Uterine fibroids are non-cancerous growths that develop from the muscle tissue of the uterus. These growths are common, affecting a large percentage of women during their reproductive years. For many, however, fibroids are a source of pelvic discomfort and pain. This pain is not monolithic; it arises from several distinct biological and mechanical processes, which depend heavily on the growth’s characteristics.
How Fibroid Location Determines Symptoms
The specific symptoms experienced are often determined by where the fibroid is situated within the uterine structure. Subserosal fibroids grow on the outside wall of the uterus, often protruding into the pelvic cavity, making them most likely to cause pressure symptoms on neighboring organs.
Intramural fibroids are embedded within the muscular wall of the uterus, known as the myometrium, and are the most commonly diagnosed type. These growths can distort the uterus’s overall shape and size, which influences both pressure and menstrual pain. Submucosal fibroids, though the least common, form just beneath the lining of the uterine cavity. Even small submucosal fibroids can cause the most significant symptoms related to bleeding and cramping.
Pain Caused by Physical Mass and Pressure
Chronic, persistent pain is often a direct result of the fibroid’s physical size and weight, a phenomenon known as mass effect. As fibroids grow larger, they occupy increasing space within the confined pelvic and abdominal cavities. This leads to a constant feeling of heaviness, fullness, or a dull ache in the lower abdomen.
Fibroids, particularly subserosal ones, can exert pressure on adjacent structures outside the uterus. A fibroid growing toward the front of the body can compress the bladder, causing a frequent and urgent need to urinate or difficulty fully emptying the bladder. Conversely, a fibroid pressing toward the back of the pelvis can constrict the rectum or parts of the bowel, leading to chronic constipation or a feeling of rectal fullness.
Fibroids growing on the posterior wall of the uterus can impinge upon sensitive pelvic nerves. When a large fibroid presses on the sciatic nerve or its roots, it results in referred pain that is often described as chronic lower back or leg pain. This sciatica-like symptom involves shooting or tingling sensations down the leg. This mechanical compression is a source of chronic discomfort, distinct from the sharp, cyclic pain associated with menstruation or tissue death.
Acute Pain from Tissue Degeneration
Acute pain occurs when a fibroid outgrows its limited blood supply, leading to acute symptoms. Rapid growth can cause the demand to exceed the supply, resulting in localized ischemia. The resulting process is called degeneration, where the fibroid tissue begins to die, often triggering intense, sudden pain.
One specific type, known as red degeneration, involves bleeding into the fibroid tissue itself and is often accompanied by an intense inflammatory response. The dying cells release chemical mediators that cause severe, localized pain. This degenerative pain is typically self-limiting, often resolving over a period of a few weeks once the tissue death stabilizes.
Another cause of acute pain involves pedunculated fibroids, which are attached to the uterus by a narrow stalk. If this stalk twists, a condition known as torsion, the blood supply to the fibroid is immediately cut off entirely. This twisting causes sudden, extremely sharp pain and is a medical emergency requiring prompt attention.
The Connection to Severe Menstrual Pain
Fibroids can increase the severity of menstrual pain, or dysmenorrhea, primarily through their effect on the uterine lining and muscle activity. Submucosal fibroids, in particular, can distort the uterine cavity, leading to a larger surface area of the uterine lining to shed each cycle. This often results in menorrhagia, which is abnormally heavy and prolonged menstrual bleeding.
To expel the excessive blood and tissue, the muscular wall of the uterus must contract more forcefully and frequently than normal. The uterus essentially attempts to push out the fibroid along with the uterine lining, which creates intensified cramping and pain during menstruation. This forceful muscular action is chemically mediated by an increased release of prostaglandins, powerful hormone-like compounds that stimulate painful uterine contractions.