How have leeches been used in medicine?

The use of leeches in modern medicine made its comeback in the 1980s after years of decline, with the advent of microsurgery such as plastic and reconstructive surgeries. In operations such as these, one of the biggest problems that arises is venous congestion due to inefficient venous drainage. This condition is known as venous insufficiency. If this congestion is not cleared up quickly, the blood will clot and arteries that bring the tissues their necessary nourishment will become plugged and the tissues will die. It is here where the leeches come in handy. After being applied to the required site, they suck the excess blood, reducing the swelling in the tissues and promoting healing by allowing fresh, oxygenated blood to reach the area until normal circulation can be restored. The leeches also secrete an anticoagulant (known as hirudin) that prevents the clotting of the blood