Male sexual development in utero: testicular descent on prenatal magnetic resonance imaging

To visualize in utero male fetal testicular descent on magnetic resonance imaging (MRI) and to correlate it with gestational age.

This retrospective study included 202 MRI examination results of 199 male fetuses (17-39 gestational weeks) with normal anatomy or minor congenital abnormalities, following suspicion of anomalies on prenatal ultrasound examination. Using a 1.5-Tesla unit, multiplanar T2-weighted sequences were applied using a standard protocol to image and identify the scrotal content. The relative frequencies of unilateral and bilateral testicular descent were calculated and correlated with gestational age.

Between 17 and 25 gestational weeks, neither unilateral nor bilateral testicular descent was visualized on MRI. Testicular descent was first observed at 25 + 4 weeks, in 7.7% of cases. 12.5% of 27-week fetuses showed unilateral descent and 50% showed bilateral descent. Bilateral descent was observed in 95.7% of cases, on average, from 30 to 39 weeks.

Our results chart the time course of testicular descent on prenatal MRI, which may be helpful in the identification of normal male sexual development and in the diagnosis of congenital abnormalities, including the early detection of cryptorchidism.