FIRE Stones:Impact of forced diuresis on the residual fragment rate after flexible ureteroscopy for destruction of kidney stones with laser: protocol for a randomized controlled two-parallel group multicenter trial with blinding evaluation.

Abstract Background Lithiasis is a common and recurrent disease. Flexible ureteroscopy (fURS) is the cornerstone of laser treatment of kidney stones. Kidney stones destruction requires its laser pulverization into small fragments in order to remove them through the ureter or improve their spontaneous expulsion along the urinary tract. However, most of the time, all the micro-fragments and dust created cannot be extracted using our surgical tools, and may stay intra-renally at the end of the procedure. Adjuvant treatments (such as forced diuresis, inversion or mechanical pressure) were previously described to improve the expulsion of stone fragments after extra-corporeal shock wave lithotripsy. Nevertheless, the impact of adjuvant treatment after fURS remains unclear and mainly theoretical. Objective The primary objective is to show that the injection of 40 mg of Furosemide in slow intravenous during 10 minutes, after the procedure, increases the stone-free rate 3 months after a fURS for destruction of kidney stones with laser. Methods/design The study will be a two-parallel group randomized, controlled, multicentric trial with a blinding evaluation. Nine French departments of urology will participate. Patients will be randomized in 2 groups: the experimental group (injection of 40mg of Furosemide at the end of the surgery) and a control one (usual care). Patients will be followed up for 3 months (+/- 2 weeks) after the surgery. Then, we will perform a low dose abdomino-pelvic CT-scan. The primary outcome is the stone-free rate at 3 months. A centralized review of the images will be performed by two specialized radiologists, in a blind and crossed way to allow a homogenization of the results. The secondary outcomes will include the rate of early post-operative urinary tract infection (UTI), the evaluation of post-operative pain and the safety of the use of Furosemide in patients treated by fURS for renal stone laser destruction. As secondary objectives, it is also planned to look at the effect of the prescription of an alpha-blocker as usual treatment on stone-free rate, and to assess the agreement between the imaging analysis of the urologist and the specialized radiologist. Discussion Lithiasis is a public health problem. It affects about 10% of the general population. This prevalence is increasing (multiplied by 3 in 40 years), partly due to changes in the population's eating habits over the years. The lithiasis patient is a patient with a chronic disease requiring annual follow-up and who may suffer from multiple recurrences, with a recurrence rate at 5 years of 50%. Trial registration ClinicalTrials.gov Identifier: NCT05916963, first received: 22 June 2023. https://clinicaltrials.gov/study/NCT05916963 EU Clinical Trials Register EudraCT Number: 2022-502890-40-00.