Mechanism of ureteral stent flow: A comparative in vivo study

Background and Objectives: The flow characteristics of ureteral stents have yet to be clearly defined. In this study, flow mechanics were studied in s everal silicone-based stents including 4.8F, 7F, and 10.3F pigtail; 7F Towe r; and a prototype mesh stent, Materials and Methods: Forty-five female Yucatan minipigs underwent bilater al laparoscopic occlusion of their renal vessels to stop urine production. A nephrostomy tract was established by retrograde puncture. A stent was pla ced in the ureter, and three measurements were taken with flow from a bag o f irrigant 20 cm above the kidney: stent occluded with a guidewire (extralu minal flow), stent unobstructed (total flow), and laparoscopically placed e xtraureteral ligature (luminal flow). Results: Luminal flow and, to a lesser extent, total flow appeared to incre ase as the internal and external diameters of the stent increased. The Towe r stent, which had no sideholes, had much lower flow rates in all categorie s, while the prototype mesh stent showed greater total flow compared with t he other stents, Extraluminal flow did not increase with stent size greater than 7F, Conclusions: Luminal flow, but not extraluminal flow, increased with an inc rease in the internal diameter of the stent. In general, the least favorabl e Bow occurred with a Tower stent, which had the smallest internal diameter . The greatest flow was seen with the prototype mesh stent.