When something shows up on a routine ultrasound and your doctor says “we need a better look,” the next step isn’t always obvious. There are several ways to evaluate the inside of the uterus, and the differences between them matter more than most patients realize.
A saline infusion sonohysterogram (SIS) is a targeted uterine imaging procedure that uses sterile saline solution to expand the uterine cavity during ultrasound, creating contrast that reveals abnormalities a standard pelvic ultrasound can miss. It’s the right first step for many women – but not all of them. Knowing the difference is what drives the right decision.
Key Takeaways
- A saline infusion sonohysterogram (SIS) is a minimally invasive office procedure, not a surgery, and most women return to normal activity the same day.
- SIS is most useful for evaluating abnormal uterine bleeding, suspected polyps, fibroids, or unexplained infertility before moving to more invasive testing.
- The main alternatives are standard pelvic ultrasound, hysteroscopy, and MRI – each with distinct strengths and specific conditions where they outperform SIS.
- Not every uterine concern needs the same test. The right choice depends on what your provider is looking for and what they already know.
- At Synergy Women’s Health, diagnostic decisions start with the least invasive appropriate option and escalate only when clinical findings require it.
What Does a Saline Infusion Sonohysterogram Actually Show?
A standard transvaginal ultrasound gives a good view of the uterine walls and ovaries, but the uterine cavity itself tends to collapse on itself. There’s no contrast. Small polyps, submucosal fibroids, or thin adhesions can hide completely.
SIS solves that by introducing a small amount of saline through a thin catheter placed in the cervix. The fluid gently opens the cavity, and the ultrasound can then see the interior walls clearly. What was invisible becomes visible.
The procedure typically takes 15 to 30 minutes, is performed in the office, and requires no sedation. Mild cramping is common. Most women describe it as similar to a Pap smear with a little more pressure. It’s not painless, but it’s manageable for most people.
What it can reveal: endometrial polyps, submucosal fibroids (those that protrude into the cavity), uterine septum, adhesions (scar tissue), and irregular thickening of the uterine lining.
When Is SIS the Right Choice?
SIS sits in a specific diagnostic window. It’s more informative than a standard ultrasound and less invasive than a hysteroscopy. That middle position is exactly where it earns its place.
Consider a common scenario: a woman in her early 40s has been experiencing irregular bleeding between periods. Her routine pelvic ultrasound looks unremarkable. Before moving to an in-office hysteroscopy or scheduling an endometrial biopsy, an SIS can confirm whether there’s actually something structural in the cavity worth investigating further. If it’s clean, she’s spared a more invasive procedure. If it shows a polyp, the next step is clear.
SIS is also a standard part of fertility evaluation. When a woman is preparing for IVF or has had recurrent implantation failure, confirming a normal uterine cavity is a prerequisite. A cavity that looks fine on standard ultrasound can still have a small polyp or septum that SIS catches before it becomes the reason an embryo transfer fails.
The test that prevents the wrong next step is often more valuable than the test that diagnoses the final answer.
How Does SIS Compare to the Alternatives?
This is where the decision gets real. There are four main options for uterine cavity evaluation, and each has a different job.
| Test | What It Does Best | Limitations | Typical Setting |
|---|---|---|---|
| Standard pelvic ultrasound | First-line screening, ovarian and uterine structure | Can’t see inside the cavity clearly | Office or Imaging center |
| Saline infusion sonohysterogram (SIS) | Cavity evaluation, polyps, fibroids, septum | Can’t biopsy or treat; not ideal with active infection | Office |
| Hysteroscopy | Direct visualization AND treatment in one step | More invasive; may require OR or anesthesia | Office or operating room |
| MRI (pelvis) | Deep fibroids, adenomyosis, complex anatomy | Expensive, no real-time cavity detail, no biopsy | Imaging center |
Standard pelvic ultrasound is always the starting point. It’s fast, non-invasive, and covered by most insurance. But it’s a screening tool, not a diagnostic one for intrauterine abnormalities. If something looks off, or if the clinical picture doesn’t match what the ultrasound shows, SIS is the logical next step.
Hysteroscopy is the gold standard for definitive diagnosis and treatment. If your provider already suspects a polyp that needs removal, or if a previous SIS found something that requires biopsy, hysteroscopy is the right tool. It sees everything and can treat at the same time which results in a diagnostic and therapeutic treatment. The tradeoff is that it’s more invasive, may require the operating room, and carries higher procedural cost and recovery time.
MRI is reserved for specific situations, particularly when adenomyosis or deep intramural fibroids are suspected and the question isn’t “is there something in the cavity” but “how extensive is the disease in the muscle wall.” MRI doesn’t compete with SIS for cavity evaluation. They’re answering different questions.
What SIS Can’t Do – And Why That’s Important to Know
SIS shows structure. It doesn’t provide tissue. If the lining looks thickened or irregular, SIS can confirm the abnormality, but it can’t tell you whether the cells are normal. That requires an endometrial biopsy, which is a separate procedure.
SIS also can’t be performed if there’s an active pelvic infection or if pregnancy is possible. Timing matters. The procedure is typically scheduled in the first half of the menstrual cycle, after bleeding has stopped but before ovulation, to avoid any risk to an early pregnancy and to get the clearest view of the lining.
If you have significant cervical stenosis (a narrow cervical opening), catheter placement can be difficult or uncomfortable enough to limit the procedure’s success.
Knowing what a test can’t do is how you avoid ordering the wrong one.
If you’re trying to figure out whether SIS, hysteroscopy, or something else is the right next step for your specific situation, the team at Synergy Women’s Health can walk through that with you directly.
How Synergy Women’s Health Approaches Uterine Evaluation
At Synergy Women’s Health, the approach to diagnostic testing follows a clear principle: start with the least invasive appropriate option and escalate only when the clinical picture requires it. That means not ordering an MRI when an SIS will answer the question, and not stopping at a standard ultrasound when the symptom pattern suggests something more is going on.
Dr. Karen Ogryzlo, MD, co-owner of the practice and board-certified OB/GYN, and Dr. Michelle Sang, board-certified OB/GYN and board-certified in Anti-Aging Medicine, lead a team that also includes nurse practitioners with focused experience in gynecologic care. The practice has been serving women in Portland since 2011.
For patients whose symptoms or test results point toward a deeper investigation, such as hormonal contributors to abnormal bleeding or a functional medicine lens on recurrent gynecologic issues, Dr. Sang’s integrative approach is available as an additional layer. Not every patient needs that. But for those who do, it’s there.
The goal isn’t to run every test. It’s to run the right ones.
If you’re dealing with abnormal bleeding, preparing for fertility treatment, or following up on an inconclusive ultrasound, exploring your options through a consultation is a reasonable next step.
Frequently Asked Questions
Is a saline infusion sonohysterogram painful?
Most women describe it as similar to period cramping, ranging from mild to moderate. The discomfort typically peaks when the saline is introduced and passes quickly. Taking an over-the-counter pain reliever like ibuprofen about an hour before the procedure can help. Your provider will talk through what to expect beforehand.
How long does it take to get results from an SIS?
The images are reviewed in real time during the procedure, so your provider can often share preliminary findings the same day. A formal report from the radiologist or interpreting physician may follow within a day or two, depending on the clinical setting.
Will my insurance cover a saline infusion sonohysterogram?
SIS is a standard gynecologic diagnostic procedure and is covered by most major insurance plans when ordered for a medically indicated reason, such as abnormal bleeding or infertility evaluation. Coverage details vary by plan. Synergy Women’s Health accepts most major insurance, and the front office team can help clarify your specific benefits before the appointment.
Can SIS be done if I’ve had a C-section or uterine surgery?
Yes, in most cases. Prior uterine surgery doesn’t automatically disqualify you from having an SIS. Your provider will review your surgical history and may adjust the approach slightly, but previous C-sections or myomectomies don’t typically prevent the procedure from being performed.
What’s the difference between SIS and a hysterosalpingogram (HSG)?
Both use fluid to evaluate the cavity of the uterus, but they’re answering different questions. An HSG uses contrast dye and X-ray to check whether the fallopian tubes are open, making it a tubal patency test. SIS uses saline and ultrasound to evaluate the uterine cavity specifically. If you’re being evaluated for infertility, you may need both at different points in the workup.
Do I need to do anything to prepare for an SIS?
Your provider will give you specific instructions, but preparation is usually minimal. You’ll typically be asked to schedule the procedure in the first half of your cycle, take a pain reliever beforehand, and arrange for someone to drive you home if you anticipate significant discomfort. There’s no fasting or sedation required.
What happens if the SIS finds something abnormal?
Finding an abnormality on SIS is information, not a diagnosis. If a polyp, fibroid, or other structural issue is identified, your provider will discuss what it means, whether it requires treatment, and what the next step looks like. In many cases, the next step is an office hysteroscopy to remove or biopsy the finding. Your provider will explain the options so you can make an informed decision about how to proceed.
If you’re in Portland and want to talk through uterine symptoms, fertility concerns, or a recent inconclusive ultrasound with a team that takes the time to actually explain what’s happening, Synergy Women’s Health is a good place to start.
About the Author
Dr. Sang integrates traditional OB/GYN practice with functional medicine and regenerative therapies. Her care philosophy blends root-cause diagnostics with cutting-edge tools to help patients achieve long-term hormonal, metabolic, and immune balance. She is passionate about optimizing longevity and vitality at every age.
Education: Harvard University (BA), OHSU (MD)
Board Certified: OB/GYN & Anti-Aging Medicine
Special interests: hormone therapy, chronic condition management, peptide therapies