What is a hysterosalpingogram (HSG)?

A hysterosalpingogram (HSG) is a specialized fluoroscopic (X-ray) imaging study that assesses the anatomy of the fallopian tubes to ensure they are patent (open), as well as the uterine cavity to ensure there are no structural abnormalities such as polyps, fibroids, scar tissue, or a septum (membrane that divides the uterus into two cavities).ⁱ An HSG X-ray can help determine if there is a blockage of the cervix, uterus, or fallopian tubes that could prevent implantation. When a female presents with infertility, an HSG is usually one of the first tests performed because it rules out or confirms anatomic issues of the cervix, uterus, and fallopian tubes that may be limiting fertility.ⁱⁱ

What is involved in a hysterosalpingogram procedure?

A hysterosalpingogram, sometimes referred to as an HSG test or HSG exam, is an outpatient procedure that does not require sedation or anesthesia and typically takes three to five minutes. The patient is placed in stirrups with her knees bent, as one would be positioned for a standard gynecologic speculum exam like a Pap test. There is an X-ray machine above the exam table that takes pictures of the uterine cavity and the fallopian tubes during the procedure as dye is injected through the cervix.

• Sterilization of cervix: First, the doctor places a speculum into the vagina to see the cervical opening and sterilizes the cervix with an antiseptic wash such as betadine. The physician may use an instrument called a tenaculum, which grasps the cervix to keep it stable and bring it into view for the physician.
• Insertion of catheter: Then, a thin catheter is placed through the cervix until the tip is inside the uterus. The catheter is held in place either with a plug on the outside of the cervix that is shaped like an acorn, or by a balloon inside the cervix or lower uterus. The acorn tip or balloon keeps the catheter in place and prevents leakage of contrast dye out of the uterus. There may be cramping discomfort when the balloon is inflated. The doctor will make note of how easily the catheter passes through the cervix. If there is cervical narrowing (called cervical stenosis), it may be difficult or even impossible to pass the catheter. The speculum may be removed once the catheter is in place.
• Injection of contrast: Next, a contrast dye (known as contrast media, contrast material, or X-ray dye) is instilled slowly into the uterus through the catheter. This contrast dye can either be water-based or oil-based. Both versions have been shown to be safe and effective.ⁱⁱⁱ The contrast dye is often warmed before being inserted into the body to reduce pain and limit the chance of the fallopian tubes spasming from exposure to cold contrast. If the fallopian tubes spasm, there may appear to be a narrowing or blockage even though the tubes are open.
• Straightening of uterus: If the uterus sits at an angle, the doctor may gently pull on the catheter to straighten the uterus so that accurate X-ray images can be taken. It is important that this step be taken so that the X-ray procedure does not accidentally diagnose a problem with the uterus that is simply due to inappropriate uterine positioning.
• Completion of X-rays: Several X-ray pictures are taken as the dye moves through the uterine cavity and into the fallopian tubes to get a picture of the uterus and the tubes. The contrast agent will outline the inner contour of the uterus. If there is any structural abnormality in the uterus, a “filling defect” will be seen. A filling defect is an area where contrast does not flow or where there is an abnormal contour to the lining.
• Passage of dye: The dye will then enter both fallopian tubes and spill out into the abdomen. If one or both tubes are blocked, the doctor can identify the location of the blockage. A normal result shows the standard uterine contour (upside-down triangle) as well as passage of the contrast dye into and through both fallopian tubes and out the end of the tubes into the pelvis with no areas of narrowing. An abnormal result would show an abnormal contour of the uterus, or a blockage or narrowing of one or both fallopian tubes. If there is a blockage at the end of a tube, you will see a large, dilated fluid-filled tube (hydrosalpinx), which is also abnormal.

Note: Straightening the uterus and injecting contrast dye can cause significant cramping and are often the most uncomfortable portions of a hysterosalpingogram. However, these parts of the procedure usually last less than one minute.

Is a hysterosalpingogram painful?

Several studies have documented the level of discomfort patients experience during a hysterosalpingogram. One study from 2015 comparing cervical catheters measured the level of pain experienced on average by patients at different points during the procedure. A visual analogue pain scale was used with a range of pain levels from 0 to 5 (0 does not hurt; 5 hurts the most). On average, patients rated pain at 2.1 to 2.5 out of 5 after the catheter was placed, 2.6 to 3.7 out of 5 during contrast injection, and 2.1 to 3.1 out of 5 one hour after the procedure.^iv

The most painful part of the procedure is typically when the contrast dye is inserted,^v though patients who have blockages within the uterus or a tubal obstruction may experience more pain than those who do not have blockages.^vi Overall, one can expect to have some cramping pain while the HSG is taking place. However, for most patients, the discomfort is manageable and generally goes away very soon after the procedure is complete.

Reducing pain during a hysterosalpingogram

There are several steps that have been shown to reduce pain during the procedure:^vii,viii

• Using warm contrast media
• Injecting a local anesthetic such as lidocaine into the cervix (called a paracervical block)
• Applying an anesthetic cream to the cervix (paracervical analgesic cream)
• Using very light anti-anxiety or sedating medications

Taking a non-steroidal anti-inflammatory (NSAID, such as ibuprofen [Advil®, Motrin®] or naproxen [Aleve®]) before the procedure has been shown to have mixed results in offering pain relief.^ix Some doctors will still recommend taking an over-the-counter pain-reliever 30 to 60 minutes before the procedure, but it may or may not help decrease pain.

Are there any risks associated with a hysterosalpingogram?

Complications after a hysterosalpingogram are uncommon; in a 2020 study of 5,165 females undergoing an HSG, the number of complications was small, with slightly more minor complications using oil-based dye (5.1 percent) compared to water-based dye (1.8 percent).^x Complications included intravasation of contrast (contrast entering veins), allergic reaction, and uterine infection.

Aside from these complications, pelvic pain and pressure during the procedure are common and can trigger patients to develop vasovagal syncope, or a fainting spell. These vasovagal events typically improve by stopping the procedure, encouraging the patient to take deep, slow breaths, and tilting the exam table so that the head is below the feet.

If the patient has an iodine allergy, it can cause an allergic reaction which can be severe in some cases (anaphylaxis).^xi

Dye can also get pushed into the blood stream through small blood vessels in the reproductive organs, in a process called intravasation. It is typically not dangerous unless one has an allergy to the contrast dye.^xii,xiii If oil-based contrast is used as opposed to water-based, there is an extremely small risk that if the oil gets into the blood stream, it can cause a blood clot in the lungs that can be life-threatening.^xiv

Uterine and pelvic infection, such as pelvic inflammatory disease, are very rare after an HSG. The rate of infection after HSG was approximately 0.3 percent in a 2020 study of over 5,000 HSGs.^xv There was no difference between patients receiving pre-treatment with antibiotics and patients not receiving antibiotics.^xvi No major complications were reported, including blood clots, and there were no side effects with lasting consequences for the patients. The rate of allergic reaction was 0.03 to 0.1 percent with no patients having a severe allergic reaction.^xvii

Certain patients have a higher risk of post-procedure infection, including individuals with a history of pelvic inflammatory disease or people who have dilated, fluid-filled tubes (hydrosalpinx). Doctors often recommend these patients receive oral antibiotics prior to the procedure. Certain symptoms in the few days following the HSG may be a sign of pelvic infection. Fever, ongoing abdominal pain, or foul-smelling vaginal discharge should be assessed by a physician.^xviii

Due to potential risks to a developing embryo/fetus, HSG is not performed during pregnancy or when a female may be pregnant. Because of this, HSGs are scheduled between the end of a menstrual period and prior to ovulation, usually between cycle days 5 to 10.^xix A negative pregnancy test may be required in some cases.

Can a hysterosalpingogram improve fertility?

There is a theory that a hysterosalpingogram may increase the chance of becoming pregnant. It is based on the idea that the contrast dye may have a tubal flushing effect that opens tubes that are partially or completely blocked. Some experts have also hypothesized that oil-based contrast may have an anti-inflammatory effect on the tubes, but it is not observed in all cases and the results are inconsistent. One randomized control trial of over 1,100 females showed that, when oil-based contrast is used during an HSG, there were higher rates of live births (38.8 percent) following the test than for females having an HSG with water-based contrast (28.1 percent).^xx 

What are the next steps if my hysterosalpingogram is abnormal?

There are several different results a patient might get from a hysterosalpingogram, from a normal test to signs of abnormalities in the uterus and fallopian tubes.

Normal HSG test

In this case, no blocked tubes and no uterine abnormalities were seen on the HSG test. Therefore, a structural (anatomic) obstruction or abnormality is less likely to be the cause of infertility.

It is worth noting that there is a false negative rate for detecting intrauterine abnormalities, meaning there is a chance that the test will be read as normal but there is still a structural problem within the uterus. Evidence from a 2019 study suggests that approximately 20 percent of patients with a normal HSG result had an abnormality of the uterine lining when visualized with a hysteroscopy (camera). For this reason, some experts recommend hysteroscopy as an additional or potentially better option for examining uterine architecture.^xxi

Uterine abnormality

Uterine abnormalities are common findings with an HSG. In one study of HSG performed for infertility work-up, 50 percent of patients had an abnormality of the uterus.^xxii

There are several uterine abnormalities that can be diagnosed via HSG:

• Synechiae (uterine adhesions or scar tissue that forms inside the uterus)
• Fibroids (benign tumors/muscle balls of the uterine wall)
• Polyps (non-cancerous outgrowths of the lining of the uterus)
• Cervical stenosis (tightening of the cervical canal)^xxiii‍
• Congenital malformations:
  • Unicornuate uterus (only half the uterus developed when a patient was born)
  • Septate uterus (the uterine cavity is divided by a wall in the middle; can be partial or complete)
  • Bicornuate uterus (uterus has a “Y” shape with the top wall extending partially into the cavity)

HSGs only show the inner contour of the uterus so the procedure cannot differentiation between a bicornuate uterus and a partial septum without a pelvic ultrasound.

If an abnormality of the uterus is diagnosed, management of the condition depends on the type of abnormality. Often, an additional test such as a hysteroscopy or pelvic ultrasound may be recommended to gather more information. In many cases, patients may be referred for a hysteroscopic surgical procedure to correct the abnormality. Hysteroscopy is used to remove polyps and fibroids, excise scar tissue, and resect uterine septa.^xxiv,xxv

Tubal abnormality

Blocked fallopian tubes are also a common finding on HSG. In various studies, between 17 and 48 percent of patients undergoing HSG were found to have an abnormality of one or both fallopian tubes.^{xxvi,xxvii,xxviii} Between 2.8 and 11.2 percent of patients had blockage of both tubes.^xxix,xxx

If both tubes appear to be blocked on the HSG, especially if the blockage is proximal (close to the uterus), a patient may be recommended a second procedure to confirm bilateral occlusion. False-positive rates, often caused by spasm, are quoted as high as 40 percent.^xxxiAdditional procedures include hysterosalpingo contrast sonography (HyCoSy), laparoscopy, or repeat HSG.

If complete bilateral obstruction is confirmed, IVF is required to achieve pregnancy.^xxxii If only one tube is obstructed, physicians may try ovarian hyperstimulation to induce ovulation of more than one egg. In some cases, patients may also be referred for IUI or IVF.^xxxiii

Alternative tests: Saline infusion sonogram (sonohysterogram) vs. HSG

A saline infusion sonogram (SIS) or sonohysterogram is a procedure where saline is injected into the uterus, similar to the way contrast is injected during an HSG. But instead of using an X-ray and dye to take pictures of the lining of the uterine cavity, transvaginal ultrasound and saline are used.

To evaluate the tubes, air is mixed with the saline to form bubbles, which are pushed into the uterus while the sonographer or doctor watches them exit the uterus into the pelvis around the ovaries. The exam to evaluate both the uterine cavity and tubes is called hysterosalpingo contrast sonography (HyCoSy).^xxxiv

Some studies have suggested that SIS with HyCoSy may be less painful than HSG.^xxxv HyCoSy and HSG have similar accuracy in diagnosing uterine or tubal blockage.^xxxvi

Conclusion

While it can be intimidating to hear a doctor recommend a hysterosalpingogram as part of a fertility plan, the test can prove invaluable when it comes to diagnosing structural issues inside of the uterus and fallopian tubes that may prevent fertilization or implantation.

The procedure itself can cause a bit of discomfort but is generally considered safe when the proper precautions are taken. The results can offer further insight into additional steps needed to facilitate conception.