TL;DR: Black tarry stool, or melena, is a serious medical emergency indicating upper gastrointestinal bleeding that requires immediate veterinary evaluation.
What does it mean if my dog has black, tarry stool?
Black, tarry, or sticky stool is medically referred to as melena. Unlike bright red blood, which indicates bleeding in the lower digestive tract, melena consists of blood that has been digested. This means the bleeding is occurring in the upper gastrointestinal tract, such as the esophagus, stomach, or the first part of the small intestine. The dark color and sticky texture are the result of blood reacting with stomach acid and digestive enzymes.
Is black, tarry stool a veterinary emergency?
Yes, the urgency level for melena is High. Black tarry stool is almost always a sign of a serious underlying condition that requires immediate veterinary intervention. Potential causes include:
- Internal bleeding from a stomach ulcer
- Ingestion of toxins, such as rodenticides
- Organ failure
- Severe infections
If your dog exhibits melena alongside pale gums, extreme lethargy, or vomiting, they should be taken to an emergency animal hospital without delay.
Why should I take a photo of my pet's stool to help with triage?
Providing your veterinarian with a clear photograph of the stool can significantly speed up the triage process. A photo helps the medical team in the following ways:
- Confirms the presence of melena versus other types of discoloration caused by diet or medication.
- Allows the vet to better estimate the severity of the blood loss based on color and consistency.
- Helps the clinic prepare the necessary diagnostic tools or stabilization treatments before you even arrive.
Clinical Context (Merck Veterinary Manual)
Black, tarry feces (melena) in dogs indicate hemorrhage in the stomach or upper part of the small intestine. The vomitus in a dog with a bleeding lesion, such as a gastric ulcer or neoplasm, may contain frank blood or have the appearance of coffee grounds. Blood and fibrinous casts in the feces can indicate a hemorrhagic, fibrino-necrotic enteritis of the small or large intestine.
Chapter: Gastroenterology, Infectious Disease
Source: The Merck Veterinary Manual, 11th Edition (Page 156)