Introduction: There is no consensus about the optimal time intervals between SWL repeated sessions. The study was conducted to assess the ideal interval between repeated SWL for renal stones. Methods: The study protocol was approved by local ethical committee (ID: MD.20.05.327) and was registered to clinicaltrial.gov (NCT04575480). A randomized controlled trial was conducted between July 2020 and March 2022. Eligible patients with single renal stone < 2 cm who required multiple SWL sessions were randomly assigned to one of three groups. Patients underwent 2nd session after (3,7 and 14 days) for groups (1,2 and 3) respectively. Tubular damage was assessed through estimation of changes in urinary execration of KIM-1, N-GAL and IL-18. While glomerular damage was assessed by the protein/ creatinine ratio and changes in renal DTPA isotope scan. Treatment success were assessed by NCCT after 3 months. Results: The study included 166 patients. All patient's demographics were comparable between groups. There was significant elevation of protein /creatinine ratio and all tubular biomarkers post 1st and 2nd SWL when compared with pre-SWL values (P <0.0001 in all). All tubular damage biomarkers' values returned to pre-SWL at the planned day for the 3rd session in group 2 and 3 only (table 1). At 3 month follow up all urinary biomarkers and protein /creatine ratio were less than pre-SWL values in all groups. However, a significant decrease in ipsilateral renal split function was observed in group 1 only (p. value=0.005,0.887 and0.337 for group 1, 2 and 3 respectively . SWL treatment succeeded in 73.6% in group 1, 83.7% in group 2 and 81% in group 3 . Conclusions: At least 7 days' interval is required between repeated session for treatment of renal stones to allow for complete recoverability of kidney glomerular and tubular functions. SOURCE OF Funding: we received funding from Urology and Nephrology Center - Mansoura University, Egypt
