OBJECTIVE: to evaluate the accuracy of bladder scanners in measuring bladder volume and to compare their precision. METHOD: MEDLINE and Cochrane databases were searched from January 1, 1990 to December 30 RESULTS: 177 studies were screened, of which 23 were included in the final analysis. According to the literature, there is no clinically significant difference in the measurement of bladder volume using urethro-vesical catheterization, bladder scanner, or conventional ultrasound. Studies comparing different types of bladder scanners did not show any difference in accuracy. CONCLUSIONS: Bladder scanners are precise tools to evaluate bladder volume in urological patients, applicable in daily practice. Knowledge of the patient's medical history is crucial to better interpret the measurement.