Summary
Pyloric stenosis, also known as "chronic hypertrophic pyloric gastropathy," is a narrowing of the structure required for passage of partially digested food from the stomach into the small intestine (the pylorus, a stomach valve of sorts). It occurs primarily in dogs and is rare in cats.
This aberration of the stomach's normal emptying mechanism is caused by physical obstruction of the pylorus. Hence, the inability of food to pass down to the rest of the gastrointestinal tract for further digestion, nutrient absorption and normal waste excretion.
This obstruction can occur for one of two different reasons:
1. A congenital thickening of the smooth muscle of the pylorus. In other words, pets are born with an abnormal muscle in this sensitive location. Animals with this form usually show signs after weaning and up to a year of age.
2. A gradually acquired form of the disease in which either the smooth muscle, the delicate lining of the stomach (the mucosa), or both, become thickened, thereby obstructing the pylorus. It's cause is unknown but it's believed that high gastrin levels (a hormone) may lead to this abnormal thickening process. These animals tend to be older when diagnosed. They tend to be about ten years old when symptoms arise.
Symptoms and Identification
The most common symptoms include chronic, intermittent vomiting and regurgitation (because the mechanical obstruction means food can't get down to where it needs to go), weight loss (because nutrients aren't reaching the intestines for absorption) and respiratory problems (because aspiration of stomach contents can occur as foods are brought back up).
Diagnosis of the problem can be difficult if the complete closing down of the pylorus is intermittent, but it usually relies on X-rays after barium administration. These "barium studies" often show a thin line of minimal amounts of this contrast material getting through the pylorus into the intestines, thus strongly suggesting the diagnosis of pyloric stenosis.
Endoscopy (using a fiberoptic device to view the area) will assist the diagnosis by visualizing the thickness of the pylorus and by allowing for tissue sampling of the affected area. Fluoroscopy is another technique used to visualize the motion of material as it passes through the area.
Surgery is sometimes required to establish the definitive diagnosis.
Certain blood test findings will also point to the presence of the disease.
Affected Breeds
For the congenital form of the disease, brachycephalic breeds (short nosed dogs) are primarily affected. This includes Boxers, Boston Terriers and Bulldogs. Among cats, the Siamese is most affected.
For the acquired form, the Lhasa Apso, Shih Tzu, Pekingese and poodle are documented to be the most predisposed breeds.
Treatment
Treatment of the condition is typically surgical. A widening of the pylorus is typically accomplished through one of various methods, depending on the degree of the disease's severity and the potential for it to worsen. Here's a list of the most common procedures.
1. Pyloromyotomy (opens the area by incising through the muscle layer)
2. Pyloroplasty (opens the area with a flap procedure)
3. Gastroduodenostomy (bypasses the pylorus)
4. Gastrojejunostomy (bypasses the pylorus and the first section of the small intestine)
The latter two procedures are typically selected for the most severe cases, in which repair of the pyloric mechanism proves an inadvisable option.
Veterinary Cost
The cost of diagnosis is not necessarily very high, as $300 to $600 barium studies can often elucidate the problem. Follow-up endoscopy or fluoroscopy to confirm the diagnosis, however, will undoubtedly prove more expensive, usually at $500 to $1,500, if not more depending on the facility.
For owners who elect to move forward and treat the problem through surgical exploration, expenses ranging from $1,500 to $5,000 are to be expected, depending on the technique, the surgeon's experience and the geographic location of the facility.
Prevention
It's been proposed that high levels of gastrin (a hormone) in pregnant females may predispose dogs to the development of the acquired form of this disease. Pre-pubertal spaying (before the first heat) of non-breeding females within predisposed breeds is therefore considered wise.
Because chronic stress, undiagnosed gastric ulcers and other forms of chronic gastritis are predisposing factors for gastrin increases, treating these processes early may well prevent pyloric stenosis.
Because of its hereditary nature, removing all affected animals from their breeding programs and preventing their reproduction is considered a fundamental course of action. This is true for both acquired and congenital forms of pyloric stenosis.
References
DeNovo R. Antral pyloric hypertrophy syndrome. In: Kirk R, ed. Current veterinary therapy X. Philadelphia: WB Saunders, 1989.
Matthiesen D. Chronic gastric outflow obstruction. In: Slatter D, ed. Textbook of small animal surgery. 2nd ed. Philadelphia: WB Saunders, 1993.
Stanton M. Gastric outlet obstruction. In: Bojrab MJ, ed. Disease mechanisms in small animal surgery. 2nd ed. Philadelphia: Lea and Febiger, 1993.
Elizabeth LaFond, DVM, Diplomate ACVS, Gert J. Breur, DVM, PhD, Diplomate ACVS and Connie C. Austin, MPH, PhD; Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907.