Can a left tubal mass be due to tubal endometriosis?

Can a Left Tubal Mass Be Due to Tubal Endometriosis?

Yes, a left tubal mass can absolutely be due to tubal endometriosis, though it is relatively uncommon and often occurs in the context of multi-organ endometriosis. 1

Prevalence and Clinical Context

• Tubal endometriosis occurs in 14.48% of premenopausal women undergoing salpingectomy, with prevalence rising to 37.37% in patients with known endometriosis and 43.94% in those with multi-organ endometriosis. 1

• Left-sided tubal involvement is more common than right-sided (52.17% vs 40.37%), making a left tubal mass particularly consistent with endometriosis. 1

• Tubal endometriosis is more likely when hydrosalpinx or hematosalpinx is present (43.47% of cases with tubal endometriosis vs 23.79% without). 1

Imaging Characteristics

Transvaginal ultrasound (TVUS) is the initial imaging modality of choice and can demonstrate:

• An extraovarian or adnexal mass separate from the ovary, which may represent tubal endometriosis when other gynecologic pathology is excluded. 2

• Tubal masses in endometriosis typically show limited vascularity on color Doppler, and the presence of significant blood flow should prompt investigation for neoplasm. 2

• Dynamic TVUS assessment including evaluation of the uterine sliding sign and assessment for hypoechoic nodules can aid diagnosis. 2

MRI should be obtained when TVUS is inconclusive or to map deep infiltrating endometriosis, with sensitivity of 82-90% and specificity of 91-98% for endometriosis overall. 2, 3

Key Distinguishing Features from Other Tubal Pathology

Versus Tubal Ectopic Pregnancy:

• Ectopic pregnancy presents with a tubal ring (round/oval fluid collection with hyperechoic rim) and positive β-hCG. 2, 4
• Absence of positive pregnancy test excludes ectopic pregnancy. 4

Versus Pelvic Inflammatory Disease (PID):

• PID typically presents bilaterally (82% of cases) with thick-walled masses (>5mm), cogwheel sign, and well-vascularized tissue on color Doppler. 2
• Tubal endometriosis shows limited vascularity, contrasting with the hypervascularity of acute salpingitis. 2
• Chronic tubal inflammatory disease shows thin walls and "beads-on-a-string" sign (97% and 57% respectively), whereas tubal endometriosis has different pathologic features. 2

Versus Hydrosalpinx:

• Simple hydrosalpinx shows thin walls without the inflammatory markers (incomplete septa, cogwheel sign) seen in acute PID. 2
• Tubal endometriosis can coexist with hydrosalpinx/hematosalpinx, increasing diagnostic complexity. 1

Pathologic Location and Characteristics

• Tubal endometriosis preferentially affects the proximal tube mucosa with surrounding inflammation and fibrotic lesions, rather than the distal tube serosa/sub-serosa. 1

• The diagnosis can be histologically challenging as endometriotic glands may be sparse or absent (stromal endometriosis), and the stromal component can be obscured by histiocytes, fibrosis, or smooth muscle metaplasia. 5

Risk Factors Suggesting Tubal Endometriosis

Consider tubal endometriosis more strongly when:

• Abnormal uterine bleeding is present (adjusted odds ratio 3.10). 1
• Previous endometriosis surgery (adjusted odds ratio 4.22). 1
• History of tubal ligation (adjusted odds ratio 2.33). 1
• Presence of pelvic endometriosis elsewhere, particularly with increasing severity of disease (correlation coefficient 0.26) or pelvic adhesions (correlation coefficient 0.25). 1

Diagnostic Algorithm

1. Obtain β-hCG to exclude ectopic pregnancy as first priority given overlapping imaging features. 4

2. Perform TVUS with color Doppler to characterize the mass, assess vascularity, and evaluate for bilateral involvement. 2

3. If TVUS shows unilateral left-sided mass with limited vascularity, no bilateral involvement, and negative β-hCG, tubal endometriosis becomes more likely, especially with known pelvic endometriosis. 2, 1

4. Obtain MRI pelvis if TVUS is inconclusive or to map extent of disease prior to surgical planning. 2, 3

5. Laparoscopy with histologic confirmation remains the gold standard for definitive diagnosis, particularly when imaging is equivocal or surgical management is planned. 3

Critical Pitfalls to Avoid

• Do not assume bilateral involvement excludes endometriosis—while PID is more commonly bilateral, endometriosis can affect both tubes, particularly in multi-organ disease. 2, 1

• Normal imaging does not exclude tubal endometriosis, as microscopic or subtle disease may not be visible on standard imaging protocols. 3, 6

• Expanded protocol TVUS by expert sonographers significantly improves sensitivity but requires special training (minimum 40 examinations) and is not widely available. 3

• Preoperative imaging reduces surgical morbidity and incomplete procedures, making comprehensive evaluation worthwhile even when diagnosis seems clear. 3