There are few things more frightening for an owner than watching their horse collapse without warning or apparent cause. By the same token, unraveling the cause behind an equine collapse often presents veterinarians with a diagnostic challenge, and in many cases the root cause of a horse’s collapse can’t be determined.

At the 2013 American College of Veterinary Internal Medicine Forum, held June 12-15 in Seattle, Wash., Neil P.H. Hudson, MA, VetMB, PhD, DEIM, DipVetClinStud, MRCVS, a senior lecturer at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies, reviewed with veterinarians how to diagnose a collapsed horse and listed some common diagnoses.

Hudson said there are several definitions for equine collapse, but noted for the purpose of his lecture he would define collapse as "an animal becoming acutely recumbent (lying down) with or without the loss of consciousness