Sonohysterography a tiny catheter is placed in the cervix and fluid injected into the uterine cavity while monitoring the process by ultrasound. The discomfort is about the equivalent to a Pap smear. Below, one can see a normal uterine cavity. Polyps or fibroids within the cavity of the uterus would appear as distinct opacities. Also see information sheet on Sonohysterogram from ASRM.