Dog Hemorrhagic Gastroenteritis (AHDS): Bloody Diarrhea Signs

Hemorrhagic gastroenteritis (HGE) — now more precisely called acute hemorrhagic diarrhea syndrome (AHDS) — causes sudden, severe bloody diarrhea in dogs, often accompanied by vomiting and rapid dehydration. Most dogs respond dramatically to IV fluids within 24–48 hours, but without treatment, hemoconcentration can progress to shock. Small and toy breeds are most commonly affected.

Last reviewed: June 2026

What Is Hemorrhagic Gastroenteritis (AHDS) in Dogs?

Hemorrhagic gastroenteritis (the traditional name) has been renamed acute hemorrhagic diarrhea syndrome (AHDS) to better reflect its GI-specific nature, since the stomach is often not the primary site. AHDS is characterized by sudden-onset bloody diarrhea — often described as "raspberry jam" in consistency — with rapid hemoconcentration (elevated PCV and protein despite active blood loss).

The underlying mechanism appears to involve Clostridium perfringens NetF toxin causing intestinal epithelial cell death and massive fluid secretion into the gut lumen. The condition is not contagious and does not typically involve bacterial invasion of the intestinal wall.

Small breeds — Miniature Schnauzers, Yorkshire Terriers, Maltese, Dachshunds, Poodles — are significantly over-represented. Dietary indiscretion, stress, or a change in food can be precipitating factors, but no trigger is identified in many cases. According to a large case series published in the Unterer et al., 2018, JVIM, the condition is more common in young to middle-aged small-breed dogs, with a median age of 5 years.

Signs of AHDS in Dogs

• Sudden, copious bloody diarrhea — often raspberry-jam appearance, onset within hours
• Vomiting — may occur before or alongside diarrhea
• Rapid onset of lethargy and weakness — hemoconcentration depletes circulating fluid volume quickly
• Abdominal discomfort — hunching, guarding, reluctance to move
• Loss of appetite
• Dogs can progress from apparently normal to severely ill within 4–8 hours

The hematocrit (PCV) may be strikingly elevated — often 55–65% — even as total protein drops from protein loss through the damaged gut wall. This pattern (high PCV + low protein) is characteristic of AHDS.

Treatment of Dog AHDS

IV fluid therapy is the cornerstone of treatment and is highly effective when started early. Crystalloid fluids (lactated Ringer's, Normosol) restore intravascular volume rapidly. Most dogs show marked improvement within 12–24 hours.

Additional treatments:

• Anti-emetics (maropitant, ondansetron) for vomiting
• Antibiotics: once routine, now reserved for cases with evidence of sepsis or bacterial involvement — routine antibiotic use in uncomplicated AHDS is no longer standard due to antimicrobial stewardship concerns
• GI protectants (sucralfate, omeprazole) for mucosal healing
• Bland diet transition once vomiting resolves

As described in Nelson & Couto's Small Animal Internal Medicine, oral food intake is typically reintroduced within 24–36 hours once vomiting has stopped, with a bland diet (boiled chicken and rice or prescription GI food) for 3–5 days before transitioning back to a regular diet.

When to See a Vet

Call your vet today if:

• Your dog has bloody diarrhea of any amount — even one episode warrants same-day evaluation
• Your dog has vomited and also has bloody diarrhea simultaneously
• Your dog is lethargic, seems weak, or is reluctant to walk after a bout of bloody diarrhea
• Your small-breed dog ate something unusual or had dietary stress in the past 24 hours

Go to the ER immediately if:

• Your dog is collapsed or cannot stand
• Gums are pale, white, or tacky (signs of shock)
• Bloody diarrhea is continuous — more than 3–4 bouts in 2 hours
• Your dog is trembling, cold to the touch, or has a rapid weak pulse

Frequently Asked Questions

How much does treating AHDS in dogs cost? A same-day exam and bloodwork to confirm AHDS runs $200–400. IV fluid hospitalization for 24–48 hours costs $500–1,200. Anti-emetics, GI protectants, and monitoring add $100–300. Total typical AHDS episode cost is $700–2,000. Complicated cases with septic complications can run higher.

How quickly do dogs recover from hemorrhagic gastroenteritis? Most dogs treated promptly with IV fluids show dramatic improvement within 24 hours and are discharged within 1–2 days. Stool may remain loose or discolored for several days but serious illness resolves quickly in straightforward AHDS.

Is AHDS contagious to other dogs or people? AHDS is not contagious. It is not caused by a transmissible virus or bacterium that spreads between dogs or from dog to human. There is no need to quarantine an AHDS dog from other household pets.

Can I treat my dog's bloody diarrhea at home? No — AHDS can progress to life-threatening shock within hours. Home management is not appropriate. Any dog with bloody diarrhea, especially combined with vomiting and lethargy, should be seen by a vet the same day or immediately.

Does hemorrhagic gastroenteritis come back? Recurrence is possible, affecting roughly 10–15% of dogs within a year. Identifying and managing dietary triggers — avoiding rich foods, scraps, or sudden food changes — may reduce recurrence risk.

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