Urinary NAG excretion after anesthesia-free extracorporeal lithotripsy of renal stones: a marker of early tubular damage.

Second generation lithotripters require a higher number of shocks per session as well as an increased rate of secondary treatments for complete stone disintegration compared to the original spark gap lithotripter. The clinical relevance of biological side effects caused by such treatment are less known. We evaluated urinary excretion of N-acetyl-glucosaminidase (NAG) before and after lithotripsy in 50 patients treated with a low pressure spark gap lithotripter (Dornier HM3) and in 36 patients treated with a piezoelectric lithotripter (Wolf Piezolith 2200) in an attempt to evaluate their side effects on renal tissue. The urinary excretion of NAG increased after both spark gap lithotripsy using the modified HM3 and piezoelectric lithotripsy. These changes may be associated with slight tubular damage that would occur after anesthesia-free lithotripsy in patients subjected both to a high number of shocks and to secondary treatments.