Phlebology as a branch of medicine studying venous diseases is faced with some critical conditions requiring immediate surgical intervention. The authors present several patients with venous diseases. Considering own experience and literature data, the authors recognized not only intraoperative complications, but also acute lesions of inferior vena cava caused by thrombosis, embolism, bleeding and inflammation as emergency situations in the treatment of patients with venous diseases. These conditions pose a direct threat to the patient’s life and necessitate emergency diagnosis and active surgical strategy. Successful treatment of these circumstances depends on the coordinated work of a multidisciplinary team, including surgeons, vascular surgeons, endovascular surgeons and cardiologists.