Narrowing of the Pyloric Canal in Dogs

The pyloric canal connects the stomach to the small intestine. A small band of muscles called the pyloric sphincter opens and closes during digestion to allow food to pass into the small intestine. If the pyloric sphincter is too narrow or the passage becomes blocked, food will have nowhere to go. This is called pyloric stenosis; it usually results from a thickening of the muscles and mucosa and sometimes a tumor or lesion can occur in this area as well. Pyloric stenosis leads to the development of chronic pyloric hypertrophic gastropathy (CHPG) with symptoms of vomiting and often weight loss and dehydration. This is a congenital condition is many brachycephalic breeds. Puppies are born with an abnormality in the smooth muscles of the pyloric canal and will develop symptoms as soon as they start eating solid food. Other breeds may develop the condition later in life. Left untreated, CHPG can be fatal since the dog will be unable to absorb adequate nutrition. In most cases, the muscles can be reopened with surgery so that food can pass properly and the dog will recover.

If the pyloric canal becomes too narrow, it will cause blockage between the stomach and the small intestine and dogs will have symptoms of chronic vomiting. Veterinarians call this pyloric stenosis. In dogs, it can usually be treated successfully with surgery.

Dogs should be evaluated by a veterinarian any time they have symptoms of chronic vomiting that occur one or more times per week. The following signs could suggest narrowing of the pyloric canal.

• Chronic intermittent vomiting
• Vomiting undigested food several hours after eating
• Projectile vomiting
• Regurgitation
• Failure to gain weight (in puppies)
• Weight loss
• Thirst
• Aspiration pneumonia

Types

There are two types of pyloric stenosis.

Congenital 

Dogs with an inherited condition often develop symptoms upon weaning. This is more common in brachycephalic breeds.

•  Boxers
• Boston Terriers
• Bulldogs

Acquired 

Dogs can acquire the condition at any point in their lives. The acquired version is more common in some breeds.

• Lhasa Apso
• Shih Tzu
• Pekinese
• Poodle
• Rottweiler

Many factors can contribute to a dog developing pyloric stenosis, especially conditions which increase the amount of gastrin in the stomach and cause inflammation in the mucosa.

• Ulcers
• Chronic gastritis
• Tumor
• Stress

The condition is more common in male than in female dogs. It is also usually more serious in small dogs that already have less space in their stomach.

The veterinarian will thoroughly examine your dog and likely take bloodwork and urine tests. Other potential causes will have to be eliminated, including infection or an autoimmune response that is causing chronic gastritis. If all other tests come back normal, and your dog has been showing symptoms for some time, the veterinarian may suspect pyloric stenosis. Breed and age factors can be relevant, so the veterinarian will need a complete family history. Taking note of when the symptoms first started is also important.

Abdominal x-rays will be taken. Veterinarians often add contrast dyes to make it easier to see what is happening to the fluids in the stomach. X-rays will usually show that the stomach is enlarged and that it is not emptying into the intestine at the appropriate time. In many cases, endoscopy is needed to make a definitive diagnosis. This procedure involves inserting a camera down the throat to take pictures of the inside of the stomach. The dog will be anesthetized for this procedure. The veterinarian will also be able to check for tumors and cancerous lesions at the same time and may take biopsies of the gastrointestinal walls. The veterinarian could decide to perform exploratory surgery instead of endoscopy.

Surgery is the most common treatment for pyloric stenosis. Dogs with severe symptoms of vomiting may need to be treated supportively until they are healthy enough for surgery. Your dog might need intravenous fluids or medication to resolve the alkalosis that can occur after vomiting stomach acid.

The veterinarian will usually perform a pyloromyotomy or a pyloroplasty. These types of surgeries involve opening the pyloric sphincter and widening it so that food can pass into the intestine properly. If there is a tumor this will be removed, and the vet will do a biopsy to determine if it is cancerous. The dog will likely need to stay in a veterinary hospital several days after surgery to recover, and may need to be on a special diet until the stomach has healed. The vet might prescribe antibiotics to limit infection as well as anti-emetic medication.

In most cases, surgery is successful. If the dog still has mild symptoms of vomiting the veterinarian may prescribe medication and suggest frequent small meals to limit the problem. This treatment could also be recommended instead of surgery for mild conditions, or for dogs that are not healthy enough to have surgery.

The prognosis for pyloric stenosis is good and most dogs will make a full recovery. This is a common condition in dogs, and it is frequently treated successfully. Some conditions may need to be managed by limiting meal size and medication, or the veterinarian may recommend certain food that is easier for your dog to digest. In a few cases, a second surgery could be required if severe symptoms persist. If the condition is cancerous, it could pose more of a problem, but this is rare.