Ozkan B et al, 2015: Does ureteral stenting matter for stone size? A retrospectıve analyses of 1361 extracorporeal shock wave lithotripsy patients.
Ozkan B, Dogan C, Can GE, Tansu N, Erozencı A, Onal B.
Acıbadem Unıversıty, Faculty of Medıcıne, Department of Urology, Istanbul, Turkey.
Unıversıty of Istanbul, Cerrahpasa School of Medıcıne, Department of Urology, Istanbul, Turkey.
INTRODUCTION: The aim of our study was to determine the efficacy of ureteral stents for extracorporeal shock wave lithotripsy (SWL) treatment of pelvis renalis stones and to compare the results and complications in stented and non-stented patients.
MATERIAL AND METHODS: Between 1995 and 2011, 1361 patients with pelvis renalis stones were treated with SWL. Patients were subdivided into three groups according to stone burden: ≤1 cm(2) (group 1; n = 514), 1.1 to 2 cm(2) (group 2; n = 530) and >2 cm(2) (group 3; n = 317). Each group was divided into subgroups of patients who did and did not undergo ureteral stent implantation before SWL treatment. The efficacy of treatment was evaluated by determining the effectiveness quotient (EQ). Statistical analysis was performed by chi-square, Fisher's exact and Mann-Whitney U tests.
RESULTS: Of the 514, 530 and 317 patients in groups 1, 2 and 3 respectively, 30 (6%), 44 (8%) and 104 (33%) patients underwent auxiliary stent implantation. Steinstrasse rates did not differ significantly between stented and non-stented patients in each group. The EQ was calculated as 62%, 33% and 70% respectively in non-stented, stented and totally for group 1. This ratio calculated as 58%, 25% and 63% for group 2 and 62%, 26% and 47% for group 3. Stone-free rates were significantly higher for non-stented than for stented patients in groups 2 and 3.
CONCLUSIONS: Stone free rates are significantly higher in non-stented than in stented patients with pelvis renalis stones >1 cm(2), whereas steinstrasse rates are not affected.
Cent European J Urol. 2015;68(3):358-64. doi: 10.5173/ceju.2015.611. Epub 2015 Oct 15. FREE ARTICLE
An old story updated. The unique quality of this report as compared to similar studies is the fact that all procedures through the treatment period of 25 years were done by one experienced urologist. It is a large retrospective series comparing ESWL of renal stones with stent vs.no stent. However it is not a matched pair analysis nor were the groups comparable:
A stent was placed in “solitary kidney patients, patients with renal ectasia of grade ≥2, and patients with obstruction symptoms lasting a long period of time (>1 month)”.
Only the stented patients with a single kidney and without obstruction or ectasia would have been comparable to the non-stented. But the group was too small (n=21) and in fact only 15 of these patients were stented. Thus the study probably compares 163 obstructed and stented kidneys with 1183 non-obstructed, unstented kidneys. Fragments may not pass easily in a flabby, previously dilated collecting system
The stone free rate is not clearly defined: ”The procedure was ended when full fragmentation of the stones was observed in the fluoroscopic control. The procedure was considered unsuccessful in cases where fragmentation was not achieved at the end of the 3rd session and/or in patients who wanted
to try another treatment.” But 185 patients had >4 sessions.
Unfortunately the authors offer no proper explanation for the different results in the groups. Their arguments are: “We believe that the difficulty the stent creates in focusing on the stone and the additional sessions performed for the stones traveling down the ureter plays a significant role in these findings. Furthermore, in such cases stents can also block the particles that could migrate downwards under normal conditions.”
The answer is probably hidden in the method and material section. This is a frequent problem in retrospective analyses without a special question.