Residency · Residency · Obstetrics Gynecology

Gynecologic Ultrasound: Uterine and Adnexal Pathology

Introduction

Gynecologic ultrasound is the primary imaging modality for evaluating pelvic pathology in non-pregnant women. Transvaginal sonography (TVS) provides superior resolution of the uterus, endometrium, and adnexa compared to transabdominal imaging. A systematic approach to image acquisition and interpretation enables accurate diagnosis and guides management of a broad spectrum of conditions, from benign leiomyomas to malignant ovarian neoplasms.

Uterine Pathology

Leiomyomas (Fibroids)

Leiomyomas are the most common pelvic tumor, with a prevalence of 70-80% by age 50. Sonographically, they appear as well-circumscribed hypoechoic masses with whorled internal echotexture; calcifications produce hyperechoic foci with posterior shadowing. The FIGO classification system divides them into submucosal (types 0-2), intramural (types 3-5), and subserosal (types 6-7). Submucosal fibroids are best demonstrated with saline infusion sonography. Degeneration alters the typical appearance: cystic degeneration shows anechoic areas, while red (carneous) degeneration in pregnancy presents with acute pain and heterogeneous echotexture. Sonographic features raising concern for leiomyosarcoma include rapid growth, irregular borders, heterogeneous echotexture with necrosis, and increased peripheral vascularity, though no feature reliably distinguishes sarcoma from fibroid.

Adenomyosis often coexists with fibroids and produces asymmetric myometrial thickening, myometrial cysts, heterogeneous echotexture, and a poorly defined junctional zone.

Endometrial Pathology

Endometrial thickness varies with the menstrual cycle: thin and echogenic in the proliferative phase (4-8 mm), thickest and trilaminar in the late proliferative phase, and uniformly echogenic in the secretory phase (7-14 mm). In postmenopausal bleeding, an endometrial thickness of 4 mm or less on TVS (without HRT) has a 99% negative predictive value for endometrial cancer. Endometrial polyps appear as focal echogenic thickening with a vascular pedicle (feeder vessel sign on Doppler). Endometrial hyperplasia presents as diffuse thickened echogenic endometrium. Endometrial carcinoma shows heterogeneous thickening, irregular endometrial-myometrial interface, and increased vascularity; any postmenopausal bleeding with thickness greater than 4 mm requires tissue sampling.

<image>Transvaginal ultrasound illustration comparing normal endometrial appearances across the menstrual cycle phases (early proliferative, late proliferative/trilaminar, and secretory), with endometrial thickness measurements annotated</image>

Uterine Anomalies

Mullerian duct anomalies affect 3-5% of women. The septate uterus (most common anomaly associated with adverse outcomes) shows a single external fundal contour with internal septum; 3D ultrasound is the gold standard for differentiating it from bicornuate uterus. Bicornuate uterus demonstrates a fundal cleft greater than 1 cm with two distinct endometrial cavities. Unicornuate uterus appears banana-shaped and deviated laterally.

Adnexal Pathology

Ovarian Cysts

Simple cysts (thin-walled, anechoic, posterior enhancement) less than 5 cm in premenopausal women are nearly always functional and resolve within 1-3 cycles. Hemorrhagic cysts show characteristic reticular (lace-like) internal echoes without internal vascularity. Corpus luteum cysts have a thick crenulated wall with a ring of fire on color Doppler. Dermoid cysts (the most common benign ovarian neoplasm in reproductive age) produce complex echogenic appearances with tip of the iceberg sign, dermoid mesh, and fat-fluid level. Endometriomas show homogeneous low-level internal echoes (ground-glass appearance); wall nodularity raises concern for malignant transformation.

Ovarian Neoplasms and Malignancy Assessment

O-RADS (Ovarian-Adnexal Reporting and Data System) provides standardized risk stratification from O-RADS 1 (normal) to O-RADS 5 (high malignancy risk). Features suggesting malignancy include solid components with internal vascularity, thick septations (greater than 3 mm), papillary projections, ascites, and peritoneal nodularity. The IOTA Simple Rules use five B-features and five M-features to triage masses. Tumor markers complement but do not replace ultrasound assessment.

<image>Transvaginal ultrasound illustration showing characteristic appearances of common adnexal masses: simple cyst, hemorrhagic cyst with reticular echoes, endometrioma with ground-glass echogenicity, and dermoid cyst with echogenic Rokitansky nodule and posterior shadowing</image>

Ectopic Pregnancy and Adnexal Emergencies

Ovarian torsion presents as an enlarged ovary with peripheral follicle displacement (string of pearls sign) and absent or diminished Doppler flow, though the presence of flow does not exclude torsion. Tubo-ovarian abscesses appear as complex, thick-walled, multiloculated masses with internal debris. Paratubal/paraovarian cysts are simple thin-walled cysts separate from the ipsilateral ovary.

Saline Infusion Sonography (SIS) and Sonohysterography

SIS is indicated for abnormal uterine bleeding, suspected polyps or submucosal fibroids, or recurrent pregnancy loss. Sterile saline distends the cavity during TVS, delineating intracavitary lesions with 95% sensitivity for endometrial polyps. Contraindications include active pelvic infection, pregnancy, and cervical stenosis.

<image>Saline infusion sonography illustration demonstrating a pedunculated endometrial polyp outlined by intracavitary saline, with the vascular pedicle visible on color Doppler, alongside a type 1 submucosal fibroid protruding into the cavity</image>

Clinical Pearls

A trilaminar endometrial pattern is characteristic of the late proliferative phase and should not be confused with pathology. Endometrial thickness of 4 mm or less in postmenopausal bleeding effectively excludes endometrial cancer (NPV 99%). Hemorrhagic cysts should show no internal vascularity on Doppler -- flow within a "clot" suggests a solid component and possible neoplasm. 3D ultrasound is the imaging standard for differentiating septate from bicornuate uterus, a distinction critical for surgical planning. O-RADS classification provides a standardized, evidence-based framework for adnexal mass management decisions.

References

1. Defined terminology and morphologic criteria for adnexal lesions. International Ovarian Tumor Analysis (IOTA) Group. Ultrasound Obstet Gynecol. 2000;16(5):500-505.
2. Andreotti RF, Timmerman D, Strachowski LM, et al. O-RADS US Risk Stratification and Management System. Radiology. 2020;294(1):168-185.
3. American College of Obstetricians and Gynecologists. The role of transvaginal ultrasonography in evaluating the endometrium of women with postmenopausal bleeding. Committee Opinion No. 734. Obstet Gynecol. 2018;131(5):e124-e129.
4. Defined sonographic criteria for diagnosis of uterine anomalies. ASRM Practice Committee. Fertil Steril. 2016;106(3):530-540.

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