The Effects of Dilution on Ureteral Stone Passage

In the distant past, I critiqued the Cochrane Review regarding the use of alpha-blockers for ureteral stone passage. I combed through each individual study cited and found, almost universally, they were small, biased, and probably unreliable. Pooling together these poor data, then, was simply a larger pile of junk.

Following the publication of that Cochrane Review, however, were a handful of well-done clinical trials – and they have shown little reliable beneficial effect on stone passage. There was a small inclination towards benefit for those patients demonstrated to have >5mm distal stone disease, but the magnitude of effect was small enough these trials were underpowered to find a difference.

This systematic review and meta-analysis, then, essentially combines this more recent high-quality evidence with the truckload of older evidence from the Cochrane review. With the larger combined sample size, they are now better able to find stronger associations between treatment with alpha-blockers and successful stone passage in these larger stones. Predictably, however, the quality and reliability of their evidence has diminished by simple diluation.

Alpha-blockers are generally benign therapy in ureteral stones, but, if they’re not going to help, they should be avoided. The authors suggest their empiric use should be encouraged, as stone size is not always part of the initial diagnostic evaluation. Most stones are small, however – and the resulting number needed to treat to successfully pass one additional ureteral stone is probably forbiddingly high in such an empiric strategy.
“Alpha blockers for treatment of ureteric stones: systematic review and meta-analysis”
http://www.bmj.com/content/355/bmj.i6112