Estimating bladder capacity in children.

Bladder capacity in children can be estimated accurately by using the formula: Bladder capacity jowmsj = age (yean) + 2. The increased application ofurodynamics to children has created a number of technical and interpretive problems not the least of which is a simplified age-adjusted standard for normalcy. Material and Methods In an attempt to formulate an estimate of ageadjusted normal values for bladder capacity, we studied 35 nonenuretic, uninfected children of different ages with cystometrics under anesthesia at the time of urologic surgery unrelated to the bladder (e.g., hypospadias repair). Actual bladder capacity was determined to be that volume above which the slope of the relatively flat cystometric curve abruptly changed and pressure per unit volume increased in a linear fashion. The results indicated that bladder capacity could be expressed as a simple formula related to the age of the child. Bladder capacity (ounces) = age (years) + 2 Comment To validate this formula we compared it graphically to Starfield’s* data which derived bladder capacity in 203 normal, nonenuretic children of different ages by measurements of voided volumes during diuresis. Figure 1 indicates that the two curves are nearly congruent. While this formula is only an estimate of bladder capacity in children, which may be inaccurate *Star&Id, B.: Functional bladder capacity in enuretic and nonenuretic children, J Pediatr 70: 777 (1967). *’ r 0 MeasuredBladder Functional _ Capacity (Starfield) 16 0 Estimated Bladder Capacity (Age +2 years) Ounces