Introduction: Main goal of this study was to construct longitudinal testicular growth charts for healthy adolescent boys with and without a varicocele, and evaluate the effect of varicocele grade, peak retrograde flow, and spontaneous reflux in standing position on testicular development. Methods: Between march 2015 and January 2022, after local ethical approval, 775 adolescent boys were recruited for 6 monthly longitudinal follow up with testicular ultrasound. During each measurement, Tanner stage was assessed and testicular volume was calculated using the Lambert formula. In varicocele boys, the clinical grade was assessed, the peak retrograde flow (PRF) (during Valsalva in supine position) was measured as well as the spontaneous reflux in standing position. Boys with one measurement or with a medical condition (except varicocele) affecting testicular growth were excluded. (Generalized) Linear Mixed models were used to construct longitudinal growth charts and evaluate the effect of varicoceles with low PRF ( < 38.4 cm/s) and high PRF (> 38.4 cm/s) on testicular development. A separate analysis was performed for the different varicocele grades and for the spontaneous reflux in standing position (SR > 20 cm/s and SR < 20 cm/s). Results: After exclusion we analyzed 857 measurements of 399 healthy boys and 453 measurements of 143 varicocele boys. Varicocele boys tend to have a slower testicular development compared to healthy boys, however only the right testicular volume in varicocele boys with high PRF grew significantly slower compared to healthy boys during pubertal development. At Tanner 5 no significant difference in testicular volume was seen between the 3 groups. Similar results (significant slower right testicular growth) were found for grade 3 varicoceles as well as for SR > 20 cm/s. When combing the different parameters only boys with grade 3 varicocele together with a high PRF had a significant slower growth curve, higher testicular volume in the earlier tanner stages and lower at the later tanner stages compared to healthy adolescent boys. The growth curves from those boys with grade 3 varicocele and low PRF and those with grade 2 varicocele with high or low PRF were not significantly different from the healthy boys Conclusions: The developed growth charts can be used as reference curves in clinical practice. A grade 3 varicocele combined with a high PRF is a negative prognostic factor for testicular development. SOURCE OF Funding: no funding
