Simple, age-based formula for predicting renal length in children

To determine a simple, age based formula for predicting ideal renal length in children. Renal size is a valuable marker in the evaluation of children with urological disorders. Although many authors have described complex nomograms and multivariate formulas for determining renal size, we propose a simple and accurate formula.

All renal ultrasound (US) studies performed over a 9-year period in patients <18 years of age were retrospectively evaluated, excluding patients with a history of urinary tract disease or with abnormal renal US findings.

Ultrasounds were performed in 778 children <18 years who met inclusion criteria. Sixty-one percent of the patient population was ≥1 year of age at the time of the US. Forty-four percent of the children were male. In children 1 year of age or older, the formula was length (cm) = age (years) × 0.3 + 6, R(2) = .81. In infants younger than 1 year, renal length was poorly estimated by a simple age-based formula.

Our proposed formula can be used to predict renal length in children older than 1 year.