The device for blocking (e.g., embolizing) the side branches of an anatomical passageway under endoscopic guidance. The device comprises an elongate catheter body having a side branch blocking apparatus, such as an embolization catheter, disposed therein and further incorporating an endoscope (e.g., an angioscope). The incorporated endoscope is useable to A) visually locate side branches which emanate from the anatomical passageway and b) visually observe the operation of the side branch blocking apparatus. Also disclosed are methods for utilizing a device of the forgoing character, including methods for performing in situ embolization of the side branches of a vein, under angioscopic visualization. The endoscopic component of the device may also be utilized to visually observe the use and/or effect of one or more separate device, such as valvulotome(s) used for cutting venous valves located within the lumen of a vein.