Gastric Volvulus (Bloat) in Dogs: A Life Threatening Emergency
Bloat is a life-threatening emergency that affects dogs in the prime of life. The mortality rate for gastric volvulus approaches 50 percent. Early recognition and treatment are the keys to survival.
Anatomy of Bloat
Bloat actually refers to two conditions. The first is gastric dilatation,in which the stomach distends with gas and fluid. The second is volvulus, in which the distended stomach rotates on its long axis. The spleen is attached to the wall of the stomach, and therefore rotates with the stomach.
Gastric dilatation may or may not be complicated by volvulus. If volvulus occurs, the stomach may twist 180 degrees or less (technically called a torsion). An actual volvulus is a twist of 180 degrees to 360 degrees or more.
During volvulus, the pylorus is pulled out of position and becomes displaced to the left of the gastroesophageal junction. This pinches off the duodenum and prevents fluid and air from escaping from the stomach through the pyloric canal. Simultaneously, the gastroesophageal junction becomes twisted and obstructed, preventing the dog from belching and vomiting. Gas and fluid are trapped in the closed-off stomach, which becomes hugely distended as the material ferments. Interference with blood circulation results in necrosis of the wall of the stomach.
This sequence produces a number of other problems, including acute dehydration, bacterial septicemia, circulatory shock, cardiac arrhythmias, gastric perforation, peritonitis, and death.
Bloat can occur in any dog at any age, but typically occurs in middle-aged to older dogs. There may be a familial association. Large-breed dogs with deep chests are anatomically predisposed. These breeds include the Great Dane, German Shepherd Dog, St. Bernard, Labrador Retriever, Irish Wolfhound, Great Pyrenees, Boxer, Weimaraner, Old English Sheepdog, Irish Setter, Collie, Bloodhound, and Standard Poodle. Chinese Shar-Pei and Basset Hounds have the highest incidence among midsize dogs. Small dogs are rarely affected, with the exception of Dachshunds, who are also deep-chested.
Bloat develops suddenly, usually in a healthy, active dog. The dog may have just eaten a large meal, exercised vigorously before or after eating, or drank a large amount of water immediately after eating.