Anatomic, functional, and pathologic changes from internal ureteral stent placement.

The anatomic, hydrodynamic, functional, and pathologic changes associated with unilateral internal ureteral stenting were evaluated in 20 female canines. Selective glomerular filtration rates (GFR) were measured with technetium 99m diethylenetriamine pentaacetic acid (DTPA) renal scans (N = 14) prior to and several weeks after unilateral internal stent placement. Cystometry and cystography were done at weekly intervals to determine if reflux occurred and to measure the intravesical pressure to produce this reflux (N = 16). Ureteral lumenal capacities of mid 6-cm ureteral segments of stented and unstented ureters were compared. The mid-ureteral lumenal volumes were three times greater in the stented ureters (p < 0.002). There were no significant differences in the selective GFR before and after stenting. Low-pressure vesicoureteral reflux occurred at a mean intravesical pressure of 13.7 cm of water and was present in 84.6 percent (11/13) of the canines whose stents did not migrate or obstruct from encrustation. There were no significant alterations in serum chemistries or blood counts. Fluoroscopic imaging also showed ineffective ureteral peristalsis. This study confirms that internal ureteral stents cause vesicoureteral reflux and significant lumenal dilation without altering renal function.