Why Do Small Dogs Develop Pyloric Stenosis and Pylorospasm?

Why Do Small Dogs Develop Pyloric Stenosis and Pylorospasm?

Health & Safety

In dogs, the pylorus is a muscular passage that's found in between their stomach and their small intestine. In normal conditions, this remains closed to allow the stomach to fill up with food before it is stimulated to open by the stomach's contractions. This then allows any food to pass out of their stomach and into the dog's duodenum which is their small intestine.

When a condition known as pylorospasm occurs, this muscle does not relax in order to let the food pass out of the stomach which results in dogs experiencing bouts of vomiting of undigested food they've just eaten. The condition known as pyloric stenosis is where the pylorus narrows and this too interferes with food being passed out of the stomach which again causes dogs to vomit. The condition is often congenital but it could also develop because a dog has experienced a chronic infection which has been left untreated. It could also develop due to a tumour forming on the pylorus.

How a Dog's Stomach Works

A dog's stomach is designed to store large amounts of food ready for the digestive process to start. The food leaves the stomach once is has been digested which is typically within 12 hours of them having eaten it. It is the gastric folds found inside the stomach that grind the food for it to be digested but it is the acids and enzymes secreted by the inner stomach lining that breaks down the food first. Partially digested food leaves the stomach through what is known as the pyloric sphincter so it can enter into the small intestine called the duodenum.

However, it is the pyloric sphincter which can for some unknown reason cause a health issue for dogs when it starts to spasm or to constrict which results in the opening becoming smaller and narrower. This is the condition known as a condition called Pyloric Stenosis. It is typically smaller and more nervous breeds of dog that tend to develop this particular condition although why this actually occurs, is still unknown.

The Symptoms to Watch Out For

You may find that your dog suffers intermittent bouts of vomiting around an hour or so after they've been fed. This is one of the more typical signs of a dog suffering from the condition. The food appears to be undigested and on occasion a dog will only bring up part of their meal because the narrowing sphincter has allowed some of the food to enter the stomach without causing the dog to be sick.

If dogs are fed a watery diet, the food passes that much easier through the narrower hole and the same can be said of any water they drink. However, bulkier food can cause a real problem and in a worst case scenario restricts the amount of food a dog can digest which then leads to dramatic weight loss.

The Risks Involved

A lot of dogs live out very normal lives with occasional bouts of vomiting and vets believe this is because the muscular spasms are not consistent. However, if the condition is severe and a dog just cannot digest food because they keep sicking it up, it is because the pyloric stenosis is more constant. The result is weight loss and if not detected or treated, it can prove fatal.

Living with the Condition

Unfortunately, diagnosing the condition is not always that easy and a full history of a dog would be needed to show how often they vomit and over what period of time this has been going on in order for the severity of the condition to be evaluated correctly. An X-ray may show a narrowing of the pyloric sphincter and will help a vet when it comes to recommending how best to go about resolving the condition. In most instances this involves surgery where the narrow band can be severed which then prevents the spasms or constrictions from occurring.

Vets might also suggest they widen the stomach outflow area which enables food to pass more easily into the duodenum. The good news is that the outcome of this type of surgery boasts a great success rate and dogs that had the condition go on to lead long and happy lives once they have had the surgery.


When it comes to treating pylorospasm, this is very often more management than anything else and involves careful control over a dog's diet, giving them the right type of medication to prevent spasms from occurring and on the odd occasion a dog may need to be given some sort of tranquilliser. However, with careful management dogs live out long and happy lives even if they need prolonged treatment and management.

Pyloric stenosis on the other hand might need surgical intervention to make the spylorus larger and even if the condition is congenital the outcome is very good with dogs living comfortable and happy lives.


It is smaller dogs with more nervous dispositions that tend to develop and suffer from these conditions. However, the good news is that dogs recover from any surgery they receive very well and with careful management can live out happy and healthy lives. If you have any concerns that your pet is vomiting a little too often and notice they are losing weight and condition, you should take them to the vet so they can be examined to see if either of these conditions are causing the problem. Once diagnosed, the vet would then recommend a management plan or treatment for your dog to get them back on the road to recovery.

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