An HSG is an x-ray test that mainly shows whether the fallopian tubes are open and what shape the uterine cavity is. A saline sonogram uses ultrasound and saline to outline the inside of the uterus. A hysteroscopy uses a thin camera passed through the cervix to look directly at the cavity, and can sometimes treat problems at the same time. Your doctor chooses based on the question they are trying to answer.
A fertility evaluation often includes a look at the uterus and fallopian tubes, because structural problems can interfere with conception or pregnancy and are not visible on a standard pelvic exam. The challenge is that three different tests can sound like the same thing. This guide breaks them down side by side. If you are specifically preparing for an HSG, our detailed guide on what to expect from a hysterosalpingogram covers the day itself.
The Question Behind the Test
Each test answers a slightly different question:
- Are the fallopian tubes open? This is the main job of an HSG.
- What does the inside of the uterine cavity look like? A saline sonogram or hysteroscopy is aimed at this, and an HSG gives a rough outline.
- Is there something to remove or fix? A hysteroscopy can sometimes both find and treat certain problems.
Your doctor will weigh your history, symptoms, ultrasound findings and treatment plans. There is no single best test for everyone.
Side-by-Side Comparison
| HSG | Saline sonogram (SIS/SHG) | Hysteroscopy | |
|---|---|---|---|
| Type of test | X-ray with contrast dye | Ultrasound with saline | Direct view with a thin camera |
| Best at showing | Whether the tubes are open and the cavity outline | The lining and shape of the cavity | The cavity itself, close up |
| Can it treat? | No | No | Sometimes, using small instruments |
| Radiation | Yes, very low | No | No |
| Usual setting | Outpatient imaging or clinic | Clinic | Office or operating room |
HSG: Tubes and Cavity Shape
The American Society for Reproductive Medicine describes an HSG as an x-ray procedure that checks whether the fallopian tubes are open and whether the uterine cavity looks normal. A thin catheter is placed in the cervix, contrast dye is gently injected, and x-ray images show its path through the uterus and tubes. It does not evaluate the ovaries, diagnose endometriosis, or detect fibroids outside the uterine cavity.
It is usually done after your period ends and before ovulation, takes less than 5 minutes, and is considered very safe, with serious complications reported at less than 1 percent. Cramping is common and usually lasts 5 to 10 minutes, though some people have cramps for hours, so ASRM suggests arranging a ride home. It should not be done if you might be pregnant, and tell your doctor about any iodine, contrast dye or seafood allergy. The most common serious complication is pelvic infection, more likely with a history of tubal disease, so call your doctor for increasing pain or fever in the following day or two.
Saline Sonogram: Ultrasound Plus Saline
A saline infusion sonogram, also called a sonohysterogram, uses a transvaginal ultrasound while a small amount of sterile saline is placed in the uterus through a thin catheter. The fluid gently separates the walls, so the ultrasound can outline the lining and show polyps, fibroids bulging into the cavity, or scar tissue more clearly than a standard scan.
It avoids radiation and iodine contrast. ASRM's HSG fact sheet notes that this ultrasound alternative is considered inferior to HSG for judging whether the tubes are open, which is why the two tests are chosen for different questions. If your main concern is a possible polyp or fibroid, our posts on endometrial polyps and fibroid location explain why position inside the uterus matters.
Hysteroscopy: A Direct Look Inside
In a hysteroscopy, a thin lighted scope is passed through the vagina and cervix into the uterus, usually with fluid or gas to open the cavity so the doctor can see it on a screen. Because the doctor sees the cavity directly, it is the most detailed way to examine it. It can also be diagnostic or operative. Small instruments can sometimes remove a polyp, a fibroid in the cavity, scar tissue, or a uterine septum during the same procedure. See our post on uterine septum and fertility for one condition that is often treated this way.
Hysteroscopy can be done in an office with little or no sedation, or in an operating room under anesthesia, depending on what is planned and your preferences. Ask which applies to you, what recovery looks like, and whether any tissue removed will be sent to a lab.
None of the three evaluates the ovaries or reliably diagnoses endometriosis. If your doctor suspects it, they may discuss other approaches, including a laparoscopy, a surgical option that views the tubes directly and can test whether they are open by passing dye through them.
How a Doctor Picks
Common Reasoning
These tests are one piece of a wider workup. For the full picture of what comes before and after, see fertility testing explained and, for hormone testing, day 3 hormone labs.
Questions to Ask Before Booking
- What question are we trying to answer with this test?
- Is there a reason to choose this one over the other two?
- What will I feel, and what can I take beforehand to ease cramping?
- Do I need someone to drive me, and when can I go back to work?
- If something is found, can it be treated now or will I need a second procedure?
- What do the results mean for timing in my treatment plan?
Frequently Asked Questions
The Bottom Line
Think of the three tests as three different tools. The HSG is the standard way to check the tubes and cavity outline, the saline sonogram gives a radiation-free look at the cavity, and the hysteroscopy offers the closest view and sometimes a way to fix what it finds. Ask your doctor what they want to learn, then choose the test that answers that question with the least burden on you.