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Hysterosalpingography (HSG) and Sonohysterography (SIS) are common tests for checking tubal patency. Although their purpose is the same, they work differently and have certain pros and cons to consider. Knowing how both work can give you a better idea about your next steps.
Why Tubal Patency Testing Matters
Before learning about HSG and SIS, you should understand why testing for tubal patency is important in a fertility evaluation.When your fallopian tubes are not functioning properly, the egg cannot travel from your ovary to your uterus. Even if everything seems normal in the conception process, a blockage may still prevent eggs from being fertilised.
Checking the patency of your tubes allows your doctor to determine whether a physical blockage is affecting your ability to conceive. Based on the results, medical staff can then prepare the most appropriate treatments or interventions for your condition.
What Is HSG (Hysterosalpingography)?
Hysterosalpingography, commonly referred to as HSG, is an X-ray imaging test. During the test, the doctor injects a special dye into the uterus via the cervix. During the test, X-rays are taken to check if the dye travels without problems through the tubes.What to Expect During HSG?
The procedure is typically done after your period ends and before you ovulate. The X-ray is taken in a position similar to lying during a pap smear. A speculum is used to access the cervix, and then a catheter is inserted. This way, the contrast dye is inserted into your uterus.You may experience some cramping as the dye moves through your reproductive system. The process usually finishes in less than half an hour.
Benefits of HSG
- Provides a clear outline of the uterine cavity and fallopian tubes.
- Helps identify tubal blockages and structural abnormalities.
- It may improve the chances of conception by flushing minor blockages.
Limitations of HSG
- Involves radiation exposure (though minimal).
- Can be uncomfortable or mildly painful.
- Doesn’t offer detailed imaging of the uterine lining.
What Is SIS (Sonohysterogram or Saline Infusion Sonography)?
Sonohysterography, often referred to as SIS, uses ultrasound instead of X-rays. In this test, sterile saline (salt water) is infused into your uterus through a catheter, and ultrasound imaging monitors how the fluid flows through the uterus and fallopian tubes.What to Expect During SIS?
SIS is typically scheduled mid-cycle. You'll be asked to lie down while your doctor inserts a speculum and a small catheter into your cervix. Once saline is introduced, a transvaginal ultrasound probe is used to observe its flow through your reproductive tract.The process takes about 20–30 minutes and is usually more comfortable than an HSG.
Benefits of SIS
- No radiation is involved.
- Offers excellent visualisation of the uterine cavity and endometrium.
- Helps detect polyps, fibroids, and other uterine abnormalities.
- Usually more comfortable than HSG.
Limitations of SIS
- Not as definitive for tubal blockages as HSG.
- Tubal patency is inferred, not directly observed.
- Air bubbles during the procedure can occasionally lead to false positives.
HSG vs. SIS: A Side-by-Side Comparison
| Feature | HSG | SIS |
| Imaging Technique | X-ray with contrast dye | Ultrasound with saline |
| Tubal Patency Accuracy | High | Moderate |
| Uterine Cavity Visualisation | Moderate | Excellent |
| Comfort Level | Mild to moderate discomfort | Generally more comfortable |
| Radiation Exposure | Yes | No |
| Detection of Uterine Abnormalities | Limited | Strong |
| Procedure Duration | 15–30 minutes | 20–30 minutes |
Which Test Should You Choose?
This largely depends on your symptoms, medical history, and what your doctor is specifically looking to find. If your primary concern is whether your fallopian tubes are open, HSG tends to be more reliable. It provides clearer images of the fallopian tubes, and the contrast dye offers a more conclusive answer.On the other hand, if you're experiencing irregular bleeding or recurrent miscarriages, SIS may provide better insights into your uterine cavity. It can identify structural abnormalities, such as fibroids or polyps, that may interfere with implantation or pregnancy.
Your doctor may recommend both tests, starting with one and following up with the other if the results are unclear.
How to Prepare for These Tests?
Before undergoing either procedure, your doctor might prescribe antibiotics to prevent infection. You may also be advised to take an over-the-counter pain reliever about an hour before the procedure to minimise discomfort.The procedure should be scheduled after your period ends but before ovulation begins. This timing ensures that you're not pregnant during the test and provides the clearest view of your reproductive system.
Are There Any Risks?
Both HSG and SIS are generally safe when performed by trained professionals. However, like any medical procedure, there are small risks involved.With HSG, there's a slight risk of infection, especially if there's an undiagnosed pelvic infection already present. Rarely, allergic reactions to the contrast dye may occur.
The risks for SIS are minimal. Occasionally, the catheter or the saline solution insertion may cause mild cramping or spotting afterwards.
How Soon Can You Try to Conceive After These Tests?
Unless advised otherwise by your doctor, you can usually try to conceive in the same cycle after either procedure. Some women report higher chances of conception shortly after HSG, possibly due to the flushing effect of the contrast dye.Choosing between HSG and SIS isn’t something you need to do alone. Your doctor will guide you based on your symptoms, fertility history, and what they hope to diagnose or rule out. While HSG provides a better view of the fallopian tubes and is more accurate for assessing tubal patency, SIS offers a broader look into your uterus and may help identify other structural issues. Understanding both options better equips you to take an active role in your fertility journey.
FAQs for Testing for Tubal Patency: HSG vs. Sonohysterogram (SIS)
- Is one test more painful than the other?
You may find HSG slightly more uncomfortable than SIS because of the use of contrast dye and the pressure it creates in your uterus. However, the discomfort is usually short-lived and manageable. - Can these tests treat any fertility issues, or are they just diagnostic?
These tests are primarily diagnostic, but in some cases, HSG can have a mild therapeutic effect by flushing minor blockages in the fallopian tubes, potentially improving fertility. - Do I need anaesthesia for HSG or SIS?
No, general anaesthesia is not required for either test. Although you might be offered a mild pain reliever before the procedure, you’ll remain fully awake throughout.
