Causes and Specific Therapy - Hemorrhage in the gastrointestinal tract may have a number of different pathogenetic mechanisms.
Specific therapy for gastrointestinal hemorrhage will depend upon the etiopathogenesis as well as the site of hemorrhage.
Nasal Disease. Causes of epistaxis include systemic processes (quantitative and qualitative platelet disorders, coagulation factor abnormalities,
polycythemia, and hypertension) and local processes (neoplasia, foreign bodies, inflammation, infection, and trauma). Disorders
of epistaxis are not true disorders of gastrointestinal hemorrhage; instead, affected animals manifest G.I. hemorrhage as
a result of swallowing blood emanating from the nasal cavity.
Oropharyngeal Disease. Diseases of the oral and pharyngeal cavities most frequently associated with hemorrhage include severe periodontal disease,
foreign bodies, trauma, and neoplasia. The diagnosis and treatment of these disorders are usually straightforward.
Esophageal Disease. Esophageal foreign bodies should be removed promptly. Prolonged retention increases the likelihood of esophageal mucosal
damage, ulceration, and perforation. Endoscopic retrieval should be the initial approach, but some foreign bodies may require
surgical removal. Followup treatment in severe cases may include gastrostomy tube feedings, oral sucralfate suspensions (0.5-1.0
grams PO TID), and broad spectrum antiobiotics. Esophageal neoplasia are usually malignant and well-advanced at the time of
diagnosis. Chemotherapy, radiation therapy, and surgical resection are the only treatment options. The prognosis is very
poor for cure or palliation. Esophagitis is an acute or chronic inflammatory disorder of the esophageal mucosa that may also
involve the underlying submucosa and muscularis. Regurgitation is the most important sign in cats and dogs with esophagitis.
However, severely affected animals may also manifest excessive salivation, dysphagia, painful swallowing and frank hematemesis.
Gastric Disease. Gastric ulcer is the most important cause of gastric hemorrhage. Most cases of gastric ulcer are associated with drug administration
(NSAIDs, corticosteroids), systemic and metabolic disease (e.g. uremia, liver failure, hypoadrenocorticism), and toxicity.
The pathogenesis of ulcer in these cases likely involves acid/peptic injury as well as disruption of the gastric mucosal barrier.
Although occasional ulcers result from large increases in acid secretion (e.g. gastrinoma and mastocytosis), and acid and
peptic activity is critical to the formation of ulcers, ulcers generally develop only when mucosal defense is also perturbed.
Thus, drugs, systemic and metabolic disease, and toxicity must somehow interfere with the defense mechanisms of the gastric
mucosal barrier. The defense mechanisms contributing to the mucosal barrier include mucosal bicarbonate and mucus secretion,
epithelial cell renewal and restitution, mucosal hydrophobicity, mucosal blood flow, and mucosal prostaglandins. Disruption
of one or more of these components permits acid and pepsin back diffusion into the mucosa and submucosa. Treatment of gastric
ulcer includes specific (e.g. treatment of kidney failure or hypoadrenocorticism) and non-specific therapy.
Small Intestinal Disease. The diagnostic evaluation, causes and specific therapy of small intestinal hemorrhage are similar to those associated with
Large Intestinal Disease. Idiopathic colitis or inflammatory bowel disease is an important cause of lower gastrointestinal hemorrhage in many parts
of the United States. It may occur as a distinct entity or in conjunction with inflammation of the small intestine. There
are likely many inciting causes of inflammatory bowel disease, including infection, toxicity, immunologic reactions to foreign
substances, and neoplasia.
Gastrointestinal Ischemia. Except for intussusception and gastric dilatation/volvulus syndrome, ischemic events are uncommon causes of gastrointestinal
hemorrhage. Mesenteric volvulus, mesenteric thrombosis/infarction, and mesenteric avulsion are all associated with a poor
Systemic Disease. Gastrointestinal hemorrhage may be associated with a number of systemic diseases, including: liver disease, acute pancreatitis,
systemic hypertension, mastocytosis, septicemia and DIC, neoplasia and DIC, hypoadrenocorticism, Rocky Mountain spotted fever,
and Ehrlichiosis. All of these entities should be considered in the initial medical investigation of gastrointestinal hemorrhage.
Recognizing and treating the underlying primary disease will usually resolve the gastrointestinal hemorrhage.
Coagulation Disorders. Gastrointestinal hemorrhage may occur as a consequence of platelet deficiency (thrombocytopenia), platelet defects (thrombocytopathia,
myeloma), coagulation factor deficiency (genetic disorders, liver disease, anticoagulant rodenticide toxicity), or mixed coagulation