Bowel obstruction in dogs is not associated with any particular symptom. The symptoms exhibited by a dog with a blocked gastrointestinal tract are very similar to those of many other diseases in dogs making it very difficult to diagnose bowel obstruction just by looking at the dog.
Usually bowel obstruction in dogs is diagnosed by imaging but the first sign of this is usually loss of appetite and vomiting. As a result of a blocked esophagus stomach or intestines a dog will become completely uninterested in eating.
Its common to see dogs pacing or drooling when they have a blocked stomach or intestines. Also watch for any attempts to retch. A dog with a blockage will retch to try to vomit whatever is stuck in its gastrointestinal tract especially if it swallowed something that caused the blockage.
Over time the dog may start to show other symptoms such as lethargy abdominal pain diarrhea and depression. A dogs intestinal blockage can be severe and in rare cases a prolonged obstruction can lead to intestinal rupture septicemia and even death.