Sources of vitamin K include K1, which is synthesized by plants and is present in food, and K2, which is synthesized by bacteria in the intestinal tract. Vitamin K1 and K2 are fat-soluble compounds. K1 is absorbed in the proximal small intestine whereas K2 is absorbed in the ileum and colon. Vitamin K3 is a synthetic compound that is less lipid soluble and is absorbed in the ileum and colon.
- Dietary lack: Dietary lack of vitamin K has not been reported as a cause of bleeding in adult animals. However, newborn animals are more at risk for bleeding due to dietary lack of this vitamin, for several reasons. Milk does not contain much vitamin K and the intestinal flora that is an important source of vitamin K is not well established until after birth. Additionally, the liver in neonatal animals is still immature and not as effective in the synthesis of coagulation factors as it is in older animals. Nevertheless, clinical bleeding attributable to dietary vitamin K deficiency is rare in newborn as well as in adult animals.
Porcine Hemorrhagic Syndrome is a severe, sporadic, vitamin K-responsive bleeding disease in recently weaned pigs. The syndrome is thought to result from combined factors including low liver stores of vitamin K, possible low dietary levels of vitamin K, and reduced synthesis caused by antibiotics added to the rations.
- Malabsorption: Deficiency of vitamin K resulting from decreased synthesis in the intestine and/or decreased absorption is an uncommon cause of bleeding but has been recognized. Any cause of cholestasis (e.g. complete biliary obstruction) that results in decreased bile secretion into the intestine (bile is important for fat emulsification and hence fat and vitamin K absorption) or fat malabsorption (exocrine pancreatic insufficiency, severe infiltrative bowel disease) can result in decreased vitamin K. Therefore, the potential for bleeding due to vitamin K deficiency must be considered in the treatment of dogs and cats with certain types of diseases (e.g. hepatic lipidosis in cats) and for livestock raised under certain management conditions. Animals with these disorders should still get enough vitamin K from bacterial synthesis and absorption in the ileum and colon, but sometimes they do develop coagulopathies that are vitamin K-responsive. Antibiotics should be used carefully in such patients because of the potential of altering gut flora and decreasing K2 synthesis.
Vitamin K deficiency causes the same pattern of coagulation test results as does anticoagulant rodenticide poisoning.
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