Is the decrease in testicular length from ~4 cm to 3.2 cm (left) and 3.4 cm (right) on a repeat ultrasound performed four weeks later by a different sonographer likely due to measurement variation rather than true testicular atrophy in a male with bilateral testicular pain and a left grade 2 varicocele?

Testicular Measurement Variation vs. True Atrophy

The decrease from 4 cm to 3.2-3.4 cm is almost certainly due to inter-operator measurement variability rather than true testicular atrophy, as biological testicular shrinkage of this magnitude over 4 weeks in an adult without acute pathology is physiologically implausible. 1

Why This is Measurement Error

Inter-sonographer variability is a well-documented phenomenon in testicular ultrasound. The key technical factors that explain your discrepancy include:

• Caliper placement errors are the most common source of measurement variation, particularly for width measurements where even 1-2 mm misplacement can dramatically alter calculated volume 1
• Different sonographers use different measurement techniques, including whether they measure at maximum diameter versus standardized anatomic landmarks 1
• The Lambert formula (Length × Width × Height × 0.71) is the recommended calculation method, but many operators still use the older ellipsoid formula (0.52 coefficient) which systematically underestimates volume by 20-30% 1
• Probe frequency and image optimization vary between operators, affecting the ability to accurately identify testicular margins 1

True biological testicular atrophy over 4 weeks would require acute pathology such as testicular torsion, severe trauma, or acute vascular compromise—none of which are present in your case given the normal Doppler findings and absence of acute symptoms 1

Your Actual Clinical Situation

Your second ultrasound shows:

• Left testis 3.2 cm, right testis 3.4 cm (assuming these are length measurements)
• Grade 2 left varicocele with 3.4 mm vein diameter and reflux
• Normal testicular architecture and blood flow

Volume Calculations Matter

If we assume the first scan measured 4 cm length for both testes:

• 4 cm length typically corresponds to 15-18 ml volume using proper three-dimensional measurements 1
• 3.2-3.4 cm length would correspond to approximately 10-13 ml volume 1

This places you right at the critical 12 ml threshold that defines testicular atrophy, making accurate measurement absolutely essential 1

What You Should Do Next

1. Request Proper Remeasurement

Have the current sonographer remeasure the previous scan images to eliminate inter-operator variability and establish whether true change has occurred 1. This is standard practice when significant discrepancies arise.

2. Ensure Proper Measurement Technique

The repeat ultrasound should explicitly:

• Use high-frequency probes (>10 MHz) for maximum resolution 1
• Measure three perpendicular dimensions (length, width, height) in standardized planes 1
• Calculate volume using the Lambert formula (0.71 coefficient), not the ellipsoid formula 1
• Document whether measurements include or exclude the tunica albuginea 1

3. Clinical Correlation is Essential

Even if measurements confirm volumes around 12 ml, this does not automatically indicate pathology. You need:

• Semen analysis to assess actual spermatogenic function, as testicular volume alone cannot predict fertility 1
• Morning serum FSH, LH, and total testosterone (drawn 08:00-10:00 on two separate occasions) to distinguish primary testicular dysfunction from normal variation 1
• Detailed history focusing on cryptorchidism, prior testicular trauma, medication use (especially anabolic steroids, opioids, or testosterone), and fertility history 1

The Varicocele Context

Your grade 2 left varicocele is relevant but does not explain acute size changes:

• Varicoceles cause chronic, gradual testicular atrophy over months to years, not acute changes over 4 weeks 2
• The majority (80%) of men with varicoceles remain fertile despite some degree of ipsilateral testicular size reduction 2
• Testicular size discrepancy from varicocele does not reliably predict infertility in individual patients 2

Varicocele repair should be considered if:

• Documented progressive testicular atrophy on serial measurements
• Abnormal semen parameters with desire for fertility
• Persistent pain affecting quality of life

Common Pitfalls to Avoid

1. Do not panic about a single discrepant measurement without confirming it represents true biological change 1
2. Do not assume testicular volume <12 ml automatically means infertility—semen analysis is required 1
3. Do not start testosterone replacement without first clarifying fertility intentions, as it will cause complete azoospermia 1
4. Do not treat the varicocele based solely on ultrasound findings—only palpable varicoceles with documented fertility impact benefit from repair 3

Bottom Line

Request that the current sonographer remeasure your previous scan images using standardized technique. If true volume is confirmed at 12-15 ml (borderline-small range), proceed with semen analysis and hormonal evaluation to determine whether any intervention is needed. 1 The 4-week timeframe makes measurement error far more likely than true pathology. 1