar, usually increases steadily in size and more and more of its contents become irreducible. Sometimes the skin overlying it is so thin and atrophic that normal peristalsis can be seen in the underlying intestine. Attacks of partial intestinal obstruction are common and strangulation is liable to occur at the neck of a small sac or in a loculus of a large one. Nevertheless, most cases of incisional hernia are asymptomatic and broad-necked, and do not need treatment.

Treatment

Palliative. An abdominal belt is sometimes satisfactory, espe­cially in cases of a hernia through an upper abdominal incision.

Operation. Many procedures have been advocated, which is testimony to the fact that the repairs may be difficult to accomplish, but it is now clear that one technique is superior to all of the others.

Preoperative measures

In order to obtain a lasting repair, very special preparation is required. If the patient is obese, weight reduction by dieting should precede the operation. To attempt to return the contents of a very large hernia to the main abdominal cavity if they have not been there for several years is to court danger, particularly if weight reduction has not been effected. In these circumstances, not only is there a risk of failure of the hernioplasty, but there is a greatly increased risk of paralytic ileus from visceral compression and of pulmonary complications from elevation of the diaphragm. The repair of these large hernias is highly specialised surgery and should only be performed in centres with considerable experience in dealing with them. For example, one technique employed to enlarge the abdominal cavity is that of prolonged pneumo­peritoneum in which the intra-abdominal pressure is raised to 15—18 cmH2O for up to several weeks preoperatively. The technique requires careful monitoring and patient counselling to be effective but, if employed correctly, can enable a primary repair to be successful.

Operation. Three techniques have been described: simple and complex apposition and plastic fibre mesh or net closures.

Simple apposition. The hernial sac is dissected. It is then formally, if not already inadvertently, opened and the contents are reduced. Adherent omentum and bowel have to be freed by dissection before the mouth of the sac can be defined. The layers are repaired usually with nonabsorbable sutures: first the peritoneum, then the fascial (aponeurotic) layers. The lateral edges of the fascia are freed from the overlying muscles for some distance and this fascial layer is approximated with interrupted sutures at the upper and lower ends of the wound. The muscles and the remaining fascial layer are approximated. Tension-relaxing incisions may be required and should be placed well laterally.

Complex apposition. These consist of various types of layered closures (Mayo, ‘Keel’, da Silva) and should be considered obsolete and of historical interest only.

Plastic fibre mesh or net closures. These techniques are now the method of choice for all but the smallest defects (< 4 cm). The sac is dealt with as above. The layers of the fascia are dissected out and, if above the umbilicus, the posterior rectus sheath edges apposed. A sheet of polypropylene mesh is then inserted between the posterior rectus sheath and the muscle fibres, and anchored in place. If below the umbilicus, the mesh is placed in the preperitoneal space. The anterior rectus sheath is then apposed as above. If the defect is too large to close by apposition of the rectus sheath, the deficiency in the abdominal wall can be bridged by sewing the mesh to the fascia on either side of the defect, ensuring at least a 4-cm overlap of the fascial edges.

Careful haemostasis and meticulous asepsis are essential during these operations. Postoperative collections of serum can be removed by drainage, using plastic tubing led, via skin punctures lateral to the wound, into closed suction drainage bottles (e.g. Redivac).

Postoperative treatment. Gastric decompression and intravenous fluids are employed, and nothing by mouth allowed until the bowels have functioned. Early ambulation and gentle physical exercise are to be encouraged. The patient should not resume strenuous exercise for several weeks.

Results of treatment. Most series report recurrence of the hernia in between 30 and 50 per cent of cases except where mesh inlay techniques have been employed in specialist centres, where recurrence rates may be as low as 10 per cent.

Divarication of the recti abdominis

Divarication of the recti abdominis is seen principally in elderly multiparous patients. When the patient strains, a gap can be seen between the recti abdominis through which the abdominal contents bulge. When the abdomen is relaxed, the fingers can be introduced between the recti.

Treatment. An abdominal belt is all that is required. There is no risk of strangulated intestinal contents. A similar condition is seen in babies, only the divarication exists above the umbilicus. No treatment is necessary; as the child grows a spontaneous cure results.

Tearing of the inferior epigastric artery

Tearing of the inferior epigastric artery occurs in three dissimilar types of individual, namely elderly women, often thin and feeble; athletic, muscular men, usually below middle age; and pregnant women, mainly multiparas late in pregnancy. The site of the haematoma is usually at the level of the arcuate line, where the posterior sheath of the rectus abdominis is lacking.

Clinical features. The possibility of tearing of the epigastric vessels should always be considered when, following a bout of coughing or a sudden blow to the abdominal wall, an exquisitely tender lump appears in relation to the rectus abdominis. Occasionally, a haematoma occurs within the muscles lateral to the rectus sheath. Unless there is bruising of the overlying skin, the diagnosis may be difficult.

Differential diagnosis. The conditions for which the haematoma is frequently mistaken are, in the female, a twisted ovarian cyst, and in both sexes, when the lump is on the right side, an appendix abscess. The sign most likely to be of value in differentiating a haematoma of the abdominal wall from these conditions, namely tensing the abdominal musculature, is often unsatisfactory because of the pain it causes. Again, the differential diagnosis between the haematoma and a strangulated Spigelian hernia may be difficult. The absence of vomiting suggests a haematoma and the presence of resonance over the swelling favours a Spigelian hernia, while a plain radiograph of the abdomen sometimes gives positive evidence of the latter.

As a complication of pregnancy. Rupture of the inferior epigastric artery occurs occasionally during pregnancy. Surprisingly to relate, the haemorrhage into this closed space from this comparatively small artery has proved fatal.

Treatment. With rest, a comparatively small haematoma may resolve, but sometimes renewed haemorrhage causes the haematoma to rupture into the peritoneal cavity. Therefore it is safer to operate early, evacuate the clot and ligate the artery.

Infections

Cellulitis can occur in any of the planes of the abdominal wall.

Superficial cellulitis is usually discovered when an abdomi­nal wound is inspected following pyrexia. The earliest sign is when the stitches become embedded in the oedematous skin.

Later there is a blush extending for a variable distance from the incision or the stitch holes. On palpation with the gloved hand usually one area is found to be more indurated and tender than the remainder. A stitch should be removed from the immediate vicinity, and if pus or seropus escapes it should be sent for bacteriological examination; treatment should then be commenced with a broad-spectrum antibiotic.

Deep cellulitis is characterised by brawny oedema towards one or both flanks, and not infrequently of the scrotum or vulva as well. Antibiotic therapy is the mainstay of treatment. When tenderness persists, an anatomical incision dividing the muscles carefully, layer by layer, until pus or purulent fluid is encountered is often advisable.

Progressive postoperative bacterial synergistic gangrene. This is, fortunately, a rare complication after laparotomy, usually for a perforated viscus (notably perforated appendicitis). It has also occurred after gallbladder operations, colectomy for ulcerative colitis and even after drainage of an empyema thoracis. The condition is due to the synergistic action of microaerophilic nonhaemolytic streptococci and, usually, a staphylococcus. The skin in the immediate vicinity of the wound exhibits signs of cellulitis. Within a few hours, a central purplish zone with an outer brilliant red zone can be distinguished and the whole region is extremely tender. The condition advances with various degrees of rapidity (Fig. 62.23). The gangrenous skin liquefies exposing underlying granulation tissue. If the condition persists, overwhelming septicaemia and associated multiorgan failure supervene.

Treatment. Identification of the organisms and a report on their sensitivity to antibiotics is essential. Metronidazole should be given together with a powerful broad-spectrum antibiotic. Without vigorous and effective treatment the gangrene spreads to the flanks and the patient may die of toxaemia. If the infection has become established, surgical debridement of all the necrotic and infected tissue should be performed. Hyperbaric oxygen, if available, can be life-saving. Cellulitis due to bacteroides may give no bacterial growth by conventional techniques and may be missed.

Amoebic cutis. The possibility of this potentially lethal complication of amoebic colitis, liver abscess or empyema being present should always be considered (see Chapter 52). Confirmation may be difficult and an immunofluorescence test necessary.

Subcutaneous gas-forming infection. This is described in Chapter 7 (under ‘Gas gangrene’).

Neoplasms of the abdominal wall

A desmoid tumour is a tumour arising in the musculoaponeurotic structures of the abdominal wall, especially below the level of the umbilicus. It is a completely unencapsulated fibroma and is so hard that it creaks when it is cut. Some cases recur repeatedly in spite of apparently adequate excision.

Aetiology. Eighty per cent of cases occur in women, many of whom have borne children, and the neoplasm occurs occasionally in scars of old hernial or other abdominal operation wounds. Consequently, trauma, for example the stretching of the muscle fibres during pregnancy or possibly a small haematoma of the abdominal wall, appears to be an aetiological factor. They can occur in cases of familial polyposis coli (Gardner’s syndrome).

Pathology. The tumour is composed of fibrous tissue containing multinucleaterd plasmodial masses resembling foreign-body giant cells. Usually of very slow growth, it tends to infiltrate muscle in the immediate neighbourhood. Eventually it undergoes a myxomatous change; it then increases in size more rapidly. Metastasis does not occur. Unlike fibroma elsewhere, no sarcomatous change occurs.

Treatment. Unless the tumour is excised widely, with a surrounding margin of at least 2.5 cm of healthy tissue, recurrence commonly takes place. After removal of a large tumour, repair of the defect in the abdominal wall by nylon mesh is required. These tumours are moderately radiosensitive. (Intraperitoneal desmoids ate best left alone when possible.)

Fibrosarcoma of the abdominal wall is rare. It is resistant to radiotherapy and only in some cases can a wide excision, with nylon mesh repair, offer hope of a cure.

Adenocarcinoma of the colon or of other viscera may invade the abdominal wall. In such cases, the resection of this extension, along with the primary growth, may require special repair of the resulting defect.

Secondary implantation in the wound may follow any abdominal operation for carcinoma, and bladder cancer is notorious for this propensity.