Body (corpus) : Upper 2/3 of uterus

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  Fundus: Superior to ostia of fallopian tubes

Cervix : Lower 1/3 of uterus

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  Isthmus: Junction of body and cervix

Parametrium : Tissue immediately surrounding uterus

Myometrium : Smooth muscle forming bulk of uterus

Endometrium : Composed of 2 layers

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  Stratum basalis attached to myometrium, does not change

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  Stratum functionalis: Thicker, varies with cycle

Uterus is extraperitoneal in midline of true pelvis

Uterine position

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  Flexion is axis of uterine body relative to cervix

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  Version is axis of cervix relative to vagina

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  Anteversion ± anteflexion is most common

Peritoneum extends over bladder dome anteriorly and rectum posteriorly

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  Vesicouterine pouch (anterior cul-de-sac) : Anterior recess between uterus and bladder

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  Rectouterine pouch of Douglas (posterior cul-de-sac) : Posterior recess between vaginal fornix and rectum; most dependent portion of peritoneum in female pelvis

Supporting ligaments

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  Broad ligaments: Extend laterally to pelvic wall and form supporting mesentery for uterus

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  Round ligaments: Arise from uterine cornu and course through inguinal canal to insert on labia majora

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  Uterosacral ligaments (posteriorly), cardinal ligaments (laterally), and vesicouterine ligaments (anteriorly) form from connective tissue thickening by cervix

Fallopian tubes connect uterus to peritoneal cavity

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  4 segments: Interstitial (portion going through myometrium at cornua), isthmus, ampulla, infundibulum

Arteries : Dual blood supply

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  Uterine artery (UA) arises from internal iliac artery, anastomoses with ovarian artery

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    UA crosses over the ureter and enters uterus just above cervix

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  Arcuate arteries arise from UAs; seen in outer 1/3 of myometrium → radial arteries → spiral arteries (endometrium)

Neonatal: Prominent size secondary to effects of residual maternal hormone stimulation

Infantile: Corpus < cervix (1:2)

Prepubertal: Corpus = cervix (1:1)

Reproductive: Corpus > cervix (2:1)

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  7.5-9.0 cm (length); 4.5-6.0 cm (width); 2.5-4.0 cm (thickness)

Postmenopausal: Overall reduction in size, similar to prepubertal uterus

Inner layer (junctional zone): Thin and hypoechoic, < 12 mm

Middle layer: Thick, homogeneously echogenic

Outer layer: Thin, hypoechoic layer peripheral to arcuate vessels

Proliferative phase (follicular phase of ovary)

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  Cessation of menses to ovulation (up to day 14)

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  Estrogen induces proliferation of functionalis layer

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  Early: Thin, single echogenic line

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  Progressive hypoechoic thickening (4-8 mm), classic trilaminar appearance

Secretoryphase (luteal phase of ovary)

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  Ovulation to beginning of menstrual phase (days 14-28)

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  Increased echogenicity and progressive thickening up to 16 mm

Menstrual phase

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  Early: Cystic areas within echogenic endometrium indicating endometrial breakdown

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  Progressive heterogeneity with mixed cystic (blood) and hyperechoic (clot or sloughed endometrium) regions

Start with transabdominal exam, typically using curved low-frequency transducer

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  Gives “lay of the land”

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    Large lesions, particularly exophytic fibroids, may be much better seen transabdominally

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  Bladder should be partially full to push small bowel away and create an acoustic window

With rare exception (young virginal females), transvaginal exam should be performed for more detail

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  Sweep completely through uterus in both longitudinal and transverse planes

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  Angle probe posteriorly to evaluate cul-de-sac

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    Most dependent portion so free fluid and other peritoneal pathology implants in this area

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  Gently push on probe to show uterus slides easily over bowel ( sliding sign )

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    Adhesions (e.g., endometriosis) causes organs to be fixed

Measure uterus in all 3 dimensions and document all myometrial lesions

Entire length of endometrium needs to be evaluated in sagittal (longitudinal) plane

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  Measure thickest point perpendicular to endometrial stripe

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  If fluid is in the canal, measure each side separately and add measurements together

Color and pulsed-wave Doppler should be performed on any suspicious lesions

3D ultrasound additive in many cases, particularly müllerian duct (duplication) anomalies and intrauterine device evaluation

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  3D volume data sets are acquired and can be manipulated to show optimal projection

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  May also slice through data set creating individual images similar to CT

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  Perform at beginning of transvaginal scan before bladder starts to refill

Sonohysterography, with infusion of saline into endometrial cavity, may be used to evaluate endometrial pathology

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  Polyps vs. submucosal fibroid, hyperplasia, carcinoma