A sonohysterogram (SHG) is an ultrasound procedure used to better visualize the inside of the uterus and endometrium. Most often it is used to view fibroids and polyps. A sonohystogram takes around 30 minutes. A catheter is inserted through the cervix, and a small inflated balloon holds it in place. Saline is injected into the uterus and ultrasound pictures are then obtained.