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Pyloric stenosis in dogs, also known as pyloric hypertrophy (the enlargement of muscle of tissue) syndrome, is the narrowing of the portion of the stomach called the pylorus. The pylorus is the valve-like opening that lets food exit the stomach and enter the intestine (medically speaking, "stenosis" means "narrowing"). The pylorus is controlled by muscles that surround it and when those muscles thicken they cannot work properly. This results in the opening being completely or partially closed off not allowing for food to exit the stomach normally.
Causes: Why Does Canine Pyloric Stenosis Occur?
Pyloric stenosis in dogs may occur for a few different reasons.
The first of which may be congenital (meaning your dog can be born with it) selective thickening of the smooth muscle of the pylorus. Dogs are born with a form of canine PS and telltale signs normally appear sometime after weaning, and the transition to solid food, usually between four and 12 months old.
Another reason may be because of the gradual acquired thickening of the smooth muscle, the mucosal lining of the stomach — or a combination of the two. The cause of this form is unknown. Dogs with this form of canine pyloric stenosis are usually middle-aged or older when symptoms first appear.
Brachycephalic or short-nosed breeds, including Boston terriers, boxers and bulldogs are more prone to congenital pyloric stenosis. And small breed dogs including Lhasa apsos, shih tzus, Pekingeses and Malteses may be more at risk for acquired PS.
Signs of Pyloric Stenosis
The most common signs of pyloric stenosis in dogs observed by pet parents is chronic intermittent vomiting (the dynamic process where dogs use their stomach muscles to expel contents in the digestive tract that appear as digested), usually occurring several hours after eating. The vomiting may also be projectile in nature. In the congenital form of canine pyloric stenosis, vomiting starts after the dog is weaned and starts eating solid food. Other potential clinical signs associated with PS in dogs include:
- Regurgitation: a passive expulsion of contents in the digestive tract where the dog appears to burp up the contents do not appear to be digested.
- Decreased appetite
- Weight loss
- Respiratory problems such as, aspiration pneumonia secondary to the vomiting. Aspiration is the result of something foreign being passed into the lungs or airways by accident — in this case, vomit, as a result can lead to an infection of the lungs or airways resulting in pneumonia.
These signs are related to the severity of the pyloric thickening and normally do not resolve with treatment of the symptoms with medication. If your dog is experiencing any of these, further evaluation by a veterinarian is recommended.
How Veterinarians Diagnose Pyloric Stenosis
Since there can be many potential underlying causes for chronic vomiting, diagnostic testing is necessary for further evaluation. Full blood work including a complete blood count (CBC), chemistry profile and urine sample evaluation as well as abdominal X-rays are normally required. In many cases, the blood and urine tests may be normal, or they could show mild dehydration or electrolyte (essential minerals needed for key body functions) abnormalities. However, even if the blood work is normal, it helps to rule out other causes of vomiting. X-rays of the abdomen may show a stomach that is distended with fluid if there is an obstruction of the pylorus. Chest X-rays should be done if there are any concurrent respiratory problems to evaluate for aspiration pneumonia or other abnormalities in the chest.
If there is concern for pyloric stenosis, additional abdominal X-rays taken after oral administration of a contrast medium called barium that helps the vet better examine the abdomen, are often performed. Delayed emptying of the stomach and narrowing of the pylorus may also strongly suggest a diagnosis of canine pyloric stenosis. If available, a live motion X-ray called a fluoroscopy or an abdominal ultrasound may be done to evaluate for pyloric stenosis prior to more invasive diagnostic tests.
If there is concern for canine pyloric stenosis, the use of a camera to look at the pylorus may be utilized. Biopsy samples of the pyloric tissue can also be obtained via endoscopy. Biopsies are important to rule out other causes for thickening of the pyloric tissue.
In some cases of pyloric stenosis in dogs, exploratory surgery is needed to obtain a diagnosis of canine pyloric stenosis.
A Tailored Course of Treatment
Treatment for pyloric stenosis in dogs typically involves surgery, as most cases result in obstruction of the stomach. A procedure called a pyloroplasty is the most common surgery performed, and it allows for removal of the thickened pyloric mucosal tissue and widening of the pylorus where food exits the stomach. In some cases of extensive disease of the pylorus, a more involved surgery in which the affected pylorus is removed may be necessary.
If there are no post-operative complications, the majority of dogs who have surgery for treatment of PS do well and are able to return to their normal lifestyle.
Jessica Seid is an emergency veterinarian practicing in the New England area. She is graduate of North Carolina State College of Veterinary Medicine and has been in the field for 10 plus years. When not at work helping her patients, she enjoys spending time with her husband, daughter and their French Bulldog.