What is pyloric stenosis in dogs?

If you’ve never heard of pyloric stenosis, you’re not alone. But this rare condition can be very distressing for dogs and their owners. Petplan veterinary expert Brian Faulkner explains what causes pyloric stenosis, the symptoms and how it can be treated.

What is pyloric stenosis?

The pylorus is the muscular opening from the stomach that allows semi-digested food to travel into the small intestine. Stenosis — which means narrowing — occurs when the pylorus is either partially or completely blocked. This blockage is due to a thickening of the muscles surrounding the opening. As a result, food can’t leave the stomach normally.

Your vet may also refer to pyloric stenosis as pyloric hypertrophy or chronic hypertrophic pyloric gastropathy — but these all mean the same thing. 

What causes canine pyloric stenosis? 

There are two main causes of pyloric stenosis: congenital and acquired. In the congenital cases, a dog will be born with abnormally thick muscle surrounding the pylorus. Usually, puppies with congenital pyloric stenosis will start developing symptoms around the time they’re weaned onto solid foods.

In acquired pyloric stenosis, a blockage can happen when either the muscles surrounding the pylorus, or the muscles that make up the stomach lining, gradually thicken over time. In some cases, these both become thickened. It’s not known what causes the thickening of these muscles, but it’s thought it may be linked to high levels of the hormone gastrin. Dogs with acquired pyloric stenosis tend to develop symptoms later in life.

Which breeds are affected by pyloric stenosis?

Congenital pyloric stenosis is more common in short-nosed, or brachycephalic breeds, including:

• Boxer
• Boston Terrier
• Bulldog

Acquired pyloric stenosis seems to be more common in certain small breeds, including:

• Lhasa Apso
• Maltese
• Pekingese
• Shih Tzu

Symptoms of pyloric stenosis

One of the most common symptoms of this condition is persistent vomiting. This is quite a common problem, however, and a symptom of many health conditions. It is more often caused by a dog eating something that’s upsetting their digestive system, or ingesting a foreign body.

In pyloric stenosis, vomiting usually starts an hour or two after your dog has eaten. Any food that’s vomited back up will look pretty much as it did when your dog ate it — undigested.

Sometimes vomiting is accompanied by other symptoms, including:

• Decreased appetite
• Dehydration
• Unexplained weight loss
• Respiratory problems

The severity of these symptoms is linked to how badly the pylorus is blocked. If your dog’s pylorus is only partially blocked, then vomiting may not occur after every meal, making this condition more challenging to diagnose. If your dog is regularly vomiting, you should always speak to your vet for advice.

How is pyloric stenosis diagnosed?

Diagnosis of pyloric stenosis can be tricky and may initially be determined by eliminating other factors like gastrointestinal upsets or ingestion of a foreign body. Your vet may also ask you to keep track of when your dog vomits, and how often.

If your vet suspects pyloric stenosis then they may recommend a barium x-ray. Barium is a contrast medium that can be seen on an x-ray and will help your vet determine if the pylorus is blocked. Sometimes other diagnostic tests like abdominal ultrasounds, biopsies or a fluoroscopy will also be offered.

How is pyloric stenosis treated?

Surgery is usually recommended and the most common procedure is a pyloroplasty. This involves removing any thickened tissue surrounding the pylorus, to widen it and allow food to pass through normally. Sometimes, in more severe cases, other procedures may be offered if the pylorus can’t be widened — for example, surgical removal. The diagnosis and treatment of pyloric stenosis may be covered by your pet insurance to help you access the best care for your dog.