Pelvic ultrasound (transvaginal)

Background

• Also known as endovaginal ultrasound
• Used to evaluate female reproductive organs including uterus, ovaries, fallopian tubes, cervix, and vagina

Indications

• Abnormal uterine bleeding
• Abnormal abdominal or pelvic exam
• Pelvic pain
• Confirm intrauterine pregnancy
• Gestational dating during pregnancy
• Fetal monitoring and surveillance
• Evaluation of placenta
• Evaluate for spontaneous abortion
• Evaluate for ectopic pregnancy
• Uterine fibroids
• IUD placement confirmation
• Ovarian torsion
• Ovarian cysts

Technique

• Probe and transducer
  • Endocavitary probe (high frequency, low penetration)
  • Probe "dot" stays on left side of ultrasound screen
    • Corresponds with anterior structures (if probe marker held at 12:00) and right-sided structures (if probe marker held at 9:00)

• Patient positioning
  • Lithotomy position
  • Gently advance probe into vaginal canal
  • May be more comfortable for patient to insert probe into vagina herself

Findings

• Endometrial stripe: Measured from thickest echogenic area (from one basal endometrial interface to the other, including canal)
  • Pre-menopausal:
    • During menstruation: 2-4mm
    • Early proliferative phase: 5-7mm
    • Late proliferative phase: 11mm
    • Secretory phase: 7-16mm
    • After D&C or SAB: >5mm
      • Consider retained POC if thicker
  • Post-menopausal:
    • With vaginal bleeding: <5mm
    • Without vaginal bleeding: <11mm

• Adnexa:
  • Simple ovarian cyst: <2.5-3cm

• Pregnancy:
• 4-5 weeks:
  • Gestational sac
    • First sign of early pregnancy, usually seen between 3-5 weeks gestation
    • Double decidual sac sign:
      • Two concentric rings (uterine lining and gestation lining) around anechoic gestational sac
      • Highly suggestive of intrauterine pregnancy (before yolk sac or embryo embryo visualized)
      • 

        Double decidual sac sign
    • Intradecidual sign:
      • Thickened decidua on one side of uterine cavity surrounding anechoeic sac
      • 

        Intradecidual sign
  • Pseudgestational sac
    • May be erroneously interpreted as true gestational sac in ectopic pregnancy
    • Irregularly shaped
    • Located in endometrial cavity, instead of eccentrically within endometrium
    • No yolk sac present
    • May not have double decidual sac sign
• 5.5-6 weeks:
  • Yolk Sac
    • Circular (or sometimes as two parallel lines) echogenic structure with thick walls within gestational sac
    • Only seen in intrauterine pregnancy
    • Multiple yolk sacs is earliest sign in multiple gestational pregnancy
  • Double bleb sign:
    • Yolk sac and amniotic cavity that look like two bubbles within gestational sac

Double bleb sign (yolk sac and amniotic cavity

• 6-7 weeks
  • Fetal Pole
    • First visual manifestation of fetus (or "embryo")
    • Thickening of margin on yolk sac
    • 

      Fetal pole (Thickening of yolk sac on one side)

Images

Normal

Normal thickened endometrial stripe during secretory phase

Normal thin endometrial stripe during menses

Abnormal

Ectopic pregnancy at the cervix

Free fluid in cul-de-sac, no gestational sac visualized in uterus

Simple ovarian cyst

Hemorrhagic cyst with blood clot