Testing & Diagnostics
This is the standard, basic x-ray study of the uterus
Hysterosalpingogram (HSG) is the standard x-ray study of the uterus and the fallopian tubes. It is designed to visualize the inside of a uterus (the uterine cavity). HSG also gives us a basic assessment of whether the fallopian tubes are patent (unobstructed).
This basic procedure is offered by most hospital radiology departments and can be performed by a radiologist or a gynecologist. Most fertility centers refer their patients to such outside radiology facilities for HSG and rely on the outside radiologists’ interpretation for diagnosis. However, at CHR, images from HSG are interpreted in-house, which allows our expert physicians to detect subtle problems in tubal function that HSG interpretation by a non-fertility specialist, like a general radiologist, often overlooks.
The process is simple. The patient is asked to lie down just as if she were to have a PAP smear. A speculum is placed in the vagina and the opening to the uterus (called the cervix) is visualized by the doctor. After cleaning the cervix with an iodine solution, a long, narrow, flexible catheter is inserted through the opening of the cervix until the tip is inside the uterine cavity. A balloon on the end of the catheter is inflated to hold the catheter in place. The catheter is connected to plastic tubing through which a special dye is passed into the uterus. This dye looks like water to the naked eye, but it appears on x-ray film because it blocks the passage of the x-rays. On the film, everywhere the dye flows looks white.
As the dye fills the uterus, x-rays are taken every few seconds. This reveals any abnormalities inside the uterus such as a split cavity, uterine fibroids or adhesions.
As more dye flows into the uterus, some will begin to fill the fallopian tubes. If the tubes are unobstructed (patent) along their entire course, eventually the dye will "spill" out the other side.
Digital images taken during hysterosalpingogram can be manipulated in a number of different ways to help a physician distinguish subtle abnormalities. Typically, 50 to 60 images are generated from a basic HSG.
Spilling of the dye, however, does not necessarily indicate normal fallopian tubes. It takes an experienced expert with thorough understanding of the female reproductive functions to correctly interpret "normal" tubal anatomy on HSG. Indeed, in our opinion, the interpretation of HSG films is likely the most frequently falsely interpreted test in medicine.
We constantly see patients who come to CHR with diagnosis of "normal tubes" on HSG, who, when we closely examine their x-ray films, turn out to have obvious tubal disease. These patients are often given the dubious diagnosis of "unexplained infertility" only because their tubal problem wasn’t discovered during previous HSG procedures. Part of the problem may lie in the fact that the HSG procedure falls between medical specialties, as radiologists, not reproductive endocrinologists, perform almost all HSG.
Our radiology colleagues focus on whether the tubes are "open" when they perform and interpret HSG. This is a fundamentally different question from what we, fertility specialists, try to answer by HSG: For us, the question is whether the tubes are "normal." Normal tubes, of course, have to be open; open tubes, however, do not always function normally. A normal fallopian tube “grabs” the egg from the ovary at ovulation, and leads it into the tube. An open tube may have functional problems that prevent it from "grabbing" the egg. Such subtle tubal issues really require a fertility specialist to be diagnosed.
Sometimes, during hysterosalpingogram (HSG), a physician might discover that the dye does not flow into the tube(s) because of an obstruction or "spasm" of the muscle around the opening of the tube.
With an HSG alone, it is impossible to distinguish an obstruction (which will cause infertility) from spasm (which is not a problem for fertility prospects). Furthermore, if a true obstruction exists, with an HSG alone, there is no way to bypass it. Selective hysterosalpingogram is a way to overcome this problem. It is both a diagnostic and a therapeutic procedure.
With selective salpingography, a thinner, flexible catheter is run inside the HSG catheter. With the help of the x-ray machine, this smaller catheter is directed right into the opening of the fallopian tube. Once this is done, dye can be introduced directly into the fallopian tube.
In this way, it is possible to distinguish a normal, patent, fallopian tube whose opening is in spasm from tubes with true obstruction. Fallopian tubes with an actual obstruction can also be opened by the higher pressures, which can be achieved with selective salpingography, though this is not always possible.
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Last Updated: November 15, 2014