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Gastric dilatation-volvulus

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Gastric dilatation volvulus (GDV), also known as bloat or gastric torsion, is an acute condition seen in dogs where the stomach has filled with gas or fluid, expanded, and has twisted on itself. It is life–threatening even with treatment. Blood supply to the stomach and many other abdominal organs can be compromised, causing many fatal complications in the body. It is an emergency condition that has a 10-30% fatality rate, even with treatment.

What organs are involved?

GDV primarily concerns the stomach. The stomach chemically and mechanically digests food it receives from the oesophagus. The food then passes through the pyloric region of the stomach to the duodenum, part of the small intestine. When GDV occurs, potentially both the entrance and exit (pylorus) can be blocked.

The rotation and expansion of the stomach causes blood supply to other organs and tissues to be compromised, particularly the spleen. The spleen, involved with the filtration of blood cells, can suffer such blood loss that the tissue begins to die — this is called necrosis.

The portal vein carries blood from the intestines to the liver. It lies close to the stomach and may also get compressed by the torsion of the stomach, limiting blood flow return to the heart. 

Risk factors

Large and giant breed dogs are at a much higher risk of developing GDV than smaller dogs. Studies suggest this is because of their deep thoracic cavity*. Such dog breeds include Great Danes, St Bernard’s, Weimaraners, Gordon Setters, Irish Setter, Doberman Pinschers, and Old English Sheepdogs. Smaller dogs can occasionally develop GDV, such as Poodles and Bassett Hounds.

Having a first-degree relative that has developed the condition, such as parents or siblings, increases the risk of also developing GDV by 63%* **. Pure-bred dogs are also more at risk than mixed breeds, however the reason for this is not known.*

According to the Kennel Club, stress and anxiety are major triggers for the stomach to become filled with gas due to aerophagia, the swallowing of air “usually seen in stressed, kennelled dogs” (*blah).

Another major risk factor is to do with dogs’ eating habits. Dogs that eat one large meal daily are more likely to develop GDV than dogs that eat smaller meals more often*. Rapid ingestion of food can also increase the risk of bloat*, as well as heavy exercise after eating.

Lastly, the condition has a higher association with older dogs*, although it is not unknown in younger dogs. There is a 20% increase in risk for each year of increase in age according to Purdue University*.

 
Clinical presentation

Some dogs develop gastric bloat on its own without the torsion before developing GDV later in life. -**************
The vet will first ask the owner about the history of the patient or if the owner was aware of any of the usual complaints in dogs that later develop GDV. Possible complaints include:

abdominal distention
abdominal pain
ptyalism: excess saliva and drooling
retching or vomiting, often non-productive
acute collapse.

Upon physical examination, the vet may come across the following findings:

Abdominal distention: The stomach has enlarged to a point where it is obvious from just looking at the dog. It is very uncomfortable and the dog may not endure being touched or palpated here.

Excessive salivation: This is often a sign of nausea or gastrointestinal issues. The dog is continuing to produce saliva but it cannot swallow it.

Sudden, non-productive retching: The dog is trying to get empty the stomach of any food or gas that it causing the bloat. It is non-productive, meaning no vomit is brought up, because the entrance to the stomach is twisted closed.

Tachypnea (rapid breathing): The enlarged stomach pushes on the diaphragm which does not allow the lungs to fully expand with breathing. The dog will breathe rapidly to compensate for the lower oxygen intake into the lungs. If blood circulation is affected, respiratory rate will increase to increase oxygen levels in the blood. Heavy breathing can also be a sign of stress or anxiety in dogs.

Dyspnea (difficult breathing): This can be due to the pain the dog is experiencing and from the pressure being exerted on the diaphragm, making breathing more laboured.

Restlessness: This is usually a sign of discomfort.

Weakness or collapse: Typically seen in the late stages of GDV due to the severe shock. Other advanced symptoms include pale mucous membranes, fast heart rate, and weak pulse.

Pathophysiology

So what is actually going on when dogs develop GDV?

The stomach has an abnormal volume of gas, as well as a build up of gastric juices. It hasn’t yet been discovered why, but the stomach fails to empty itself, and begins to distend.  *Some research indicates that failure of the pyloric sphincter mechanism results in the build up. The stomach then rotates around the oesophagus by 90 — 360 degrees. Once it has twisted, the entrance (oesophagus) and the exit (pylorus) are blocked, preventing any passing of food or gas. If there is food in there, it will continue to be digested, increasing the gas and fluid content of the already enlarged stomach. There is obvious abdominal swelling on the dog.  

Some of the blood supply to the stomach is cut off (ischaemia) due to the twisting, which leads to tissue damage in areas of reduced blood flow. Prolonged ischaemia would cause necrosis (death of tissue) of some regions. If the stomach then ruptures, it would release gas, fluid, bacteria, and food into the abdominal cavity which could cause infection of the abdominal lining (the peritoneum). 
The blood supply of the spleen may also be compromised as its vessels run behind the stomach and could get squashed or distorted due to the stomach volvulus. Blood inside the spleen would be blocked from entering the circulation again, leading to the enlargement of the spleen. This reduces blood flow back to the heart but could also cause necrosis of the spleen tissue.

A distended stomach could compress other significant blood vessels. The caudal vena cava, a major vein returning all caudal blood to the heart, could get trapped by the stomach, as well as the portal vein, which carries blood from the intestines to the liver. 

The venous return to the heart is severely compromised due to these compressed blood vessels and build up of blood in the rear section of the animal. There is not enough blood to carry oxygen and nutrients through the body — this is hypovolaemia. Heart rate will increase, though weak, and blood vessels will constrict to try and maintain steady blood supply to the organs. Blood supply to non-critical areas is reduced. This includes mucous membranes such as the gums, which will become pale from low blood supply.

The distended stomach also pushes on the diaphragm, decreasing the lung capacity and thus decreasing the intake of oxygen. This causes rapid, shallow breathing, and contributes to the hypoxia (low oxygen levels) throughout the abdomen.

Prolonged hypovolaemia means that blood flow to the major organs (brain, heart, lungs, kidneys, liver) becomes critically low — hypovolaemic shock. At this point the condition has become fatal.

Diagnosis

Early stage gastric dilatation-volvulus requires further diagnosis. After the clinical exam and considering the history of the patient, it is likely that the vet will already suspect GDV, however this must be confirmed by taking a radiograph. The radiograph can identify whether volvulus has occurred or just dilatation on its own. Usually fluid therapy, gastric decompression and analgesia are given before taking a radiograph. The radiograph view will usually be right lateral to have the best view of the stomach. 

The right lateral radiograph will show an enlarged, gas-filled gastric cavity. Gas shows up on radiographs as black shadows where the radio waves cannot pass through. It will be instantly evident on the radiograph that the stomach is distended. The positioning of the stomach will be abnormal with volvulus – the pylorus will be positioned dorsally, whereas it’s usually positioned on the right, ventrally. 
   
Treatment

The management of GDV starts with aggressive fluid therapy to target the hypovolaemic shock. A catheter is placed in one or both of the forelimbs (into the cephalic veins), and a blood sample can be taken to check the levels of various *** in the blood (red blood cell count, ions, oxygen, carbon dioxide, proteins). An electrolyte solution like Hartmann’s should be administered though the catheter to correct the blood volume and contents. If the volume of red blood cells is very low, a blood transfusion may be given. The dog’s cardiovascular activity should be monitored frequently.

Analgesia (pain relief) should also be administered as GDV can be extremely uncomfortable. The stomach torsion and dilatation as well as the ischaemia will cause a lot of pain.

Decompression of the stomach is essential, and can be the first action taken in case or a rapidly life-threatening situation. It can be done by passing a stomach tube down the oesophagus. However, if the tube cannot be passed through the oesophageal sphincter at the stomach entrance. Instead, gastrocentesis can be performed. A large bore needle can be passed through the abdominal wall into the stomach.

Following this, surgery is required to correct the position of the stomach as soon as the dog has stabilised. The stomach may be twisted up to 360 degrees, so the surgeon must carefully reposition it, as well as further decompression if necessary. 

Once repositioned, the stomach should be assessed for any ischaemic tissue damage, as should other abdominal organs – particularly the spleen. Any necrotic tissue is removed. Splenectomies can be performed if damage is extensive.

Lastly, the patient will undergo a procedure called gastropexy, where the stomach is attached to the abdominal wall to prevent GDV from developing again in the future. This can also be done as a preventative method.

Post-operative care

After the surgery, it is imperative that the patient gets intensive care and monitoring. *The cause of the shock has been fixed, but the dog will still be suffering from its after-effects for several days*.

The dog’s heart rate and temperature should be monitored for at least 48 hours after surgery. The heart rate will tell you how the heart is recovering. The temperature can indicate if there is an infection developing. Antibiotics can be prescribed for any necrotic damage.

Blood tests should also be taken to check for blood pressure (which may indicate the circulatory volume in the veins), oxygen and carbon dioxide, and electrolytes.

Prevention

There are certain changes the owner can make to help reduce the risk of their dog developing GDV, as a preventative measure or after having developed it already.

Instead of feeding the dog one large meal daily, smaller meals should be given more frequently. Rapid intake of large quantities of food increases the risk of developing GDV. If a dog typically eats very quickly, there are methods to try and slow them down, such as dividing the food between the holes of a muffin tin**.

As stress seems to trigger GDV in at-risk dogs, feeding times should avoid aggravating the dog. Heavy exercise should not be encouraged before or after meals. Any meal changes should be implemented gradually.

Dogs that have developed GDV or have first-degree relatives, such as parents, siblings, or offspring, should not be bred. Breeders and owners should communicate about any occurrence of GDV.

Some dog breeds have a high incidence rate for developing GDV, so owners may want to consider a prophylactic gastropexy — to prevent any future occurrence of GDV. It can be performed at spay or castration. 

Conclusion

Gastric dilatation-volvulus is a life-threatening condition. A key factor in ensuring a dog’s wellbeing is awareness. 

Dogs are stoic, and often don’t show signs of suffering until the condition has advanced.

Owners should be aware of the signs of dogs developing GDV as the condition develops very quickly, so spotting the signs as soon as possible could save the dog’s life. 

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