<p>Perioperative and periprocedural bleeding complications substantially increase the morbidity and mortality. The main causes are intervention-related or trauma-related factors, patient-related factors, such as congenital or acquired hemostatic disorders as well as pre-existing medicinal anticoagulation as a&#xa0;result of the underlying disease. Despite the variety of currently available test procedures, the constellation of a clinically relevant bleeding situation without tangible pathological laboratory findings or causes often occurs. This constellation, called bleeding disorder of unknown cause (BDUC), requires a structured diagnostic and therapeutic approach to improve the outcome of the patient, to avoid a&#xa0;therapeutic polypragmasia and to limit the administration of hemostatics to that which is absolutely necessary. The close monitoring of these patients, whose quality of life is often restricted, is meaningful and necessary.</p>