A STUDY OF URINARY STONES REQUIRING LARGE DOSE EXTRACORPOREAL SHOCKWAVE (ESWL) TREATMENT

Objectives: To identify factors that may play a role ih the increased resistance of renal stones to extracorporeal shockwave lithotripsy (ES WL) treatment. Methods: A retrospective study on 290 ESWL patients who received more than 10,000 shocks. The following factors were studied: Age, sex, stone size, site, multiplicity, difficulty of x-ray stone v isualization during localization for ESWL treatment; previous surgery for stone disease; degree of hydronephrosis; stone clearance at 6 mont hs after 20,000 shocks; staff versus resident ESWL machine operator an d finally the type of stone. Results: One hundred and fifty-five (53%) patients had solitary renal stones, Ninety-four (32%) patients had mu ltiple renal, forty (14%) had ureteric and one (0.3%) patient had blad der stone. Of the 155 solitary stones, which is the largest group requ iring high dose ESWL therapy, only 46 (30%) were of surface area equal to or greater than 500 mm(2) indicating that other factors are also i mportant besides the size in this regard, The majority of the stones a nalyzed were of very hard consistency: 60% calcium oxalate, 8% contain ed urate and 5% composed of cystine: Early analysis of post-ESWL passe d stone fragments and reviewing the medical records of those patients with previous history of stone disease to identify stone type from pre viously passed renal stones or stones obtained surgically, helps early recognition of stone composition and possibly predicts treatment outc ome. Conclusions: We observed that some patients with certain renal an d ureteric stones, even of moderate or small sizes, require a higher E SWL dose than others. Increased stone hardness may explain slow stone clearance in this group of patients. Understanding this possibility he lps to make a realistic anticipation of the period of morbidity and tr eatment cost.