Determination of mean glomerular volume in nephrectomy specimens.
BACKGROUND
Mean glomerular volume (VG) determined by Cavalieri, maximal profile area (MPA), and Weibel-Gomez methods correlated in paraffin-embedded needle biopsies; the Disector method did not correlate, probably because of sampling limitations. The relationship of these methods in other types of specimens has not been established.


METHODS
Sections of whole kidneys from 19 rats, 10 treated with furosemide to increase VG, were immersion-fixed, embedded in glycol methacrylate, serially sectioned at 5 microns through 150 microns of tissue, and stained with Jones' silver stain. VG was determined by the Cavalieri, MPA, Disector, and Weibel-Gomez methods with three samples from each animal to assess the correlation, agreement, and repeatability of each of these methods. Methods were considered to correlate if p < 0.01 on linear regression analysis and to agree if the line of identity (x = y) fell within the 95% confidence interval for the slope of the regression curve. Repeatability was assessed with the coefficient of variation for each technique.


RESULTS
Other methods correlated with the Cavalieri method (MPA r = 0.86, Disector r = 0.66, Weibel-Gomez r = 0.87), although none of these methods agreed with Cavalieri VG. These results were similar when treated animals, untreated animals, and all animals were analyzed. Cavalieri and MPA methods showed 7% coefficient of variation with repeated samples; the Disector method showed higher variation (12%), and Weibel-Gomez showed significantly higher variation when compared with the other methods (25%).


CONCLUSIONS
MPA, Weibel-Gomez, and Disector methods all provide estimates of VG that correlate with Cavalieri VG; however, none gives the same value. Reasons for these discrepancies may include assumptions regarding glomerular shape and size distribution inherent in the various methods and the experimental conditions. Tissue availability will often dictate VG method, and consistency of method within an experiment is critical.
Lane
P H
PH
Department of Pediatrics, St. Louis University School of Medicine, Missouri, USA.
D000818:Animals; D005069:Evaluation Studies as Topic; D007678:Kidney Glomerulus / Q000473:pathology*; D008297:Male; D009392:Nephrectomy; D010336:Pathology / Q000379:methods; D051381:Rats; D011919:Rats, Inbred Strains