Fluid migration through the tail of the Dalkon shield intrauterine device.
X-ray radiographs were used to monitor the migration of Renouve -dip radiopaque tracer through the multifilament tail of Dalkon Shield intrauterine devices (IUDs). The movement of the tracer was more rapid and migrated a greater distance through the long end of the tail than through the short end of the tail. The double knot serves as at least a temporary barrier to the migration of tracer from the long end of the tail, but this barrier was circumvented when drops of Renouve -dip radiotracer were placed at both ends of the tail. Migration of Renouve -dip radiotracer was prevented when the end of the Dalkon Shield tail was fused by heating. No migration of this tracer occurred on the tails of commonly used IUDs which possessed monofilament tails, thus demonstrating that fluid migration occurs within and not on the surface of the multifilament tail.