An artificial model for studying fluid dynamics in the obstructed and stented ureter

Abstract

-Fluid dynamics in the obstructed and stented ureter represents a non-trivial subject of investigation since, after stent placement, the urine can flow either through the stent lumen or in the extra-luminal space located between the stent wall and the ureteric inner wall. Fluid dynamic investigations can help understanding the phenomena behind stent failure (e.g. stent occlusions due to bacterial colonization and encrustations), which may cause kidney damage due to the associated high pressures generated in the renal pelvis. In this work a microfluidic-based transparent device (ureter model, UM) has been developed to simulate the fluid dynamic environment in a stented ureter. UM geometry has been designed from measurements on pig ureters. Pressure in the renal pelvis compartment has been measured against three variables: fluid viscosity (µ), volumetric flow rate (Q) and level of obstruction (OB%). The measurements allowed a quantification of the critical combination of µ, Q and OB% values which may lead to critical pressure levels in the kidney. Moreover, an example showing the possibility of applying particle image velocimetry (PIV) technology to the developed microfluidic device is provided.

Fluid mechanical modeling of the upper urinary tract

“…In addition to studies evaluating the overall performance of stents, growing interest on the mechanism of development of biofilm and encrustations has also sparked experimental models at smaller scales. Carugo et al (2013) and Clavica et al (2014) designed an in-vitro transparent model based on porcine ureter characteristics. The ureter model incorporates a small cylindrical chamber (20 mm in diameter and 36 mm in height) as the renal pelvis proximal to the ureter.…”

“…The results established a relation between the fluid viscosity, flow rate, and the renal pressure, showing that a small increase in the obstructed area will significantly increase the renal pressure for a given viscosity and flow rate. Notably, these studies (Carugo et al, 2013;Clavica et al, 2014) are the first to perform flow visualization experiments inside a transparent ureter model using fluorescent particles. Microscopic images revealed laminar vortices in the cavity downstream of the obstruction (similar to that in Figure 3(e)).…”

A Microfluidic-Based Investigation of Bacterial Attachment in Ureteral Stents

“…A common stent design includes two double-J ends to prevent stent migration, and side-holes punched through its wall in order to promote urinary drainage and bypass the obstructed ureteral section [4][5][6][7]. Although they are widely used in clinical settings, normal ureteral stent function can be compromised by problems or side effects, including urothelial irritation, stent migration, encrustation due to attachment of crystalline particles, and biofilm formation due to bacterial colonisation [8][9][10]. In addition to reducing a patient's quality of life, these complications inevitably lead to an increased economic burden, since stent replacement, additional clinical procedures, and aftercare may be required [11,12].…”

Urine flow analysis using double J stents of various sizes in in vitro ureter models

“…When inserting the currently available DJSs, the amount of urine that can maintain renal function is often not retained in the flow from the kidney to the bladder. Previous studies have evaluated urine flow in a stented ureter using a straight ureter model and a DJS. However, these models were not based on human anatomy, especially the ureter's curvature within the human body or its diameter under the condition of no ureteral peristalsis.…”