Background/Aims: We obtained reference data for testicular volume measured by ultrasound in asymptomatic boys aged 0.5–18 years. In addition, we assessed the validity of the Prader orchidometer per age group by correlating it with the volume measurement by ultrasound. Methods: The study only included healthy boys with two scrotal testes at birth and at the time of the examination. For each boy the testicular volume of both testes was measured by ultrasound and the Prader orchidometer. Testicular volumes were measured for boys aged from 1 to 18 years. The boys’ ages were rounded down to the last birthday if it had occurred less than 6 months previously or rounded up to the next birthday if it was going to be within 6 months. Results: The volume measurement by the Prader orchidometer according to reference curves showed a statistically significant correlation. Moreover, the testicular volumes measured by the Prader orchidometer showed an accurate goodness of fit with US measurements (R² = 0.956). Conclusion: Normative values are provided for testicular volume measured by ultrasound in boys aged 0.5–18 years. An accurate correlation was found between volume measurements by ultrasound and by the Prader orchidometer (R² = 0.956). Therefore, volume measurement by the Prader orchidometer, as generally used in the practice by doctors, can be used as a valid parameter for monitoring testicular growth.

We performed a systematic review and critique of the literature on the frequency of undescended testis (UDT) among boys from birth to adolescence. Special attention was given to whether previous testicular position was taken into account to distinguish between congenital and acquired UDT. We searched Medline, Embase, Cinahl and the Cochrane Library. Any study reporting on the frequency of UDT was included. Study population age, number of boys studied, period of examination, primary examiner, area of study, study design, ethnicity, definitions used and previous testicular position were analysed. A total of 46 studies met the inclusion criteria. Twenty-three of the 46 (50%) studies involved newborns. Definitions were described in half of the studies; however, the definitions used were heterogeneous. Previous testis position was described in 11% (5/46) of the studies. At birth, in term and/or birth weight >2.5 kg infants, the UDT rate ranged from 1.0 to 4.6%, and in premature and/or birth weight <2.5 kg infants from 1.1 to 45.3%. At the age of 1 year UDT in term and/or birth weight >2.5 kg infants was seen in 1.0-1.5%, at 6 years in 0.0-2.6%, at 11 years in 0.0-6.6% and at 15 years in 1.6-2.2% of boys. The frequency of UDT shows variable figures in the literature. The actual frequency of acquired UDT essentially remains unclear because of the shortage of studies performed at an older age, and of studies reporting on previous testicular position.

The prevalence of classic testicular microlithiasis in asymptomatic boys is 2.4% and increases with age.

RESULTSOn referral, 340 testes were not in the scrotum (182 uni-and 79 bilateral). Of the 340 testes, 82 (24%) in 61 boys were diagnosed as retractile, whereas the remaining 258 in 221 boys were undescended. The previous testicular position was known in 208 of 221 boys (94%), with 244 UDTs. In 65 of these 244 (26.6%) the testis had never been scrotal (congenital UDT); in 179 (73.4%) a previous intrascrotal position was recorded in early childhood (acquired UDT) at least once, in 149 (61%) at least twice and in 117 (48%) at least three times. The mean age at referral for congenital UDT was 2.1 years and for acquired UDT was 8.4 years. CONCLUSIONSThese results show that acquired UDT is frequent, and occurs at about three times the rate of congenital UDT. Because these boys are referred for treatment later in childhood, the acquired UDT probably accounts for the high rate of (late) orchidopexy.

The prevalence of acquired UDT for 6-year, 9-year and 13-year olds was, respectively, 1.2% (25/2042), 2.2% (23/1038) and 1.1% (4/353). In addition, congenital UDT is treated during the early years of life and, in contrast with popular belief, screening programmes for detecting UDT in the early years are successful.