Background and Aims: Renal transplantation is the treatment of choice for end-stage renal failure, offering improved survival and quality of life. Nevertheless, the course of the disease can be marred by a number of incidents, particularly of a urological nature. Indeed, during renal transplant surgery, some teams use JJ catheters to drain the urinary tract and protect the uretero-vesical anastomosis, as in the case of our patients. Method: We report two cases of early calcification of double JJ catheters after renal transplant surgery. Results: Case N° 1 Man aged 49, chronic renal insufficiency of undetermined cause; renal transplantation in March 2023 from a living donor; postoperative evolution was favorable; after 40 days of surgery, he was hospitalized for anuric acute renal failure (ARF) although there was a JJ catheter that appeared calcified on CT scan. A second JJ catheter was inserted, and the first catheter was removed with great difficulty and effort, as it showed a series of calcifications. Resumption of diuresis and recovery of renal function postoperatively. Case N°2 An 18-year-old girl underwent renal transplantation in October 2022 from a cadaveric donor. Her initial nephropathy was nephronphthisis. Post-transplant follow-up was straightforward and the patient was discharged after a 3-week stay. After removal of the JJ, she developed obstructive AKI due to urethral stenosis, hence the indication for ureteroureteral reimplantation and placement of the JJ, which calcified after 2 months. Conclusion: The inlaying of double J catheters is responsible for morbidity in addition to intolerance phenomena. Factors predictive of calcification have been subdivided into three groups: factors related to patient characteristics, factors related to the double J catheter and biological factors.