AHDS is characterized by peracute onset of vomiting, followed by lethargy, anorexia, hematemesis, and large volumes of malodorous hemorrhagic diarrhea.1 In a prospective study of 108 dogs with AHDS, diarrhea occurred a median of 10.5 hours after the onset of vomiting.1
Dogs with AHDS have severe mucosal necrosis and minor neutrophilic infiltrate of the small and large intestines, resulting in secretory and malabsorptive diarrhea.2 Transudation of water, electrolytes, and protein, and disrupted sodium transport mechanisms leads to significant fluid loss.3 Subsequent hypovolemia and dehydration occur early during the disease.
Hypovolemia results in tachycardia, peripheral vasoconstriction (ie, pale mucous membranes, delayed capillary refill times, cool distal extremities), low rectal temperature, depressed mentation, and diffuse muscle weakness.1