The invention is applied in medicine. It relates to a valve mechanism for the closure of vessels by means of a balloon. It is the object of the invention to develop a mechanism which decouples a balloon from a catheter simply, quickly and reliably and maintains a constant size and shape. The invention is intended to achieve the object of developing a valve mechanism using a low-viscosity contrast medium. According to the invention, this is achieved by a valve mechanism which comprises a cylindrical bolt having a spherical head, and furthermore a catheter having a lateral opening and a balloon which is fastened on a catheter so that it can be pulled off by an elastic thread. After pulling off the catheter the bolt closes the balloon filled with contrast medium.
