Foda K, Abdeldaeim H, Youssif M, Assem A

Department of Urology, College of Medicine, University of Alexandria, Alexandria, Egypt

Abstract

OBJECTIVE: To define the parameters that accompanied a successful extracorporeal shock wave lithotripsy (ESWL), namely the number of shock waves (SWs), expulsion time (ET), mean stone density (MSD), and the skin-to-stone distance (SSD).

METHODS: A total of 368 patients diagnosed with renal calculi using noncontrast computerized tomography had their MSD, diameter, and SSD recorded. All patients were treated using a Siemens lithotripter. ESWL success meant a stone-free status or presence of residual fragments

RESULTS: Three hundred one patients were ESWL successes. A significant positive correlation was elicited between number of SWs and stone diameter, density and SSD; between ET and stone diameter and density. Multiple regressions concluded 2 equations: Number of SWs = 265.108 + 5.103 x1 + 22.39 x2 + 10.931 x3 ET (days) = -10.85 + 0.031 x1 + 2.11 x2 x1 = stone density (Hounsfield unit [HUs]), x2 = stone diameter (mm), and x3 = SSD (mm). Receiver operating characteristic curves demonstrated a cutoff value of ≤934 HUs with 94.4% sensitivity and 66.7% specificity and P = .0211. The SSD curve showed that a distance ≤99 mm was 85.7% sensitive, 87.5% specific, P <.0001.

CONCLUSION: Stone disintegration is not recommended if MSD is >934 HUs and SSD >99 mm. The required number of SWs and the expected ET can be anticipated.

Urology. 2013 Nov;82(5):1026-31. doi: 10.1016/j.urology.2013.06.061. Epub 2013 Sep 14

PMID:24044913 [PubMed - in process]