Individual influencing factors of the normal adult kidney size

Objective To explore the relationship between the size of the kidney and gender, age, height, weight, waist circumference then derive an estimation formula of a normal kidney size for different people. Methods We investigated 1 000 normal cases who accepted the examination in Tianjin Medical University General Hospital from December 2011 to April 2012, including 462 males, 538 females, aged 21-78 years. All the investigated subjects were healthy except for hypertension, diabetes, coronary heart disease. Blood urea nitrogen (BUN) and creatinine (Cr), fasting glucose, uric acid, routine urine test were all in the normal range. Height, weight, and waist circumference were measured for all the subjects. The renal length and transverse diameter in supine coronal sections, anteroposterior diameter in vertical cross-section of the renal hilum were measured by the same technical experts with Philip iU22 C5-1, 3.5 MHz convex array probe. Results The right and left kidney size both are significantly related to height (right r=0.845, left r=0.876, P 0.5). Linear regression formula for the kidney length and the height (H, cm) : Kidney length of men: right 0.059×H+0.144; left: 0.061×H+0.287. Kidney length of women: right 0.039×H+3.679; left: 0.035×H+4.454. Regardless of gender, the formula of left kidney length: 0.052×H+0.721. Linear regression formula about the left kidney length and the height, body weight and body surface area (unit: H cm, W kg, BSA m2): 0.114×H+0.139×W-10.287×BSA+2.112. Conclusion There is the best correlation between kidney length and height. Height, weight, body surface area have great influence on kidney size. Key words: Ultrasonography; Body height; Body weight; Body surface area; Renal size