Bladder capacity in infants.

Bladder capacity was measured at micturating cystourethrography and normal ranges were established for children up to 1 year of age. Bladder capacity was compared with patient weight and distance from first lumbar to third lumbar vertebrae (L1 to L3). The simplified formula--Capacity (mL) = 7 x weight (kg)--was shown to give a reliable estimate of the expected bladder capacity in infants independent of age; this is useful in those infants whose weight lies outside the normal range for their age. Similarly, a formula was deduced relating expected bladder capacity to the measured L1 to L3 distance on an anteroposterior radiograph, which is of potential use to radiologists.