Pyloric Stenosis

Pyloric stenosis is a common abnormality involving the stomach. The condition results from the thickening of the muscles of the pyloric sphincter, the "exit" of the stomach. The thickening of the sphincter slows or blocks the flow of the digested food from the stomach to the small intestine. What causes this condition is unknown; however, excessive secretion of some hormones stimulated by gastric acid in the stomach can produce pyloric spasm. Breeds affected with primary pyloric stenosis include the Lhasa Apso, Maltese, Pekingese, Shih Tzu, Boxer and Boston Terrier. Male dogs are more often affected than female.

Clinical signs of the primary pyloric stenosis generally include vomiting, which may occur soon after eating, but in many cases can be delayed for up to 24 hours after a meal. Normally, the stomach should be completely empty within 7 to 8 hours after the ingestion of food. Thus, the vomiting of food eaten 24 hours previous is essentially indicative of pyloric stenosis. Bloating is often observed after consuming a meal. In most cases, the appetite remains normal, although most dogs are underweight. Treatment is through dietary modification and drug therapies that involve placing the pyloric muscle at rest with gastric decompression and anticholinergics. In more severe cases, surgery may be required, but the prognosis is generally good.

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Secondary pyloric stenosis, also called cicatricial stenosis, can occur following remission of the main clinical effects after accidental ingestion of packaging materials used to contain household cleaning products, or of products used to unblock sinks, drains and wastepipes. Dermal and ocular discharges may occur following contact. The cicatricial pyloric stenosis is slow in onset and generally fatal.

pylorus - the aperture of the stomach opening into the duodenum. The pyloric sphincter serves as a "gate", closing the opening from the stomach to the intestine.
stenosis - narrowing or contraction of a body passage or opening.
sphincter - the circular muscle that constricts the passage or closes a natural opening. When relaxed, the sphincter allows materials to pass through the opening. When contracted, it closes the opening.
gastric decompression - the return to normal environmental pressure by stomach tube or transperitonel tap; it is an essential part of treatment for acute gastric dilation in dogs and horses.


  1. Textbook of Small Animal Medicine. John K. Dunn
  2. UC Davis Book of Dogs. Mordecai Siegal

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