Development of Formulas for the Estimation of Renal Depth and Application in the Measurement of Glomerular Filtration Rate in Koreans

Yoo, Ie Ryung; Kim, Sung Hun; Jung, Yong Ahn; Jung, Hyun Suk; Lee, Hae Gyu; Park, Young Ha; Lee, Sung Yong; Son, Hyung Sun; Jung, Soo Gyu; Kim, Hyun Mi; Lee, Hyung Goo

Abstract

PURPOSE: There is no established formula for estimating renal depths in Korean. As a result, we undertook this study to develop a new formula, and to apply this formula in the calculation of glomerular filtration rate (GFR).
MATERIALS AND METHODS
We measured the renal depth (RD) on the abdominal CT obtained in 300 adults (M:F=167:133, mean age 50.9 years) without known renal diseases. The RDs measured by CT were compared with the estimated RDs based on the Tonnesen and Taylor equations. New formulas were derived from the measured RDs in 200 out of 300 patients based on several variables such as sex, age, weight, and height by multiple regression analysis. The RDs estimated from the new formulas were compared with the measured RDs in the remaining 100 patients as a control. In 48 patients who underwent Tc-99m DTPA renal scintigraphy, GFR was measured with three equations (new formula, Tonnesen and Taylor equations), respectively, and compared with each other.
RESULTS
The mean values of the RDs measured from CT were 6.9 cm for right kidney of the men (MRK), 6.7 cm for left kidney of the men (MLK), 6.7 cm for right kidney of the women (WRK), and 6.6 cm for left kidney of the women (WLK). The RDs estimated from Tonnesen equation were shorter than the ones measured from CT significantly. The newly derived formulas were 12.813 (weight/height)+0.002 (age)+ 2.264 for MRK, 15.344 (weight/height)+0.011 (age)+0.557 for MLK, 12.936 (weight/height)+ 0.014 (age)+1.462 for WRK and 13.488 (weight/height)+0.019 (age)+0.762 for WLK. The correlation coefficients of the RD measured from CT and estimated from the new formula were 0.529 in MRK, 0.729 in MLK, 0.601 in WRK, and 0.724 in WLK, respectively. The GFRs from the new formula were significantly higher than those from the Tonnesen equation significantly, which was the most similar to normal GFR values.
CONCLUSION
We generated new formulas for estimating RD in Korean from the data by CT. By adopting these formulas, we expect that GFR can be measured by the Gates method accurately in Korean.