Effects of Gastrointestinal Obstruction
Regardless of whether they are partial or complete, gastrointestinal (GI) obstructions cause ingested food, fluids and bodily secretions to accumulate in the stomach and/or the small intestine, at some point upstream from the site of the blockage. This not only creates a physical barrier to the normal flow of food and the process of digestion, but it also puts abnormal pressure on key blood vessels that supply blood, oxygen and other nutrients to the highly sensitive, gastrointestinal tissues. When this happens, the blood supply to the digestive tract is interrupted.
The stomach and intestines are not very tolerant of disruptions to their blood supply. It does not take long for gastrointestinal tissue to start dying once its blood supply is compromised, a process called necrosis. Necrotic tissue rapidly becomes fragile and predisposed to perforating. Basically, when the arteries that supply blood to the digestive tract are impaired, affected tissue starts falling apart, which in turn permits food particles, fluids, stomach and pancreatic acids, enzymes, bacteria and other gastrointestinal content to spill into the abdominal cavity. This can quickly cause an extraordinarily painful and extremely dangerous condition known as “septic peritonitis.” “Sepsis” refers to the presence of pathogenic microorganisms (bacteria, virus, fungus, protozoa or algae) or their toxins in blood or other tissues. The “peritoneum” is the sensitive tissue lining the abdomen. Peritonitis can kill a dog if it is not caught and aggressively treated very early in the course of the disease.
Dogs with GI obstructions usually will have some degree of abdominal discomfort, ranging from mild to severe, depending on the nature and extent of the blockage. They may become nauseous, lethargic, weak and depressed and may vomit and strain to defecate. They often aren’t hungry, because they feel “stopped up.” They may become bloated from accumulating gas, which can be life-threatening.
Symptoms of Gastrointestinal Obstruction
The observable symptoms of GI obstruction may vary depending upon where the obstruction is located and whether it is partial or complete. However, most dogs with GI obstructions develop one or more of the following clinical signs:
- Vomiting, which is always accompanied by forceful abdominal contractions, is the hallmark of gastrointestinal obstruction. It must be differentiated from regurgitation, which is a much more passive process and usually, although not always, occurs fairly soon after a meal.
- Abdominal discomfort and pain (biting at the belly; going into a praying position)
- Dark, tarry stools (due to the presence of digested blood; melena)
- Reduced or infrequent passage of feces (with a partial blockage, feces may continue to pass normally
- Straining to defecate
- Abdominal bloating; gas accumulation
- Loss of appetite
- Weight loss
- Excessive drooling
Dogs at Increased Risk
Dogs that tend to swallow inappropriate things, like sticks, stones, bones, yarn and the like, have an increased chance of developing blockage of their stomachs or intestinal tract. Brachycephalic breeds - those with broad heads and very short, flat faces - are predisposed to being born with a condition called “congenital pyloric stenosis,” which is one of the things that can contribute to gastric outflow obstruction. These breeds include Boxers, Boston Terriers, Bulldogs, King Charles Cavalier Spaniels, Pekingese and Pugs. Lhasa Apsos, Pekingese, Poodles and Shih Tzus are predisposed to developing acquired chronic hypertrophic pyloric gastropathy (CHPG), another potential cause of gastric outflow obstruction. Gastric dilatation and volvulus (GDV; bloat; torsion) is seen most often in large, deep-chested breeds, like the Great Dane, German Shepherd Dog, Saint Bernard, Irish Wolfhound, Labrador Retriever, Great Pyrenees, Old English Sheepdog, Boxer and Doberman Pincer. GDV is a fairly common and potentially life-threatening condition that is a true medical emergency.