[Congenital deficiency of factor XI: diagnosis and therapy in surgical patients (author's transl)].

Factor XI deficiency has to be diagnosed preoperatively since it may be symptomless until revealed by bleeding after surgical procedures. Replacement therapy prior to operation is advocated and its management defined; because the effects of plasma infusion on factor XI level are not constant and because of the wide variation in the half life of infused factor, it is strongly advised that regular measurement should be made when possible. Ovariectomy in a factor XI deficient patient was carried out with correct haemostasis.