I am an adult male who had scrotal ultrasounds showing testicular length decreasing from 4 cm to 3.1–3.4 cm over four weeks, with semen analyses of 56 million/mL and 43 million/mL; is this likely testicular atrophy?

Testicular Size Measurement Variability, Not True Atrophy

Your ultrasound measurements are almost certainly due to technical measurement error rather than true testicular atrophy, and your semen parameters confirm normal testicular function. 1

Why This is Measurement Error, Not Atrophy

Technical measurement variability is extremely common in testicular ultrasound. Studies demonstrate a 16% inter-observer error in testicular size estimation, with differences tending to increase with larger testicular size 2. Your measurements show exactly this pattern—a dramatic drop from 4 cm to 3.1-3.4 cm over just 4 weeks, which is biologically implausible in an adult without acute pathology like torsion or trauma 1.

True biological change in testicular size over 4 weeks is extremely unlikely in adults unless there is acute pathology such as torsion, trauma, or severe infection. 1 You have none of these conditions based on your presentation.

Common Sources of Measurement Error:

• Incorrect caliper placement during width measurement is the most frequent technical error, particularly when the probe is not positioned at the true maximal transverse diameter 1
• Different sonographers or techniques between the two scans can produce systematic measurement differences of 2-4 ml 2
• Using the wrong volume formula—the traditional ellipsoid formula (0.52 coefficient) systematically underestimates volume by 20-30% compared to the Lambert formula (0.71 coefficient) that should be used 1

Your Semen Parameters Confirm Normal Function

Your sperm concentrations of 56 million/ml and 43 million/ml are well above the WHO lower reference limit of 16 million/ml, confirming normal testicular function. 1 This directly contradicts the ultrasound findings suggesting severe atrophy.

If your testes were truly 3.1-3.4 cm (corresponding to volumes of approximately 6-8 ml using proper measurement), you would be expected to have severe oligospermia or azoospermia, not normal sperm counts. 1 Testicular volumes below 12 ml are definitively associated with impaired spermatogenesis and elevated FSH levels, which you clearly do not have given your normal sperm production 1.

What You Should Do Next

Request a repeat scrotal ultrasound with explicit attention to proper measurement technique. 1 Specifically request:

• High-frequency probes (>10 MHz) to maximize resolution and accurate caliper placement 1
• Three perpendicular dimensions (length, width, height) measured on axial slices 1
• Volume calculation using the Lambert formula (Length × Width × Height × 0.71) rather than the traditional ellipsoid formula 1
• The same sonographer should ideally perform the measurement, or the current operator should remeasure the previous scans to minimize inter-scan variability 1

Compare measurements to the contralateral testis—a size discrepancy greater than 2 ml or 20% warrants further evaluation to exclude pathology, but symmetric measurements support measurement error rather than unilateral disease 1.

When to Worry About True Atrophy

True testicular atrophy would present with:

• Testicular volumes definitively <12 ml on properly performed ultrasound 1
• Elevated FSH levels (>7.6 IU/L) indicating compensatory pituitary response to testicular dysfunction 1
• Severe oligospermia (<5 million/ml) or azoospermia, not the normal counts you have 1
• Progressive decline over months to years, not sudden changes over 4 weeks 1

Critical Pitfalls to Avoid

Do not pursue invasive testing or fertility preservation based on these measurements alone. 1 Your normal semen parameters indicate preserved testicular function regardless of the ultrasound discrepancy.

If repeat ultrasound confirms volumes <12 ml despite normal sperm counts, obtain hormonal evaluation (FSH, LH, testosterone) to correlate imaging with actual testicular function. 1 However, given your normal semen analyses, this scenario is highly unlikely.

Avoid exogenous testosterone or anabolic steroids completely, as these will suppress your currently normal spermatogenesis through negative feedback, potentially causing azoospermia that can take months to years to recover 1.