What are some reliable resources for viewing images of normal uterus and ovaries, particularly for gynecological ultrasound?

Understanding Normal Uterine and Ovarian Anatomy on Ultrasound

Recommended Imaging Resources and Approach

For viewing normal uterine and ovarian anatomy, transvaginal ultrasound (TVUS) is the primary imaging modality of choice, supplemented by transabdominal ultrasound when needed, with systematic examination in at least two orthogonal planes. 1, 2

Systematic Examination Technique

Uterine Imaging Protocol

• Examine the uterus in both short and long axis planes, tracing completely from fundus to cervix to ensure comprehensive visualization 1, 3
• Position the transducer aligned with the long axis of the uterus, which is frequently angled right or left of the midline rather than directly midline 1
• For transabdominal approach: Place the transducer on the lower abdomen just above the symphysis pubis, using the distended bladder as an acoustic window with the bladder dome positioned just above the uterine fundus 1, 3
• For transvaginal approach: Achieve best imaging with an empty bladder, positioning the patient supine with legs flexed and pelvis elevated 1

Ovarian Imaging Protocol

• Scan both ovaries in at least two planes (short and long axis), examining completely through each paired organ 1
• Locate ovaries by sliding the transducer to the contralateral side and angling back toward the ovary of interest 1
• In reproductive-age women: Normal ovarian volume is typically <10 mL with variable follicle counts depending on menstrual cycle phase 1
• In postmenopausal women: Normal ovaries measure approximately 2.2 × 1.2 × 1.1 cm with average volume of 2.6 cm³, though ovaries may not be visible in 15-40% of cases due to atrophy 4, 5

Documentation Standards

The following elements should be systematically documented for complete evaluation: 3

• Date of last menstruation 3
• Transducer frequency used 3
• Approach/route (transabdominal vs transvaginal) 3
• Three dimensions and volume of each ovary 3
• Endometrial thickness and appearance (3-layer evaluation useful for screening) 3
• Any ovarian cysts, corpus luteum, or dominant follicles ≥10 mm 3
• Other uterine or ovarian pathology 3

Normal Anatomic Variations by Physiologic State

Menstrual Cycle Effects

• During menstruation: Uterine zonal architecture may appear indistinct, and ovarian stroma may shrink with lower signal intensity 6
• During periovulation: Ovarian stroma reaches maximum size with high signal intensity, and functional cysts are commonly seen 6
• Corpus luteum: Appears as a <3 cm cystic lesion with thick wall, may contain internal echoes or hemorrhage, typically demonstrates peripheral vascularity on color Doppler 7

Pregnancy-Related Changes

• First trimester: TVUS visualizes both ovaries in 95% of cases, while transabdominal approach identifies both in only 33% 8
• Second and third trimester: Ovarian visualization decreases significantly, with transabdominal ultrasound identifying both ovaries in only 16% of cases by late pregnancy 8
• Ovarian position shifts: Right ovary moves from 1 cm cranial to iliac spine (15-24 weeks) to 2.5 cm cranial (30-41 weeks); left ovary remains approximately 1 cm above iliac spine throughout pregnancy 8

Postmenopausal Changes

• Normal postmenopausal ovaries: Median volume 1.2-1.3 cm³, with surface-epithelial inclusion cysts commonly seen 6, 4
• Visualization rates: Both ovaries detected in 60% of postmenopausal women; at least one ovary visible in 85% 5

Critical Technical Considerations

Common Pitfalls to Avoid

• Failing to examine in two complete orthogonal planes can miss important findings such as interstitial pregnancy or fibroids located off the endometrial canal 1, 3
• Not tracing completely from fundus to cervix risks mistaking a gestational reaction from large ectopic pregnancy for the actual uterus 1, 3
• Inadequate bladder distension significantly limits visualization with transabdominal approach 1, 3
• Relying solely on transabdominal ultrasound for follicle counts is unreliable; transabdominal approach is suitable only for determining if ovarian volume exceeds 10 mL 1

When to Use Alternative Imaging

MRI serves as the gold standard for specific indications: 1, 9

• When ovaries are not adequately visualized by ultrasound (particularly in obese patients) 1
• For diagnosing and classifying Müllerian duct anomalies with 100% accuracy 9
• T2-weighted MRI can determine antral follicle counts and may be superior to TVUS for detecting follicles ≥3 mm 1

Normal Cul-de-Sac Findings

• Small to moderate fluid in the pouch of Douglas is normal in healthy females, varying with menstrual cycle phase 1
• Large amounts of fluid are abnormal, though may not always indicate significant pathology 1
• Echogenic fluid suggests blood or pus rather than simple physiologic fluid 1