Dog gastroenteritis can manifest with severe symptoms indicating a life-threatening condition, including weakened breathing, a slowed heart rate, decreased body temperature, and bloody stools. A dog that refuses to eat or drink might only survive for approximately 3 to 7 days.

Several critical signs can signal the fatal progression of gastroenteritis in dogs. Firstly, a significant decline in vital signs is observed. This includes shallow and slowed breathing, a weak and slow heartbeat, a body temperature dropping below normal, and a faint or absent pulse. Secondly, the presence of hematemesis (vomiting blood) and melena (bloody stools) is a grave indication. In advanced stages of gastroenteritis, extensive bleeding within the digestive tract can lead to these severe symptoms. Finally, a diminished or absent reflex response, such as a lack of pupillary reflex, is a sign of critical deterioration.
A dog that is both anorexic and dehydrated, further complicated by vomiting, can typically survive for roughly 3 to 7 days. This limited survival time is due to three main factors:
First, a dog not consuming any food or water will not survive more than a week, as the body will rapidly deplete its energy reserves.
Second, if the dog is also experiencing vomiting, this indicates that the gastrointestinal tract is not absorbing nutrients and fluids effectively, exacerbating the dehydration and nutrient deficiency.
Third, without any nutritional intake, even the strongest of dogs can only withstand such a lack of sustenance for a maximum of seven days. These factors combined greatly increase the risk of a fatal outcome. Immediate veterinary care is crucial when these signs are noticed.