It's a good place to start. I have heard it can cause some cramping but that's all. I did not have this, but I did have an extensive ultrasound. Your results will be more definitive. I found out that I have a fibroid outside of my uterus and one that is in the wall, which is not even 1 CM. We also saw what we thought was a polyp.
Then I had a Hysteroscopy where they actually take a camera into the uterus and they put me to sleep with Propofol. The fibriod is not distorting my uterus at all and should not be causing my miscarriages (I also had one chemical and one MMC). What we thought was a polyp was retained products of conception. They did a d&c - which was about 4 weeks after Misoprostol. Although I did not find a cause for my miscarriages, after the procedure I feel great and I even ovulated this past weekend.
In the end, the ultrasound let to good things. Even if everything is fine with your HSG test, it will rule out possible issues. If they find something than they have something to fix.