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

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Background: 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. Methods: 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. Results: 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. Conclusion: 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. Keywords: testicular volume, ultrasonography, andrology, sub-Saharan Africa, Somalia