Leech therapy: The use of leeches in medical treatment. Once used as an almost universal cure, leeches were largely abandoned by medicine but in the second half of the 20th century refound a role. That role is largely in plastic and reconstructive surgery. Leeches can assist, for example, in the reattachment of severed body parts such as a finger, hand, toe, leg, ear, nose or the scalp.
The surgeon usually has little difficult connecting the two ends of small arteries, since arteries are thick-walled and relatively simple to suture. However, veins are thin-walled, fragile, and difficult to suture. The surgeon may thus get blood flowing in the reattached arteries but not in the veins. With the venous circulation severely compromised, the blood going to the reattached body part becomes congested and stagnant. The reattached part turns blue and lifeless and is at risk of being lost. It is then that leeches are summoned to treat the threatening venous insufficiency, but only when there is adequate arterial flow.