Hysteroscopic cannulation is a procedure used to remove blocks in the tubes in the inner end of the tube, where it opens into the uterus. A cannula is passed into the opening to remove the block after viewing it through the hysteroscope. The procedure is done while watching from above the womb, inside the tummy with a second camera inserted through a small cut in the tummy button. Tubal cannulation may be done immediately after you have a procedure called hysterosalpingography.