Glomerular stereology: Why, what and how to measure glomerular structure

Quantitative methods are frequently used to analyse the structure of renal glomeruli. However, on most occasions, measurements are made on glomerular profiles (the two-dimensional samples of glomeruli seen in histological sections), and provide little or no information about the structure of whole, three-dimensional glomeruli. Stereology is the discipline concerned with the quantitative analysis of three-dimensional structures. With stereology one can estimate the total number of glomeruli in kidneys, as well as mean glomerular volume, the number of cells in glomeruli, and the length and surface area of glomerular capillaries. In addition to providing a means for detecting structural differences between glomeruli from different specimens, stereology provides quantitative structural information that can be correlated with quantitative physiological, biochemical and molecular data. Over the past decade we have witnessed the development of a new generation of unbiased, cost-efficient stereological methods that are ideally suited to analysing glomeruli. Some of these methods are introduced in this review, and then three recent studies from our laboratories that successfully utilized these methods are described. These studies concerned hypertension, kidney development, and the pathogenesis of focal and segmental glomerulosclerosis.