Several conditions cause symptoms nearly identical to endometriosis, including chronic pelvic pain, painful periods, and discomfort during sex. The most commonly confused conditions are adenomyosis, irritable bowel syndrome, interstitial cystitis (painful bladder syndrome), uterine fibroids, pelvic inflammatory disease, pelvic congestion syndrome, and polycystic ovary syndrome. Some of these can even occur alongside endometriosis at the same time, making the picture harder to sort out.
Endometriosis takes an average of seven to ten years to diagnose, partly because its symptoms overlap so heavily with other conditions. Understanding what else could be causing your pain helps you have more productive conversations with your doctor and push for answers faster.
Adenomyosis: The Closest Match
Adenomyosis is the condition most frequently confused with endometriosis because it involves the same type of tissue behaving in a similar way. In endometriosis, uterine lining tissue grows outside the uterus, typically on the ovaries, bladder, intestines, or pelvic walls. In adenomyosis, that tissue grows inward, burrowing into the muscular wall of the uterus itself. This causes the uterus to thicken and enlarge, and the embedded tissue bleeds during menstruation, triggering pain from within the muscle.
The symptom profiles are close but not identical. Endometriosis pain tends to flare during your period and may ease between cycles, while adenomyosis pain can persist all the time, regardless of where you are in your cycle. About one-third of people with adenomyosis have no symptoms at all. When symptoms do appear, they range from mild to severe and typically include heavy menstrual bleeding, cramping, and a feeling of pressure in the lower abdomen. Many people are eventually diagnosed with both conditions simultaneously.
Irritable Bowel Syndrome
Endometriosis frequently involves the bowel. When endometrial tissue grows on the intestines or the walls of the pelvic cavity, it causes bloating, cramping, constipation, diarrhea, nausea, and pain during bowel movements. These are also the hallmark symptoms of IBS. The overlap is so significant that many people with endometriosis spend years being treated for a digestive problem before anyone considers a gynecological cause.
The key difference is timing. Endometriosis-related gut symptoms typically worsen around menstruation, while IBS symptoms tend to be triggered by food, stress, or irregular patterns that don’t follow a monthly cycle. That said, the two conditions can coexist, and having endometriosis on bowel tissue doesn’t rule out also having IBS. If your digestive symptoms reliably spike in the days before or during your period, it’s worth raising endometriosis with your doctor rather than accepting an IBS diagnosis alone.
Interstitial Cystitis (Painful Bladder Syndrome)
Interstitial cystitis causes chronic pelvic pain, lower back pain, and pain during sex, which are three of endometriosis’s most recognizable symptoms. It also causes an urgent and frequent need to urinate, sometimes up to 60 times a day, along with pain that builds as the bladder fills and eases after urination. When endometriosis grows directly on the bladder (called bladder endometriosis), the resemblance between these two conditions becomes especially difficult to distinguish without imaging or surgery.
These two conditions co-occur at remarkably high rates. In studies of women with chronic pelvic pain, the overlap between endometriosis and interstitial cystitis ranged from about 16% to 78%, depending on the population studied. Several large studies found co-occurrence rates between 42% and 66%. This means that if you’ve been diagnosed with one, there is a meaningful chance the other is also present, particularly if treatment for a single diagnosis isn’t fully controlling your symptoms.
Uterine Fibroids
Fibroids are noncancerous growths in or on the uterus, and they affect a large percentage of women by age 50. Both fibroids and endometriosis cause pelvic pain and heavy menstrual bleeding, which is why they’re commonly confused.
The nature of the pain differs in ways that can help you tell them apart. Fibroid pain is most closely tied to the heaviness of bleeding itself. Periods tend to be prolonged and extremely heavy, sometimes with clots, and the pain comes with that flow. Endometriosis pain is more cyclical overall but can be severe even between periods. Endometriosis is also more strongly linked to chronic pelvic pain that persists outside of menstruation and to pain during intercourse. Fibroids can additionally cause a sensation of fullness or pressure in the lower abdomen, frequent urination from the fibroid pressing on the bladder, and lower back pain from pressure on nearby structures.
Pelvic Inflammatory Disease
Pelvic inflammatory disease (PID) is an infection of the reproductive organs, usually caused by sexually transmitted bacteria. It shares several symptoms with endometriosis: lower abdominal pain, pain during sex, and burning during urination. But PID has features that endometriosis does not. Abnormal vaginal discharge, usually yellow or green with an unusual odor, is a hallmark of PID. Fever, chills, nausea, and vomiting can also accompany the infection.
PID tends to come on more acutely than endometriosis, which builds gradually over months or years. If you develop sudden pelvic pain alongside discharge, fever, or flu-like symptoms, an infection is a more likely explanation than endometriosis. PID is confirmed with vaginal cultures and blood tests showing infection markers. Untreated PID can cause scarring and fertility problems, so the distinction matters for timely treatment.
Pelvic Congestion Syndrome
Pelvic congestion syndrome (PCS) is caused by enlarged, varicose-like veins in the pelvis that pool blood and create a persistent, aching pain. Like endometriosis, PCS causes pelvic pain, pain during sex, lower back pain, and fatigue, and symptoms of both conditions can worsen with changes in the menstrual cycle.
The distinguishing feature of PCS is how pain responds to position and activity. PCS pain typically gets worse when you stand for long periods, sit for extended stretches, or change posture, and it eases when you lie down. Endometriosis pain is more tightly tied to your menstrual cycle and doesn’t shift predictably with body position. PCS can also cause visible varicose veins on the upper thighs, buttocks, or vulva, which endometriosis does not. On the other hand, PCS is not associated with abnormal uterine bleeding, prolonged periods, or fertility challenges, all of which point more toward endometriosis.
Polycystic Ovary Syndrome
PCOS and endometriosis both involve hormonal disruption and can both cause painful cramps and difficulty getting pregnant. Beyond that, their symptom profiles diverge considerably. Endometriosis is driven by excess estrogen, while PCOS is driven by excess androgens (male hormones). This hormonal difference produces very different outward signs.
PCOS is more likely to cause missed or very irregular periods, weight gain, abnormal hair growth on the face or body, thinning hair on the scalp, insulin resistance, and dark skin patches in body folds. Endometriosis is more likely to cause worsening cramps over time, pain during sex, pain with bowel movements or urination during your period, heavy bleeding, and spotting between periods. People with PCOS may miss periods because they aren’t ovulating, while people with endometriosis more commonly experience periods that are heavier or more painful than normal. The two conditions can coexist, but they require different treatment approaches because of their opposite hormonal drivers.
Why Diagnosis Takes So Long
The sheer number of conditions that mimic endometriosis is a major reason diagnosis is delayed. Laparoscopic surgery has long been considered the definitive way to confirm endometriosis, but imaging technology has improved substantially. Ultrasound can detect deep endometriosis with about 79% sensitivity and 94% specificity. MRI performs similarly overall, though accuracy depends on where the tissue is growing. MRI is better at identifying disease on the ligaments supporting the uterus and in vaginal tissue, while ultrasound is better at spotting growths on the rectum and sigmoid colon. For both imaging methods, specificity is excellent, ranging from 95% to 100%, meaning a positive finding is highly reliable.
In 2026, the American College of Obstetricians and Gynecologists published updated guidance designed to shorten the time to diagnosis. The new approach allows doctors to make a presumptive diagnosis based on your history, symptoms, and physical exam findings rather than waiting for surgery to confirm it. This means you can start treatment while imaging studies continue, rather than enduring months or years of workup before getting relief. If your symptoms overlap with multiple conditions on this list, tracking when pain occurs relative to your cycle, what makes it better or worse, and whether you have urinary or bowel symptoms alongside pelvic pain gives your doctor the clearest possible picture to work from.