Diagnostic Ultrasound - Abdomen and Pelvis

Ovaries
Anatomy: Pelvis
GROSS ANATOMY
Overview
• Ovaries located in true pelvis, although exact position
variable
○ Only pelvic organ entirely inside peritoneal sac
○ Laxity in ligaments allows some mobility
○ Location affected by parity, bladder filling, ovarian size,
and uterine size/position
○ Located within ovarian fossa in nulliparous women
– Lateral pelvic sidewall below bifurcation of common
iliac vessels
– Anterior to ureter
– Posterior to broad ligament
○ Position more variable in parous women
– Pregnancy displaces ovaries, seldom return to same
spot
• Fallopian tube drapes over much of surface
○ Partially covered by fimbriated end
• Composed of medulla and cortex
○ Vessels enter and exit ovary through medulla
○ Cortex contains follicles in varying stages of
development
○ Surface covered by specialized peritoneum called
germinal epithelium
• Ligamentous supports
○ Suspensory ligament of ovary (infundibulopelvic
ligament)
– Attaches ovary to lateral pelvic wall
– Contains ovarian vessels and lymphatics
– Positions ovary in craniocaudal orientation
○ Mesovarium
– Attaches ovary to broad ligament (posterior)
– Transmits nerves and vessels to ovary
○ Proper ovarian ligament (utero-ovarian ligament)
– Continuation of round ligament
– Fibromuscular band extending from ovary to uterine
cornu
○ Mesosalpinx
– Extends between fallopian tube and proper ovarian
ligament
○ Broad ligament
– Below proper ovarian ligament
• Arterial supply: Dual blood supply
○ Ovarian artery is branch of aorta, arises at L1/L2 level
– Descends to pelvis and enters suspensory ligament
– Continues through mesovarium to ovarian hilum
– Anastomoses with uterine artery
• Drainage via pampiniform plexus into ovarian veins
○ Right ovarian vein drains to inferior vena cava
○ Left ovarian vein drains to left renal vein
• Lymphatic drainage follows venous drainage to preaortic
lymph nodes at L1 and L2 levels
Physiology
• ~ 400,000 follicles present at birth but only 0.1% (400)
mature to ovulation
• Variations in menstrual cycle
○ Follicular phase (days 0-14)
– Several follicles begin to develop
– By days 8-12, dominant follicle develops, while
remainder start to regress
○ Ovulation (day 14)
– Dominant follicle, typically 2.0-2.5 cm, ruptures and
releases ovum
○ Luteal phase (days 14-28)
– Luteinizing hormone induces formation of corpus
luteum from ruptured follicle
– If fertilization occurs, corpus luteum maintains and
enlarges to corpus luteum cyst of pregnancy
Variations With Age
• At birth: Large ovaries ± follicles due to influence of
maternal hormones
• Childhood: Volume < 1 cm³, follicles < 2 mm diameter
• Above 8 year old: ≥ 6 follicles of > 4 mm diameter
• Adult, reproductive age: Mean volume ~ 10 ± 6 cm³, max 22
cm³
• Postmenopausal: Mean ~ 2-6 cm³, max 8 cm³ and may
contain few follicle-like structures
IMAGING ANATOMY
Ultrasound
• Scan between uterus and pelvic sidewall
○ Ovaries often seen adjacent to internal iliac vessels
• Medulla mildly hyperechoic compared to hypoechoic cortex
• Dominant follicle around time of ovulation
○ Cumulus oophorus: Nodule or cyst along margin of
dominant follicle represents mature ovum
• Corpus luteum may have thick, echogenic ring
○ Doppler: Vascular wall or "ring"
○ Hemorrhage common
• Echogenic foci common
○ Nonshadowing, 1-3 mm
○ Represent specular reflectors from walls of tiny
unresolved cysts or small vessels in medulla
• Doppler: Low-velocity, low-resistance arterial waveform
• Volume (0.523 x length x width x height) more accurate
than individual measurements
ANATOMY IMAGING ISSUES
Imaging Recommendations
• Transabdominal (TA) US with full bladder is good for
overview of pelvic organs
○ Detects ovaries and masses superior to uterus that may
be missed by TV US
• Transvaginal (TV) US is excellent in assessing detail of
ovaries and characterizing lesions compared to TA US
○ Lesions higher in pelvis can be missed because of limited
field of view
• Postmenopausal ovaries can be difficult to detect because
of atrophy, paucity of follicles and surrounding bowel
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