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Full thickness replacement of the abdominal wall with synthetic mesh (a report of 2 cases).
Synthetic meshes have been used to reinforce abdominal wall repairs since many years.[11],[13] The peritoneum, and, when possible, the fascia are repaired on either side of the mesh.[10] Recent experimental and clinical work challenge many of the dogmas about abdominal wall closure; it has been shown that a synthetic mesh alone can provide adequate replacement for the full-thickness of the abdominal wall, substituting adequately for all layers including peritoneum, muscle, fascia and skin, in an emergency situation.[1],[3],[6],[7],[14] We present our experience and observations in two cases where a synthetic mesh was used to replace the full-thickness of abdominal wall and emphasize the fallacy of several conventional beliefs.
Case 1 A 35 year old female patient presented with a desmoid tumour of the lower anterior abdominal wall. At surgery the tumour was found to be involving the rectus sheath, muscle, peritoneum, omentum, a loop of the ileum and the fundus of the urinary bladder. The skin was free. Wide excision of the tumour produced a defect of 14 cm x 5 cm involving the full-thickness of the abdominal wall except skin. As it was not possible to close the peritoneum or the musculo-aponeurotic defect (without excesssive tension) the defect was bridged by a single layer of polypropylene mesh placed directly between intestines and skin [Fig. 1] and overlapping the wound margins by 1.5 cm. A Redivac suction tubing was positioned between the mesh and the skin. Drainage was profuse for the first 48 hours, but gradually became negligible by the sixth day. The wound healed without complications. At three months follow up, the repair was firm and strong with no obstructive symptoms or incisional hernia. Case 2 A 50 year old male presented with a midline supraumbilical, 10cm x 4cm incisional hernia, following previous surgery for a duodenal ulcer. He also had a gastric ulcer, visualised on endoscopy, which had net responded to conservative treatment. Haematological investigations were within normal limits. The patient was explored through a midline, supraumbilical incision (excising the previous scar) with a view to perform definitive surgery for the gastric ulcer and to repair the hernia. The patient was found to have miliary tuberculosis (confirmed on biopsy) involving the entire peritoneal cavity including stomach and duodenum. There was minimal ascites. It was decided to close the abdomen, performing only a speedy, simple repair of the hernia. A tense anatomical closure was considered ill-advised. Hence the defect was bridged with a single layer of prolene mesh. Since the peritoneum was very flimsy, omentum alone was partially interposed between the mesh and the intestines. Skin was closed over a drainage tube. The post-operative period was stormy. The patient required cardiorespiratory support for persistent hypotension and chest infection. The skin stitches had to be removed because of wound infection, leaving the mesh and underlying intestines exposed to the exterior. The mesh was kept covered with moist antiseptic gauze dressings. Ascitic fluid leaked for 8-10 days. The patient ultimately recovered from the acute crisis. It was possible to observe the behaviour of the exposed mesh. Initially a bed of granulation tissue formed on the under surface. Slowly this penetrated the interstices of the mesh, progressively incorporating it. The wound became narrower as a result of wound contraction and epithelial growth from the margins. At this juncture, crimping of the mesh was observed, with small areas of the mesh forming ridges that rose above the general surface. These parts of the mesh remained free of granulation tissue. Hence we never obtained a uniformly granulating surface that would accept a skin graft. At three months the mesh was completely covered with epithelium. The mesh was incorporated into a fibrous sheet which was firm and strong with no tendency towards herniation.
Large defects of the abdominal wall may be encountered during the repair of giant incisional hernia[12] or following acute losses as a result of trauma,[8] surgical excision for tumours[9] (Case 1), infection,[3] gas gangrene[7] or electric burns.[1] Conventional methods of closure of such large defects are tedious and unsuitable in acute conditions-especially in the presence of infection, respiratory complications or multisystem failure. A polypropylene mesh provides an easy, safe, and quick way of repairing abdominal wall defects by substituting for the full-thickness of the abdominal wall. This is useful in emergency as well as planned surgery and is of special value in the presence of infection and multisystem failure[14] as observed in our second case. Some points need to be emphasized. Peritoneal closure is not essential in abdominal wall closure, with or without a mesh. Experimental and clinical work reveal: 1) that the peritoneum regenerates de novo and not from the cut edges of a defect,[4],[5] 2) absence of peritoneum does not make the wound weak,[2] 3) a mesh left in direct contact with the bowels is rapidly lined by peritoneum with minimal adhesions[6] and does not carry an increased risk of adhesive obstruction.[1],[14] These observations are found to be valid in both of our cases, none of whom developed adhesive intestinal obstruction in a follow up of 1 year. Infection is not a contraindication to the use of a mesh as seen in our second case; in fact transmesh drainage may be of special therapeutic value in cases with peritonitis.[14] At the end of complete healing the block of fibrous tissue incorporating the mesh, has enough strength to prevent development of any incisional hernia.[6] This is quite evident from our present cases, neither of whom developed an incisional hernia subsequently. A primary skin cover over the mesh is not essential. Subsequent cover may be achieved by permitting spontaneous epithelialisation and wound contraction (Case 2), by split thickness skin grafting or by mobilisation of skin flaps. Crimping of the mesh (Case 2) can be avoided by taking stitches perpendicular to the edge of the mesh, avoiding gathering' and by suturing the mesh flat with no bulging.[6] It is important to ensure that wound margins are viable and that non-absorbable synthetic stitches are used.[14]
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