Testicular Volume Assessment
Your testicles at 13ml each are below the normal adult range and indicate testicular hypotrophy, though not severe atrophy. Normal adult testicular volume ranges from 15-25ml, with volumes below 15ml considered small 1.
Understanding Your Testicular Size
13ml represents mild to moderate testicular hypotrophy rather than severe atrophy, which typically refers to volumes below 10ml or marked shrinkage from a previously normal size 1.
The subjective feeling that they are "smaller" may reflect either:
- Progressive volume loss over time (true atrophy)
- Baseline developmental hypotrophy that has been present since puberty
- Normal variation in scrotal appearance based on temperature and cremasteric muscle tone 1
Critical Next Steps for Evaluation
You need a comprehensive urological evaluation to determine the cause and assess fertility implications. This should include:
Hormonal assessment: Measure serum testosterone, LH, FSH, and prolactin to distinguish primary testicular failure from hypothalamic-pituitary dysfunction 1.
Semen analysis: This is essential to assess actual fertility potential, as testicular volume correlates with but does not definitively predict sperm production 1, 2.
Physical examination by a urologist: Specifically evaluate for:
Scrotal ultrasound with Doppler: This can identify structural abnormalities, assess testicular parenchyma, and detect varicoceles if physical exam is inconclusive 1.
Common Causes of Testicular Hypotrophy
The most frequent etiologies to consider include:
Varicocele: Causes progressive testicular atrophy in subfertile men, with both testes often smaller than normal even when varicocele is unilateral 2, 3.
Primary hypogonadism: Congenital conditions like Klinefelter syndrome or acquired testicular damage 1.
History of cryptorchidism: Even after orchidopexy, bilateral disease commonly results in reduced testicular volumes and impaired fertility 4, 5, 6.
Prior testicular torsion: Can cause ischemic atrophy, sometimes affecting both testes 7.
Mumps orchitis or other infections: Post-inflammatory atrophy 1.
Fertility and Cancer Risk Implications
Fertility potential: Testicular volume below 15ml is associated with reduced fertility, but many men with volumes of 12-15ml remain fertile 2, 3. Semen analysis is the definitive test.
Cancer surveillance: Smaller testes, particularly if associated with cryptorchidism history, carry increased testicular cancer risk (2.75-8 times baseline) 5, 6. Monthly testicular self-examination after puberty is recommended for early detection 6.
Critical Pitfall to Avoid
Do not assume that testicular size alone determines fertility or that nothing can be done. If a varicocele is identified, surgical correction may prevent further atrophy and potentially improve fertility parameters 2, 3. Delaying evaluation allows potentially reversible causes to progress 3.