肾动态显像测定肾小球滤过率中两肾深度差对分肾功能的影响

目的利用CT直接测量肾脏深度评价Tonnesen公式法估算两肾深度差的准确性和深度差对Gates法计算分肾功能的影响。方法 43例患者利用单光子发射计算机断层/X线计算机层扫描（SPECT/CT）行腹部CT平扫,根据CT横断层图像测量两侧肾脏深度。CT平扫后行核素肾动态显像,Gates默认以Tonnesen公式法估算肾脏深度并得到肾小球滤过率（GFR）与分肾GFR。将CT所测肾脏深度值输入处理软件,获得不同肾脏深度测量值下的GFR和分肾GFR。采用配对t检验比较两种方法得到的肾脏深度及两肾深度差间的差异,对深度差和由此产生的分肾功能变化行Pearson相关性分析。将两肾深度差与患者年龄、体质量/身高、体质量指数（BMI）和体表面积行多元线性回归,分析可能影响深度差的因素。结果与CT测量法相比,Tonnesen公式法低估了两肾深度（右肾：t=-10.83,P〈0.01;左肾：t=11.56,P〈0.01）;Tonnesen公式法估算的深度差为（0.038±0.007）cm,CT测量法得到的深度差为（0.63±0.44）cm,Tonnesen公式法明显低估了两肾深度差（t=-8.81,P〈0.01）。有20%的患者两肾深度差大于1 cm,且深度差与由此产生的分肾功能变化（｜R（CT）-R（Tonn）｜）成正相关系（r=0.564,P〈0.01）。随着深度差的增加,Tonnesen公式法难以准确反映分肾功能的变化。深度差与患者年龄、体质量/身高、BMI、体表面积均不相关（复相关系数R=0.283,均P〉0.01）。结论 Tonnesen公式法不能准确计算肾脏深度差,从而难以获得可靠的分肾功能,未发现与深度差相关的因素。临床上应用SPECT/CT的CT功能直接测量肾脏深度代替Tonnesen公式,可以获得准确的两肾深度及深度差,从而提高Gates法测量分肾GFR的准确性。

Effects of renal depth difference on the split renal function in the measure of glomerular filtration rate through renal dynamic imaging

Objective To evaluate of the difference between right/left renal depth and split renal function estimated by Tonnesen formula using the renal depth directly taken by CT.Methods Renal depth was measured by CT scan before dynamic 99Tcm-diethylenetriamine pentaacetic acid（DTPA） renal scintigraphy（DRS） was performed by SPECT/CT in 43 patients,and the difference between right/left renal depth was calculated.Renal depth and the depth difference between right/left kidneys estimated by Tonnesen formulation was compared with that of CT using Paired t-test.Glomerular filtration rate（GFR） was recalculated by Gates method using different values of the renal depth measured by CT.Simple correlation analysis was used between the CT renal depth difference and the variant of split function estimated by CT compared to Tonnesen formulation.A multivariate regression analysis was carried out to determine the relationship among the CT renal depth difference and age,the ratio of weight to height,body mass index（BMI） and body surface area（BAS）,to discuss which factors could affect the renal depth difference.Results Compared with CT,the renal depth was underestimated by Tonnesen formulation（right kidney：t=-10.83,P〈0.01;left kidney：t=11.56,P〈0.01）,and the difference between right/left renal depth was also substantially underestimated by Tonnesen formulation（t=-8.81,P〈0.01）.The proportion of patients that the CT renal depth difference was more than 1cm was 20%.The variant of split function estimated by CT compared to Tonnesen formulation（｜R（CT）-R（Tonn） ｜） was positively correlated with the difference between right/left renal depth（r=0.564,P〈0.01）.It accounts for that along with the increase of the difference between right/left renal depth,Tonnesen formulation was difficult to accurately reflect the variant of split function.The age,the ratio of weight to height,BMI and body surface area（BAS） were all uncorrelated with the difference between right/left renal depth（multiple correlation coefficient was 0.283,the P values were all less than 0.01）.Conclusion The difference between right/left renal depth calculated by Tonnesen formula was not accurate,thus affected the accuracy of split renal function.The correlative factors to the difference between right/left renal depth were not found.SPECT/CT can improve the accuracy of split renal GFR measurement by means of measuring renal depth using CT and calculating the difference between right/left renal depth in patients undergoing DRS.