What Is an SIS Test (Saline Infusion Sonogram)?
An SIS test, or saline infusion sonogram, is a specialized ultrasound procedure in which sterile saline is infused into the uterus to provide clearer images of the uterine cavity. Clinically, this test is often referred to as a saline infusion sonogram (SIS), sonohysterogram, or sonohysterography (SHG test). The SIS test is widely used in fertility and reproductive health for evaluating the structure of the uterus, detecting uterine abnormalities (such as polyps, fibroids, adhesions, or septa), and helping guide fertility treatment planning.
During an SIS procedure, a thin catheter is inserted through the cervix, and a small amount of sterile saline is instilled into the uterine cavity. The saline gently expands the uterus, allowing detailed ultrasound images to be captured. Unlike a standard pelvic ultrasound, the SIS test enhances visualization of the uterine lining, making it easier for clinicians to identify subtle abnormalities that could impact fertility or pregnancy outcomes.
Key Takeaways
- An SIS test (saline infusion sonogram) is a specialized ultrasound using sterile saline to assess the uterine cavity.
- The SIS procedure is used to detect uterine abnormalities such as polyps, fibroids, adhesions, and septa.
- SIS is less invasive and more comfortable than some other uterine evaluation methods and typically does not require anesthesia.
- SIS is commonly performed when someone experiences recurrent pregnancy loss, unexplained infertility, or abnormal uterine bleeding.
- SIS vs HSG: Unlike hysterosalpingography (HSG), the SIS does not assess fallopian tube patency, but is superior for evaluating the uterine lining.
- SIS test results can help determine the need for further evaluation, surgery, or tailor fertility treatments like IVF or IUI.
- Most people tolerate the SIS well; discomfort is usually mild and brief, comparable to menstrual cramps.
- SIS cost varies, but it is often less expensive than other imaging procedures and may be partially or fully covered by insurance plans.
- SIS is considered a safe procedure, with rare and generally mild side effects.
- Discussing SIS results with a fertility specialist can help inform next steps for family-building or further investigations.
Table of Contents
- What Is an SIS Test (Saline Infusion Sonogram)?
- How Does the SIS Procedure Work?
- Why Is the SIS Test Important for Fertility?
- Who Typically Needs an SIS Test?
- SIS Test vs. HSG and Other Uterine Evaluation Methods
- Step-by-Step: What to Expect During the SIS Procedure
- SIS Test Results: What Do They Mean?
- Risks, Discomfort, and How to Minimize Them
- SIS Test Quick Facts Table
- Myths vs. Facts About the SIS Test
- Frequently Asked Questions About SIS Tests
- References and Further Reading
- Disclaimer
How Does the SIS Procedure Work?
The SIS test, also called a saline infusion sonogram or sonohysterography (SHG), is an office-based gynecologic ultrasound procedure. Here is how it works:
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Timing: The SIS is usually performed after menstruation, but before ovulation (days 6-12 of a typical cycle), to minimize the risk of interfering with an early pregnancy and for optimal visualization of the uterine lining PubMed.
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Preparation: The person undergoing the SIS procedure typically empties their bladder. Some providers may recommend taking an over-the-counter pain reliever beforehand.
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Insertion of Speculum and Catheter: A speculum is gently inserted into the vagina, exposing the cervix. After cleaning the cervix, a thin, flexible catheter is passed through the cervical canal into the uterus.
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Saline Infusion: Sterile saline is slowly injected through the catheter. The saline distends the uterine cavity, separating the walls and enhancing visualization of the endometrial lining during ultrasound.
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Ultrasound Imaging: Transvaginal ultrasound is performed simultaneously, producing clear images or videos of the inside of the uterus. If abnormalities are present, their size, location, and characteristics can be documented.
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Conclusion: The speculum and catheter are removed. The procedure usually takes about 15-30 minutes.
Did you know? The SIS test does not expose you to any ionizing radiation, unlike an X-ray-based HSG.
Why Is the SIS Test Important for Fertility?
The SIS test plays a vital role in fertility evaluation and management. Determining the health of the uterine cavity is crucial because even subtle abnormalities can affect the chances of successful embryo implantation and pregnancy PubMed.
Some key reasons why SIS is important in fertility:
- Detecting Polyps and Fibroids: Polyps and fibroids can interfere with embryo implantation, increase risk of miscarriage, or cause abnormal uterine bleeding.
- Identifying Adhesions (Synechiae): Scar tissue within the uterus can hinder conception or lead to recurrent miscarriage.
- Evaluating Septate or Bicornuate Uterus: Congenital uterine anomalies can impact fertility and increase miscarriage rates.
- Assessing Uterine Lining Quality: An optimally receptive endometrium is crucial for the successful establishment of pregnancy.
- Guiding Further Interventions: SIS findings help clinicians decide whether hysteroscopic surgery, further imaging, or a tailored fertility treatment strategy is warranted.
Key Point: Many uterine abnormalities that impact fertility are treatable, and the SIS test can help identify and guide treatment of these issues.
Who Typically Needs an SIS Test?
The SIS procedure may be recommended for people with:
- Unexplained Infertility
- Recurrent Pregnancy Loss
- Abnormal Uterine Bleeding
- Suspected Uterine Anomalies
- Pre-IVF or Pre-IUI Assessment
Certain groups are more likely to benefit, such as those:
- Over age 35 who are planning assisted reproduction
- With a history of uterine surgery, pelvic infection, or dilation and curettage (D&C)
- Experiencing persistent abnormal bleeding or spotting, especially after menopause
Scenario Example: Maria, 36, is planning IVF after two early miscarriages. Her doctor recommends an SIS test to rule out uterine factors like polyps or adhesions that might impact embryo implantation.
SIS Test vs. HSG and Other Uterine Evaluation Methods
Uterine imaging can be performed by a variety of methods, each with its own strengths and limitations:
| Feature | SIS (Saline Infusion Sonogram) | HSG (Hysterosalpingogram) | Standard Transvaginal Ultrasound | Hysteroscopy |
|---|---|---|---|---|
| Uterine Cavity | Excellent visualization | Moderate visualization | Limited cavity detail | Excellent, direct view |
| Endometrial Polyps | Highly sensitive | Occasionally seen | Often missed | Highly sensitive |
| Fibroids | Well detected if cavity-distorting | Only submucosal seen | Well seen if large | Highly sensitive |
| Fallopian Tubes | Not assessed | Patency evaluated | Not assessed | Not assessed |
| Invasiveness | Minimally invasive | Mildly invasive, uses dye/X-ray | Non-invasive | More invasive, requires anesthesia |
| Radiation | None | Yes | None | None |
| Cost/Accessibility | Moderate/Very accessible | Moderate/Moderate | Lower/Highly accessible | Higher/Requires OR setting |
SIS vs. HSG
- SIS focuses on the uterine cavity’s structure; it offers detailed images of the lining and detects abnormalities affecting fertility.
- HSG evaluates tubal patency (whether the fallopian tubes are open) as well as the general shape of the uterus. It uses X-ray and contrast dye.
- In many fertility evaluations, both tests may be recommended to obtain a full picture of uterine and fallopian tube health.
Step-by-Step: What to Expect During the SIS Procedure
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Before the Procedure
- You may be advised to schedule your SIS right after your period ends but before ovulation.
- Some people take ibuprofen or acetaminophen an hour beforehand to minimize cramping.
- Inform your provider if you have allergies, especially to latex or antiseptics.
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Upon Arrival
- You'll empty your bladder and undress from the waist down.
- Consent will be reviewed and any last questions addressed.
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During the Procedure
- You lie on an exam table like for a Pap smear.
- A speculum is gently inserted, and the cervix is cleaned.
- A thin catheter is passed through the cervix into the uterus.
- Saline is slowly instilled. You may feel mild cramping or fullness.
- The transvaginal ultrasound probe is used to visualize the distended uterine cavity.
- Images and video clips are obtained.
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After the Procedure
- The speculum and catheter are removed.
- You may experience mild spotting and light cramping for a few hours.
- Most people can resume normal activities immediately.
Did you know? Many people find the SIS less uncomfortable than an HSG because it does not require dye injection under X-ray.
SIS Test Results: What Do They Mean?
The SIS provides high-resolution images of the inside of the uterus. Results may show:
- Normal Uterus: Smooth endometrial lining, no visible lesions—a reassuring finding.
- Polyps: Small, soft growths that protrude into the cavity.
- Fibroids: Firm, muscular growths that can distort the cavity.
- Adhesions (Synechiae): Bands of scar tissue, which may partially or completely obstruct the cavity.
- Septum or Congenital Anomaly: Abnormal structural partition or shape of the uterine cavity.
Your doctor will interpret the results in the context of your symptoms and fertility history. In many cases, abnormal findings on SIS can be followed by hysteroscopy for direct visualization and possible removal of lesions.
Reference Table: Common SIS Findings and Possible Fertility Impact
| Finding | Description | Possible Fertility Impact |
|---|---|---|
| Normal | Smooth, even endometrium | Optimal for implantation |
| Polyp | Soft, grape-like tissue projecting into cavity | May decrease implantation, increase miscarriage risk |
| Submucosal Fibroid | Firm mass distorting cavity | Can block embryo implantation, raise miscarriage risk |
| Adhesion | Scar tissue bands | May impede conception, disrupt lining |
| Septate Uterus | Division of cavity by fibrous tissue | May increase miscarriage risk |
Key Point: Only some findings on SIS require treatment—your provider will guide you regarding recommended next steps.
Risks, Discomfort, and How to Minimize Them
The SIS test is considered very safe with a low risk of complications. Possible risks and how to minimize them include:
| Risk | How Common? | How to Minimize/Respond |
|---|---|---|
| Mild Cramping | Very common | Take ibuprofen as advised; rest |
| Light Spotting | Common | Use pantiliner; notify if heavy bleeding |
| Infection | Very rare (<1%) | Provider uses sterile technique; report fever, worsening pain |
| Allergic Reaction | Extremely rare | Inform provider of allergies |
| Faintness/Dizziness | Occasionally | Eat beforehand; notify provider if you feel faint |
Did you know? Severe pain, heavy bleeding, or fever after SIS are not typical. Contact your provider if you experience worrisome symptoms.
Most people describe SIS pain as mild to moderate, similar to menstrual cramps. Most discomfort is brief and resolves quickly after the procedure.
SIS Test Quick Facts Table
| Aspect | Details |
|---|---|
| Full Name | Saline Infusion Sonogram (SIS), Sonohysterography (SHG) |
| Also Known As | SIS, SHG test, saline sonogram, sonohysterogram |
| Purpose | Evaluate uterine cavity for polyps, fibroids, adhesions, septa |
| Procedure Duration | 15-30 minutes |
| Radiation Exposure | None |
| Typical Indications | Infertility, recurrent miscarriage, abnormal bleeding |
| Pain Level | Mild to moderate, brief cramping |
| Recovery Time | Usually immediate; light activity possible afterward |
| Cost | $300–$800 (varies by region and insurance; check with provider) |
| Insurance Coverage | Often covered if medically indicated |
| When in Cycle | Days 6-12 (post period, pre-ovulation) |
Myths vs. Facts About the SIS Test
| Myth | Fact |
|---|---|
| SIS is only for people with infertility | SIS helps with abnormal bleeding and diagnosis of uterine issues for anyone |
| SIS is very painful | Most people experience only mild, temporary cramping |
| SIS can check if my tubes are blocked | SIS shows uterine cavity, but not fallopian tube patency |
| SIS exposes you to radiation | SIS uses ultrasound; no radiation involved |
| SIS always requires anesthesia | Most SIS procedures use only local anesthesia, if any |
| Cost makes SIS inaccessible | SIS is less expensive than many other imaging tests and is often covered by insurance |
Frequently Asked Questions About SIS Tests
What does an SIS test mean in fertility?
An SIS test is a procedure used to visualize the inside of the uterus and look for abnormalities that may affect fertility.
SIS stands for saline infusion sonogram, a technique where sterile saline is instilled into the uterus while ultrasound images are taken. It can detect problems such as polyps, fibroids, adhesions, or structural defects that might hinder conception or increase risk of miscarriage.
How is the SIS (saline infusion sonogram) performed?
The SIS is performed by inserting a thin catheter through the cervix, infusing sterile saline, and using a transvaginal ultrasound to obtain images of the uterine cavity.
The saline expands the cavity, so any irregularities or lesions are easier to detect. The process is done in a fertility clinic or gynecology office and typically takes 15-30 minutes.
Is the SIS test painful?
Most people describe SIS pain as mild and brief, similar to menstrual cramps.
Occasionally, some may experience more intense cramping, especially if the cervix is tight. Discomfort usually fades quickly after the procedure, and over-the-counter pain relief is sometimes recommended beforehand.
What findings can the SIS test detect?
SIS can detect uterine polyps, fibroids, adhesions (synechiae), septa, and other structural abnormalities.
It is considered more sensitive than standard ultrasound for these findings. Accurate diagnosis can help guide fertility treatments or surgical interventions.
What is the difference between SIS and HSG?
SIS examines the uterine cavity using saline and ultrasound, while HSG (hysterosalpingogram) assesses both the uterus and the fallopian tubes using X-ray and dye.
HSG is the test of choice for evaluating tube openness, whereas SIS is best for detailed endometrial cavity visualization. Sometimes, both tests may be recommended.
When in my menstrual cycle should I get the SIS test?
The best time for SIS is just after your period ends but before ovulation, typically days 6-12 of your cycle.
This timing avoids interfering with a possible early pregnancy and allows for optimal visualization of the lining.
What does a normal SIS look like?
A normal SIS shows a smooth, regular endometrial lining with no intracavitary masses, adhesions, or septa.
This finding is reassuring and suggests that the uterine environment is favorable for embryo implantation and pregnancy.
What if my SIS test shows a polyp or fibroid?
If a polyp or fibroid is detected, your provider may recommend further evaluation, possibly with hysteroscopy, and discuss removal if it might affect fertility or cause symptoms.
Not all findings require surgery; your doctor will individualize recommendations based on the size, location, and your reproductive plans.
Can SIS detect blocked fallopian tubes?
No, the SIS is not designed to assess tubal patency (whether fallopian tubes are open). HSG or specialized ultrasound techniques are needed for this purpose.
However, sometimes fluid seen in the tubes during SIS may suggest a blockage, which should be confirmed with other tests.
How long do SIS test results take?
In most clinics, the doctor can discuss the results of your SIS immediately after the procedure.
If further imaging or assessment is needed, you may be referred to a fertility specialist or scheduled for additional testing.
Is the SIS test safe?
Yes, the SIS is considered a very safe procedure with a low complication rate.
Serious risks like infection or injury are rare. Mild side effects, such as cramping or spotting, resolve quickly.
How much does the SIS test cost?
SIS test cost varies widely, typically ranging from $300 to $800, depending on region, clinic, and insurance coverage.
Many health insurance plans cover the SIS test when it is medically necessary, but out-of-pocket costs can fluctuate, so check with your provider.
Is the SIS test covered by insurance?
In many cases, SIS is covered by insurance if performed for infertility evaluation, abnormal bleeding, or other clinically indicated reasons.
Coverage and out-of-pocket costs depend on your specific plan. Always verify with your insurance company and provider.
Can I go back to work or normal activities after the SIS?
Most people can resume normal activities—including work—soon after the SIS test.
Mild cramping or spotting is common but usually not severe enough to require downtime.
Are there any ways to make the SIS more comfortable?
Taking ibuprofen before the procedure, emptying your bladder, and practicing deep breathing can help.
Communicate any anxiety or discomfort to your provider, who may adjust technique or use local numbing as needed.
When should I see a fertility specialist based on SIS findings?
If your SIS reveals significant uterine abnormalities—especially if you have trouble conceiving, recurrent loss, or persistent bleeding—you should discuss your options with a reproductive endocrinologist (REI) or gynecologic surgeon.
Early evaluation and treatment can improve your chances of a successful pregnancy.
References and Further Reading
- American Society for Reproductive Medicine. "Saline Infusion Sonohysterography: A Technique for Assessing Uterine Cavity." https://www.asrm.org/
- Society of Radiologists in Ultrasound. "ACR–SRU Practice Parameter for the Performance of Sonohysterography." https://www.acr.org/
- American College of Obstetricians and Gynecologists. Sonohysterography. https://www.acog.org/
- de Kroon CD, et al. "The performance of sonohysterography and hysteroscopy in the evaluation of the uterine cavity." https://pubmed.ncbi.nlm.nih.gov/16522300/
- Dubinsky TJ, et al. "Sonohysterography for endometrial abnormalities: how does it compare with TVUS and hysteroscopy?" https://pubmed.ncbi.nlm.nih.gov/9336588/
- Timor-Tritsch IE et al. "Sonohysterography: A Review." https://pubmed.ncbi.nlm.nih.gov/8920957/
- Valle RF. "Hysteroscopic evaluation of abnormal uterine bleeding." https://pubmed.ncbi.nlm.nih.gov/17447882/
- Practice Committee of the American Society for Reproductive Medicine. "The clinical utility of saline infusion sonohysterography in the evaluation of the infertile patient." https://pubmed.ncbi.nlm.nih.gov/28318638/
- Deichert U, et al. "Diagnostic and therapeutic value of sonohysterography in reproductive medicine." https://pubmed.ncbi.nlm.nih.gov/11091601/
- SOGC Clinical Practice Guideline. "Diagnosis and management of congenital uterine anomalies." https://www.jogc.com/
Disclaimer
This article is for informational and educational purposes only and does not constitute medical or mental health advice. It is not a substitute for speaking with a qualified healthcare provider, licensed therapist, or other professional who can consider your individual situation.
