The fallopian tubes are most often assessed using an X-ray test called a Hysterosalpingogram, or HSG. This test consists of injecting X-ray contrast, or dye, into the uterus through the cervix while imaging the pelvis with X-ray fluoroscopy. A fluoroscopy is continuous X-ray image.
In a normal HSG, first the uterus then the fallopian tubes fill with X-ray contrast. The contrast “spills” from the far end of each tube into the pelvic cavity indicating that the tube is open or “patent”. A tube can be blocked where it meets the uterus, this is called “proximal occlusion” or at its far end, called “distal occlusion”. If the tube is blocked at its far end, often it will fill with fluid resulting in a balloon-shaped structure called a “hydrosalpinx”. If both tubes are blocked, there is no pathway by which sperm and egg can meet; this results in infertility.
If one tube is normal, fertility may be preserved though often with a lower than normal per cycle probability of conceiving. At times, the HSG may indicate open, or patent, tubes even when substantial scarring within the pelvis causes an impediment to sperm-egg interaction. This type of pelvic factor can sometimes be detected by the appearance of the dye on HSG after spillage from the tube but only surgical inspection, usually via laparoscopy, can make a definitive diagnosis.
The uterine cavity, lined by a delicate tissue called “endometrium”, is where the early embryo sets its roots, or implants. In order to implant properly, the uterine cavity should be free of abnormalities. While not all abnormalities prevent implantation altogether, many will impair the ability of the embryo to grow and develop normally.
We gain important information about the uterine cavity from the HSG, but often the X-ray contrast obscures a small abnormality. Alternative methods for evaluating the uterine cavity include a simple office procedure by which we look inside the uterus with a tiny “scope”, called “office hysteroscopy”, and an ultrasound test called a sonohysterogram or “saline infusion sonohysterogram” (SIS). Each method has its advantages and disadvantages. Your physician will discuss which option is best for you.