Determining which patients with varicocele require treatment is a challenge for the pediatric urologist. Although one in six adolescents may have a clinically detectable varicocele, the vast majority of these boys present without symptoms. Furthermore, despite an association of varicocele with infertility, approximately 80% of such adolescents will be fertile. To address the question of infertility, we assembled the largest North American series of boys
with varicocele, semen analyses, and ultrasound-derived testis volume measurement. We used testis volume measurement as a biomarker to determine which boys were more likely to have semen analyses (at Tanner V) suggestive of future infertility, defining this per the World Health Organization 10th percentile as a total motile sperm count (TMC) of < 20 million.
We hypothesized that decreasing total testis volume, the sum of the volumes of the right and left testis as determined by ultrasound, would be associated with increasing likelihood of a low TMC. We further hypothesized that increasing asymmetry, as defined as a testis volume differential of > 20% and calculated as (Volumeright - Volumeleft)/ Volumeright x 100, would be associated with low TMC. We calculated testis volume using the Lambert formula: length x width x height x 0.71.
One hundred boys were analyzed, 89% of whom had grade II or III varicocele. They presented at a mean age of 15.2 years, had a mean total testis volume of 30.4 cc’s, and 31% of boys presented with a testis volume differential greater than 20%. We used statistical methods (a Youden J-statistic) to determine objectively the optimal cutoff value for total testis volume, which was determined to be 30 cc’s. The median TMC was 42 (IQR: 9.2–105.8) and 61% of boys had TMC > 20.
In a multivariable model which accounted for age at presentation and the presence of a large (grade III) varicocele we found that a testis volume differential > 20% was associated with twice the odds (OR 2.1, p=0.04) of a low TMC, and a total testis volume < 30 cc’s quadrupled the odds (OR: 4.2, p<0.001) of a low TMC. Thus, low total testis volume and high levels of asymmetry in testis size are both independent and poor prognostic factors with respect to total motile sperm count. We believe that these testis volume factors are important in counselling patients and families with respect to the impact of varicocele on fertility, and emphasize that semen analysis remains the gold standard for this determination.
Written by: Dr. David A. Diamond, Dr. Michael P. Kurtz Boston Children’s Hospital - Department of Urology
Reference
Kurtz MP1, Zurakowski D2, Rosoklija I2, Bauer SB2, Borer JG2, Johnson KL2, Migliozzi M2, Diamond DA2