Pelvic ultrasound (transvaginal)

Background

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

Indications

General

• Pelvic pain
• Abnormal pelvic or abdominal exam

Uterus

• Vaginal bleeding
• Fibroids
• IUD placement

Ovaries and adnexa

• Ovarian cyst
• Ovarian torsion
• Ovarian masses
• Tubo-ovarian abscess
• Hydrosalpinx

Pregnancy

• Confirm intrauterine pregnancy
• Gestational dating
• Fetal monitoring and surveillance
• Evaluation of placenta
• Spontaneous abortion
• Intrauterine fetal demise
• Ectopic pregnancy
• Heterotopic pregnancy
• Molar pregnancy

Technique

General

• Use 5 MHz endocavitary probe (high frequency, low penetration)
• Apply surgical lubricant inside and outside probe cover
• Place patient in lithotomy position
• Gently advance probe into vaginal canal and position adjacent to cervix
  • May be more comfortable for patient to insert probe into vagina herself
• Apply gentle pressure to lower abdominal wall with one hand and manipulate probe with other hand

Longitudinal scan

• Probe marker pointing at 12:00
• Shows anterior structures on left side of screen
• Begin midline at endometrial stripe
• Scan from right to left through uterus
• Move probe laterally to view adnexa and ovaries

Transverse scan

• Rotate probe 90 degrees counterclockwise so probe marker is pointing at 9:00
• Shows right-sided structures on left side of screen
• Start at endometrial stripe and scan throughout uterus
• Locate cornual flare (junction of uterus and fallopian tubes)
• Move probe laterally along fallopian tube to locate ovary
• Ovaries identified by follicular (anechoic or hypoechoic) structures

• 

  Uterus in longitudinal plane

• 

  Cornual flare (uterus and fallopian tube junction) in transverse plane

• 

  Normal ovary with follicles

Normal Findings

Uterus

• Anteverted: Fundus pointing to anterior abdominal wall
• Retroverted: Fundus pointing to posterior wall
• 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

• 

  Normal thickened endometrial stripe during secretory phase

• 

  Normal thin endometrial stripe during menses

Pregnancy (1st trimester)

• 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
  • "Intradecidual sign"
    • Thickened decidua on one side of uterine cavity surrounding anechoeic sac

• 5-6 weeks:
  • Yolk Sac
    • Circular (or sometimes as two parallel lines) echogenic structure with thick walls within gestational sac
    • Definitive evidence of 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

• 6-7 weeks
  • Fetal Pole
    • First visual manifestation of fetus (or "embryo")
    • Thickening of margin on yolk sac
  • Cardiac activity present (FHR ~100-115 bpm)
  • Crown rump length: ~5mm
• 8-9 weeks
  • Limb buds appear
  • Head identifiable
• 9-10 weeks
  • FHR ~170-180 bpm
  • Fetal movement visible
  • End of embryonic period

• 

  Double decidual sac sign

• 

  Intradecidual sign

• 

  Double bleb sign (yolk sac and amniotic cavity)

• 

  Fetal pole (Thickening of yolk sac on one side)

Abnormal Findings

Abnormal Pregnancy

• Gestational sac >10mm without visible yolk sac
• Gestational sac >18mm without fetal pole
• Collapsed gestational sac
• Pseudgestational sac
  • Endometrial breakdown during ectopic pregnancy
  • 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
• Absence of fetal heart beat in embryo with CRL >5mm
• FHR <90 bpm
• Molar pregnancy
  • Many small, irregular cystic structures in endometrium
  • "Snowstorm appearance"

• 

  Gestational sac greater than 10mm without yolk sac

• 

  Gestational sac greater than 18mm without fetal pole

• 

  Collapsed gestational sac

• 

  Pseudogestational sac

• 

  Molar pregnancy with multiple cystic lesions in endometrium ("snowstorm appearance")

Ectopic pregnancy

• Implantation of blastocyst outside of endometrium
• Occur in fallopian tubes, cervix, ovaries, peritoneal cavity, or scar of prior uterine surgery
• Most definitive sonographic sign is gestational sac with yolk sac, embryo, or fetal heart beat outside of the endometrium
• Tubal pregnancy
  • "Tubal ring" sign: echogenic thick-walled anechoic sac visualized between uterus and ovary (separate from ovary when pressure applied to fallopian tube with probe)
• Interstitial Pregnancy
  • Implantation of gestational sac in muscular wall of uterus at proximal regional of fallopian tubes
  • "Interstitial line" sign: hyperechoic line from endometrial stripe to cornual region adjacent to interstitial gestational sac
• Cervical Pregnancy
  • Implantation of gestational sac below internal cervical os
  • Can cause life-threatening hemorrhage
  • Must distinguish between cervical ectopic and spontaneous abortion at level of cervix:

______

• 

  Ectopic pregnancy

• 

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

• 

  Ectopic pregnancy between ovary and uterus, suggestive of tubal ectopic

• 

  Interstitial pregnancy

• 

  Cervical pregnancy

Ovarian Cysts

• Physiologic cysts
  • <3cm diameter
  • Ovarian follicle or corpus luteum
  • Typically don't cause complications
• Functional cysts
  • May produce hormones
  • Are associated with complications: hemorrhage, enlargement, rupture, torsion

• 

  Simple ovarian cyst

• 

  Hemorrhagic cyst with blood clot

Ovarian Torsion

• Bimodal age distribution: young women (15-30yo) and post-menopausal women
• Typically occur in enlarged ovaries (5-10cm)
• Sonographic signs:
  • Enlarged ovary from edema, engorgement, hemorrhage
  • Midline ovary
  • Free pelvic fluid
  • Underlying ovarian lesions
  • Doppler findings:
    • Decreased/absent venous or arterial flow
    • Absent/reversed diastolic flow
    • Can have normal flow (from dual supply from uterine and ovarian arteries)