CPD ACCREDITED ARTICLE
• Gastric factors : An increased gastrin concentration , decreased stomach motility , and delayed gastric emptying have been mentioned as risk factors but have never been demonstrated . 5-8
• Dietary habits : Diet , large amounts fed at each feeding , the frequency of feedings ( one meal a day ), a fast eating style , and exercise or stress after a meal are contributing factors for the development of GDV . 5-8
• Signalment and physical attributes : Large-breed dogs , dogs with a large thoracic depth-to-width ratio , underweight dogs , and older animals are at higher risk to develop GDV . Dogs with a happy personality might be at less risk . 6-9
• Splenectomy : The removal of a large spleen has been associated with the development of GDV in some case reports ; however , studies have not proven splenectomy to be a risk factor for the development of GDV in dogs .
GDV Progression The stomach moves in a clockwise rotation . Displacement of the pylorus occurs from the right side toward the ventral midline . It passes over the fundus and body to the left abdominal wall close to the lower esophageal sphincter . At the same time , the fundus goes in a ventral direction toward the right abdominal wall . The pyloric antrum ends up in a dorsal position on the left side . Because of the attachment of the omentum to the greater curvature of the stomach , the omentum covers the stomach after volvulus .
The displacement of the spleen may be related to the degree of volvulus . The spleen is usually engorged or can undergo torsion on its own pedicle . Thrombosis of the splenic artery can also occur . Usually , 180 degrees of stomach rotation is seen , but 360-degree rotation is possible . Counterclockwise rotation is not really possible , or it is limited to 90 degrees since the pylorus cannot move dorsally in the abdominal cavity .
Gastric dilatation causes compression of the caudal vena cava and portal vein . 10-13 Sequestration of blood in the spleen , kidneys , and gastrointestinal tract occurs . Compression of the caudal vena cava and portal vein induces a decreased venous return , resulting in hypovolaemic shock . Hypotension and venous stasis result in cellular hypoxia and anaerobic metabolism . Elevated portal pressure compromises microcirculation in the viscera and reduces oxygen delivery to the gastrointestinal tract . The pancreas in the presence of ischaemia produces myocardial depressant factor ( MDF ). 12
Ischaemia , acidosis , liberation of the MDF by the pancreas , and the production of free oxygen radicals induce myocardial ischaemia and reduce cardiac contractility . 12-14 Subendocardial ischaemia and necrosis combined with tachycardia and acid-base imbalance induce arrhythmias . Vascular stasis , hypoxia , and acidosis can induce disseminated intravascular coagulopathy ( DIC ).
Mechanical limitation of diaphragmatic movement by a dilated stomach and decreased pulmonary compliance results in respiratory dysfunction . Tissue hypoxia results from decreased cardiac output and respiratory impairment . Increased gastric intraluminal pressure , portal hypertension , and venous stasis with thrombosis cause gastric mucosa stasis , hypoxia , and oedema . Gastric wall necrosis can then develop in the fundus along the greater curvature . Because of distention of the stomach , vascular wall disruption causes mucosal hemorrhage . Avulsion of branches from the short gastric arteries during rotation of the stomach contributes to blood loss , hypovolemia , and restriction of blood flow to the stomach .
Clinical Signs Dogs with GDV are usually presented for evaluation of unproductive vomiting , retching , hypersalivation , and a distended abdomen . They have progressively distending and tympanic cranial abdomens , and they may be restless . As the severity of the distention increases , the dog can become weak , laterally recumbent , and tachypneic .
Dogs with GDV often present with weak peripheral pulses , pale mucous membranes , prolonged capillary refill times , tachycardia , and tachypnoea . Abdominal pain is rarely present on palpation .
Dogs with mesenteric volvulus also present with severe abdominal distention . Usually , these dogs are in a lot of pain and deteriorate rapidly in severe septic shock .
Persistence of the clinical signs of GDV for more than five hours has been associated with a poor prognosis . 15 The severity of the clinical signs on presentation has been found to be an indicator of patient survival . 16 In general , dogs that are bright and alert when presented have better prognoses than do dogs that are laterally recumbent . It has been shown that recumbent patients have 4.4 times greater probability of dying than do dogs that are ambulatory . If a patient is comatose , it has 36 times greater probability of dying . Dogs that appear depressed on presentation have a three times greater probability of dying . 16
Diagnosis GDV is often diagnosed based on a patient ' s history , signalment , and physical examination results . Radiographic evaluation is required to confirm the diagnosis .
Signalment GDV is most commonly seen in large- and giant-breed dogs . It can also be seen in small dogs and cats . Dogs from 10 months to 14 years old have been affected . No sex predilections have been demonstrated .
Physical examination results On physical examination , it is classic to find a large distended abdomen . On percussion , a tympanic sound is produced . Abdominal palpation may be uncomfortable .
Issue 06 | DECEMBER 2016 | 27