Objective: The present study analyzed the hydrodynamic behaviour of the double-J stent.
Methods: Thirty-two double-J stents of different sizes and biomaterials (16 new and 16 removed from patients) were hydrodynamically evaluated using two models: a) nephroureterocystectomy surgical blocks harvested from pigs and b) an in vitro experimental model of the upper urinary tract. The following parameters were measured: initial and final weights, encrusted material weight, inside and outside diameters, number, size and distribution of sideholes, wall thickness, drainage area and length of time the catheter was indwelling in the patient.
Results: Double-J stent placement in a normal upper urinary tract constitutes a partial obstruction that is proportional to the caliber of the catheter. Ureteral-flow reduction is 83%, 61% and 58% for 5FR, 6FR, and 7FR catheters, respectively. Extraluminal obstruction of the catheter reduces ureteral flow more than intraluminal obstruction (74%, 43% and 25% for extraluminal versus 83%, 66%, 57% for intraluminal for 5FR, 6FR and 7FR, respectively). Vesicoureteral and vesicorenal reflux pressures were 6.2 +/- 0.3 cm H2O and 35.2 +/- 2 cm H2O, respectively.
Conclusion: Selection of a double-J stent must be individualized on the basis of indication, time indwelling, sex and route of insertion.