What should I look for in a transvaginal Ultrasound (USG) for a patient with irregular menses?

Transvaginal Ultrasound Findings to Evaluate in Patients with Irregular Menses

For patients with irregular menses, transvaginal ultrasound should be the first-line imaging modality, combined with transabdominal ultrasound for complete assessment of pelvic structures. 1

Key Structures to Evaluate

1. Endometrium Assessment

• Endometrial thickness and morphology:

  • In premenopausal women: No validated upper limit cutoff exists, but abnormal echogenicity and texture correlate with underlying pathology 1
  • Document phase of menstrual cycle as thickness varies normally
  • Look for heterogeneity, focal thickening, or masses within the endometrial cavity

• Endometrial lesions:

  • Polyps: Look for focal thickening with possible vascular pedicle on Doppler
  • Hyperplasia: Diffuse thickening with possible cystic changes
  • Submucosal fibroids: Focal masses distorting the endometrial cavity

2. Myometrial Assessment

• Adenomyosis: Look for:

  • Heterogeneous myometrium
  • Myometrial cysts
  • Asymmetric thickening of anterior or posterior wall
  • Poorly defined endometrial-myometrial junction
  • Sensitivity and specificity of 82.5% and 84.6% respectively 1

• Leiomyomas (fibroids):

  • Document number, size, location (submucosal, intramural, subserosal)
  • Assess for degeneration, calcification, or necrosis
  • Note impact on endometrial cavity

3. Ovarian Assessment

• Ovarian morphology:

  • Volume (abnormal if ≥10ml) 2
  • Follicle count (polycystic morphology if ≥20 follicles per ovary) 2
  • Presence of dominant follicle or corpus luteum
  • Look for ovarian cysts or masses

• Polycystic ovarian morphology:

  • Common cause of irregular menses
  • Look for multiple small peripheral follicles in a "string of pearls" pattern
  • Increased ovarian volume and stroma

4. Additional Findings

• Adnexal masses:

  • Document size, location, complexity, vascularity
  • Simple cysts up to 3 cm generally require no follow-up 2
  • Simple cysts 3-10 cm should have follow-up ultrasound in one year 2

• Free fluid:

  • Note presence, location, and estimated volume
  • Assess for complex features suggesting hemorrhage or infection

Technical Considerations

1. Combined approach:

   • Transvaginal ultrasound provides superior resolution for detailed assessment 1
   • Transabdominal ultrasound offers broader overview and is necessary for enlarged structures 1

2. Doppler assessment:

   • Essential component of pelvic ultrasound 1
   • Helps distinguish fluid from vascular soft tissue
   • Evaluates vascularity of endometrial and myometrial lesions
   • Visualization of vascular pedicle has specificity of 62-98% for endometrial polyps 1

3. Timing considerations:

   • Document day of menstrual cycle during examination
   • Avoid scanning during menses as this can interfere with proper visualization 2
   • Consider sonohysterography for further evaluation of focal endometrial abnormalities 1

Common Pitfalls and Limitations

1. False-normal appearance:

   • Up to 14% of patients with abnormal bleeding may have polyps or submucosal fibroids despite normal-appearing endometrium on conventional transvaginal ultrasound 3
   • Consider sonohysterography if clinical suspicion remains high despite normal ultrasound

2. Coexisting pathologies:

   • Detection of adenomyosis is limited when coexisting with leiomyomas (sensitivity drops from 97.8% to 33.3%) 1
   • Carefully evaluate for multiple pathologies

3. Overlapping features:

   • Benign and malignant conditions may have similar ultrasound appearances 4
   • Cystic changes are seen in 76% of benign conditions but also in 24% of endometrial malignancies 4

4. Limitations in specificity:

   • Transvaginal ultrasound cannot always reliably distinguish between benign proliferation, hyperplasia, polyps, and cancer 5
   • Tissue sampling may be required for definitive diagnosis

When ultrasound findings are inconclusive or further characterization is needed, consider sonohysterography or MRI for additional evaluation 1.