目的 对比估计肾小管长度的两种体视学方法：轮廓计数法和直径法。  方法  从2月龄正常雄性SD大鼠获取9个肾脏，采用定向法制作等向随机切片（甲基丙烯酸树脂包埋），用过碘酸-雪夫（PAS）试剂和苏木素染色后进行体视学测量：计数切片上各段肾小管（包括集合管，不包括髓袢细段）轮廓（切面）中心管腔的数量，由此估计肾小管的长度；抽选近似圆形、椭圆形、有明显管腔的肾小管轮廓，测其直径（圆形轮廓）或短径（椭圆形轮廓），据其平方的平均计算肾小管（假设为圆柱结构）横断面积，然后结合肾小管的体积估计其长度。  结果  据轮廓直径估计的各个肾脏内肾小管的总长与据轮廓计数估计的结果之比，平均为1.43（变异系数7.2%），即轮廓直径法高估了大于40%的肾小管长度。  结论  用肾小管的短径来估计其长度的方法不可靠。

Objective  To compare the two stereological method  based on profile counts and diameters for the estimation of renal tubular length.   Methods  Nine kidneys from 2-month-old normal male SD rats were obtained and isotropic random sections (methacrylate resin-embedded) were prepared with the orientator for stereological measurement after staining with periodic acid-Schiff (PAS) reagent and hematoxylin. The length of renal tubule segments (including collecting ducts, not including the thin segments of Henle’s loops) was estimated by counting the number of central lumens of renal tubular profiles on sections. Approximate round or elliptical renal tubular profiles with an apparent lumen were sampled and their diameters (round profiles) or short diameters (elliptical profiles) were measured; from the mean of squared diameters, the cross-sectional area of renal tubules (assumed as cylindrical structures) was calculated for the length estimation in combination with the volume of renal tubules.   Results  The ratio of the total length of renal tubules per kidney as estimated with profile diameters to that estimated with profile counting was 1.43 on average (coefficient of variation 7.2%), i.e. the method  with profile diameters overestimated the renal tubular length by more than 40%.   Conclusion  The method  of estimating renal tubule length with the short diameters is not reliable.