Maturational changes in arterial impedance of the normal testis in boys: Doppler sonographic study

The use of color Doppler sonography to diagnose scrotal disorders in children has been hampered by the small size of the vessels and the slow blood flow compared with those in adults. Spectral analysis is the best means available of confirming the vascular origin of questionable color-flow signals arising from testes of small volume. The range of normal and abnormal Doppler sonographic arterial waveforms arising from the testis in boys, as distinct from those in adults, has never been described. The purpose of our study was to establish the normal range of testicular arterial impedance, measured as resistive index (RI), in both prepubertal and pubertal/post pubertal boys.

Bilateral scrotal color Doppler sonography was performed in 33 healthy boys aged 3 days to 17.5 years. The mean RI in the parenchymal artery was measured in 44 testes and plotted against testicular volume. Chi-square statistics were used to test differences in mean RI, testicular volume, and age between testes with volumes of 4 cm3 or less and testes with volumes greater than 4 cm3.

In testes with volumes of 4 cm3 or less, the mean RI ranged from 0.39 to 1.00 (mean, 0.87), and in testes with volumes greater than 4 cm3, the RI ranged from 0.43 to 0.75 (mean, 0.57). In 20 of 30 testes with volumes of 4 cm3 or less, the RI of parenchymal arteries was equal to 1.00 (i.e., diastolic flow was undetectable). Mean RI, testicular volume, and age were significantly different between testes with volumes of 4 cm3 or less and testes with volumes greater than 4 cm3 (p < .001 for all variables).

Mean testicular RI in our samples of pubertal and postpubertal boys is decreased compared with the mean RI in prepubertal boys. Diastolic arterial flow may not be detectable in normal testes with volumes of 4 cm3 or less. Despite the existence of a statistically significant difference in mean RI between prepubertal and pubertal/postpubertal testes, substantial variability exists within each group, particularly among the prepubertal testes. Norms of testicular flow previously established for adults are therefore not routinely applicable to prepubertal boys with testicular volumes less than 4 cm3. However, RI values in normal pubertal and postpubertal boys where testicular volumes exceed 4 cm3 are comparable to those previously described in adults.