Bladder capacity (ounces) equals age (years) plus 2 predicts normal bladder capacity and aids in diagnosis of abnormal voiding patterns.

Standardization of the bladder capacities of children will improve the precision of urodynamic evaluation. In an attempt to develop a practical guide to predict the normal bladder capacity during childhood the bladder capacities of 132 children without a clinically abnormal pattern of voiding were measured. When the bladder capacities are correlated by age the following linear relationship exists: normal bladder capacity (ounces) equals age (years) plus 2. The bladder capacities of 68 children with primary enuresis, frequency or infrequent voiding were then measured. Children with clinically infrequent voiding demonstrated large bladder capacities and those with frequency or enuresis demonstrated small bladder capacities compared to normal children. The formula appears to be a useful guide to predict normal bladder capacity by age and also to aid in the diagnosis of abnormal voiding patterns.