Gastric Dilatation and Volvulus

Description

Gastric Dilatation and Volvulus (GDV) is an acute, life-threatening emergency affecting large and giant breed dogs. The condition is characterized by accumulation of gas in the stomach, malpositioning of the stomach, increased intragastric pressure and shock. Successful management relies on prompt diagnosis and appropriate emergency treatment as the disease will rapidly progress to death if untreated.

Commonly affected breeds include German Shepherds, Great Danes, Irish Wolfhounds, St Bernards and Doberman Pinschers. GDV has also been reported to occur in cats, primates and rarely small breed dogs such as Dachshunds and Miniature Poodles.

Risk factors

The exact aetiology of the condition is unknown but a number of risk factors have been identified. Studies have shown that dogs with a reduced thoracic width to depth ratio are at an in increased risk of developing GDV. Female dogs are also more likely to develop GDV than males and stressed, anxious dogs are more likely to develop GDV than calm, placid dogs. Other risk factors include obesity, feeding a dry food diet and exercise after feeding.

Pathogenesis

An obstruction to gastric emptying due to fluid or gas leads to gastric distention and a rapid increase in intra-gastric pressure. As the stomach dilates, the pylorus shifts through an angle of between 180 and 360^o from its normal position to a dorsal, cranial and leftward location. More than 90% of all gastric volvuli rotate in a clockwise direction when viewed from the surgeon's perspective with the dog in dorsal recumbency.

The most immediate effect is impairment of the gastric blood supply, leading to severe congestion of the gastric wall and infarction and ulceration of the gastric mucosa. Venous return to heart is reduced due to mechanical compression of the caudal vena cava by the distended stomach, leading to decreased cardiac output and hypovolaemic shock. Gastric distension also causes a mechanical impediment to movement of the diaphragm resulting in reduced tidal volume, hypoxia and hypercapnia.

In addition to the above systemic effects, diplacement of the stomach may lead to avulsion of the gastric branches of the splenic artery. Significant haemorrhage may occur as a result and this may lead to the development of ischaemia-induced gastric necrosis.

History and Clinical signs

The clinical signs of GDV are usually acute in onset and may follow a period of exercise and/or feeding of a large meal. Affected dogs typically display non-productive vomiting and abdominal distension. Acute onset restlessness, abdominal pain, hypersalivation and abdominal typmany are other common features of GDV. On physical examination, the dog may be collapsed or reluctant to stand. Signs of cardiovascular shock may be present including tachycardia, pale mucous membranes, prolonged capillary refill time and poor peripheral pulses. An irregular heart rate combined with pulse deficits indicates the presence of cardiac arrhythmias.

Diagnosis and Management

Fluid therapy

Diagnosis is usually based on the patient's signalment and a history of unproductive vomiting and abdominal distension. Initial emergency treatment should be aimed at managing the dog's hypovolaemic shock. It may be beneficial to provide oxygen supplementation whilst the dog is being stabilised. Large bore (16 or 18 gauge) catheters should be placed into the cephalic or jugular veins and a proportion of the shock dose of Compound Sodium Lactate (90ml/kg/h) should be administered intravenously based on the severity of the dog's clinical signs. Hypertonic saline or colloid fluids may be indicated in very large dogs or those who have not responded to a bolus dose of crystalloid fluids.

Gastric decompression

Following a period of aggressive fluid therapy, gastric decompression should be performed. A lubricated large-bore stomach tube is premeasured (from nostril to last rib) and marked. A roll of 2 inch adhesive tape should be inserted behind the canine teeth and the dog's mouth should be held closed around the banadage. The stomach tube can then be introduced through the bandage into the oesophagus. and should not be advanced beyond the marked point. It is important to mimimise stress when this procedure is carried out. Sedation is not usually required but suitable drugs for this include Butorphanol, Fentanyl or Diazepam. It the animal is resistant to orogastric intubation or becomes stressed, trocharization of the most tympanic area caudal to the ribs with a 14 to 16 gauge catheter may be performed. This may allow susequent completion of orogastric intubation for further decompression.

Radiography

Abdominal radiography may be beneficial in confirming a diagnosis of GDV and distinguishing between GDV and gastric dilatation. Radiography should not be carried out until gastric decompression has been performed and intravenous fluids have been started. A radiograph performed in right lateral recumbency shows a dorso-cranially positioned pylorus to the left of the midline. The stomach will appear compartmentalised (the classic 'double bubble' pattern) with a soft tissue strip separating the two compartments. The oesophagus may appear dilated with air or fluid. Evidence of air in the abdomen indicates that perforation has occurred and requires an exploratory surgical procedure. Loss of contrast in the abdomen may indicate peritonitis or haemoabdomen.

Other diagnostic tools

Plasma lactate concentration has been reported to have a strong link with the patient's prognosis due its association with gastric necrosis and systemic hypovolaemia. A plasma lactate greater than 6 mmol/L is associated with a poor prognosis. Electrocardiography (ECG) is essential as cardiac arrhythmias may occur in up to 40% of dogs with GDV. Most arrhythmias are ventricular in origin and occur within 36 hours of admission. Ventricular tachycardia is the most common rhythm disturbance seen but many other arrhythmias may occur.

Treatment

Once the patient has been stabilised, the volvulus should be surgically reduced via a cranioventral midline laparotomy. The aims of surgery include gastric decompression and repositioning, assessment of the abdominal organ viability, removal of necrotic tissue and gastropexy. Gastrectomy of devitalised tissue may be required and splenic damage due to avulsion or torsion may require partial or complete splenectomy. Although many types of gastropexy have been described, the belt-loop and circumcostal techniques are the most commonly used in GDV surgery. Use of tube gastrostomy is associated with a higher morbidity rate due to alteration of gastric motility and development of cellulitis around the tube.

Post-operative complications and care

The most common complications following GDV sugery include cardiac arrhythmias, shock, hypokalaemia and surgical complications such as dehiscence. Ventricular tachycardia is the most common abnormal rhythm and continuous ECG monitoring is recommended for the 24-48 hours following surgery. Intravenous fluid therapy should be continued and the haemodynamic, acid-base and electrolyte balance should also be closely monitored. If vomiting occurs the patient should be evaluated for possible peritonitis.

Prognosis

Simple GDV mortality rates are around 15%. Patients suffering from gastric necrosis or requiring gastric resection or splenectomy have a higher mortality rate at over 30%.

References

• Hall, E.J, Simpson, J.W. and Williams, D.A. (2005) BSAVA Manual of Canine and Feline Gastroenterology (2nd Edition) BSAVA
• King, L. and Hammond, R. (1999) BSAVA Manual of Canine and Feline Emergency and Critical Care BSAVA
• Tilley, L. P., and Tilley, L. P. (2008) Manual of canine and feline cardiology Elsevier Health Sciences
• Tivers, M. and Brockman, D. (2009) Gastric dilation–volvulus syndrome in dogs 1. Pathophysiology, diagnosis and stabilisation 31(2):66 In Practice
• Tivers, M. and Brockman, D. (2009) Gastric dilation–volvulus syndrome in dogs 2. Surgical and postoperative management 31(3):114 In Practice
• Wingfield, W. E. (2001) Veterinary Emergency Medicine Secrets Elsevier Health Sciences

Also known as:

GDV