What’s the difference between a Hysterosalpingogram (HSG) and a Sono-Hysterogram?
Posted Sep 17 2010 4:10am
This just happens to be one of my most frequently asked questions, and it’s a good one. Both are can be very important tests. Some women need only one, some both. In this blog you will see pictures and explanations. I enjoyed putting this blog together because I like taking things that are a little complicated and breaking them down into simple pieces to help make the readers understand every day things that were never made clear to them. Despite this I realize that there are some of you that get very intimidated when shown pictures of anything medically related, so I am sorry if some of this compounds your frustration. Give this one a shot and see how it goes.
Hysterosalpingogram, also known as the hysterogram or HSG. Hystero means uterus, salpingo means tube, so it’s a test to evaluate both the uterus and tubes. It’s a dye test that uses an x ray. As far as the patient is concerned, it starts with a speculum, like a pap smear. The doctor, through various techniques mentioned in previous blogs, squirts some dye into the uterus and it then runs out the tubes. The dye is actually as clear as water, but it’s called dye because it is white on an x ray. The dye then shows the shape of the interior of the uterus and the tubes.
Let’s start with the uterus. This is picture of a HSG x ray.
The uterus is perfect. The tubes are abnormal, but I am starting with this one because the view of the uterus is so ideal. You can see that is triangular in shape with the top being relatively straight across. The hsg only shows us where the dye is, which is inside the uterus and inside the tubes. It does not tell us anything about the middle or outside of the uterus or tubes. The next picture is the same as above except I outlined the outside of the uterus and the approximate location of the ovaries.
You can see that the overall uterine size is greater than what is shown by the hsg, and how the outer uterus and ovaries are invisible using x rays.
The next picture shows what happens to an HSG when there are fibroids on the middle and outside of the uterus. I drew in some hypothetical fibriods in red. Fibriods like these would be invisible on hsg. As you can see, the shape of the inside of the uterus has not changed. So it is possible to have fibroids, and have a normal looking hsg. Fibriods that are closer to the cavity will make the HSG look abnormal. We will later see how certain fibroids can affect the look of the HSG, but in this case many fibroids did not change the HSG picture.
Now we will look an HSG that shows an abnormal uterus.
This hsg is abnormal. There is a black spot in the center, and this could be a number of things, all of which are abnormal. The center is dark because the dye cannot get to the center of whatever is growing in there. It is most likely a polyp, but it could be a small fibroid or even some scar tissue(less likely). The overall triangular shape of the uterus is good. This shows how an HSG can be used for diagnosing uterine problems such as polyps or fibroids that are growing in the cavity.
This is a good time to move over to salinosonohysterograms (sonohysts for short). Commonly called a saline infusion sonohysterogram (SIS). We will come back to HSGs in a bit. The sonohyst does not use an x-ray or x-ray dye. It instead is performed with a regular old ultrasound machine. Prior to performing the ultrasound, the doctor starts with a speculum and then puts a very little plastic tube inside the uterus and squirts some saline (salt water). The saline goes into the uterus and out the tubes.
Here is a normal uterine cavity on ultraound without the saline, its the regular old ultraound.
The next picture is the same, but I added white lines to show you the outline of the entire uterus.
Here is an ultrasound of a uterine polyp (could also be a fibroid). It’s that olive shape in between the arrows. No saline yet.
Here I put a circle around it to make sure you see what I am talking about.
And below is a sonohysterogram of a similar polyp. The doctor put a little saline inside the uterine cavity. Saline or any watery fluid looks black on ultrasound. The black surrounds the polyp and makes it much easier to see. The arrows are not important, they are just pointing out the stalk of the polyp.
Here I would like to end on one very important point. Performing this sonohysterogram was not necessary. We can all see that the polyp is very obviously visible in the picture without the water. There is really no reason to do the sonohysterogram. However time and time again, the doctor will say, "it looks like a polpy, lets do a sonohysterogram to be sure." Yes the picture using the sonohysterogram is prettier, but what he is doing is having you undergo one more unnecessary test, that you may have to pay for, and it’s expensive. So if you are confronted with a sonohysterogram, ask your doctor if he is sure if it really needs to be done. Ask if it will give you any more information than you already have. The sonohysterogram is a great test and I use it all of the time, but not if I know the answer before it’s started.
We will discuss both again next time. You will learn why the sonohysterogram is not a good test for showing open or closed tubes.
Thanks again for reading and please read disclaimer 5.17.06.