What size intramural (within the muscular wall of the uterus) uterine leiomyoma (fibroid) is likely to cause menorrhagia (irregular menstrual bleeding)?

From the Guidelines

Intramural uterine fibroids can cause irregular menstrual bleeding at any size, but they typically need to be at least 2-3 cm in diameter to disrupt the endometrium enough to cause noticeable bleeding irregularities. However, the relationship between fibroid size and bleeding is not straightforward, as noted in the 2024 study by the American College of Radiology 1. Even small fibroids (1-2 cm) that distort the uterine cavity or are located just beneath the endometrium (submucosal component) can cause significant bleeding, while some larger fibroids may cause no bleeding symptoms at all. The location of the fibroid is often more important than its size - those that impinge on or distort the uterine cavity are more likely to cause bleeding regardless of size.

Fibroids cause abnormal bleeding by increasing the surface area of the endometrium, disrupting normal endometrial vasculature, and interfering with uterine contractility during menstruation, as discussed in the 2024 study by the American College of Radiology 1. They may also cause local inflammatory changes and alter prostaglandin production. If you're experiencing irregular bleeding, an ultrasound evaluation is recommended to assess both the size and location of any fibroids, as this information is crucial for determining appropriate treatment options, according to the 2024 study by the American College of Radiology 1.

Some key points to consider when evaluating the relationship between fibroid size and bleeding include:

• The size of the fibroid is not the only factor that determines the likelihood of bleeding, as noted in the 2024 study by the American College of Radiology 1
• The location of the fibroid is often more important than its size, as discussed in the 2024 study by the American College of Radiology 1
• Small fibroids (1-2 cm) can cause significant bleeding if they distort the uterine cavity or are located just beneath the endometrium, as noted in the 2024 study by the American College of Radiology 1
• Larger fibroids may cause no bleeding symptoms at all, as discussed in the 2024 study by the American College of Radiology 1
• Ultrasound evaluation is recommended to assess both the size and location of any fibroids, as this information is crucial for determining appropriate treatment options, according to the 2024 study by the American College of Radiology 1.

It's also important to note that medical management options are available for patients with uterine fibroids, including anti-inflammatory medications, hormonal therapies, and other treatments, as discussed in the 2024 study by the American College of Radiology 1. These options can help reduce bleeding symptoms and improve quality of life for patients with uterine fibroids.

From the Research

Uterine Fibroid Size and Irregular Menstrual Bleeding

• The size of an intramural uterine fibroid that can cause irregular menstrual bleeding is not explicitly stated in the provided studies, but it is mentioned that fibroids can cause abnormal uterine bleeding, and the risk of having a major uterine procedure increases with fibroid size 2, 3, 4.
• A study found that the risk of having a major uterine procedure was 2% for those without fibroids and increased with fibroid size, reaching 47% for those with fibroids ≥ 4 cm in diameter at baseline 4.
• Another study found that fibroids ≥ 3 cm in diameter causing significant symptoms, pain or pressure, and wishing to retain their uterus may consider myomectomy 2.
• It is also mentioned that uterine artery embolisation is only recommended if surgery was planned for symptomatic fibroids and if the fibroids are <20 weeks in size, but no specific size is mentioned for irregular menstrual bleeding 2.

Fibroid Growth and Symptoms

• A study found that average fibroid growth was 89% per 18 months, but varied by baseline fibroid size, with small fibroids (<1 cm diameter) having an average growth rate of nearly 200% 5.
• The same study found that fibroids ≥ 2 cm in diameter had average growth rates well under 100%, and that a 2-cm fibroid is likely to take 4-5 years to double its diameter 5.
• Symptoms of uterine fibroids include abnormal menstrual bleeding, pelvic pressure, bowel dysfunction, urinary frequency and urgency, urinary retention, low back pain, constipation, and dyspareunia 3, 6.

Diagnosis and Treatment

• Ultrasonography is the preferred initial imaging modality for diagnosing uterine fibroids 3.
• Management of uterine fibroids should be tailored to the size and location of fibroids, the patient's age, symptoms, desire to maintain fertility, and access to treatment, and the experience of the physician 2, 3.
• Medical therapy to reduce heavy menstrual bleeding includes hormonal contraceptives, tranexamic acid, and nonsteroidal anti-inflammatory drugs 3.
• Surgical treatment includes hysterectomy, myomectomy, uterine artery embolization, and magnetic resonance-guided focused ultrasound surgery 2, 3.