Is it normal for one ovary to not be visible on ultrasound in a female patient of reproductive age?

Is It Normal for One Ovary to Not Be Seen on Ultrasound?

Yes, it is relatively common and usually normal for one ovary to not be visualized on pelvic ultrasound in reproductive-age women, occurring in approximately 20% of cases, and this finding carries a very low risk of missing significant pathology. 1

Frequency and Clinical Significance

• Non-visualization of one or both ovaries occurs in approximately 20.6% of pelvic ultrasounds, making this a frequent clinical scenario rather than an exceptional finding 1
• When ovaries are not visualized on ultrasound and no other concerning findings are present, the negative predictive value for malignancy approaches 100%, meaning the risk of missing ovarian cancer is essentially zero 2, 3
• Among non-visualized ovaries that later underwent surgical pathology, 64.6% were completely normal, and when abnormalities were found, the majority (88%) were benign lesions ≤1 cm in size 1

Technical and Anatomic Factors

• MRI without IV contrast may be useful in the few patients for whom the ovaries are not adequately visualized with ultrasound, particularly in obese patients or when precise ovarian assessment is clinically necessary 4
• The ovary may be positioned high and superficial, making it better visualized via transabdominal rather than transvaginal approach in some cases, though transvaginal ultrasound with ≥8 MHz transducer remains the optimal method when feasible 4
• Common associated findings with non-visualized ovaries include uterine fibroids and hemoperitoneum, which can obscure ovarian visualization 2

Age-Related Considerations

• Non-visualization increases with age, but even at 80 years of age, one or both ovaries can still be visualized in two out of every three women 5
• Having only one ovary visualized on an initial ultrasound exam advances the timeline for complete non-visualization by approximately 10 years across all ages, and by more than 20 years in women under 40 years of age 5
• Body mass index (BMI) is not a limiting factor for transvaginal ultrasound ovarian imaging, contrary to common assumptions 5

When to Pursue Additional Imaging

• Additional imaging with MRI is rarely necessary when an ovary is not visualized on ultrasound, as the theoretical risk of detecting ovarian carcinoma ranges from 0% to 1.3% 3
• If MRI is performed for non-visualized ovaries, only 6.9% reveal any discordant findings, with 5.2% being physiologic (functional or hemorrhagic cysts) and only 1.6% being non-physiologic benign findings 3
• The only malignancies detected in non-visualized ovaries occurred in the setting of obvious peritoneal carcinomatosis already visible on the initial ultrasound, meaning isolated non-visualization without other concerning findings does not require follow-up imaging 1

Important Clinical Pitfalls

• Transabdominal ultrasound should be relied upon only if the ovaries are not adequately evaluated via transvaginal approach, as it is generally not suitable for accurate follicle counting but can reliably assess ovarian volume 4
• When evaluating for polycystic ovarian morphology (PCOM), if only one ovary is visible and meets criteria (≥20 follicles or volume >10 mL), this is sufficient for diagnosis as there is little left-right variation in follicle number per ovary 4
• Rare congenital absence of the ovary and fallopian tube can occur, and if clinical suspicion exists (such as in infertility workup), diagnostic laparoscopy may be considered 6
• In the emergency department setting, non-visualization of the ovary on either CT or ultrasound has a combined negative predictive value of 94% for the absence of ovarian pathology, and typically does not require additional imaging to exclude ovarian disease 2