What is acute haemorrhagic diarrhoea syndrome in dogs?

In dogs, acute haemorrhagic diarrhoea syndrome (previously called haemorrhagic gastroenteritis HGE) occurs when large amounts of fluid seep into the gut. It’s not known precisely what causes all cases of AHDS in dogs, but it can lead to severe vomiting and bloody diarrhoea in dogs. Sometimes the diarrhoea contains so much blood it resembles raspberry jam. While AHDS can be seen in dogs of all ages and breeds, it is commonly diagnosed in the following breeds: labrador retrievers, miniature pinschers, miniature Schnauzers, miniature poodles, Maltese and Yorkshire terriers. The average age of dogs diagnosed with AHDS is five, and most cases occur without warning.

What to do if your dog is showing signs of AHDS?

AHDS is a life-threatening condition. Untreated, it can quickly lead to hypoglycaemia, which is low blood sugar, or hypovolemic shock, which occurs when a dog’s blood or fluid levels drop dramatically. You should contact your vet immediately if your dog or puppy shows signs of the disease, as it can be fatal.

An image of a brown dog laying down on the floor looking sad for Vets Now article on dog gastroenteritis
Acute haemorrhagic diarrhoea syndrome in dogs is a life-threatening condition. Untreated, it can quickly progress to hypoglycemia.

What causes acute haemorrhagic diarrhoea syndrome in dogs?

The cause of AHDS in dogs has been the subject of vigorous debate and research, but it remains unknown. Theories have ranged from bacterial infections, allergic reactions to food, parasites and toxins. It often affects highly strung dogs, so stress, anxiety and hyperactivity have been cited as possible contributing factors.

How is AHDS in dogs diagnosed?

Your vet should be able to give you a diagnosis based on your dog’s symptoms and the results of a blood test. Dogs with acute haemorrhagic diarrhoea syndrome usually have a higher than normal packed cell volume (PCV), which measures the proportion of red blood cells in their bloodstream. It’s likely your vet will also take steps to rule out other causes of gastrointestinal issues and blood in the stools such as parvovirus, Addison’s disease, intestinal parasites and rat poison intoxication. This may involve carrying out additional tests including x-rays, ultrasound, a biochemistry panel and taking urine and faecal samples.


Haemoconcentration is one of the most dependable findings in dogs with AHDS. It occurs when there is a very high percentage volume of red blood cells compared to fluid volume of blood. It’s usually caused by a dramatic loss of water and electrolytes such as sodium, potassium and chloride.

Why is my dog not eating after AHDS?

Dogs with AHDS will often appear severely ill and, in most cases, won’t regain their appetite for at least a few days. Your vet will unlikely feed your dog during the first 24 hours of treatment. After that, once their condition has started to improve and they’re no longer being sick, water and small, bland meals can be offered.

An image of a dog looking unwell for Vets Now article on haemorrhagic diarrhoea in dogs, answering the question 'my dog is pooping blood and diarrhea?'
acute haemorrhagic diarrhoea syndrome in dogs occurs when large amounts of fluid seeps into the gut.

You might also be interested in:

Treating AHDS in dogs

As AHDS can result in severe dehydration, aggressive intravenous fluid therapy (putting a dog on a drip) is usually the mainstay of treatment. Anti-nausea and anti-diarrhoea medication may also be administered if your dog is repeatedly sick. Research has shown that antibiotics have no benefit in treating the majority of cases of AHDS and are only necessary in dogs with other underlying conditions or dogs who show signs of possible sepsis. In the most severe cases, plasma may be needed to correct low blood protein levels.

AHDS survival rate

The prognosis for AHDS in dogs is generally good as long as treatment is early, appropriate and aggressive. In most cases, dogs with AHDS will need to be hospitalised for at least 24 hours, with the average hospital stay being 3 days in dogs with AHDS. It’s estimated fewer than 10% of dogs who are treated for AHDS will die. However, there is a 10 to 15% chance of the condition recurring. The outlook may be worse for very young dogs, or those with other illnesses.

Prevention of AHDS in dogs

Prevention advice is based mainly on common sense. For example, owners should try to ensure their dogs live in a low-stress environment, are fed a high-quality balanced diet and given parasite preventive medications as directed by their daytime vet.