Japan's comprehensive undescended testis screening program: incidence of ascending testis after screening

Screening for undescended testis (UDT) in Japan is performed as a neonate, then at 1, 3, 10, and 18 months old, and 3 years old. Incidence of ascending testis (AT) after screening was reviewed.All orchiopexy/orchiectomy at a single institute between July 2005 and June 2022 were reviewed retrospectively.376 boys had 422 procedures; 54/422 (12.8%) were in 48 boys ≥ 4 years old (mean age: 6.7 years; range: 4-13); testes were normal (n = 22; 40.7%), small (n = 25; 46.2%), or atrophied (n = 7; 1.3%). There were 47 orchiopexies and 7 orchiectomies for atrophy. Incidence of AT in boys ≥ 4 years old was 24/422 (5.7%). Of these, 16/422 (3.8%) developed after normal descent and 8/422 (1.9%) were associated with retractile testis (AT + RET). Other indications included delayed treatment for UDT (n = 13), late referral by pediatricians (n = 10), and iatrogenic UDT (n = 6). Surgical intervention in boys ≥ 4 years old (12.8%) was less than that reported in the West (range: 30-50%) as was AT: (5.7% versus 15.4%) and AT + RET (1.9% versus 13.8%).Comprehensive UDT screening probably contributed to the lower incidence of surgery and AT (especially AT + RET) in boys ≥ 4 years old.