Differential Diagnoses for 46-Year-Old Female with Left Lower Quadrant Pain and Abnormal Uterine Bleeding

The three most likely diagnoses are: (1) uterine fibroids with possible degeneration, (2) adenomyosis, and (3) endometriosis.

1. Uterine Fibroids (Leiomyomas)

Fibroids are the most probable diagnosis given the patient's age, menorrhagia, intermenstrual spotting, and severe pelvic pain. 1

Fibroids commonly present with abnormal uterine bleeding (heavy menstrual bleeding), pelvic pressure, and pain in women of reproductive age, particularly in the perimenopausal period 1, 2
The severe pain (8/10) lasting 10 days suggests possible acute complications such as fibroid degeneration, torsion of a pedunculated fibroid, or prolapse 3
Fibroids are the second most common cause of acute pelvic pain in perimenopausal women 4
The left lower quadrant location could indicate a laterally positioned fibroid or one undergoing acute changes 3
Key clinical pitfall: While the prior transvaginal ultrasound was normal, fibroids can develop or grow significantly over several years, especially approaching menopause 1
The pattern of heavy 5-day periods with intermenstrual spotting is classic for fibroid-related bleeding 1, 2

Adenomyosis should be strongly considered given the progressive nature of menorrhagia and severe dysmenorrhea in a woman in her mid-40s. 4, 2

Adenomyosis typically affects women in their late reproductive years and presents with heavy menstrual bleeding, severe dysmenorrhea, and chronic pelvic pain 2, 5
The pain pattern—severe during menstruation requiring NSAIDs for control—is characteristic of adenomyosis 5
Focal adenomyosis (cystic variant) can present with severe chronic pelvic pain and dysmenorrhea, though it is less common 5
Important consideration: Adenomyosis can coexist with fibroids and may not have been evident on the prior ultrasound performed years ago 5
The progressive worsening of symptoms over time (implied by the current severity) fits the pattern of adenomyosis 4

Endometriosis must be included in the differential, particularly given the secondary dysmenorrhea pattern and intermenstrual pain. 6, 4

Endometriosis affects 2-10% of reproductive-aged women and commonly presents with secondary dysmenorrhea, deep dyspareunia, and sacral backache with menses 4
The pain characteristics—commencing before menstrual onset and severe in nature—align with endometriosis-related pelvic pain 6
Left-sided pain could indicate endometriotic implants on the left ovary, uterosacral ligament, or bowel 6
Critical point: Small endometrial implants are not well detected on imaging, and a normal prior transvaginal ultrasound does not exclude endometriosis 6
Approximately 50% of endometriosis patients have associated infertility, which correlates with this patient's documented fertility issues 4
The depth of endometriosis lesions correlates with pain severity, not the type of lesions 6

Transvaginal ultrasound is the first-line imaging modality and should be performed immediately. 6, 4

TVUS has 82.5% sensitivity and 84.6% specificity for detecting secondary causes of dysmenorrhea 4
Combined transabdominal and transvaginal approach should be used to assess for fibroids, adenomyosis, ovarian masses, and signs of endometriosis 6
Look specifically for: fibroid size/location/degeneration, uterine enlargement suggesting adenomyosis, endometriomas, and free fluid 6, 2

If ultrasound is inconclusive or shows complex findings, MRI without IV contrast should be the next step. 6

MRI excels at differentiating adenomyosis from fibroids and can detect deep infiltrating endometriosis 6
MRI can visualize the endometrium even in the presence of fibroids and adenomyosis due to multiplanar capability 6

Red flags present in this case that mandate thorough evaluation: 4