A hysterosalpingogram (HSG) is a specialized diagnostic imaging procedure that provides a detailed view of a woman’s reproductive anatomy. This test uses fluoroscopy, a type of continuous X-ray, along with the injection of a contrast dye to visualize the inside of the uterus and the path of the fallopian tubes. The HSG allows healthcare providers to assess the structure of the uterine cavity and determine if the fallopian tubes are open, or patent. This procedure is an outpatient test that typically takes less than 30 minutes for the entire process.
Clinical Reasons for Testing
The most frequent reason a physician recommends an HSG is during an infertility investigation. Blocked fallopian tubes are a common cause of female infertility, and the HSG is the standard method for checking their patency. The test determines if the dye flows freely through the entire length of the tubes and spills out into the abdominal cavity, which confirms they are open.
The HSG also helps diagnose structural issues within the uterine cavity that could interfere with conception or pregnancy. These issues include abnormalities such as intrauterine adhesions, endometrial polyps, or submucosal fibroids. Physicians may also order the procedure to investigate recurrent miscarriage or to assess the results of a prior tubal sterilization procedure.
Timing Relative to the Menstrual Cycle
The timing of the HSG is carefully controlled to ensure patient safety and achieve the clearest imaging results. The procedure should always be scheduled during the follicular phase of the menstrual cycle, which is the time between the end of menstruation and before ovulation. This window typically falls between Cycle Day 6 and Cycle Day 12, counting the first day of full menstrual bleeding as Day 1.
This specific timing is necessary for two primary reasons: safety and image quality. Performing the test before ovulation minimizes the chance that the patient could be in the very early stages of an unknown pregnancy. The X-ray exposure and the procedure itself could potentially harm a developing embryo, which is why a pregnancy test is often performed just before the HSG.
The second reason for this timing is to ensure the uterine lining, or endometrium, is thin. Immediately after menstruation, the lining is at its thinnest, which allows for optimal visualization of the uterine cavity’s shape and any structural abnormalities. A thick uterine lining, which develops closer to ovulation, could obscure the images and lead to an inaccurate interpretation of the results.
Preparation and Procedure Overview
Before the HSG, patients are often advised to take an over-the-counter nonsteroidal anti-inflammatory drug (NSAID) about an hour before the scheduled time to help manage potential cramping. A course of prophylactic antibiotics may be prescribed if the patient has a history of pelvic infection, as this can reduce the low risk of post-procedure infection. Patients should discuss any known allergies to iodine or contrast dye with their healthcare provider beforehand.
During the procedure, the patient lies on an examination table similar to a standard gynecological exam. A speculum is inserted into the vagina to visualize the cervix, which is then cleaned before a thin catheter is placed through the cervical opening into the uterus. The speculum is then removed, and the patient may be asked to reposition slightly so the X-ray machine is correctly aligned.
The contrast dye is slowly injected through the catheter, which causes the uterus to fill and the dye to flow into the fallopian tubes. A series of X-ray images are taken as the dye moves, allowing the radiologist to watch for blockages and assess the uterine shape. A successful result is confirmed when the dye is seen spilling from the ends of the tubes into the abdominal cavity, where it is harmlessly absorbed by the body. After the procedure, it is common to experience mild cramping, light spotting, and a discharge of the excess contrast dye. Patients can typically resume normal activities immediately.
When an HSG Should Not Be Performed
There are several conditions that make performing an HSG unsafe, which are known as contraindications. The procedure should not be performed if there is a known or suspected pregnancy, as the X-rays and uterine manipulation pose a risk to the fetus. Adherence to the specific timing relative to the menstrual cycle is strictly enforced for this reason.
An active pelvic infection, such as Pelvic Inflammatory Disease (PID) or an active, untreated sexually transmitted infection, also prevents the procedure from taking place. Injecting the dye in the presence of an active infection could potentially spread the bacteria further into the pelvic cavity, leading to serious complications. Furthermore, the HSG should be postponed if the patient is experiencing heavy, unexplained uterine bleeding, as this can interfere with the imaging.