Effects of Flexible Ureteroscopy on Renal Blood Flow

Aim of this study is to investigate the effects of increased intrarenal pressure during flexible ureteroscopy on renal blood flow.

Patients undergoing flexible ureteroscopy (F-URS) and laser lithotripsy for kidney stones according to European Association of Urology (EAU) guidelines on Urolithiasis will be included in the study after having signed an informed consent form. The pre- and post-operative evaluation and management will be performed according to EAU Guidelines on Urolithiasis. Additionally, as a non-invasive test, bilateral renal power Doppler US will be performed to patients pre- and post-operatively. The pre-operative Doppler US will be performed 2 days prior to surgery and the post-operative Doppler US will be performed in the first 24 hours following surgery. The changes on blood flow in renal artery and arcuate artery will be recorded.

Aim of this study is to investigate the effects of increased intrarenal pressure during flexible ureteroscopy on renal blood flow.

Patients undergoing flexible ureteroscopy and laser lithotripsy for kidney stones according to EAU guidelines on Urolithiasis will be included in the study after having signed an informed consent form. The pre- and post-operative evaluation and management will be performed according to EAU Guidelines on Urolithiasis. Additionally, as a non-invasive test, bilateral renal power Doppler US will be performed to patients pre- and post-operatively. The pre-operative Doppler US will be performed 2 days prior to surgery and the post-operative Doppler US will be performed in the first 24 hours following surgery. The changes on blood flow in renal artery and arcuate artery will be recorded.

Flexible ureteroscopy has been a key component of kidney stone management in the last 20 years. Even for stones larger than 2 cm, flexible ureteroscopy can be performed with high success and low complication rates. Ureteral access sheaths are key contributors to flexible ureteroscopy as they provide easy and repeated access to upper urinary tract and decreased intrarenal pressures due to easy flow back of the irrigation solution.

The increased pressures during flexible ureteroscopy have been an important research area in the last years. Due to irrigation solution and irrigational pumping to provide a clearer vision during flexible ureteroscopy, intrarenal pressures rise and after a certain point pyelo-sinusoidal, pyelo-venous and pyelo-lymphatic backflow starts. It has been shown that this backflow starts when pressure rises above 40 cmH2O (centimeters-water / unit of pressure measurement). Schwalb et al. demonstrated in their study that in kidneys subject to high intrarenal pressure, denudation and flattening of the caliceal urothelium, submucosal edema and congestion are observed. Due to these deleterious effects on urothelium, renal extravasation and bacterial translocation can occur and complications may arise.

Renal Doppler US, due to its non-invasive nature, has been widely used to measure localized blood flow in the kidneys, to evaluate hemodynamic parameters in acute kidney injury. Intrarenal backflow and its consequences such as submucosal edema and congestion may decrease blood flow especially around the calyces subject to high pressures and this situation may result in acute kidney injury.

Eligibility Criteria:
Inclusion Criteria:

* Patients between ages 18-65
* Patients undergoing flexible ureteroscopy + laser lithotripsy according to EAU Guidelines on Urolithiasis

Exclusion Criteria:

* Pregnant patients
* Patients with already-diagnosed urological malignancies
* Patients ineligible for flexible ureteroscopy due to concomitant co-morbidities