Background Undescended testis (UDT) is the most common genital anomaly seen in boys and can be treated surgically by orchiopexy. The age at which orchiopexy should be performed is controversial for both congenital and acquired UDT.

Objectives Performing a decision analysis in order to develop a guideline on UDT.

Methods A decision analysis was performed in which all available knowledge is combined to assess the outcomes of orchiopexy at different ages, expressed in quality adjusted life years (QALY). Furthermore a sensitivity analysis was performed to assess whether the determined optimal age of orchiopexy is influenced by gaps in current knowledge.

Results Surgery at the earliest age (at detection of UDT) will lead to the lowest loss in QALY for UDT compared to no surgery. For bilateral UDT (both congenital and acquired) this was caused by increased paternity and for unilateral UDT by cosmetic aspects. Sensitivity analyses did not change the preferences for strategies. However, given the modest differences in outcomes, there is room for patient preference with respect to performance and timing of surgery in case of unilateral UDT.

Discussion The choice for no surgery in case of unilateral UDT was not acceptable for the expert group. Therefore, a consensus based guideline was developed in which surgery was recommended also for unilateral UDT. More clinical evidence on issues related to timing may in the future modify these results and hence this advice.

Implications for Guideline Developers/Users A decision analyses provides a clear insight in the data available and argumentations made.