Benign Ovarian Cysts: The presence of clear, septated ovarian cysts with stable sizes and low CA125 levels over time, in conjunction with an unremarkable abdominal CT scan, suggests a benign nature of the cysts. The fact that the patient is asymptomatic further supports this diagnosis.

Simple Ovarian Cysts: These are common in postmenopausal women and can be multiple. The description of the cysts as clear and septated, with no significant change in size or CA125 levels, aligns with simple ovarian cysts.
Functional Ovarian Cysts: Although less common in postmenopausal women, functional cysts (such as follicular cysts) can occur, as hinted at by the mention of follicular changes on the CT scan.

Ovarian Cancer: Despite the low likelihood based on the stable nature of the cysts and normal CA125 levels, ovarian cancer must be considered due to its potential severity and the fact that it can present with similar imaging findings. The clear and septated nature of the cysts somewhat lowers the suspicion, but not enough to exclude it entirely without further evaluation if warranted by clinical judgment.
Borderline Ovarian Tumors: These are tumors of intermediate malignant potential and can present similarly to benign cysts but require careful consideration due to their potential for progression.

Serous Cystadenoma: A type of benign ovarian neoplasm that can be septated and filled with a clear fluid. While less likely given the clinical context, it remains a possibility.
Mucinous Cystadenoma: Another type of benign ovarian tumor, though these are typically filled with mucinous material rather than clear fluid, making this diagnosis less likely.
Other Rare Ovarian Tumors: Including but not limited to, Brenner tumors, or other sex-cord stromal tumors, which are rare and can present with a variety of imaging findings.