Acute haemorrhagic diarrhoea syndrome (AHDS/HGE)

Overview

A dramatic and rapidly dangerous syndrome in which the gut lining leaks blood and fluid into the intestine. What makes it lethal is not the visible blood but the invisible fluid shift: a dog can go into shock within hours as its circulating volume drains into its own gut. Small breeds (Miniature Schnauzer, Yorkshire Terrier, Miniature Poodle, Maltese) are over-represented. The critical thing for an owner to know is that this looks superficially like 'a bad tummy' and is not — a dog with sudden bloody diarrhoea and lethargy needs to be seen the same hour, not the next morning. Aggressive intravenous fluid support is the mainstay of treatment and is what saves these dogs; the vet will also rule out parvovirus, poisoning, and intestinal obstruction, which can look identical at presentation.

What you would notice

• Sudden, profuse, bright-red bloody diarrhoea, often described as raspberry jam
• Vomiting, frequently before the diarrhoea starts
• Rapid, dramatic collapse into lethargy — worse than the volume of loss suggests
• Pale gums, fast heart rate, shock
• Usually a previously healthy, often small-breed dog

Sources

• Merck Veterinary Manual (merckvetmanual.com)
• MSD Veterinary Manual (msdvetmanual.com)

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