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 open (patent), and the uterine cavity to ensure there are no structural abnormalities such as polyps, fibroids, scar tissue, or a septum.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 woman presents with infertility, an HSG is usually one of the first tests performed, as it rules out or confirms structural/anatomic issues of the cervix, uterus, and fallopian tubes that may be limiting fertility.ⁱⁱ

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What is involved in a hysterosalpingogram procedure?

An HSG, sometimes referred to as an HSG test or HSG exam, is an outpatient procedure that does not require sedation or anesthesia and typically takes 3-5 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 smear. There is an X-ray machine above the exam table that takes pictures of the uterine cavity and tubes during the procedure as dye is injected through the cervix.

The doctor places a speculum into the vagina to see the cervical opening. The cervix is sterilized with an antiseptic wash such as betadine. The physician may use an instrument called a tenaculum, which is used to grasp the cervix to keep it stable and bring it into view for the phyisician. This portion of the procedure can cause significant cramping similar to menstrual cramps. 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 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 (cervical stenosis), it may be difficult or even impossible to pass the catheter. The speculum may be removed once the catheter is in place.  

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 have been shown to be safe and effective.ⁱⁱⁱ The contrast dye is often warmed before being inserted into the body to limit the chance of the fallopian tubes spasming from exposure to cold contrast and to reduce pain. If the fallopian tubes spasm, this can appear as a false-positive narrowing/blockage when in reality the tube is open. 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 is done so that the X-ray procedure does not accidentally diagnose a problem with the uterus that is just an artifact of inappropriate uterine positioning. Straightening the uterus and injection of contrast dye can cause significant cramping and is often the most uncomfortable portion of an HSG. However, this part of the procedure usually lasts less than one minute.  

Several X-rays 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.  

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 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 the tube. If there is blockage at the end of the tube, you will see a large, dilated fluid-filled tube (hydrosalpinx), which is also abnormal.

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Is a hysterosalpingogram painful?

There have been a number of studies documenting the level of discomfort experienced during HSG. 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 0-5 (0 does not hurt; 5 hurts the most). On average, patients rated pain at 2.1-2.5/5 after the catheter was placed, 2.6-3.7/5 during contrast injection, and 2.1-3.1/5 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 tubes 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, but for most patients, this is manageable and generally goes away very soon after the procedure is done.  

Steps that have been shown to reduce the amount of pain during the procedure include using warm contrast media, injecting a local anesthetic such as lidocaine into the cervix (called a paracervical block), using an anesthetic cream on the cervix (paracervical analgesic cream), and using very light anti-anxiety or sedating medications during the HSG.^vii,viii Taking a non-steroidal anti-inflammatory (NSAID – such as ibuprofen [Advil®, Motrin®], naproxen [Aleve®], etc.) before the procedure has been shown in the literature to have mixed results in offering pain relief.^ix Therefore, using an over-the-counter pain-reliever before the procedure may be recommended by doctors, but it may or may not help decrease pain from the procedure. If recommended, most doctors instruct patients to take NSAIDs 30-60 minutes prior to the procedure.

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Are there any risks associated with hysterosalpingogram?

Complications after HSG are uncommon; in a 2020 study of 5 165 females undergoing 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 allergy to iodine, this 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. This 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

Infections of the uterus and pelvis, such as pelvic inflammatory disease, are very rare after 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 those receiving pre-treatment with antibiotics and those 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 0.03-0.1 percent with no patients having a severe allergic reaction.^xvii  

Certain patients have a higher risk of post-procedure infection, including those with a history of pelvic inflammatory disease or those 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 and should spur a consultation with a doctor. 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 woman may be pregnant. Because of this, HSGs are scheduled between the end of a menstrual period and prior to ovulation, usually between cycle days 5-10.^xix A negative pregnancy test may be required in some cases.  

Can HSG improve fertility?

There is a theory that HSG may increase the chance of becoming pregnant. This 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 have also hypothesized that oil-based contrast may have an anti-inflammatory effect on the tubes. This is not observed in all cases and the results are inconsistent. One randomized control trial of over 1 100 women, showed that when oil-based contrast is used during HSG, there were higher rates of live births (38.8 percent) following the test than those having HSG with water-based contrast (28.1 percent).^xx  

Saline Infusion Sonogram (Sonohysterogram) vs HSG

A saline infusion sonogram (SIS) or sonohysterogram is a procedure where saline is injected into the uterus in a way similar to the method used for injecting contrast during an HSG. Instead of using an X-ray and dye to take pictures of the lining of the uterine cavity, transvaginal ultrasound and saline is 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 come out the uterus and into the pelvis around the ovaries. The exam to evaluate both the uterine cavity and tubes is called a Hysterosalpingo Contrast Sonography (HyCoSy).^xxi Some studies have suggested that SIS/HyCoSy may be less painful than HSG.^xxii HyCoSy and HSG have similar accuracy in diagnosing uterine or tubal blockage.^xxiii

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What are the next steps if my HSG is abnormal?

There are several different results a woman might get from her HSG, including signs of abnormalities of the uterus and fallopian tubes. Below are some of the results that the doctor may discuss with the patient after the test.  

Normal

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 uterine abnormalities, meaning a chance that the test will be read as normal but there is 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 recommend hysteroscopy as an additional or potentially better option for examining uterine architecture.^xxiv

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.^xxv‍

There are a number of uterine abnormalities that can be diagnosed via HSG, including congenital malformations, 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), or cervical stenosis (tightening of the cervical canal).^xxvi

Congenital anomalies include unicornuate uterus (only half the uterus developed when a patient was born), septate uterus (the cavity is divided by a wall in the middle; can be partial or complete), and bicornate 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 better clarify the nature of the abnormality. 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.^xxvii, ^xxviii

Tubal abnormality  

Blocked fallopian tubes are also a common finding on HSG. In various studies, between 17-48 percent of patients undergoing HSG will be found to have an abnormality of one or both fallopian tubes.^{xxix,xxx,xxxi} Between 2.8-11.2 percent of patients had blockage of both tubes.^xxxii,xxxiii

If both tubes are noted 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 versus spasm. False-positive rates are quoted as high as 40 percent. ^xxxivAdditional procedures include HyCoSy, laparoscopy, or repeat HSG. If complete bilateral obstruction is confirmed, IVF is required to achieve pregnancy.^xxxv 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.^xxxvi

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Conclusion

While it can be intimidating to hear a doctor recommend an HSG 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.