Diagnostic Ultrasound - Abdomen and Pelvis
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Diagnostic Ultrasound - Abdomen and Pelvis

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Vagina SPECTRAL WAVEFORM OF VAGINAL ARTERY Anatomy: Pelvis Azygos artery Periurethral artery Vaginal artery Periurethral artery Vaginal artery (Top) Transabdominal spectral Doppler US of the azygos artery shows low-resistance flow during mid cycle. The findings are most probably due to the influence of cyclical/hormonal change. (Middle) Spectral waveform of VA by transvaginal scan shows highresistance flow, which is the most common pattern in normal females. (Bottom) Spectral Doppler ultrasound shows the VA by transperineal scan. The typical high flow resistance in the VA may decrease during sexual arousal, cyclically or related to hormonal changes. This phenomenon is useful for investigation and management of sexual dysfunction in postmenopausal women. 161

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 162

Vagina<br />

SPECTRAL WAVEFORM OF VAGINAL ARTERY<br />

Anatomy: <strong>Pelvis</strong><br />

Azygos artery<br />

Periurethral artery<br />

Vaginal artery<br />

Periurethral artery<br />

Vaginal artery<br />

(Top) Transabdominal spectral Doppler US of the azygos artery shows low-resistance flow during mid cycle. The findings are most<br />

probably due to the influence of cyclical/hormonal change. (Middle) Spectral waveform of VA by transvaginal scan shows highresistance<br />

flow, which is the most common pattern in normal females. (Bottom) Spectral Doppler ultrasound shows the VA by<br />

transperineal scan. The typical high flow resistance in the VA may decrease during sexual arousal, cyclically or related to hormonal<br />

changes. This phenomenon is useful for investigation <strong>and</strong> management of sexual dysfunction in postmenopausal women.<br />

161

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