Adenomyosis makes the uterus look enlarged, often globular in shape, and sometimes double or triple its normal size. What it “looks like” depends on whether you mean the physical symptoms you can see in the mirror, what shows up on an ultrasound or MRI, or what a surgeon or pathologist sees when examining the uterus directly. Each perspective reveals something different about this condition, where tissue that normally lines the uterus grows into the muscular wall instead.
What Adenomyosis Looks Like From the Outside
The most visible external sign is what many people call “adenomyosis belly,” a persistent bloating or fullness in the lower abdomen that doesn’t go away after your period ends. Because the uterus can swell to two or three times its usual size, this bloating isn’t the same as typical period bloating. It can make your lower belly look distended even when you haven’t eaten, and for some people it’s noticeable enough to affect how clothing fits. The swelling tends to worsen around menstruation and may improve slightly between periods, though in more advanced cases the enlarged uterus stays prominent throughout the cycle.
The other thing you’ll notice is what your period looks like. Adenomyosis typically causes heavy, prolonged menstrual bleeding, often with large blood clots. Periods may last longer than seven days, and bleeding can be heavy enough that you soak through pads or tampons quickly. The blood may appear darker than usual, and clots the size of a coin or larger are common.
What It Looks Like on Ultrasound
On a transvaginal ultrasound, adenomyosis gives the uterine wall a patchy, uneven texture rather than the smooth, uniform appearance of a healthy muscle layer. Radiologists describe this as a “diffuse heterogeneous echotexture,” meaning the wall looks mottled with lighter and darker patches instead of consistent throughout. The walls of the uterus often appear asymmetrically thickened, with one side noticeably bulkier than the other.
Several specific signs help distinguish adenomyosis on ultrasound. Echogenic subendometrial lines and buds, which look like bright streaks or nodules extending from the uterine lining into the muscle, are the most reliable marker, picking up about 83% of cases in validation studies of the current diagnostic guidelines. Small dark circles called myometrial cysts may also appear within the muscle wall. These cysts correspond to actual fluid-filled endometrial glands trapped in the wrong location. They’re highly specific to adenomyosis (showing up in healthy uteruses only about 14% of the time), but they’re only visible in about a quarter of cases, so their absence doesn’t rule anything out. Fan-shaped shadowing, a pattern of dark streaks radiating outward from the lining, is another characteristic finding.
What It Looks Like on MRI
MRI provides the clearest picture and is often used when ultrasound results are inconclusive. The key feature is a thickened junctional zone, which is the boundary layer between the uterine lining and the muscular wall. In a healthy uterus, this zone appears as a thin, dark band on MRI. In adenomyosis, it becomes widened and irregular.
The most widely accepted diagnostic threshold is a junctional zone thicker than 12 millimeters. At that cutoff, MRI achieves a diagnostic accuracy of 85% and a specificity of 96%, meaning it very rarely misidentifies a healthy uterus as having adenomyosis. Within the thickened zone, bright spots on certain MRI sequences represent the misplaced endometrial glands, and small bright foci may indicate tiny areas of bleeding within the muscle wall.
What a Surgeon Sees During a Procedure
When viewed through a hysteroscope (a camera inserted through the cervix), the inner surface of an adenomyosis-affected uterus shows several distinctive changes. The lining may have a “strawberry pattern,” with scattered red spots from increased blood vessel density. Small hemorrhagic cysts can bulge into the uterine cavity, and there may be visible defects or irregularities in the endometrial surface. Areas of hypervascularization, where the tissue appears redder and more blood-rich than normal, are also suggestive. None of these signs alone confirms adenomyosis, but together they build a recognizable picture.
From the outside of the uterus during laparoscopic surgery, the organ often looks globally enlarged and rounded rather than its typical pear shape. The surface may appear slightly bluish or congested in areas where the embedded tissue is close to the outer wall.
What It Looks Like Under a Microscope
The definitive view of adenomyosis comes from examining tissue under a microscope, which is why a completely certain diagnosis historically required a hysterectomy. What pathologists see is endometrial glands and the supporting tissue (stroma) that normally stays within the uterine lining sitting deep inside the muscular wall where they don’t belong. The glands themselves look normal, resembling the basal (deepest) layer of the endometrium. They’re surrounded by their usual supportive tissue, essentially forming small islands of lining tissue embedded in muscle.
In the focal form, called an adenomyoma, these islands cluster into a distinct nodular mass with smooth muscle growing around the edges. Unlike fibroids, which are made entirely of muscle cells, adenomyomas contain both glandular tissue and muscle, giving them a mixed appearance.
How It Looks Different From Fibroids
This distinction matters because fibroids and adenomyosis can coexist and sometimes mimic each other on imaging. On ultrasound, fibroids typically appear as well-defined round masses with distinct borders. They’re usually darker (hypoechoic) and may contain bright spots from calcification. Adenomyosis, by contrast, creates poorly defined areas with blurry margins and a more diffuse, mottled pattern. When adenomyosis forms a focal mass (adenomyoma), it has indistinct edges and may contain small cystic spaces, while fibroids tend to have sharper boundaries and a more uniform internal texture.
On MRI, fibroids appear as distinct round masses that compress surrounding tissue, creating a visible capsule. Adenomyosis shows a widened, irregular junctional zone without a clear capsule. The practical difference for you: fibroids can be surgically removed individually, while adenomyosis is woven into the muscle wall itself, making it harder to excise without removing part of the uterus.