Urolithiasis is a common health problem worldwide affecting approximately 10% of the population at some stage in their lives. The aim of this study is to evaluate the efficacy of adjuvant treatment with tamsulosin for improving the stone-free rate after a single session of extracorporeal shock wave lithotripsy (ESWL) in the treatment of radiopaque kidney stones.

Urolithiasis is a common health problem worldwide affecting ∼10% of the population at some stage in their lives. It affects approximately 5% of women and 12% of men in the United States, and it has been suggested that the incidence is increasing. Because of its efficacy and low morbidity, extracorporeal shock wave lithotripsy (ESWL) is an effective treatment for kidney stones smaller than 20 mm in diameter. The objective of this therapy is to achieve an adequate fragmentation of the calculus that allows a spontaneous expulsion of the fragments, and finally, a stone-free state, which is not always possible.

The presence of adrenergic receptors in the ureter has suggested the involvement of the sympathetic nervous system in its peristaltic activity. It has also been shown that alpha 1 adrenergic antagonist medications such as tamsulosin are capable of inhibiting the basal tone and the ureteral peristalsis, causing dilation and facilitating the migration of stones. Some authors have reported the efficacy of this type of medication for spontaneous calculus expulsion, but there is no conclusive evidence of the adjuvant effectiveness of tamsulosin after ESWL for stone clearance and even less among a Mexican population.

This is a single center, randomized, non-placebo-controlled study with a sample of adults (men and women ≥18 years old) with a single radiopaque kidney stone (5-20 mm) in diameter. Post-ESWL session, the patients will be randomly divided into two groups (the control group and the tamsulosin group). After discharge, all patients will be instructed to drink a minimum of 2 L water daily. The control group will receive standard treatment for analgesia consisting of oral diclofenac (75 mg/12 h) as needed. The tamsulosin group will receive standard treatment for analgesia plus oral tamsulosin (0.4 mg/day) for eight weeks.

Patients will attend follow-up visits every two weeks during the first month of treatment and a final visit at the end of the second month. During each visit, vital signs will be taken, a physical examination will be conducted, and possible adverse effects will be monitored; additionally, a plain X-ray of the kidney, ureter, and bladder (KUB) will be taken at two and four weeks for evaluating possible complications associated with residual fragments, as well as an abdominal CT scan at eight weeks after the ESWL in order to determine stone-free status.

Data will be analyzed using R Statistical Software. Descriptive statistics will be determined for the patients' clinical characteristics, grouped by the treatment assigned (control group and tamsulosin group) and will be compared using the Mann-Whitney U test or the chi-square test depending on the variable type. The strength of the association between the ESWL treatment with adjuvant tamsulosin and the stone-free rate will be evaluated by calculating the relative risk (RR) and the number needed to treat (NNT). In all cases, an alpha=0.05 was considered significant.

Inclusion Criteria:

• A single radiopaque kidney stone (5-20 mm) in diameter visible on CT scan of the abdomen.

Exclusion Criteria:

• A lower calyx stone.
• A history of spontaneous stone passage.
• A previous failed ESWL.
• Treatment with alpha adrenergic antagonists, calcium channel inhibitors or steroids.
• Severe obesity (BMI≥40).
• Pregnancy.
• Serum creatinine ≥2 mg/dl.
• Renal artery aneurysm and/or abdominal aorta aneurysm.
• The presence of a ureteral stent.
• Anatomical abnormalities or previous surgery on the upper urinary tract.
• Bone deformities.
• Presence of a urinary tract infection.
• Coagulation disorders.
• Poorly controlled hypertension.