While the idea of using leeches to suck blood may seem positively medieval, theyโ€™re still frequently used in hospitals today to salvage tissue with inadequate blood supply by pulling out congested blood. Itโ€™s also used to create anastomosis (a connection between blood vessels) when the veins are too fine to connect or circulation is impaired.

Theyโ€™re most commonly used in finger replantation, skin grafts, and reconstructive surgeries.