Uterine fibroids, also known as leiomyomas or myomas, are non-cancerous growths that develop from the smooth muscle tissue of the uterus. These growths can vary significantly in size, ranging from microscopic seedlings to large masses that can alter the shape and size of the uterus. While many fibroids remain asymptomatic, their impact is heavily determined by their precise location within the uterine structure. Understanding where a fibroid is growing is the first step in predicting its potential effects and guiding treatment.
Locations Within the Uterine Wall
The vast majority of uterine fibroids are classified based on the layer of the uterine wall where they originate and grow. The uterine wall is composed of three main layers, and fibroids are named according to their proximity to these distinct areas.
Intramural fibroids are the most common type, developing directly within the muscular wall of the uterus, known as the myometrium. Because they are embedded within the thickest part of the organ, they can cause the uterus to enlarge, potentially leading to increased menstrual bleeding or feelings of pelvic pressure.
Subserosal fibroids are located on the outer surface of the uterus, developing just beneath the serosa. As these fibroids grow, they project outward into the pelvic or abdominal cavity. They can grow quite large and press on adjacent organs.
Submucosal fibroids are the least common type, but they often cause the most significant symptoms. These growths are situated just beneath the endometrium and protrude into the uterine cavity, disrupting the normal function of the lining.
Fibroids Outside the Main Uterus
While most fibroids are contained within the uterine wall, certain structural variations and rarer locations exist outside the main body of the uterus. These distinct placements are important because they can present unique risks or symptoms compared to the three main types.
Pedunculated fibroids are a variation of either subserosal or submucosal types, characterized by being attached to the uterine wall by a narrow, stalk-like structure called a pedicle. A pedunculated subserosal fibroid projects from the outer uterine wall into the abdominal cavity on its stalk. The primary risk associated with these types is torsion, where the stalk twists, cutting off the fibroid’s blood supply and causing sudden pain.
Cervical fibroids are a rare occurrence, developing within the muscle tissue of the cervix, the lower, narrow part of the uterus. Since the cervix is naturally more compact, even small growths in this area can lead to significant obstruction or pressure-related symptoms.
Other extremely rare locations include interligamentous fibroids, which grow laterally between the folds of the broad ligament that supports the uterus. These growths are complex because they are positioned near major pelvic blood vessels and nerves, making surgical planning particularly challenging.
How Location Influences Symptoms and Treatment
The location of a fibroid is often a more important factor than its size in determining the symptoms a patient experiences. Submucosal fibroids, for example, are known to cause heavy menstrual bleeding (menorrhagia) and prolonged periods, even when they are small. They can also be a factor in infertility or recurrent pregnancy loss due to their effect on the uterine cavity.
In contrast, subserosal fibroids, especially larger ones, rarely cause heavy bleeding but are more likely to cause symptoms related to bulk and pressure. They can press on the bladder, leading to frequent urination, or on the rectum, causing constipation. Intramural fibroids can cause both heavy bleeding and pressure symptoms, depending on whether they bulge inward toward the cavity or outward toward the outer surface.
The location also dictates the most appropriate method for surgical removal, known as myomectomy. Submucosal fibroids that protrude significantly into the cavity are often removed using hysteroscopy, where instruments are inserted through the cervix and vagina. This approach is highly effective for these interior growths.
Fibroids that are intramural or subserosal generally require an approach that accesses the growths from outside the uterus. These are typically removed via laparoscopic or robotic surgery, which uses small abdominal incisions, or in some cases, traditional open abdominal surgery.