Endometrial polyp on ultrasound: what it looks like and what to do next

What an endometrial polyp is

A polyp is a patch of the womb lining that has grown more than the lining around it and projects into the cavity of the uterus, either on a thin stalk or on a broad base. It can measure anything from a few millimetres to a few centimetres, and there may be one polyp or several. You may also see it called a uterine polyp. Polyps are found most often in women over 40, but they can occur at any age after periods have started.

Many polyps cause no symptoms at all and are picked up by chance on a scan. When an endometrial polyp does cause symptoms, they are usually these:

• bleeding or spotting between periods, less often after sex;
• heavy or prolonged periods;
• bleeding or spotting after the menopause;
• difficulty getting pregnant when no other cause has been found.

An endometrial polyp is not the same as a cervical polyp, which grows from the canal of the cervix, can be seen during an ordinary speculum examination and is simpler to remove.

What a polyp looks like on ultrasound

On a transvaginal ultrasound a polyp appears as an oval or rounded shape inside the cavity of the uterus, usually brighter than the surrounding lining, with a smooth, clear outline. Sometimes small cysts can be seen inside it. The line where the front and back walls of the cavity meet is pushed apart or interrupted at the site of the polyp. In my report I give the size in millimetres, the position in the cavity and the day of the cycle.

Other findings can look similar, which is why a diagnosis is not made from a single image:

• A submucosal fibroid. It grows from the muscle wall and is usually darker on the screen and denser. I have explained how a fibroid differs from other findings in the article on fibroids and cysts.
• Thickening of the whole lining. In endometrial hyperplasia the lining is usually thicker than normal throughout the cavity rather than in one place. But hyperplasia can also be limited to one area, and occasionally a tumour looks just like a polyp. Ultrasound cannot reliably tell them apart; only histology, the examination of the tissue under a microscope, gives the final answer.
• A blood clot or a fold of the lining. These disappear after the next period, whereas a polyp generally stays.

Best day of the cycle for a pelvic ultrasound

The best time is days 5-10 of the cycle, just after the period has ended. On those days the lining is thin and dark on the screen, so a bright polyp stands out clearly against it. In the second half of the cycle the lining becomes thick and bright, and a small polyp is simply lost in it. What lining thickness counts as normal on different days is covered in the article on the endometrium on ultrasound.

If you have no periods, for example after the menopause or on hormonal contraception, the scan can be done on any day. I have described how to get ready for the scan in the article on preparing for a pelvic ultrasound.

What "possible polyp" means

This wording, or simply "polyp?", is used when something resembling a polyp is seen in the cavity but the doctor cannot be sure. It happens most often when the scan was done in the second half of the cycle or just before a period. What to do next:

• Repeat the scan on days 5-10 of the next cycle. A clot or a fold of the lining will have gone by then. Can a polyp go away on its own? Some small ones, up to 10 mm, do in time: in studies, roughly one in four had disappeared after a year of follow-up.
• If the finding is still there, there are two options. If you have not reached the menopause, a small polyp that causes no symptoms can be monitored. In all other cases the next step is hysteroscopy: a look inside the cavity of the uterus with a thin telescope (a hysteroscope) passed through the cervix. It both confirms the diagnosis and allows the polyp to be removed there and then.
• Sometimes, before hysteroscopy, a scan is arranged in which fluid is passed into the cavity of the uterus: the fluid separates the walls, and the finding can be seen from all sides.

On its own, "possible polyp" does not mean anything urgent. The main exception is bleeding or spotting after the menopause, even if it happens once and is very light: in that case do not wait for a repeat scan but see a doctor straight away, because a sample of the lining has to be taken and examined, usually at hysteroscopy. You should also not put off a visit if bleeding between periods comes back cycle after cycle, if you are over 45 and your periods have become heavy or irregular, or if you take tamoxifen.

When to watch and when to remove

Is an endometrial polyp cancer? The vast majority of polyps are benign. The risk that a polyp contains precancerous or cancerous cells is low: about 1-2 in 100 before the menopause and around 5 in 100 after it. It is also higher when there is bleeding. So what is advised depends on the situation.

Watching is an option if the polyp is small, up to 10 mm, you have no symptoms and you have not yet reached the menopause. A follow-up scan is done after the next period and then according to a plan we agree at your appointment.

Removal is usually advised if:

• you have bleeding outside your periods, or heavy periods;
• the polyp was found after the menopause, especially if there has been any bleeding;
• the polyp is large or growing;
• you are having difficulty getting pregnant or IVF is planned;
• you take tamoxifen or have other risk factors for endometrial cancer.

Uterine polyp removal is done at hysteroscopy, so the doctor can see exactly what is being removed, and the polyp is always sent for histology: only that gives the final answer about what kind of tissue it is. "Blind" scraping of the womb (curettage) is no longer recommended for this, because it can miss the polyp. Hysteroscopy is carried out in hospital or in an outpatient procedure room, and I do not perform it myself: I will write you a referral and explain how to prepare. Polyps sometimes come back, so I advise a follow-up scan after removal.

Endometrial polyp and pregnancy

A small polyp does not always stop you getting pregnant, and many women only learn they have one after giving birth. But if you have been trying to conceive without success, the polyp is usually removed. In a randomised trial, pregnancy was roughly twice as likely after a polyp was removed before intrauterine insemination (IUI). There is no evidence of that strength for IVF, but if a polyp is found before the treatment cycle begins, removal is usually advised as well. This is exactly why the cavity of the uterus is checked before IVF and IUI.

I choose the tests you need before pregnancy at a pregnancy planning visit, and if you have bleeding between periods I start with an examination and a scan at a visit for menstrual disorders. I see patients at ul. Głębocka 9/U1 in Warsaw, no referral needed; booking requires a PESEL number or an identity document.

Quick answers

Sources

The primary sources this text rests on. Links open in a new tab.

1. AAGL Practice Report: Practice Guidelines for the Diagnosis and Management of Endometrial Polyps. J Minim Invasive Gynecol, 2012American Association of Gynecologic Laparoscopists: how polyps are detected, when they are monitored and when they are removed at hysteroscopy
2. Leone F. et al. Terms, definitions and measurements to describe the sonographic features of the endometrium and intrauterine lesions (IETA consensus). Ultrasound Obstet Gynecol, 2010international IETA consensus: how the endometrium and findings inside the cavity of the uterus are described on ultrasound
3. NICE guideline NG88. Heavy menstrual bleeding: assessment and management (2018, updated 2021)UK National Institute for Health and Care Excellence: investigation of heavy periods and a suspected polyp, and when hysteroscopy is needed
4. Perez-Medina T. et al. Endometrial polyps and their implication in the pregnancy rates of patients undergoing intrauterine insemination. Hum Reprod, 2005randomised trial: removing a polyp before insemination raised the pregnancy rate
5. Uglietti A. et al. The risk of malignancy in uterine polyps: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol, 2019systematic review of 51 studies: cancerous changes in polyps are rare and more common after the menopause and when there is bleeding

This text describes the general picture and does not replace a consultation. Timings and indications differ from woman to woman and are decided at the appointment, from your history and test results.