What theoretical knowledge is necessary for gynaecological (American Institute of Ultrasound in Medicine (AIUM)) ultrasound scans?

Theoretical Knowledge Required for Gynecological Ultrasound Scans

Core Anatomical Knowledge

Practitioners performing gynecological ultrasound must possess comprehensive understanding of pelvic anatomy including the uterus, ovaries, fallopian tubes, and surrounding structures, as systematic scanning through all tissue planes in at least two orthogonal directions is mandatory. 1

Uterine Anatomy

• The uterus must be examined in both short and long axis from fundus to cervix to avoid missing pathology such as interstitial pregnancies or fibroids that may lie off the endometrial canal 1
• Understanding of normal zonal architecture of the uterine corpus, which varies with menstrual cycle phase and may be indistinct during menstruation 2
• Recognition that pregnancy-related decidual changes can mimic gynecologic tumors 2

Ovarian Anatomy

• Complete scanning of both ovaries in short and long axis through the entire organ is required to identify peripheral cysts and adjacent masses 1
• Knowledge that ovarian stroma undergoes dynamic changes: shrinking with lower signal intensity during menstruation, reaching maximum size with high signal intensity during periovulation 2
• Understanding that functional cysts are common in reproductive-age women and typically resolve spontaneously, while surface-epithelial inclusion cysts are common in postmenopausal ovaries 2

Additional Pelvic Structures

• Fallopian tubes: Normal tubes originate from the cornua and can be visualized when distended by fluid (hydrosalpinx or tubo-ovarian abscess) 1
• Cul-de-sac (Pouch of Douglas): Small to moderate fluid is normal depending on menstrual cycle; large amounts or echogenic fluid suggests blood or pus 1

Technical Scanning Knowledge

Transabdominal Approach

• Provides larger field of view for visualizing uterus, adnexa, and entire pelvic contents including free fluid 1
• Requires adequate bladder filling for optimal visualization 3
• Limited by patient body habitus and bowel gas 1

Transvaginal Approach

• High-frequency probe proximity to reproductive organs minimizes interference from bowel gas and adipose tissue 1
• Should be performed with emptied bladder for optimal visualization 3
• Color Doppler is a standard component of pelvic ultrasound examination, with spectral Doppler added when indicated (particularly for torsion evaluation) 1
• Real-time imaging must be used throughout the procedure 3
• Chaperone presence is required for all transvaginal examinations 3

Combined Approach

• Transabdominal and transvaginal ultrasound are complementary and typically performed together per ACR-ACOG-AIUM-SPR-SRU guidelines 1
• Combined approach allows comprehensive evaluation of structures positioned too high for transvaginal visualization alone 3

Pathology Recognition

Benign Conditions

• Differentiation between simple cysts, hemorrhagic cysts, endometriomas, and dermoid cysts 4
• Recognition of leiomyomata (fibroids) and their complications including hemorrhage, torsion, and infarction 1, 5
• Identification of adenomyosis, which frequently coexists with fibroids 5
• Detection of endometrial polyps and distinguishing focal versus diffuse endometrial pathology 1

Malignancy Assessment

• Ultrasound demonstrates 94-100% sensitivity for detecting tubo-ovarian malignancy 1
• Recognition of suspicious features including enhancing mural nodules, solid components, and abnormal vascularity 6
• Understanding that ultrasound cannot definitively distinguish benign from malignant endometrial pathology, requiring tissue sampling 1

Emergency Conditions

• Ovarian torsion: Diagnosed with 70-95% sensitivity by identifying enlarged ovary with peripheral follicles and abnormal Doppler flow 1
• Ectopic pregnancy: Primary focus is identifying intrauterine pregnancy to minimize likelihood of ectopic pregnancy 1
• Pelvic inflammatory disease (PID): 90% sensitivity for ovarian involvement, 93% for tubal involvement 1

Physiologic State Considerations

Radiologists must understand how normal reproductive organs appear according to various physiologic states including menstrual cycle phase, pregnancy, and menopausal status. 2

• Menstrual cycle affects uterine zonal architecture and ovarian stroma appearance 2
• Pregnancy induces changes that may mimic pathology and must be correctly diagnosed to avoid unnecessary intervention 2
• Postmenopausal changes include atrophic endometrium and surface-epithelial inclusion cysts 2

Clinical Integration Knowledge

• Understanding when ultrasound findings require endometrial sampling or hysteroscopy for definitive diagnosis 1
• Recognition of ultrasound limitations requiring advanced imaging (MRI) for adenomyosis, deep endometriosis, or fibroid characterization 5, 4
• Knowledge of when CT or MRI findings eliminate need for redundant ultrasound evaluation 6

Common Pitfalls to Avoid

• Do not rely solely on transabdominal ultrasound in early pregnancy or obese patients, as resolution may be inadequate 3
• Interstitial pregnancy: Pregnancy within 5-7 mm of myometrial edge is concerning 1
• Ovarian torsion can occur despite identified intrauterine pregnancy when ovarian mass or cyst is present 1
• 26.8% of postmenopausal women experience pain during transvaginal ultrasound, a potential limitation 1