OBJECTIVES: To prospectively assess if urinary tract infection (UTI) after extracorporeal shock wave lithotripsy (ESWL) enhances immediate renal damage in patients with renal stones.METHODS: Levels of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and beta2 microglobulin were measured in the urine of 171 patients, before and after ESWL for treatment of up to 3 cm renal stones. Standard investigation included urine sample before and after treatment. Patients were divided in two groups in accordance to presence of positive bacterial urine sample after ESWL. Changes in biomarker values pre and post- ESWL were assessed via X2 test for both groups and compared between the two groups for post-treatment values.RESULTS: Despite pre-treatment antibiotic therapy, 21.6% of the patients presented with UTI after ESWL. In the group with clear post-treatment urine samples there was a 5.8, 2.2, and 0.7 fold increase of CPK, LDH, and beta2 microglobulin levels after ESWL, respectively (p<0.001), indicating some degree of immediate renal damage. In patients with UTI, the levels of the enzymes elevated by 80, 15, and 2.2 fold after ESWL, respectively, which represents a significantly increased elevation comparing with the sterile urine group (p<0.001).CONCLUSIONS: ESWL results in transient immediate renal damage, which is exaggerated in patients with persistent or treatment prompted UTI. Long-term importance of this finding must be determined.