Analysis of trends in testicular atrophy index values with age in patients with unilateral palpable cryptorchidism

Cryptorchidism affects the growth of testicular volume. Testicular volume is associated with reproductive function. The testicular atrophy index evaluates the degree of damage caused by cryptorchidism, but it remains unclear whether changes in testicular atrophy index are related to age. We selected patients who underwent surgery for unilateral palpable cryptorchidism. Testicular volume was measured using ultrasonography. The testicular atrophy indices of the undescended testes were then reviewed, and their correlation with age was analyzed. We studied 228 cases (age range: 6–53 months). Scatter plots were constructed, and Loess curves were fitted, revealing a turning point at 24 months of age. The patients were divided into age groups of 6–24 months and 25–53 months. The testicular volume of the cryptorchid side was smaller than that of the normal side in both groups (both P < 0.001). In the 6–24-month group, the testicular atrophy index was positively correlated with age, testicular volume on the cryptorchid side was not correlated with age, and testicular volume was positively correlated with age on the normal side. In the 25–53-month group, testicular atrophy index and testicular volumes on either side were not correlated with age. A palpable unilateral cryptorchid testis is smaller than the contralateral testis. The testicular atrophy index increases with age between 6 months and 24 months, but not between 25 months and 53 months. Testicular volume increased with age on the normal side between 6 months and 24 months, but not on the cryptorchid side. Trends in testicular atrophy index with age contribute to the decision of operation time.