Stone clearance in lower pole nephrolithiasis after extra corporeal shock wave lithotripsy – the controversy continues

BACKGROUND To determine factors influencing the clearance of fragments after extra-corporeal shock wave lithotripsy (ESWL) for lower pole calyceal (LPC) stones. METHODS In the period between July 1998 and Oct 2001, 100 patients with isolated lower polar calyceal calculi or= 14 years, were included in the study. Intravenous urograms (IVU) were reviewed to define the LPC anatomy (width of the infundibulum and pelvicalyceal angle). Study end points i.e. stone free status; number of shock waves used and number of sessions were correlated with variables like LPC anatomy, body mass index and stone size. RESULTS At three months follow up the clearance for stone size 90 degrees ) had stone clearance of 94 and 100% respectively. For the infundibular width of < 4 mm, the stone clearance was 93% were as for > 4 mm, it was 100%. For body mass index (BMI) less than and > 30 kg/m2, the stone clearance was 92 and 95% respectively. CONCLUSIONS There is a trend towards more ESWL sessions and shock wave requirement in patients with acute pelvi-calyceal angle and narrow infundibulum but it is not statistically significant. Size (<or= 20 mm) and BMI has no relation with stone clearance. With modern lithotripter, stones up to 20 mm could primarily be treated by ESWL, irrespective of an un-favorable lower polar calyceal anatomy and body habitus.