Small Animal Surgical Emergencies. Группа авторов

assessment of tissue viability is the most practical and useful method. The gross appearance of the stomach wall is a useful indicator. If the wall is discolored (gray, green, purple or black), has areas of seromuscular tearing or is much thinner on palpation, ischemia is present and subsequent necrosis is likely (Figure 8.8). Gastric vessels should be gently palpated for evidence of pulses or thrombi. If a more objective assessment is required, a partial thickness (seromuscular) incision can be made to assess perfusion. Active bleeding implies that the tissue is viable whereas a lack of bleeding suggests that resection is necessary. More objective methods for assessment of gastric wall viability include fluorescein dye, scintigraphy and laser Doppler flowmetry [47–49]. These techniques, however, are not widely available and may be impractical in the clinical setting.

      Gastric Necrosis

      Gastric necrosis has been reported in 9.3–40.6% of dogs with GDV [9, 10,12–14, 22, 28,50–52]. In dogs with an area of suspected devitalized or necrotic gastric wall, surgical treatment of this, ideally with a partial gastrectomy, is mandatory. Several studies have shown that dogs with gastric necrosis or those that require gastric resection have a significantly increased mortality, with up to 62.5% of dogs not surviving (including those euthanized due to the severity of necrosis) [10, 13, 23, 29, 51, 53]. Failure to perform a partial gastrectomy in dogs with gastric necrosis will result in gastric perforation, peritonitis and SIRS and has been associated with a mortality rate of 100% [11]. Although resection and reconstruction of devitalization and necrosis of the gastric cardia and distal esophagus is possible, it is technically demanding and the prognosis for these animals is grave [9, 13]. Although rare, gastric necrosis can lead to perforation and contamination of the peritoneal cavity prior to surgical exploration. In these dogs, gastric resection and gastropexy as well as treatment for peritonitis (see Chapter 11) are required.

      Gastric Resection

Areas of gastric ischemia or necrosis are treated with a partial gastrectomy and primary closure. This can be performed with an open resection by hand or with the use of surgical stapling devices. Prior to resection, the stomach is packed off from the rest of the abdomen with moist laparotomy sponges in case of spillage of gastric contents. Stay sutures using 2‐0 or 3‐0 polypropylene are placed in healthy stomach wall to allow manipulation during resection and closure. Gastric resection has been significantly associated with the development of hypotension, peritonitis, DIC, sepsis and arrhythmias [9].

Figure 8.8 Intraoperative images of gastric necrosis at exploratory laparotomy in two dogs with gastric dilatation and volvulus. (a) Gastric necrosis of the greater curvature, note the purple and black stomach wall. (b) Severe gastric necrosis of the greater curvature; note the extensive white/gray and black areas of the stomach wall.

      Open Resection

      Intact blood vessels supplying the area to be resected are ligated and the affected portion of the stomach is sharply excised using a scalpel blade. The resection is continued until the cut edges are actively bleeding. This will ensure removal of all non‐viable tissue and allow normal healing. The stomach is then closed in two layers using an appropriately sized synthetic absorbable suture material (e.g. 2‐0 or 3‐0 polydioxanone). The mucosa and submucosa are closed with a simple continuous pattern and then the seromuscular layers are closed with a continuous or interrupted pattern, which may be appositional or inverting. The closure can be reinforced by over‐sewing a third layer with a continuous inverting pattern such as Cushing's or Lembert.

      Stapled Resection

      Partial gastrectomy can also be performed using surgical stapling devices. This technique is quicker and technically less demanding [53]. The additional expense of the stapler may be offset by the reduced operating time. Another advantage is that the resection can be performed without entering the gastric lumen and hence there is no risk of leakage and contamination as with an open resection. A linear stapler or linear cutter stapler can be used for this purpose. The size of stapler will vary on the amount of tissue to be resected and the size of the staple will depend on the thickness of the tissue. The staple line should be reinforced by oversewing with a continuous inverting suture pattern (Cushing's or Lembert).

      Gastric Invagination

      An alternative approach to gastric resection is to invaginate the affected portion of the stomach [54]. Simply, the affected area is folded inwards and healthy tissue is sutured together over it. The tissue should be sutured with two layers of a simple continuous or inverting suture pattern using synthetic absorbable material (e.g., polydioxanone). With time, the affected portion of the stomach undergoes further necrosis, is sloughed into the gastric lumen and is digested. The potential advantage of this technique is that it is technically easier and quicker than a partial gastrectomy and the technique does not enter the gastric lumen. In an experimental study of eight dogs with devitalization of a portion of gastric wall treated with invagination, 50% suffered gastric hemorrhage and melena [54]. These complications were also reported in a clinical patient with GDV and gastric necrosis that was treated with invagination [55]. This dog suffered significant hemorrhage 21 days following the procedure. For this reason, the authors would recommend partial gastrectomy over invagination in all instances. However, invagination may be a useful technique for inexperienced surgeons or when there are significant time limitations due to instability of the dog under anesthesia.

      Splenectomy

The spleen is closely associated with the greater curvature of the stomach and, as a result, splenic torsion is common in dogs with GDV. Once repositioned, the spleen should be assessed for compromise of its vascular supply, specifically avulsion or obvious thrombi. If thrombi are present, the vessels should be ligated, and the spleen removed to prevent the release of thrombi into the circulation. Otherwise, the spleen should be allowed 5–10 minutes to reperfuse following untwisting prior to further assessment. Black areas of the spleen indicate infarction and a partial or complete splenectomy should be performed. In practice, a total splenectomy is preferred as it is technically easier to perform. If the spleen has undergone a complete torsion (i.e., twisted around its pedicle) or is obviously non‐viable, it is preferable to perform a splenectomy prior to untwisting to prevent the release of thrombi and myocardial depressant factors. This may not be possible until the stomach has been repositioned. Studies suggest that splenectomy is required in 10.2–22.6% of dogs treated for GDV [7, 9, 12, 13, 23, 52]. Splenectomy has been identified as a risk factor for mortality, particularly when associated with gastric resection [7, 9, 12, 52].

      Gastropexy

      An appropriate gastropexy is a vital part of treatment for GDV, forming a permanent adhesion between the stomach and the body wall to prevent recurrence. Since the pylorus is the most mobile part of the stomach, the gastropexy should be between the pylorus and the right body wall.

      In a prospective study, the median survival time was significantly greater for dogs treated with surgical decompression and gastropexy compared to those treated with surgical decompression without gastropexy, with a recurrence rate of 4.3% compared with 54.5% [51]. In the same study, the mortality rate for dogs that did not have a gastropexy performed and suffered recurrence was 83.3%. In another study, dogs treated with surgical decompression without gastropexy had a 50% recurrence rate at six months, which was significantly greater than the 0% recurrence rate for dogs treated with surgical decompression and circumcostal gastropexy [56]. The mortality rate within the first year was also significantly greater for the dogs that did not receive a gastropexy.

      Gastropexy