Radiology Teaching Case: Solid Peri-Urethral Mass -"How to Think, Not Just What to Say"

📘 Radiology Teaching Case

Solid Peri-Urethral Mass

"How to Think, Not Just What to Say"

1 Clinical Presentation

Patient

41-year-old female

Chief Complaint

“Something coming out of the vagina”

💡 Teaching Point: Terminology

Patients do not know anatomy. This phrase does NOT automatically mean prolapse. Open three mental boxes:

• Pelvic organ prolapse
• Vaginal / peri-urethral mass
• Distal urethral pathology

⚠️ Common error: Anchoring bias—assuming cystocele or prolapse before imaging.

2 Epicenter Localization

This is the single most important question in pelvic mass evaluation.

• Uterus / Cervix Displaced, not involved
• Urinary Bladder Displaced
• Anal Canal Posterior, uninvolved
• Mass Location Between bladder and vagina

✅ Conclusion: Epicenter = Anterior Vaginal Wall / Peri-urethral Space

Once localized, 50% of the differential dies immediately.

3 Displacement vs Infiltration

Observations:

• Smooth, rounded margins
• Organs pushed aside, not invaded
• Urethral wall preserved

The Benign Rule:

Benign lesions displace.

Malignant lesions infiltrate.

4 Signal Analysis

T2 Signal

Low-Int

Enhance

Homogeneous

DWI

Restricted

⚠️ Diffusion ≠ Malignancy

Cellular smooth-muscle tumors (like cellular leiomyomas) restrict diffusion due to high cellular density. Never interpret DWI in isolation.

5 Differential Diagnosis

Excluded

Urethral Diverticulum

Why: Would be T2 cystic (bright), not solid.

Excluded

Aggressive Angiomyxoma

Why: Markedly T2 bright, infiltrative growth pattern.

Leading Diagnosis

Peri-urethral Leiomyoma (Cellular Subtype)

• Correct age (40s) and location
• Mass effect without invasion
• DWI explained by cellularity

How to Report (Exam-Safe)

Findings

A well-defined solid mass is seen arising from the anterior vaginal wall / peri-urethral region, showing low–intermediate T2 signal, homogeneous enhancement, and diffusion restriction. The lesion causes posterior displacement of the urethral complex without urethral wall invasion. Adjacent pelvic organs are displaced but uninvolved.

Impression

1. Imaging features are most consistent with a peri-urethral leiomyoma, likely cellular subtype.
2. Surgical excision with histopathological confirmation is advised given diffusion restriction and rare overlap with other smooth-muscle tumors.
3. Additional finding: Endometrial thickening suggestive of hyperplasia.

Final Teaching Diagnosis

Peri-urethral Leiomyoma

(Cellular Variant)

Common Mistake: Forgetting to mention the urethral relationship. Surgeons need to know if the wall is intact.