TL;DR: Black, tarry stool (melena) indicates serious internal bleeding and is a high-priority veterinary emergency. You should contact an emergency veterinarian immediately to prevent life-threatening complications like anemia or shock.
What is black tarry stool in dogs and what causes it?
Black, tarry, or sticky stool in dogs is medically known as melena. This appearance is caused by the presence of digested blood that has originated from the upper gastrointestinal tract, such as the stomach or the esophagus. The blood turns dark and sticky as it passes through the digestive enzymes of the small intestine.
Is black tarry stool a veterinary emergency for my dog?
Yes, the urgency level for melena is High. Black stools often indicate significant internal bleeding, which can quickly lead to anemia or shock. Potential causes include:
- Stomach ulcers
- Ingestion of toxins (such as rodenticide)
- Severe infections
- Organ failure
Contact an emergency veterinarian immediately, especially if your dog is also lethargic or has pale gums.
How does taking a photo of my dog's stool help the veterinarian with triage?
When you call or arrive at the vet, providing a clear photo of the stool can significantly assist the medical team in the following ways:
- It helps the triage nurse or veterinarian confirm the presence of melena versus dark stool caused by diet or medication.
- Visual evidence allows the team to prioritize your pet correctly in a busy clinical setting.
- It enables the medical team to begin life-saving diagnostics faster.
Clinical Context (Merck Veterinary Manual)
Black, tarry feces (melena) in dogs indicates hemorrhage in the stomach or small intestine. Vomitus in a dog with a bleeding lesion (gastric ulcer or neoplasm) may also contain frank blood or have the appearance of coffee grounds.
Chapter: Gastroenterology, Infectious Disease
Source: The Merck Veterinary Manual, 11th Edition (Page 156)