Why Do Men Have Testicular Asymmetry? When Is It Normal?

Testicular asymmetry means the two testicles are not exactly identical in size, position, shape, or appearance. Usually one testicle hangs slightly lower, is slightly larger, or one side of the scrotum looks a bit fuller. Perfect symmetry isn’t expected — what matters is not whether the testicles match, but whether the difference is longstanding and stable or a new change.

A difference is generally less concerning when: it has been present for a long time, one testicle has always hung lower, the size difference is small, there’s no pain or tenderness, no new lump or sudden swelling, the testicles otherwise feel normal, and the difference is stable rather than progressing. The goal isn’t perfect symmetry — it’s knowing what’s normal for you so you can notice a meaningful change.

Several conditions can cause asymmetry or enlarge one side of the scrotum:

• Varicocele — enlarged veins around the testicle, causing heaviness, fullness, palpable enlarged veins, and sometimes reduced testicular size or fertility problems
• Hydrocele — fluid accumulation around a testicle, making one side of the scrotum larger or swollen
• Epididymitis or other infections — pain, swelling, tenderness, warmth or redness, sometimes fever
• Inguinal hernia — tissue pushing through a weakened abdominal wall, more noticeable when standing, coughing, or straining
• Testicular tumor — sometimes presents as a painless lump or enlargement

These symptoms don’t automatically mean cancer, but they should be evaluated by a doctor rather than self-diagnosed.

Testicular torsion occurs when the spermatic cord twists and cuts off blood supply to the testicle. Unlike normal asymmetry, torsion causes sudden and severe pain and swelling; the affected testicle may sit higher than usual or at an unusual angle, and nausea or vomiting can occur.

This is a medical emergency. Sudden, severe testicular pain requires immediate emergency care — delayed treatment can permanently damage the testicle, and emergency surgery is often needed to restore blood flow.

A doctor examines the size, position, and consistency of each testicle, checks for lumps, tenderness, and evaluates the epididymis and spermatic cord. If the cause is unclear or a structural problem is suspected, a scrotal ultrasound, often with Doppler imaging, may be recommended to assess blood flow, fluid, and enlarged veins.

Mild natural asymmetry usually doesn’t affect fertility, but the underlying condition (such as varicocele or injury) can sometimes affect sperm production — in that case a urologist or andrologist may recommend a semen analysis.

Make an appointment if: one testicle has recently become larger or smaller, you notice a new lump or swelling, there’s persistent testicular or scrotal pain, a testicle feels unusually firm, you notice a new heaviness, the shape or position has changed, you have fertility concerns, or you’re unsure whether a difference is normal.

Seek emergency care rather than a routine appointment for sudden, severe testicular pain or rapidly developing swelling — testicular torsion needs urgent assessment.