Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066




The term "hemorrhagic gastroenteritis" basically means inflammation of the stomach and intestine with bleeding. This kind of bleeding inflammation might be seen in patients with parvovirus infection, pancreatitis, inflammatory bowel disease or any number of other conditions but when the term "HGE" is used, it usually refers to a more specific canine syndrome and is an entity in and of itself. To clarify terminology, "HGE" has been renamed "AHDS" which stands for "Acute hemorrhagic diarrhea syndrome." Because this change in nomenclature is recent, you may hear veterinary personnel using either term but, regardless, they are referring to the specific syndrome which we will now describe.

Acute hemorrhagic diarrhea syndrome is a potentially life-threatening intestinal condition of the otherwise healthy dog which manifests as sudden onset bloody, watery diarrhea. The symptoms are extremely dehydrating, often much more than might be expected from the amount of diarrhea, and if it is not promptly treated, the dog can go into shock and can die.

Vomiting is often part of the syndrome; in fact 80% of patients experience vomiting approximately 10 hours prior to the dramatic bloody diarrhea and the vomiting contains obvious blood about 50% of the time. The good news is that with hospitalization and treatment, most dogs recover rapidly. It is crucial to identify AHDS and rule out other serious conditions promptly so that the dog can get the correct treatment and the pet's family can have proper expectations.

Smaller dog breeds seem to have a predisposition towards AHDS though any dog can be affected.
Stress and hyperactivity seem to be predisposing factors.



There are no specific tests for AHDS but a test called a packed cell volume (also called “pcv” or “hematocrit”) is very helpful in making the diagnosis. This test can be performed in most veterinary hospitals using a few drops of blood. The percentage of the blood volume made up by red blood cells is measured. A normal packed cell volume for a healthy dog would be 37-55%, meaning 37-55% of the blood volume should be red blood cells (the rest is fluid and white blood cells). When the patient becomes very dehydrated, there is less fluid present in the bloodstream and the percentage of blood fluid drops (and consequently the percentage of red blood cells rises). In other words, the very dehydrated patient has a very high pcv.

The average AHDS patient will have a pcv of at least 57%.
(It will even be >60% in approximately 30% of patients)

The measurement of the pcv also usually includes some sort of measurement of total protein (sometimes called “total solids”). In AHDS, the total protein measurement from the blood sample is paradoxically normal or low.

Blood sample in a PCV tube being read against a chart
Blood sample in a PCV tube being read against a chart
(original graphic by

There are several aspects to the AHDS syndrome and they do not all have to be present to make the diagnosis. The syndrome elements your veterinarian will be looking for are:

  • Elevated pcv of 57% or more
  • Relatively low total protein
  • At least one episode of vomiting (with or without blood) approximately 10 hours prior to the diarrhea
  • A watery very bloody diarrhea that looks almost like pure blood
  • Relatively young dog (median age is 5 years)
  • Relatively small dog (median size 25 lbs)
  • Rapid response to intravenous fluids

As noted, there are many causes of a bloody diarrhea like this including intestinal foreign body requiring surgery. Expect your veterinarian to need other tests to rule out other potentially more serious conditions.



There are still many unknown factors but the cause appears to begin with infection with an intestinal bacterium called Clostridium perfringens Type A. This organism produces two toxins called "NET E" and "NET F" which are different from the usual Clostridial enterotoxin that is well known to cause diarrhea. The toxin ulcerates the intestinal lining and the intestinal blood vessels become permeable to fluid. In this way, fluid is lost into the intestine dehydrating the patient and the pcv rises while the ulcers are responsible for the bleeding.



The heart of therapy is aggressive fluid replacement. The idea is to get the pcv back to the normal range and keep the patient out of shock. Medication for nausea and pain control are included as is introduction of a low fat diet as soon as the patient is willing to accept food.  As dramatic as the diarrhea is, most patients have an equally dramatic improvement in the first 24 hours of hospitalization and the average dog is out of the hospital after 3 days total in the hospital.

Antibiotics are surprisingly controversial in this syndrome and their use depends on many patient factors (such as presence or absence of fever, white blood cell count, whether or not the expected improvement is achieved etc.

Stool can be expected to gradually return to normal over the course of about one week.

Probiotics (cultures of healthy bacteria) have been recommended to help repopulate the bowel but it is best to start these after recovery is well underway and the intestinal ulcers have healed.


 Page posted: 6/17/2009
Page last updated: 5/19/2019
Page last reviewed: 4/9/2023