To measure the force necessary to win the resistance during insertion of ureteral access sheaths (UAS) in an experimental homemade model and to compare the peak force of insertion (PFOI) of different commercially available UASs.

Three investigators (2 novice and 1 expert) inserted the UASs into 2 different adapters with diameters of 10 Fr and 8 Fr. The force of insertion was continuously measured with a digital force gauge connected to the UAS during each insertion. Four different brands of UAS with different diameters, totally 11 different UASs were used for the experiment. The PFOI of each UAS was compared among each other and adapter diameters.

The mean PFOI in adapters 1 and 2 were 1.85 N and 5.32 N, respectively. All of the mean PFOIs were significantly lower in adapter 1 compared to adapter 2, regardless of the novice vs expert surgeons and the UASs. (P <.001) In adapter 1, the mean PFOI was lowest with the UAS-1 and highest with the UAS-8. In adapter 2, the mean PFOI was lowest with the UAS-3 and highest with the UAS-9. For adapters 1 and 2, no statistical difference was found when comparing an expert and the 2 novice surgeons.

The PFOI during UAS placement is not solely correlated with UAS thickness and adapter diameters. Other factors such as hydrophilic coating, UAS flexibility, inner dilator properties, UAS smoothness, and the actual measured external diameter of UASs should be taken into consideration. The clinical relevance and ureteral injury risk of the UAS PFOI need to be studied.