Incidence and associated factors of metachronous contralateral cryptorchidism after unilateral cryptorchidism: a retrospective cohort study.

Acquired cryptorchidism is an increasingly recognized condition and may present bilaterally with a metachronous pattern. The objective of this study was to evaluate the incidence of acquired contralateral metachronous cryptorchidism and to identify associated factors in patients undergoing surgery for unilateral cryptorchidism. This retrospective cohort descriptive study included patients who underwent surgery for unilateral cryptorchidism in the Paediatric Surgery departments of Consorci Sanitari Alt Penedès-Garraf and Hospital Universitari Mútua Terrassa between 2005 and 2024. Demographic data, characteristics of cryptorchidism, and intraoperative findings from the initial surgery were recorded. A history of prematurity and obesity were also collected. A total of 275 patients were included. Contralateral acquired cryptorchidism developed in 11 of 111 patients with congenital cryptorchidism (9.9%; 95% CI 5.1%-17%) and in 29 of 164 patients with acquired cryptorchidism (17.7%; 95% CI 12.2%-24.4%). Multivariate analysis identified the following associated factors for metachronous contralateral cryptorchidism: acquired cryptorchidism at initial presentation (aOR = 4.00, 95% CI 1.60-9.99; p = 0.003), persistence of the processus vaginalis on the initially operated side (aOR = 5.94, 95% CI 2.44-14.48; p < 0.001) and prematurity (aOR = 6.38, 95% CI 1.75-23.25; p = 0.005).

conclusionThe overall incidence of metachronous cryptorchidism in patients with unilateral disease was 15%. A higher incidence was observed among patients with acquired cryptorchidism than among those with congenital cryptorchidism, although this difference did not reach statistical significance. These findings suggest that periodic follow-up until adolescence may be warranted in patients with unilateral cryptorchidism, particularly in those with acquired forms. Patients with congenital cryptorchidism require periodic follow-up until adolescence, while those with acquired unilateral cryptorchidism should be carefully monitored before surgery to detect bilateral involvement and allow simultaneous treatment. WHAT IS KNOWN: • Cryptorchidism affects 1-4% of full-term newborns, with long-term consequences for fertility and testicular cancer risk. Acquired cryptorchidism, the ascent of a previously descended testis, accounts for more than half of all cases. • The risk factors for metachronous contralateral cryptorchidism after unilateral disease remain poorly characterized, and no consensus exists on the appropriate follow-up strategy for these patients. WHAT IS NEW: • Metachronous contralateral cryptorchidism occurred in 15% of patients. The incidence was higher in patients with acquired cryptorchidism than in those with congenital cryptorchidism althouh the difference was not statistically significant. Persistence of the processus vaginalis at the time of surgery on the first side, and prematurity were other associated factors. • Prospective studies are needed to validate these associated factors and to determine whether active observation before surgery enables earlier detection of bilateral disease and synchronous orchidopexy.