Safety and Efficacy of Gravity Irrigation Versus Pressure Irrigation in Retrograde Intrarenal Surgery (RIRS): A Randomized Controlled Trial

Introduction Urolithiasis is one of the most prevalent urological diseases affecting general population across the world. The worldwide prevalence ranges from 7%- 13% in North America, 5%-9% in Europe, and 1%-5% in Asia.1 West Asia, Southeast Asia, South Asia as well as several developed countries, including South Korea and Japan, have been categorized into stone forming belt countries with prevalence ranging from 5% to 19.1%. Increasing incidence of stone disease is linked with modern life style, food habits, climate as well as increasing use of imaging (computed tomography or ultrasonography)2,3,4 Renal stones constitute about 80% of total urolithiasis. Shock wave lithotripsy(SWL), Percutaneous Nephrolithotomy(PNL), and Retrograde Intrarenal Surgery (RIRS) are available treatment modality for renal stones. According to European Association of Urology (EAU) 2020 Guidelines, when active treatment of renal stones of size <10 mm is indicated, primary treatment modality is either SWL or RIRS. For stones of size > 20 mm, PNL is first line of treatment, however if it is contraindicated then RIRS or SWL can be used. Stones of size 10-20 mm in non-lower pole calyx can be dealt with SWL or Endourology (PNL or RIRS). Lower pole calyx stones of 10-20 mm with unfavorable factors like steep infundibulo-pelvic angle, long calyx, long skin to stone distance, narrow infundibulum and shock wave resistant stones need to be treated with endourology (PNL or RIRS). However, favorable lower pole calyx stones of size 10-20 mm are recommended for SWL or Endourology.5According to AUA guidelines6, in symptomatic patients with a total non-lower pole renal stone burden ≤ 20 mm, SWL or RIRS can be offered. Patients with a total renal stone burden > 20 mm, PNL are the first line therapy. For patients with < 10 mm lower pole renal stones, SWL or RIRS is first line treatment. Patients shouldn't be offered SWL as first line therapy to lower pole stones >10 mm. Patients with lower pole stones >10mm in size need to be explained that PNL has a higher stone free rate but greater morbidity.

RIRS is occasionally associated with severe infectious complications.14 Reasons commonly attributed to it are high intra-pelvic pressure, obstruction, infected urine and stone, break in sterility of procedure etc. Ureteral Access Sheath (UAS) is one of the measure used to decrease intra-pelvic pressure during stone fragmentation.13 Irrigation for RIRS is the critical component for the success of procedure. For better vision during procedure, irrigation pressure (IP) and irrigation flow (IF) needs to be increased. To avoid detrimental effects of high pressure, intra-renal pressure (IRP) has to be lower than 22 mmHg (30 cm of water (H2O))7. High pressure irrigation raises intrarenal pressure leading to pyelo-venous and pyelo-lymphatic reflux which can lead to sepsis, septic shock, bleeding, infundibular rupture.

Some studies have estimated that at an IP of ≤ 100 cm H2O (73 mmHg), IRPs remain lower than 30 cm H2O if Ureteric Access Sheath (UAS) bigger than 10/12 F is utilized. An IP of 200 cm H2O (146 mmHg) may offer high irrigation flows but could result in IRPs > 40 cm H2O8,9. During forced irrigation and stone fragmentation, IRP can rise upto 300mmHg for short interval.15 Omar M. et al in another similar endourological procedure, PCNL which showed High Irrigation Pressure (272 cm H2O) to be associated with a higher risk of SIRS (46%) compared to low Irrigation Pressure (108.8 cm H2O) risk of 11%.10 Gravity irrigation at 100 cm of H2O (73 mmHg), exerts IRP lower than 30 cm of H2O, however in pressure irrigation IRP increases significantly higher. In this study Investigators want to compare between two groups in terms of safety and efficacy.

Rationale and Justification of study Irrigation is required in RIRS for better vision and smooth performance of surgery. However, high IP during RIRS is implicated for infective complications. Comparative study of different pressures for irrigation during RIRS is lacking. Investigators would like to study the safety and efficacy of gravity irrigation versus pressure irrigation in RIRS.

Objectives