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 abscesses
• 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

• 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):

• 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

• 5.5-6 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

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)
  • 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

Abnormal Pregnancy

• Gestational sac >10mm without visible yolk sac

[[File:Iarge gestational sac|thumb|Gestational sac greater than 10mm without yolk sac, suggestive of abnormal pregnancy]

• Gestational sac >18mm without fetal pole

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

• Collapsed gestational sac

Collapsed gestational sac, suggestive of abnormal pregnancy

• 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

Pseudogestational sac, suggestive of abnormal pregnancy

• Absence of fetal heart beat in embryo with CRL >5mm
• FHR <90 bpm
• Molar pregnancy
  • Many small, irregular cystic structures in endometrium
  • "Snowstorm appearance"

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

Ectopic pregnancy

• Implantation of blastocyst outside of endometrium
• Occur in cervix, ovaries, fallopian tubes, 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

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

Simple ovarian cyst

Hemorrhagic cyst with blood clot