Study the data of patients younger than 18 years old, who underwent a bladder augmentation, complicated by urinary calculi.
The goal of this observational study is to analyse the occurence of urinary calculi after bladder augmentation in children:~location of the calculi (kidney or bladder)~type of bladder augmentation with higher rate of urinary calculi and why~Find risk factors of urinary calculi in bladder augmentation (age, sex, other bladder procedures..)