Normal Reference Values for Testicular Volume in Adult Somali Men: A Retrospective Study

Testicular volume is a critical marker of male reproductive and endocrine health; however, reference values are population-specific. In the absence of ultrasound-based normative data for Somali men, clinicians often rely on external benchmarks that may lead to the misdiagnosis of normal variants. This study aimed to establish ultrasound-derived reference intervals, determine the Minimal Detectable Difference (MDD) for asymmetry, and develop a prediction equation for contralateral volume in Adult Somali men.

This retrospective study analyzed 212 sonographically normal Somali men (ages 18-84) at Sahan Diagnostic Center in Mogadishu, Somalia, from June 2022 to December 2025. Volumes were calculated using the standard ellipsoid formula. Statistical analyses included percentile-based reference intervals (2.5^th-97.5^th), Cohen's d for cross-population comparisons, and linear regression to derive a contralateral prediction equation.

Mean testicular volumes were 10.61±3.07 mL (right) and 10.19±3.02 mL (left), with a median of 10.0 mL for both. The 95% reference intervals were 5.7-18.0 mL (right) and 5.2-17.0 mL (left). The right testis was significantly larger than the left (p < 0.001), and no significant correlation with age was observed. The MDD for asymmetry was 4.1 mL. Notable differences were found compared to European (d = 1.90), West African (d = 1.88), and East and Southeast Asian (d = 0.76-2.01) cohorts.

These findings establish the first Somali-specific ultrasound benchmarks. Incorporating these intervals and the 4.1 mL MDD into clinical practice will improve diagnostic accuracy in andrological assessments and prevent the misapplication of non-representative global norms.