Testicular Asymmetry: Normal Variation vs. Pathology

Mild testicular size asymmetry is normal: the right testis is typically slightly larger and hangs higher; the left is lower. A difference >20% in volume or new-onset asymmetry warrants evaluation.

Normal Variants

• Right > Left volume (avg 15–20 mL vs. 12–18 mL).
• Left lower position (longer spermatic cord).

Pathological Causes of Asymmetry

• Hydrocele: Fluid around testis; transilluminates.
• Varicocele: Dilated pampiniform plexus (left > right); "bag of worms"; may impair spermatogenesis.
• Testicular torsion: Acute pain, high-riding testis, absent cremasteric reflex — surgical emergency (<6 hrs).
• Epididymitis/orchitis: Pain, swelling, erythema; STI or urinary pathogen.
• Testicular tumor: Painless firm mass; 95% germ cell (seminoma, non-seminoma).
• Atrophy: Prior torsion, mumps orchitis, trauma, undescended testis.
• Inguinal hernia: May mimic scrotal swelling.

Evaluation

• History: onset, pain, trauma, fertility concerns.
• Exam: size (orchidometer), consistency, transillumination, cremasteric reflex.
• Scrotal ultrasound: gold standard (vascular flow, mass characterization).
• Tumor markers: AFP, β-hCG, LDH if mass suspected.

Self-Exam

Monthly after warm shower: gentle roll each testis between thumb and fingers. Report new lumps, hardness, or size change promptly.