Canine Gastric Dilation Volvulus (Bloat)

What is bloat?

Bloat is over-inflation of the stomach with air or gas. It doesn't sound very serious, but bloat can be rapidly fatal. The problem becomes life-threatening when the over-inflated stomach twists and cuts off its own blood supply. The medical term for this condition is gastric dilatation volvulus, or GDV. Dilatation in this case means distention or stretching of the stomach wall. Volvulus means that the organ has twisted lengthwise, like wringing out a wet towel. A dog can have gastric (or stomach) dilatation without volvulus.

On its own, distention of the stomach reduces blood flow to the stomach wall. Twisting of the stomach further decreases blood flow. When the blood supply to the stomach is restricted, the wall of the stomach tissue begins to die. Together with the increased pressure within the stomach, it makes rupture of the stomach likely if the distention is not relieved. Stomach rupture causes peritonitis and toxemia (absorption of bacterial toxins), which can be fatal.

• The enormously distended stomach also does the following

makes breathing difficult by pressing on the diaphragm

• The diaphragm is the muscular wall between the chest and abdomen; when the diaphragm contracts, air is drawn into the lungs
• interferes with the return of blood to the heart by compressing the vena cava

-the vena cava is the large vein that returns blood from the organs, limbs, and body wall to the heart

Decreased return of blood to the heart also means decreased output of blood from the heart, so blood flow to all tissues and organs is reduced. The spleen lies beside the stomach and is connected to the stomach by a ligament, so distention (and twisting) of the stomach also reduces blood flow to and from the spleen. The impaired blood circulation also slows activity in the rest of the intestinal tract, which allows absorption of bacterial toxins from the intestine. These toxins have multiple effects on the circulation, including uncontrolled blood clotting within the vessels (disseminated intravascular coagulation, or DIC)

It is easy to see why a dog with GDV may quickly go into shock and will die without immediate veterinary treatment.

Why does bloat occur?

Why bloat occurs in some dogs is still not known. It was originally thought that bloat was the result of eating a large amount of dry food, then drinking a lot of water, which caused the food to swell in the stomach. If the dog then ran around, jumping and playing, the full stomach could have been jostled around and twisted because of its weight. However, this sequence of events does not fit with most dogs that develop GDV. Current theories involve abnormal activity of the muscles in the stomach wall. With loss of the normal rhythm of muscle activity, gas can be trapped in the stomach (gastric dilatation) and twisting (volvulus) may develop as a result.

One interesting thing about bloat is that it is most often seen in large dogs with deep chests. The breeds most commonly affected include Great Danes, Irish Setters, German Shepherds, and Afghan Hounds. Bloat is extremely uncommon in smaller dogs. Although the stomach is in the abdominal cavity, and not the chest cavity, it is still encased within the ribcage. So, it could be that the stomach has more room to move about in dogs with deep ribcages.

What are the signs of bloat?

Bloat causes the following signs:

• the dog seems to be in pain or is very depressed
• the dog may sit/lie on its haunches with its front legs stretched out in front (the "praying" position)
• the dog's belly may be enlarged or the back part of its ribcage may seem wider than normal, especially on the left side

the dog may have difficulty breathing or have shallow, rapid breathing there may be

• signs of shock-weakness, cold extremities (paws, tail, ears), high heart rate, discolored gums

These signs may rapidly worsen over a couple of hours. You should contact your veterinarian immediately if you suspect your dog may have bloat.

How is bloat diagnosed?

In most cases, rapidly worsening distention of the abdomen in a large dog is sufficient evidence for your veterinarian to suspect GDV. A radiograph (x-ray) confirms the diagnosis of gastric dilatation. It may also show that the stomach has twisted.

There is a chronic form of gastric volvulus in which the stomach either remains or repeatedly becomes partially twisted. Gastric dilatation, or distention with gas, does not occur because the twist is not complete. The gas that builds up in the stomach can be either belched up or passed into the small intestine. In these dogs vomiting is the most common sign. The diagnosis is usually made when an abnormally shaped stomach is seen on radiographs.

Can GDV be treated?

Yes, with prompt veterinary attention, the dog's life can usually be saved. Treatment involves the following emergency procedures:

• intravenous fluid therapy for shock
• relief of pressure in the stomach to prevent rupture

-if the stomach is simply distended (and not twisted), the pressure may be relieved just by passing a tube through the dog's mouth into its stomach

-if the stomach is twisted, the veterinarian may need to partially decompress it using a large needle inserted through the skin into the stomach; surgery is then done to relieve the remaining distention and correct the position of the stomach

-if the condition is so critical that the dog could not tolerate general anesthesia, the veterinarian may make an incision through the skin into the stomach, and temporarily suture the stomach wall to the skin until the dog's condition has improved

• surgical correction of the twist

-general anesthesia and abdominal surgery are usually required to correct the twist

-this procedure carries some risk with dogs in shock, but it is necessary in order to save the dog's life

-while the veterinarian is correcting the twist, they will also inspect the stomach wall and, if possible, remove any areas that are badly damaged.

During surgery, the veterinarian can also permanently suture the stomach to the body wall. This procedure, called gastropexy, is done to prevent retwisting of the stomach and repeat episodes of GDV.

Treatment may also be necessary for any abnormal heart rhythm (arrhythmia) that may develop during surgery or for the first several days after recovery. Some arrhythmias are life-threatening because they severely affect heart function. Thus, dogs that have had surgery for GDV usually need to be hospitalized and monitored closely for several days afterward.

What is the prognosis?

With immediate veterinary care, the survival rate is 60-70%. In individual cases the prognosis depends on several factors:

• severity and duration of the distention
• presence and degree of shock
• presence of other disorders (e.g. arrhythmias)
• how much of the stomach wall has lost its blood supply, and whether the devitalized areas can be removed

Can anything be done to prevent GDV or stop it from happening again?

Gastropexy (suturing the stomach to the body wall) can prevent the stomach from twisting again in most cases, although it does not prevent distention. Some veterinarians even recommend performing a gastropexy on susceptible dogs while they are young to prevent a torsion from ever happening. So far, no dietary or exercise modifications have been useful in preventing GDV in susceptible dogs. Being aware of the potential for this condition to develop, and knowing what to look for, can improve your dog's chances of survival. Always consult your veterinarian if you suspect a problem is developing.

by William M. Fraser, D.V.M.

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