[Vitamin K deficiency caused by nutritional malabsorption accompanying afferent loop obstruction:a case report].

: This case involves a 73-year-old man who visited a clinic because he was experiencing dyspnea on exertion and acid reflux. He was diagnosed with anemia and referred for a medical check-up and treatment by his primary care physician. Iron deficiency anemia and prolonged prothrombin time were confirmed with a blood test and an abdominal enhanced CT revealed marked expansion of the afferent loop after a gastrectomy. The medical check-up revealed abnormal blood coagulation due to afferent loop obstruction, which resulted in vitamin K deficiency. He was supplemented with vitamin K, and surgery was performed for the afferent loop obstruction. Postoperatively, his anemia, nutritional status, serum vitamin K levels, and prothrombin time improved steadily. In conclusion, nutrient malabsorption may occur in cases of afferent loop obstruction and abnormal blood coagulation due to vitamin K deficiency.