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HGE (Hemorrhagic Gastroenteritis) is sudden, heavy bloody diarrhea in a dog, usually with vomiting. It mostly affects small breeds, and it's an emergency because the gut loses fluid faster than a small dog can replace it. With IV fluids in hospital, fewer than 10% of dogs die.1
Key Takeaways
Bring your dog in now if the stool looks like raspberry jam, they're vomiting blood, they can't keep water down, or they seem weak or have pale gums. Call us at (519) 896-0532, or use our emergency page after hours.
HGE, short for hemorrhagic gastroenteritis, is an attack of bloody diarrhea caused by damage to the lining of the intestines.1 The intestinal wall turns leaky, and fluid, protein and red blood cells pour into the gut and leave as diarrhea. That's why dogs dehydrate so fast.1
Vets now call it acute hemorrhagic diarrhea syndrome, or AHDS. Biopsies taken during the illness found damage in the intestines but none in the stomach, so the "gastro" in the old name didn't fit.8 Both names describe the same condition.
Small and toy breeds are affected most, especially Yorkshire Terriers, Miniature Pinschers, Miniature Schnauzers, Miniature Poodles and Maltese.1,7 A study of 108 dogs with HGE put the median age at 5 and the median weight under 10 kg, and found that cases peaked in winter.7
The cause isn't proven. The strongest suspect is a toxin-producing strain of Clostridium perfringens, a common gut bacterium.1
Biopsies from dogs with HGE found C. perfringens on the damaged small intestine in every dog tested.8 A later study found the dead tissue coated in the bacteria, and every strain it typed carried the gene for NetF, a toxin that punches holes in cells.5
Those toxin genes turn up in the stool of 48% of dogs with HGE, 12% of healthy dogs, and none of the dogs with parvovirus.6 Because healthy dogs carry them too, the bacteria alone can't explain why one dog gets sick and another doesn't.6
The main sign is heavy bloody diarrhea that comes on suddenly. In severe cases it looks like raspberry jam.1
Weakness, collapse and pale gums mean fluid loss is tipping the dog into shock. A dog that stays flat once IV fluids are running may have bacteria crossing the damaged gut wall into the blood, and that dog needs more than fluids.1,3
A dog with fresh blood in the stool who's bright, eating and not vomiting usually has something milder, explained in blood in your dog's stool when they're acting normal. Soft stool with mucus and some blood after a stressful event is typical of stress colitis.
Age and vaccination history usually point toward one or the other, and a stool antigen test checks for parvo. It can miss early infections, so a negative result in a high-risk puppy may need repeating.4
| HGE (AHDS) | Parvovirus | |
|---|---|---|
| Typical dog | Small or toy breed adult, median age 57 | Puppy 6 weeks to 6 months, or any unvaccinated dog4 |
| Bloodwork | High red cell count with normal or low protein1 | Low white cell count4 |
| How it's diagnosed | Ruling out other causes1 | Stool antigen test4 |
| Contagious | No1 | Highly, and the virus survives for months in the environment4 |
| Vaccine | None | Core puppy vaccine4 |
Parvovirus is one of the two Ps in the DA2PPL vaccine. A puppy or unvaccinated dog with bloody diarrhea should be kept away from other dogs until parvo has been ruled out.
No single test confirms HGE. The diagnosis comes from the typical signs plus bloodwork, once other causes of bloody diarrhea have been ruled out.1
The classic clue is a high packed cell volume (PCV), the share of the blood made up of red cells, with normal or slightly low protein.1 Water leaves the bloodstream and concentrates the red cells, while protein leaks into the gut. On a blood test it looks like a raised red cell count, a form of polycythemia.
A normal PCV doesn't rule HGE out. The 108-dog study found a median PCV of 57%, with only about half the dogs above the normal range and 31% over 60%.7
Ruling those out usually means:1
IV fluids, started as soon as possible. They replace what's pouring into the gut.1 Dogs with very low protein or in shock may also need plasma.1
A bright dog who's still drinking can sometimes go home on fluids under the skin and a bland diet. The rest stay with us on IV fluids.
Most dogs with HGE don't need antibiotics. In a placebo-controlled trial of 60 dogs with no signs of sepsis, amoxicillin-clavulanate didn't change survival, time in hospital or how fast the signs improved.2 In a second trial, in dogs with bloody diarrhea severe enough to need IV fluids, adding metronidazole to amoxicillin-clavulanate didn't get dogs home any sooner.9
The 2024 ENOVAT guidelines recommend against antibiotics for bloody diarrhea in mild and moderate cases, based on high-certainty evidence.3 Antibiotics are kept for dogs that stay unwell despite fluids, or whose neutrophils, the white blood cells that fight bacteria, are very high or very low. In those dogs, gut bacteria may be getting into the bloodstream.1,3
Supportive care often includes:
Probiotics are optional. The ENOVAT panel recommends neither for nor against them.3 One small trial treated dogs with HGE without antibiotics. Those on a probiotic improved clearly by day 3, against day 4 on placebo.10
The first 48 hours of treatment usually bring the biggest change.7 In the metronidazole trial, run in general practice, dogs on IV fluids went home after 26 to 30 hours on average.9
Fewer than 10% of dogs treated in hospital die. The death rate is much higher in dogs that go untreated, which is why a small dog with bloody diarrhea shouldn't wait until morning.1
Recovery is usually complete, but some dogs develop gut problems later. A follow-up study a median of 4 years after an episode found signs of chronic gut disease in 28% of dogs that had HGE, against 13% of matched dogs that never had it.11 Tell your vet if diarrhea or vomiting keeps coming back.
If your dog has bloody diarrhea right now, call us at (519) 896-0532.
No. HGE isn't considered contagious. The toxin-producing strain of Clostridium perfringens linked to it also turns up in about 12% of healthy dogs that never get sick, so carrying it isn't enough to cause HGE. Parvovirus is different. It also causes bloody diarrhea and it's highly contagious, so keep a puppy or unvaccinated dog with bloody diarrhea away from other dogs until your vet has tested for parvo.
There's no proven way to prevent it, because the trigger isn't fully understood. A small dog with bloody diarrhea and vomiting should see a vet the same day, since dogs treated early do well. Keeping your dog's parvovirus vaccine up to date protects against a look-alike that is far more contagious.
Nobody knows for certain. The strongest lead is a toxin-producing strain of Clostridium perfringens, which has been found on the damaged intestine of dogs with HGE and in about half of their stool samples. Some healthy dogs carry the same strain without getting sick, so something else has to tip the balance. There's no evidence that HGE comes from anything you fed your dog or did.
Don't wait to find out. The death rate is high in dogs with HGE that go untreated, while fewer than 10% of dogs die once they're on IV fluids in hospital. A mild case in a bright dog who's still drinking can sometimes be treated at home, but that decision needs an exam first.
Small, frequent meals of a bland, low-fat, easily digested food, started once the vomiting has settled. Your vet may send home a prescription gastrointestinal diet. Dogs in one HGE trial stayed on a gastrointestinal diet for three weeks. Once the stool is back to normal, switch back to the usual food gradually over several days.
Most dogs recover fully, but some have gut trouble later. In a study that followed dogs for a median of 4 years, 28% of dogs that had HGE later showed signs of chronic gut disease, compared with 13% of similar dogs that never had it. Tell your vet if diarrhea or vomiting keeps coming back.
Yes, if it isn't treated. Dogs can lose so much fluid into the gut that they go into shock. With prompt IV fluids in hospital, fewer than 10% of dogs die, and most are much better within two days.
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