Technical Field: The present invention relates to methods for blocking tubular anatomical structures.  In particular, the present invention relates to methods for ligating the fallopian tube to achieve sterilization.  The present invention pertains in addition to devices for performing tubal ligations. 
Occlusion of tubular anatomical structures is desirable for various medical treatments.  One important application of occlusion techniques is blockage of the fallopian tubes in the female or vas deferens in the male to achieve sterilization and prevent undesired pregnancies. 
Various methods for producing occlusion or blockage of tubular anatomical structures have been considered for contraceptive purposes.  A commonly used method for blocking the fallopian tube is to tie off or clamp the fallopian tube.  The tube may be tied in two locations and the intermediate portion of tube removed.  A similar result may be obtained by grasping and folding over a portion of the tube and tying off a loop of tube that does not communicate with the remainder of the tube.  The folded segment of tube may be blocked by a loop of suture material, a elastic ligating band or O-ring, or a clamp.  Access to the fallopian tube is usually gained through endoscopic surgery, either through the abdominal wall or, less commonly, through the wall of the vagina.  Such methods are less invasive than conventional surgical methods, but still have an undesirably high risk of infection and tissue damage, and are accompanied by an undesirable recovery time and level of discomfort. 
In order to eliminate the need for endoscopic or other, more invasive, surgery, a number of approaches have been devised for blocking the lumen of the fallopian tube after accessing the interior of the fallopian tube by inserting a catheter into the lumen of the tube via the vagina and uterus. 
One approach is to block the fallopian tube by injecting an adhesive or sealant, typically a polymeric material, into the fallopian tube to form a plug.  Another approach is to insert a pre-formed occlusive device or plug into the lumen of the fallopian tube or the utero-tubal junction.  However, either type of plug may separate or dislodge from the wall of the fallopian tube, resulting in unreliable or impermanent blockage. 
Another approach for blocking the fallopian tube or other tubular anatomic structures is to induce the formation of sclerosis or scar tissue to block the tube.  Tissue damage may be induced chemically or thermally.  However, this method is relatively difficult to accomplish successfully and requires skilled personnel and specialized equipment, making it unsuited for use in certain settings.