ESTIMATION OF GLOMERULAR VOLUME - A COMPARISON OF 4 METHODS

Methods for estimating glomerular volume were compared in Zenkerfixed, paraffin-embedded biopsies from 10 patients with insulin-dependent diabetes mellitus and 6 normal kidney donors. Two methods of measurement of individual glomerular volumes were used: the Cavalieri method (considered the "gold standard") and the maximal profile area (MPA) method. Also studied were the method of Weibel and Gomez and a method based on the disector principle; both estimate mean volume (V(G)). MPA and Cavalieri showed strong correlation (r = 0.93; P < 0.001), although the MPA method consistently overestimated the true volume; six glomeruli were necessary for a reliable estimate of V(G). The disector method did not correlate with V(G) determined by Cavalieri. Weibel-Gomez did correlate with Cavalieri (r = 0.68; P < 0.05), but overestimated V(G). At least 15 profiles were needed to provide a dependable estimate of V(G) by Weibel-Gomez. The Cavalieri, MPA, and Weibel-Gomez methods all can provide reliable estimates of V(G), the latter two with appropriate correction factors. The individual glomerular volume methods, while more time consuming, provide information on variation and distribution of the glomerular population and are the methods of choice for studies of glomerular volume.