If the strings are not visible during pelvic examination, clinicians may do one or more of the following: Use a cytobrush to attempt to sweep the strings out of the cervical canal Gently probe the uterine cavity with an IUD hook, sound, or biopsy instrument (unless pregnancy is suspected), being careful not to push the IUD further into the uterine cavity or myometrium Do ultrasonography If the IUD is not seen, an abdominal x-ray is taken to exclude an intraperitoneal location.