What is the initial workup for a woman with fibroids (uterine leiomyomas) complaining of left-sided back pain?

Workup for a Woman with Fibroids Complaining of Left-Sided Back Pain

The initial workup for a woman with fibroids complaining of left-sided back pain should include pelvic ultrasound with Doppler, followed by MRI if needed to better characterize the fibroids and rule out other potential causes of pain. 1, 2

First-Line Imaging

• Pelvic ultrasound combining both transabdominal and transvaginal approaches with Doppler is the recommended initial diagnostic method, with 90-99% sensitivity and 98% specificity for detecting uterine fibroids 2
• This imaging helps determine fibroid location, size, and number, which is essential for understanding if the fibroids could be causing the back pain 1, 2
• Ultrasound can also help rule out other potential causes of left-sided back pain, such as renal pathology, which may present similarly 3

Advanced Imaging When Indicated

• MRI provides superior delineation of fibroid location, size, and number compared to ultrasound and can differentiate fibroids from adenomyosis and endometriosis 1, 2
• MRI is particularly useful when multiple fibroids are present or when the relationship between fibroids and surrounding structures needs to be better understood 2
• Saline infusion sonohysterography (SIS) should be considered if submucosal fibroids are suspected, as it improves visualization between endometrial pathologies and submucosal fibroids 2

Laboratory Assessment

• Complete blood count to assess for anemia, which may result from heavy menstrual bleeding associated with fibroids 3
• Pregnancy testing to rule out pregnancy as a cause of uterine enlargement or pain 3
• Urinalysis to exclude urinary tract infection or kidney stones that could cause left-sided back pain 3

Additional Workup Considerations

• Endometrial biopsy should be considered if the patient has abnormal uterine bleeding, particularly in perimenopausal women, to rule out endometrial pathology 3
• Assessment for rapid growth of fibroids, particularly in perimenopausal women, as this may indicate the presence of sarcoma (estimated risk of unexpected uterine sarcoma is 2.94 per 1,000, with higher risk in older patients) 3

Differential Diagnosis for Left-Sided Back Pain

• Fibroid-related causes:

  • Large posterior wall fibroids causing direct pressure on nerves or surrounding structures 3
  • Fibroid degeneration, particularly red degeneration, which can cause acute pain 4
  • Torsion of a pedunculated fibroid 4

• Non-fibroid causes that should be ruled out:

  • Urinary tract pathology (kidney stones, pyelonephritis) 3
  • Musculoskeletal conditions 3
  • Gastrointestinal disorders 3
  • Endometriosis or adenomyosis 1

Common Pitfalls to Avoid

• Inadequate assessment of submucosal fibroids that may affect fertility or cause abnormal uterine bleeding 5
• Incomplete evaluation of the entire uterus, particularly in cases of multiple fibroids 5
• Relying solely on transvaginal ultrasound for large fibroids or an enlarged uterus without complementary transabdominal ultrasound 5
• Failing to consider non-gynecological causes of left-sided back pain 3

By following this systematic approach to workup, clinicians can accurately diagnose the cause of left-sided back pain in women with fibroids and determine the most appropriate treatment plan based on the findings.