Ligature (medicine)

In surgery or medical procedure, a ligature consists of a piece of thread (suture) tied around an anatomical structure, usually a blood vessel or another hollow structure (e.g. urethra) to shut it off. With a blood vessel the surgeon will clamp the vessel perpendicular to the axis of the artery or vein with a hemostat, then secure it by ligating it; i.e. using a piece of suture around it before dividing the structure and releasing the hemostat. It is different from a tourniquet in that the tourniquet will not be secured by knots and it can therefore be released/tightened at will.