General Considerations and Clinically Relevant Pathophysiology

Classically, the GDV syndrome is an acute condition with a mortality rate of 30% to 45% in treated animals. The gastric enlargement is thought to be associated with a functional or mechanical gastric outflow obstruction. The initiating cause of the outflow obstruction is unknown; however, once the stomach dilates, normal physiologic means of removing air (i.e., eructation, vomiting, and pyloric emptying) are hindered because the esophageal and pyloric portals are obstructed.. The stomach becomes enlarged as gas and/or fluid accumulate within the lumen. The gas probably comes from aerophagia, although bacterial fermentation of carbohydrates, diffusion from the bloodstream, and metabolic reactions may contribute. Normal gastric secretion and transudation of fluids into the gastric lumen as a result of venous congestion contribute to fluid accumulation. The cause of GDV is unknown, but exercise after ingestion of large meals of highly processed foods or water has been suggested to contribute. Epidemiologic studies have not supported a causal relationship between feeding soy-based or cereal-based dry dog food and GDV. Other contributing causes include an anatomic predisposition, ileus, trauma, primary gastric motility disorders, vomiting, and stress.

Diagnosis

Signalment

GDV primarily occurs in large, deep-chested breeds (i.e., Great Dane, Weimaraner, Saint Bernard, German Shepherd, Irish and Gordon Setters, Doberman Pinscher), but has been reported in cats and small breed dogs. Shar-peis may have an increased incidence compared with other medium-sized breeds. In a recent study, Basset Hounds had a high risk of GDV, despite their relatively small size. Large breed size, degree of purity of breed, and increase of weight are significant risk factors for development of this disease. GDV may occur in any age dog, but is most common in middle-aged to older animals. Chest depth/width ratio appears to be highly correlated with the risk of bloat.

History

A dog with GDV may present with a history of a progressively distending and tympanic abdomen, or the owner may simply find the animal recumbent and depressed, with a distended abdomen. The dog may appear to be in pain and may have an arched back. Nonproductive retching, hypersalivation, and restlessness are common.

Physical Examination Findings

Abdominal palpation often reveals various degrees of abdominal tympany or enlargement; however, it may be difficult to feel gastric distension in heavily muscled large-breed or very obese dogs. Splenomegaly is occasionally palpated. Clinical signs associated with shock, including weak peripheral pulses, tachycardia, prolonged capillary refill time, pale mucous membranes, or dyspnea, may be present.

Radiography

Radiographic evaluation is necessary to differentiate simple dilatation from dilatation plus volvulus. Affected animals should be decompressed before radiographs are taken. Right lateral and dorsoventral radiographic views are preferred. In normal dogs, the pylorus is located ventral to the fundus on the lateral view, and on the right side of the abdomen on the dorsoventral view. On a right lateral view of a dog with GDV, the pylorus lies cranial to the body of the stomach and is separated from the rest of the stomach by soft tissue (reverse C sign). On the dorsoventral view, the pylorus appears as a gas-filled structure to the left of midline. Free abdominal air suggests gastric rupture and warrants immediate surgery.

Medical Management

Patient stabilization is the initial objective. A large-bore intravenous catheter(s) should be placed in either a jugular or both cephalic veins. Either isotonic fluids (90 ml/kg/hr), hypertonic 7% saline (4-5 ml/kg over 5 to 15 min), or hetastarch (5-10 ml/kg over 10 to 15 min) is administered. If hypertonic saline or hetastarch is given, adjustment of the rate of subsequent crystalloid administration is necessary. Blood should be drawn for blood gas analyses, a CBC, and a biochemical panel. Broad-spectrum antibiotics (e.g., cefazolin, ampicillin plus enrofloxacin) should be administered. If the animal is dyspneic, oxygen therapy may be given by nasal insufflation or mask.

Gastric decompression should be performed while shock therapy is initiated. The stomach may be decompressed percutaneously with several large-bore intravenous catheters or a small trocar, or (preferably) a stomach tube may be passed. The stomach tube should be measured from the point of the nose to the xiphoid process and a piece of tape applied to the tube to mark the correct length. A roll of tape can be placed between the incisors and the tube passed through the center hole. Attempts should be made to pass the tube to the measured point. Placing the animal in different positions (i.e., sitting, reclining on a tilt-table) may help if it is difficult to advance the tube into the stomach. Do not perforate the esophagus with overly rigorous attempts to pass the tube. If these attempts fail, percutaneous decompression of the stomach should be attempted. This may relieve pressure on the cardia and allow the tube to enter the stomach. Once the air has been removed, the stomach should be flushed with warm water. If blood is seen in the fluid from the stomach, prompt surgical intervention is warranted because this may indicate gastric necrosis. If the stomach tube can still not be passed, and immediate surgical correction is not possible, temporary decompression may be achieved by performing a temporary gastrostomy. Placement of a Foley catheter into the stomach percutaneously should not be done unless the stomach is simultaneously tacked to the body wall because of the high risk of peritonitis if the stomach pulls away from the tube. Disadvantages of a temporary gastrostomy are that the stomach must be closed when the permanent gastropexy is performed, and there is a high risk of peritoneal contamination. However, a temporary gastrostomy will maintain gastric decompression if the animal is being referred, or surgery is delayed. If immediate surgery is not possible in an animal in which a stomach tube was passed but that dilates rapidly after decompression, the stomach tube can be exteriorized through a pharyngostomy approach. This will prevent the animal from chewing on the tube, until definitive surgery can be performed. After the patient has been decompressed and is stable, radiographs may be taken.

Anesthesia

Numerous anesthetic protocols have been described for dogs with GDV. If the animal has been decompressed and stabilized and cardiac arrhythmias are not present, the animal may be given oxymorphone and diazepam intravenously and induced with etomidate, thiobarbiturates, or propofol. If the animal is depressed, oxymorphone and diazepam alone may be used for induction, or if necessary for intubation, etomidate may be given. Etomidate is a good choice for induction if the animal has not been well stabilized because it maintains cardiac output and is not arrhythmogenic. Alternatively, a combination of lidocaine and thiobarbiturate may be used if arrhythmias are present. For the latter, 9 mg/kg of each is drawn up and half is given initially, intravenously. Additional drug is given to effect to allow the dog to be intubated. Generally, no more than 6 mg/kg of lidocaine is given intravenously to prevent toxicity. If bradycardia occurs, anticholinergics (e.g., atropine or glycopyrrolate) may be given. Nitrous oxide should not be used in dogs with GDV. Isoflurane is the inhalation agent of choice because it is less arrhythmogenic than halothane.

Surgical Technique

Decompress the stomach before repositioning, by using a large-bore needle (i.e., 14 or 16 gauge) attached to suction. If the needle becomes occluded with ingesta, have an assistant pass an orogastric stomach tube and perform gastric lavage. Intraoperative manipulation of the cardia will usually allow the tube to be passed into the stomach without difficulty. If adequate decompression is still not achieved, or an assistant is not available, a small gastrotomy incision can be performed to remove the gastric contents, although this should be avoided if possible. For a clockwise rotation, once the stomach has been decompressed, rotate it counterclockwise by grasping the pylorus (usually found below the esophagus) with the right hand and the greater curvature with the left. Push the greater curvature, or fundus, of the stomach towards the table while simultaneously elevating the pylorus (towards the incision). Check to make sure that the spleen is normally positioned in the left abdominal quadrant. If there is splenic necrosis or significant infarction, perform a partial or complete splenectomy. Remove or invaginate necrotic gastric tissues. Avoid entering the gastric lumen, if possible. If you are uncertain whether gastric tissue will remain viable, invaginate the abnormal tissue. Verify that the gastrosplenic ligament is not torsed, and before closure, palpate the intraabdominal esophagus to ensure that the stomach is derotated. To prevent recurrence of GDV, the stomach must be permanently adhered to the body wall. Gastropexy should always be performed in conjunction with abdominal exploration and derotation of the stomach.

Permanent Gastropexy

Gastropexy techniques are designed to permanently adhere the stomach to the body wall. The most common indications are GDV (pyloric antrum to right body wall) and hiatal herniation (fundus to left body wall). Numerous gastropexy techniques have been described. Although the strength and extent of adhesions created by these various techniques differ, all of them (when properly performed) prevent movement of the stomach. To create a permanent adhesion, the gastric muscle must be in contact with the muscle of the body wall; intact gastric serosa will not form permanent adhesions to an intact peritoneal surface.

A technique for gastropexy has recently been described in which the stomach is incorporated into the abdominal incision during closure. Although this technique is easy, quick, and decreases recurrence of GDV, it results in the stomach being permanently adhered to the ventral body wall. The main advantage of this procedure is that it can be performed quickly. However, the subsequent abdominal exploration via a midline abdominal incision could perforate the stomach. Therefore, although this technique is preferable to not performing any type of "pexy," it is not generally recommended.

Muscular Flap (Incisional) Gastropexy

Muscular flap (incisional) gastropexy (Figure 1) is easier than circumcostal gastropexy and avoids potential complications associated with tube gastropexy. Make two hinged flaps in the seromuscular layer of the gastric antrum (similar to that for a circumcostal gastropexy). Then make similar flaps in the right ventrolateral abdominal wall by incising the peritoneum and internal fascia of the rectus abdominis or transverse abdominis muscles. Elevate flaps by dissecting ventral to the muscle layer. Invert the flaps, and suture the edge of the abdominal flaps to the gastric flaps, using a simple continuous suture pattern of 2-0 absorbable or nonabsorbable suture. Ensure that the muscularis layer of the stomach is in contact with the abdominal wall muscle). Suture the cranial margin first, followed by the caudal margin. Be sure to place sufficient sutures so that a loop of bowel cannot become incarcerated between the flaps.

Figure 1. From: Fossum, TW: Small Animal Surgery, Mosby Publishing Co., St. Louis, Mo, 2007.

Prognosis

With timely surgery, the prognosis is fair; however, mortality rates as high as 45% and greater have been reported. A recent study reported a mortality rate of 15% among dogs with GDV; the mortality rate was 0.9% if gastric dilation without volvulus was present (or if GDV could not be verified at surgery). The prognosis is poor if gastric necrosis or perforation occurs or if surgery is delayed. Recurrence rates for GDV differ, depending on techniques used, but most have reported rates of less than 10%. Tube gastropexy has the highest reported recurrence rate, varying from 5% to 29%. Some dogs with GDV respond to tube decompression and medical stabilization alone. Occasionally, the stomach becomes normally positioned after the air is removed; or, it was only partially rotated (less than 180 degrees) or merely dilated. However, these dogs still have a high likelihood of recurrence. Therefore gastropexy should be recommended, even when conservative management successfully alleviates the gastric malpositioning. The reported recurrence rates of dogs operated on for GDV in which the stomach has been repositioned but gastropexy not performed approaches 80%.