Predictive factors of lower calyceal stone clearance after extracorporeal shockwave lithotripsy (ESWL): the impact of radiological anatomy.

BACKGROUND This study was carried out to determine whether or not there is a significant relationship between the radiologic anatomy of the lower calyx, as seen on preoperative intravenous urography (IVU), and the outcome of stone clearance after extracorporeal shockwave lithotripsy (ESWL) for lower renal calyceal stones. METHODS Between June 1998 and April 2007, 112 patients with a solitary lower renal calyceal stone measuring 20 mm or less in size were enrolled in this retrospective study. Pretreatment IVU was reviewed for measuring the anatomical predictors, such as lower pole infundibular length, infundibular width (IW) and infundibulopelvic angle, while the stone location and size were determined on plain abdominal X-ray. All patients were treated with ESWL using a Siemens Lithostar Plus lithotriptor and were followed-up for the outcome of stone clearance 3 months after ESWL with plain abdominal X-ray films and ultrasonography. RESULTS Three months after ESWL, only 49 (43.7%) patients were stone-free. Under multivariate analysis with logistic regression, smaller stone size (10 mm or less, p = 0.005) and greater IW (4 mm or more, p = 0.029) were significant favourable predictors for better stone clearance. CONCLUSION In addition to the influence of stone size, lower pole anatomy, especially IW, has a significant impact on stone clearance for lower calyceal stone after ESWL.