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 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

Findings

Uterus

• Fundus pointing to anterior abdominal wall is anteverted
• Fundus pointing to posterior wall is retroverted

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 (1st trimester)

Double decidual sac sign

Intradecidual sign

Double bleb sign (yolk sac and amniotic cavity

Fetal pole (Thickening of yolk sac on one side)

• 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

Images

Normal

Normal thickened endometrial stripe during secretory phase

Normal thin endometrial stripe during menses

Abnormal

File:Iarge gestational sac

Gestational sac greater than 10mm without yolk sac, suggestive of abnormal pregnancy

Abnormal Pregnancy

Gestational sac greater than 18mm without fetal pole, suggestive of abnormal pregnancy

Collapsed gestational sac, suggestive of abnormal pregnancy

Pseudogestational sac, suggestive of abnormal pregnancy

Molar pregnancy with multiple cystic lesions in endometrium, "sandstorm appearance"

• 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"

Ectopic pregnancy

Ectopic pregnancy

Ectopic pregnancy at the cervix

Free fluid in cul-de-sac with no gestational sac visualized in uterus, presumed ectopic pregnancy in patient with positive pregnancy test

Ectopic pregnancy between ovary and uterus, suggestive of tubal ectopic

• 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 ring
  • Echogenic thick-walled anechoic sac visualized between uterus and ovary (separate from ovary when pressure applied to fallopian tube with probe)
• Interstitial Pregnancy
• 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:

Simple ovarian cyst

Hemorrhagic cyst with blood clot