What does it mean to have follicle-containing ovaries on a computed tomography (CT) pelvis scan?

Understanding "Follicle-Containing Ovaries" on CT Pelvis Scans

"Follicle-containing ovaries" on a CT pelvis scan indicates that the ovaries contain visible follicles, which is a normal finding in premenopausal women and represents functional ovarian tissue with potential for hormone production and ovulation. 1

What Ovarian Follicles Are

Ovarian follicles are fluid-filled sacs within the ovaries that contain immature eggs (oocytes). They appear as small cystic structures on imaging:

• Normal follicles typically measure between 2-9 mm in diameter
• They are usually peripherally located within the ovary
• Multiple follicles are normally present in functioning ovaries

Clinical Significance of Follicle-Containing Ovaries

The presence of follicles on imaging provides important information about:

1. Ovarian Function:

   • Indicates hormonally active ovaries
   • Suggests potential fertility in premenopausal women
   • May be unexpected but significant if seen in postmenopausal women

2. Differentiation from Pathology:

   • Helps distinguish normal ovaries from those with polycystic ovarian syndrome (PCOS)
   • In PCOS, ovaries typically show ≥25 follicles per ovary and increased ovarian volume (>10 mL) 1
   • Normal follicle-containing ovaries have fewer follicles and normal stroma

3. Age-Related Context:

   • Expected finding in reproductive-age women
   • May be significant if seen in adolescents with suspected developmental issues
   • Unusual finding in postmenopausal women, where follicles typically disappear

Imaging Characteristics on CT

CT has limitations in evaluating ovarian follicles compared to ultrasound or MRI:

• Follicles appear as small hypodense (dark) areas within the ovarian tissue
• CT can identify larger follicles but may miss smaller ones (under 3-4 mm)
• CT is less sensitive than transvaginal ultrasound for detailed follicle evaluation 1
• The "ovarian vascular pedicle" sign on CT can help confirm that a structure is ovarian in origin 2

When This Finding Is Important

The significance of noting "follicle-containing ovaries" varies by clinical context:

• In fertility evaluation: Indicates potential for ovulation
• In postmenopausal women: May be unexpected and warrant further investigation
• In cancer patients: May indicate preserved ovarian function before/after treatment
• In patients with amenorrhea: Helps differentiate between causes of menstrual irregularities

Limitations of CT for Follicle Assessment

It's important to note that CT has limitations for detailed follicle assessment:

• Ultrasound is superior for counting and measuring follicles 1
• MRI provides better soft tissue contrast for evaluating ovarian morphology 1
• CT lacks the capacity to provide dynamic flow information that ultrasound can offer 1

Clinical Pitfalls to Avoid

1. Don't confuse normal follicles with pathological cysts or masses
2. Remember that CT may not detect all follicles due to resolution limitations
3. The presence of follicles doesn't rule out all ovarian pathologies
4. Follicle-containing ovaries in postmenopausal women may warrant further investigation

In summary, "follicle-containing ovaries" on CT indicates visible ovarian follicles, suggesting functional ovarian tissue. While this is a normal finding in premenopausal women, the clinical significance should be interpreted in the context of the patient's age, hormonal status, and clinical presentation.