The medicinal use of leeches has a long and complex history, dating back to ancient civilisations where hirudotherapy was employed for bloodletting and humoral balance. While largely abandoned with the decline of humoral medicine, leeches re-emerged in the late twentieth century as a valuable adjunct in plastic and reconstructive surgery. Their role became particularly significant in the management of venous congestion following microsurgical replantation and flap reconstruction, where inadequate venous outflow threatens tissue viability. Leech saliva contains a combination of anticoagulants, vasodilators, and platelet inhibitors, most notably hirudin, which facilitate temporary venous drainage and improve microcirculatory perfusion. Despite their effectiveness, leech therapy carries limitations including infection risk, blood loss, and patient acceptability. Consequently, modern alternatives have been developed, such as mechanical venous drainage, chemical anticoagulation, topical vasodilators, and microsurgical revision techniques. Advances in flap design and venous supercharging have further reduced reliance on leeches. This historical review highlights the transition of leeches from archaic medical practice to evidence-based reconstructive adjunct, illustrating how traditional therapies can be refined or replaced by modern surgical innovation.