Bloody Stools in Dogs

By Rena Sherwood

Old or fresh blood in a dog's droppings is a sign that a vet needs to be contacted as soon as possible. Note any other unusual symptoms, such as a pot-bellied appearance, lethargy, loss of appetite, a reluctance to be touched around the abdomen, vomiting or diarrhea. Bloody stool in dogs usually gets worse with time. Take a fresh stool sample when taking the dog to the vet.


There are two types of bloody stool in dogs, differentiated by the color of the blood. Fresh, bright-red blood is called hematochezia. It's red because it has not gone through the dog's digestive system. Black, soft stools that resemble tar are called melena. The blood is so dark because it has gone through the dog's digestive system.


If a dog is excreting pools of strong-smelling, dark-red blood and not much else, take the dog to a vet immediately. According to "The Veterinarians' Guide to Your Dog's Symptoms," this means the dog is suffering from hemorrhagic gastroenteritis. This is a mostly mysterious digestive disease that comes on suddenly. The dog loses fluids as well as blood and may soon go into shock and die.

Causes of Bright Blood

Bright-red blood in the stools could be from an injury to the rectum or underneath the tail. One common cause is constipation. Because of the constant straining, the skin becomes irritated and bleeds. Sometimes the cause is a urinary infection. The blood from the urinary tract can coat stool if the dog squats and urinates and excretes at the same place. Parasites such as hookworms and whipworms can also be the cause of flecks or spots of blood coating the stool.

Causes of Dark Blood

There are numerous causes for dark or tarry stools in dogs, and all of them are serious. According to veterinarian Dr. Bari Spielman, these causes include eating a large quantity of blood, cancer, damage to internal organs, digestive diseases such as Giardia, other illnesses such as parvovirus, a complication from surgery or a bad side effect from starting a new medication. Another possible cause is that the dog has swallowed a foreign object or even a sharp pieces of bone, which has cut the internal organs.


Treatment varies according to the exact cause of the blood in a dog's feces. The primary goal is to get the dog stable enough for more diagnostic tests, usually by giving painkillers and intravenous fluids. Diagnostic tests include a complete blood count, X-rays and checking the stool for parasites or infectious bacteria.