A heterogeneous endometrium means your uterine lining appears uneven or mixed in texture on an ultrasound, rather than having a smooth, uniform pattern. It’s a descriptive term radiologists use when the lining doesn’t look consistent from one area to another. This finding isn’t a diagnosis on its own. It signals that something is changing the normal architecture of the lining, and the next step is figuring out what.
What a Normal Endometrium Looks Like
On ultrasound, a healthy endometrium typically has uniform echogenicity, meaning the tissue reflects sound waves evenly and appears symmetrical between the front and back walls of the uterus. During the fertile years, the lining often shows a characteristic three-layer pattern around ovulation, with distinct bright and dark bands that are easy for a sonographer to read. After menopause, the lining thins out but still looks even and well-defined.
The International Endometrial Tumor Analysis (IETA) group defines the endometrium as “non-uniform” when it appears heterogeneous, asymmetrical, or contains cystic spaces. In clinical practice, a uniform appearance generally indicates a normal endometrium. A heterogeneous one raises a flag that warrants a closer look.
What Can Cause It
Several conditions can make the endometrium look uneven on ultrasound. The most common culprits include:
- Endometrial polyps: Small tissue growths on the lining. In studies of postmenopausal women with endometrial abnormalities, polyps are by far the most frequent finding, accounting for roughly 65% of cases.
- Submucosal fibroids: Noncancerous muscle growths that push into the uterine cavity, distorting the lining’s appearance. These account for about 5% of endometrial abnormalities in postmenopausal women.
- Endometrial hyperplasia: An overgrowth of the lining, sometimes triggered by excess estrogen without enough progesterone to balance it. About 7–8% of postmenopausal women with abnormal endometrial findings have hyperplasia without concerning cell changes, while a smaller percentage have the atypical form that carries a higher risk of progressing to cancer.
- Adenomyosis: A condition where tissue that normally lines the uterus grows into the muscular wall. On ultrasound, adenomyosis creates a mottled, uneven texture, often with small cystic spaces in the muscle and a “shaggy,” indistinct border where the lining meets the wall. A globular-shaped uterus is another hallmark, present in about 95% of confirmed cases.
- Endometrial cancer: Less common but important to rule out, particularly in postmenopausal women with bleeding. In one study, about 17% of postmenopausal women with bleeding and endometrial abnormalities had endometrial cancer.
It’s worth noting that adenomyosis can be tricky to distinguish from fibroids on a standard ultrasound. In one study, about 75% of women initially suspected of having adenomyosis who turned out not to have it actually had multiple small fibroids instead.
Symptoms You Might Notice
The most common complaints tied to a heterogeneous endometrium are abnormal uterine bleeding, chronic pelvic pain, and difficulty getting pregnant. Which symptoms show up depends largely on the underlying cause.
With adenomyosis, painful periods are closely linked to how deeply the tissue invades the uterine wall. Women with deep involvement report painful periods about 78–83% of the time, while those with only shallow involvement rarely do. Women with widespread (diffuse) adenomyosis tend to have heavier bleeding, while those with more localized (focal) disease are more likely to experience fertility problems and miscarriage.
Some women have no symptoms at all. A heterogeneous endometrium can be an incidental finding on an ultrasound done for an entirely different reason.
How It Affects Fertility
Endometrial quality plays a real role in whether an embryo can successfully implant. Significantly abnormal endometrial appearance during IVF has been linked to lower pregnancy rates. While much of the fertility research focuses on endometrial thickness rather than texture, the two are related: a lining that looks uneven may also have structural issues that make implantation harder.
Thickness matters on its own, too. Implantation rates improve steadily as the lining thickens up to about 10 mm. Below 7 mm, the odds drop sharply, with more than half of pregnancies at that thickness ending in early miscarriage in one IVF study. A thicker, healthier lining can partially compensate for lower embryo quality, but when both the lining and embryo quality are poor, the chance of a successful pregnancy drops significantly.
If you’re trying to conceive and your ultrasound shows a heterogeneous endometrium, treating the underlying cause (removing a polyp or fibroid, for instance) can often restore a more favorable environment for implantation.
What Happens After This Finding
A heterogeneous endometrium on a basic transvaginal ultrasound is a starting point, not an endpoint. Standard transvaginal ultrasound catches about 71% of true endometrial abnormalities. A more detailed test called saline infusion sonohysterography, where sterile saline is gently infused into the uterus to spread the walls apart during imaging, bumps that detection rate to about 93%. It’s particularly useful for spotting fibroids that bulge into the cavity, where it catches nearly all of them compared to about 62% on a regular ultrasound.
The American College of Obstetricians and Gynecologists recommends that when a radiologist can’t clearly see a thin, distinct endometrial lining in a postmenopausal woman with bleeding, the next step should be saline sonohysterography, office hysteroscopy, or an endometrial biopsy. For postmenopausal women at higher risk of cancer based on their history or symptoms, tissue sampling is the recommended first-line test.
A key threshold to know: in postmenopausal women without bleeding, an endometrial thickness over 4 mm found incidentally doesn’t automatically require further testing, though individual risk factors matter. But any postmenopausal woman with persistent or recurrent bleeding needs a tissue sample regardless of how thin the lining measures, because rare types of endometrial cancer can develop even below 3 mm.
If an initial biopsy comes back normal but bleeding continues, that’s not the end of the workup. Persistent or recurrent bleeding after a normal blind biopsy warrants a more thorough evaluation with hysteroscopy, which lets a doctor visually inspect the cavity and take targeted tissue samples from suspicious areas.
Premenopausal vs. Postmenopausal Considerations
Context matters enormously with this finding. In premenopausal women, the endometrium naturally changes throughout the menstrual cycle. A scan done at certain points in your cycle may look less uniform simply because the lining is in transition. Your doctor will consider where you are in your cycle when interpreting the image.
In postmenopausal women, the lining should be thin and quiet. A heterogeneous appearance after menopause carries more clinical weight, especially when paired with bleeding. The combination of postmenopausal bleeding and a non-uniform endometrium is the scenario most likely to prompt a biopsy or further imaging, because the stakes of missing hyperplasia or cancer are higher in this group.