Contralateral testicular size a poor predictor of monorchidism in infants

Contralateral testicular size shows poor predictive value for monorchidism in infants with unilateral non-palpable undescended testes (NPT), a recent study has found.

Drawing from physical examination and surgical data, researchers classified 707 infants (aged 9–48 months) with unilateral undescended testes (UDT) into three groups: palpable UDT (n=609), non-palpable but viable testes (n=57), or monorchidism (n=41). Ultrasonography was performed to assess contralateral testicular length.

Contralateral testicular length and volume were significantly larger in monorchidism participants than in those with UDT and in those with NPT but viable testes (p<0.01 for all comparisons). However, the differences were small in magnitude. For instance, there was only a 1.4-mm difference in length relative to both comparator groups, while the discrepancies in volume ranged from 0.18–0.19 mL.

The optimal cut-off value for contralateral testicular length for the detection of monorchidism was calculated to be 17.5 mm. At this threshold, the resulting sensitivity and specificity values were 34.1 percent and 94.7 percent, respectively. The resulting positive and negative predictive values were 82.3 percent and 66.6 percent, respectively.

The area under the curve (AUC) for the predictive power of testicular length was 70.2 percent. Contralateral testicular volume was not better, with an AUC of 65.7 percent. Notably, 27 patients in the monorchidism subgroup had testes that were smaller than the cut-off value.

“The overall diagnostic performance of contralateral testicular size in prediction of monorchidism in patients with UDT aged between 9 and 48 months was poor,” researchers said.