Endometriosis and fibroids are two common gynecological conditions, but they’re not the same. Both can affect the uterus and cause symptoms like pelvic pain or heavy bleeding, but they differ in how they develop, how they’re diagnosed, and how they’re treated.
Endometriosis happens when tissue similar to the uterine lining grows outside the uterus—often on the ovaries, fallopian tubes, or other pelvic structures. This tissue responds to hormones and can cause inflammation, scarring, and chronic pain. For some, it also affects fertility.
Fibroids, by contrast, are benign tumors that form in or on the uterus. They don’t spread outside it. Some people with fibroids experience heavy periods, pelvic pressure, or frequent urination. Others have no symptoms at all.
What Are Uterine Fibroids and Endometriosis?
Fibroids and endometriosis are two of the most common gynecological conditions. Both affect the reproductive system, and both can cause pelvic pain or heavy periods—but they’re very different in how they develop, where they grow, and how they’re treated. Understanding these differences is key to getting the right diagnosis and care.
How Uterine Fibroids Develop
Fibroids are benign (non-cancerous) tumors that grow from the muscle tissue of the uterus. We don’t fully understand why they form, but hormones—especially estrogen—and genetics both appear to play a role. If a close relative has had fibroids, your risk may be higher.
Fibroids can develop in different areas of the uterus:
- Intramural fibroids grow within the uterine wall.
- Subserosal fibroids extend outward from the uterus.
- Submucosal fibroids push into the uterine cavity.
They can range in size from a few millimeters to several centimeters. Some cause no symptoms at all; others lead to heavy bleeding, pelvic pressure, or frequent urination, depending on their size and location.
It’s also possible for fibroids and adenomyosis (a condition similar to endometriosis) to occur concurrently.
How Endometriosis Develops
Endometriosis occurs when endometrial tissue starts growing outside the utrerus—often on the ovaries, fallopian tubes, or other pelvic organs. The cause isn’t fully understood, but one widely accepted theory is retrograde menstruation, where menstrual blood flows backward through the fallopian tubes instead of leaving the body.
This misplaced tissue responds to hormones the same way uterine lining does—it thickens, breaks down, and bleeds during each cycle. But without a way to exit the body, the blood becomes trapped, leading to inflammation, scar tissue, and pain. Over time, endometriosis can also affect fertility.
What's Actually Growing?
The core difference lies in what’s growing and where:
- Fibroids are discrete, solid masses made of muscle and connective tissue. They don’t spread beyond the uterus and typically stay where they form.
- Endometriosis involves tissue that spreads and attaches to areas it shouldn’t, potentially affecting multiple organs. It can cause adhesions—bands of scar tissue that bind organs together, making symptoms more complex and harder to pinpoint.
Both conditions are hormone-sensitive, especially to estrogen. This is why symptoms often lessen after menopause, when estrogen levels naturally drop.
Main Differences
While endometriosis and fibroids are both common gynecological conditions, they differ significantly in how they affect the body. These differences impact diagnosis, treatment, and long-term health outcomes.
One of the most important distinctions lies in the nature of the tissue: fibroids are solid, non-cancerous growths, while endometriosis involves endometrial-like tissue growing outside the uterus, where it doesn’t belong.
Where They Develop in the Body
Fibroids are confined to the uterus. They form in the muscular wall, can project into the uterine cavity, or grow outward toward the abdominal cavity. No matter the direction of growth, they’re always connected to the uterus.
Endometriosis, on the other hand, can develop almost anywhere in the body. It most commonly affects pelvic organs—like the ovaries, fallopian tubes, or the outer surface of the uterus—but has also been found in areas as distant as the diaphragm or lungs. This widespread distribution can make symptoms harder to trace and contributes to the variability in pain and severity.
How They Affect the Uterus and Surrounding Organs
Fibroids tend to cause symptoms through pressure or distortion. They can enlarge the uterus or press against the uterine lining, leading to heavy or prolonged periods. Depending on their size and position, they may also put pressure on nearby organs, causing urinary frequency or bowel changes.
Endometriosis behaves differently. The tissue outside the uterus responds to hormonal changes and bleeds during the menstrual cycle, just like the uterine lining. But because it has no way to exit the body, this blood can trigger inflammation, swelling, and scar tissue. Over time, that can lead to adhesions, where organs stick to each other or to the abdominal wall, often causing persistent pelvic pain.
Impact on Fertility
Both conditions can affect fertility, but through different mechanisms.
Fibroids may interfere with conception if they distort the shape of the uterine cavity or block the fallopian tubes. This can prevent fertilization or implantation, depending on their size and location.
Endometriosis is more strongly linked to infertility. Inflammation and adhesions can block the fallopian tubes or distort pelvic anatomy. The condition may also impact egg quality and the function of the uterine lining. Estimates suggest that 30–50% of women with endometriosis may experience fertility challenges, compared to about 5–10% of those with fibroids.
Shared Symptoms of Uterine Fibroids and Endometriosis
Endometriosis and fibroids can present with overlapping symptoms, which often makes it hard to distinguish between them without a thorough medical evaluation. Both conditions affect the reproductive system, respond to hormonal shifts, and can significantly impact daily life. But the causes—and long-term implications—are different, which makes an accurate diagnosis important.
Chronic Pelvic Pain
Pelvic pain is one of the most common symptoms associated with both conditions, but it tends to feel different depending on the cause.
Fibroid-related pain often feels like pressure or heaviness in the lower abdomen. This is especially true when fibroids grow large enough to press against surrounding tissues. Some people describe it as a dull, persistent ache—uncomfortable, but not always sharp.
Endometriosis-related pain is typically more intense and more variable. It can feel sharp, cramping, or stabbing, and may occur not just during menstruation but throughout the month. This ongoing pelvic pain can interfere with work, exercise, or sleep, and it often doesn’t respond well to over-the-counter medication.
Heavy or Prolonged Menstrual Bleeding
Both conditions can cause heavy periods, but the reasons behind the bleeding differ.
Fibroids, especially those located inside the uterine cavity, can make periods unusually heavy or prolonged. You may need to change pads or tampons frequently and may pass large clots.
Endometriosis can also lead to heavy or irregular bleeding. Inflammation and hormonal imbalances can cause prolonged menstrual periods or cause bleeding between periods, making it feel like menstruation never really stops.
Abnormal Bleeding and Other Severe Symptoms
Irregular bleeding—such as spotting between periods or bleeding after sex—can occur with either condition. In fibroids, this is often due to the uterus being unable to contract properly, while in endometriosis, the cause is more closely tied to inflammation and hormone activity.
When symptoms are severe or hard to explain, your provider may use imaging tools like transvaginal ultrasound or MRI to look for signs of fibroids or endometrial tissue outside the uterus. These tests can help clarify what’s happening and guide the next steps in care.
Bladder and Bowel Issues
As these conditions affect areas beyond the uterus, symptoms can extend to the bladder and bowel.
Fibroids can press against the bladder, leading to frequent urination or a feeling of incomplete emptying. You might wake up several times a night needing to use the bathroom. If fibroids press on the rectum, painful bowel movements and constipation can also occur.
Endometriosis involving the bowel is more likely to cause sharp, cramping pain—especially during menstruation. Bowel movements may cause severe pain or feel unusually difficult. Some describe the sensation as sharp or cutting, especially if endometrial lesions have formed on the rectum or lower colon.
Differences in Pain and Symptoms
Fibroids and endometriosis can present with similar symptoms, but how and when those symptoms show up often differ. Recognizing these patterns can help guide earlier, more accurate diagnoses and improve patient outcomes. Below are some key distinctions to be aware of when discussing symptoms with your healthcare provider.
Fibroids
Fibroids are more likely to cause a sensation of pressure or heaviness in the pelvis, especially as they grow. This can feel like something is physically occupying space in your lower abdomen. The discomfort is often steady and doesn’t necessarily change with your cycle.
Fibroid symptoms can include:
- A visible or noticeable abdominal bulge
- Clothing fitting more tightly around the waist
- A firm mass that can be felt through the abdomen (in larger fibroids)
- Frequent urination or difficulty fully emptying the bladder
- Low back or leg pain if fibroids press on nearby nerves
- Abnormal uterine bleeding
Fibroid-related bloating typically results from the size and location of the growths, not from inflammation, and tends to be persistent rather than cyclical.
Endometriosis
Endometriosis pain is closely tied to the menstrual cycle. It often starts before your period, intensifies during menstruation, and may persist afterward. Over time, the inflammation caused by misplaced endometrial tissue can lead to chronic pelvic pain that’s present throughout the month.
Common endometriosis-specific symptoms include:
- Severe menstrual cramps that don’t improve with typical pain medications
- Chronic pelvic pain that’s not limited to period days
- Pain during or after sex (especially with deep penetration)
- Fatigue, which may be related to chronic inflammation and disrupted sleep
- Digestive symptoms like diarrhea, constipation, nausea, especially during your period
- Rarely, shoulder pain during menstruation if tissue has spread near the diaphragm
These symptoms can be misleading and are sometimes mistaken for gastrointestinal or urinary conditions, which is why a full clinical evaluation is so important.
When to Seek Evaluation
Because fibroids and endometriosis can both impact fertility, quality of life, and long-term health, early evaluation matters. If you’re experiencing ongoing pelvic pain, unusual bleeding, or symptoms that disrupt your daily routine, speak with your provider. Diagnostic imaging (such as ultrasound or MRI) and a detailed symptom history are often needed to tell these conditions apart, and to create a treatment plan that improves outcomes and addresses the full picture of your health.
Diagnosing Fibroids and Endometriosis
Getting a clear diagnosis is a critical first step in treating uterine fibroids or endometriosis. While the symptoms of both conditions can overlap, the way they’re diagnosed is different.
Blood tests don’t play a primary role in diagnosing either fibroids or endometriosis, but they can support the overall evaluation and evaluate for things like anemia if you’re having heavy menstrual bleeding. Beyond these, each condition has different diagnostic requirements.
How Uterine Fibroids Are Diagnosed
Providers often begin evaluating fibroids with a pelvic exam. If fibroids are large or located on the outer wall of the uterus, they may be detectable by touch. Your provider may notice changes in the size, shape, or consistency of the uterus.
Imaging provides the most detailed information:
- Ultrasound is usually the first imaging test. It’s non-invasive and can confirm the presence, size, and location of fibroids.
- MRI may be used for more complex cases or surgical planning. It gives a more precise view of fibroid size and structure.
- Saline infusion sonography (also called SIS or sonohysterography) involves filling the uterus with saline during ultrasound to get a clearer image of fibroids inside the uterine cavity.
These imaging tools help guide decisions about treatment, especially if symptoms are severe or if fertility is a concern.
How Endometriosis is Diagnosed
Endometriosis is harder to diagnose because the tissue often doesn’t show up on standard imaging. Some larger lesions, like ovarian endometriomas (also known as “chocolate cysts”), can be seen with:
- Transvaginal ultrasound
- MRI, which may help identify deep-infiltrating endometriosis
However, smaller or more scattered implants often go undetected with imaging alone.
The gold standard for endometriosis diagnosis is laparoscopy, a minimally invasive surgical procedure. A small camera is inserted through a small incision in the abdomen to directly view the pelvic organs. If suspicious tissue is found, a biopsy can confirm the diagnosis. In many cases, treatment can be done during the same procedure.
Treatment Options
When it comes to treating endometriosis vs fibroids, there's no one-size-fits-all approach. Treatment depends on many factors including the severity of symptoms, your age, whether you want to have children, and how the condition affects your quality of life. Both conditions offer a range of treatment options from conservative management to surgical intervention, and finding the right balance is key.
Treating Uterine Fibroids
Treatment for fibroids depends on their size, location, and how much they’re affecting your quality of life. Common options include:
- Medication: NSAIDs can ease pain, and hormonal birth control may reduce heavy bleeding. GnRH agonists or medications can shrink fibroids temporarily, but are usually used short-term.
- Uterine Fibroid Embolization (UFE): A minimally invasive procedure that blocks the blood supply to fibroids, causing them to shrink. UFE offers symptom relief without surgery and preserves the uterus.
- Surgery: Myomectomy removes fibroids while keeping the uterus intact. It can be done via open surgery, laparoscopy, or hysteroscopy, depending on the fibroid location. Hysterectomy is a permanent option that removes the uterus and eliminates fibroids entirely.
Treating Endometriosis
Endometriosis treatment focuses on managing pain, slowing disease progression, and preserving fertility when needed. Approaches often include:
- Medication: Hormonal treatments like birth control, Orilissa, or Lupron can reduce symptoms by suppressing estrogen. NSAIDs may help with mild pain but are often less effective for deep or chronic pain.
- Surgery: Laparoscopic excision surgery removes endometrial implants and can relieve pain, especially in moderate to severe cases. It’s often done by specialists trained in advanced techniques.
- Long-Term Management: After surgery, many people stay on hormonal therapy to reduce recurrence. Additional support may include pelvic floor therapy, pain management strategies, or complementary treatments like acupuncture.
Making Sense of Overlapping Symptoms
Endometriosis and fibroids can both cause pelvic pain, heavy periods, and other disruptive symptoms, but they’re fundamentally different conditions that require different diagnostic tools and treatment approaches.
Accurate diagnosis is the first step toward relief, and once diagnosed, treatment plans should be tailored to your needs, goals, and symptoms.
That might include medication, hormone therapy, or minimally invasive surgery. Some people benefit from procedures like uterine fibroid embolization or advanced laparoscopic excision, especially when symptoms are severe or haven’t improved with conservative care.
The most important step is finding a provider who takes your symptoms seriously, helps you understand your options, and works with you to find an approach that fits your life.
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Frequently Asked Questions (FAQ):
What are three signs of endometriosis?
Common signs of endometriosis include painful periods (dysmenorrhea), pelvic pain that extends beyond the menstrual cycle, and chronic fatigue. Other symptoms may include pain during intercourse and heavy menstrual bleeding.
What does a fibroid belly look like?
A fibroid belly may appear swollen or distended due to the growth of fibroids within the uterus. This can lead to an enlarged abdomen that may resemble pregnancy or weight gain.
What does a fibroid flare-up feel like?
A fibroid flare-up can cause symptoms such as pelvic pain, cramping, heavy menstrual bleeding, and pressure on the bladder or bowel, leading to frequent urination or constipation.
Can you have fibroids without endometriosis?
Yes, it is possible to have fibroids without having endometriosis. Although both conditions affect the uterus, they are distinct and can occur independently of each other.
