The investigators objective is to study if some drugs can improve the success rate of extracorporeal shockwave lithotripsy for renal stones.

Extracorporeal shockwave lithotripsy is one of the modalities of treatment of renal stones. It´s a machine that breaks the renal stones extracorporeally. Some drugs, like alpha blockers and calcium channel blockers, can improve the success rates of this procedure. Our objective is to study the real effects of two drugs, tamsulosin and nifedipine, compared to placebo, in the elimination of fragments after the extracorporeal shockwave lithotripsy treatment.

Inclusion Criteria:

• radiopaque renal stone, 5 to 20 mm, located at renal pelvis or superior or middle calix

Exclusion Criteria:

• inferior calix, any contraindication for extracorporeal shockwave lithotripsy, pregnancy, coagulopathy, previous renal surgery, age under 18, abdominal aorta aneurism and urinary infection.