Bloody Diarrhoea in Dogs
Blood in a dog’s diarrhoea is always worth acting on. What fresh blood and black tarry stool each mean, and why puppies need seeing urgently.
Is this an emergency?
Bloody diarrhoea in a puppy can be parvovirus, which moves fast and is often fatal. Any dog passing blood with vomiting or lethargy needs to be seen the same day.
Blood in the stool always needs attention. How urgently depends on how much, what it looks like, and how the dog is in itself.
Two kinds of blood
Fresh red blood, often with mucus, comes from the large intestine or rectum. It looks alarming and is frequently the less serious of the two.
Black, tarry, sticky stool is digested blood from the stomach or small intestine. It looks less dramatic and is usually more serious, because it means bleeding higher up.
Tell us which you are seeing.
Parvovirus in puppies
Any puppy or unvaccinated dog with bloody diarrhoea should be assumed to have parvovirus until proven otherwise.
Parvovirus causes severe vomiting, profuse bloody diarrhoea with a characteristic smell, rapid dehydration and collapse. It is often fatal without intensive treatment, and it moves within hours.
The virus survives in the environment for months and resists most household disinfectants. Call before you arrive so we can bring the dog in without exposing other patients.
Completing the puppy vaccination course is the protection, and a puppy is not protected until the course is finished.
Haemorrhagic gastroenteritis
A sudden onset syndrome, seen especially in small breeds, with vomiting and a large volume of diarrhoea that looks like raspberry jam. Dogs lose fluid into the intestine very quickly and can go into shock within hours despite looking well beforehand.
It responds well to prompt intravenous fluids, and badly to being watched overnight.
Other causes
Dietary indiscretion and scavenging. Intestinal worms and whipworms. Bacterial infection. Foreign bodies. Anti-inflammatory painkillers, including human ones, causing gastric ulceration. Poisoning, particularly rodenticides, which stop the blood clotting. Colitis from stress. Inflammatory bowel disease. Tumours in older dogs.
What to do
Do not attempt to manage bloody diarrhoea at home. Withhold food but leave water available, and call.
Take a photograph of the stool, or bring a sample. It is genuinely useful and saves time.
Do not give human anti-diarrhoeal medication, and do not give painkillers.
When it is urgent
Immediately if the dog is a puppy or unvaccinated, if there is vomiting alongside, if the gums are pale or white, if the dog is weak, collapsed or cold, if the abdomen is painful or swollen, or if rat poison could have been eaten.
Otherwise the same day. Blood in the stool is not something to watch over a weekend.