IOAN SCARNECIU, OVIDIU GABRIEL BRATU, CALIN PAVEL COBELSCHI, CARMEN DANIELA NECULOIU, CAMELIA CORNELIA SCARNECIU, SORIN LUPU, ADRIAN BRINZA, DRAGOS MARCU, BOGDAN SOCEA, LAURIAN MAXIM THE RISK FACTORS AND CHEMICAL COMPOSITION OF ENCRUSTATION OF URETERAL DOUBLE J STENTS IN PATIENTS WITH UROLITHIASIS Ureteral stenting has become one of the most common endoscopic procedure in endourology. Its main purpose is to preserve urinary drainage if this is compromised and maintain a good renal function. Even if there were made significant improvements in the last 50 years, ureteral stenting is not without morbidity. The common ureteral stents cannot have a good long-term efficiency and at some points, it will be blocked by the encrustation and incrustation; as result, the urinary drainage will have to suffer. A total of 134 ureteral stents in 83 patients suffering from reno/ureteral lithiasis were examined. We investigated the risk factors of encrustation and analyzed the chemical compounds of it. A total of 57 stents were found encrusted. The main risk factor was represented by the indwelling time. The rate of encrustation was 18.33% in the first 5 weeks, 56% between week 6 and 12, 75% thereafter. Stents with a smaller caliber (4.8 CH) tend to be more encrusted than those with a bigger one (6 CH). The Fourier Transform Infrared Spectroscopy has found that the main chemical compound of encrustation is represented by calcium oxalate.