Purpose of review: To discuss studies evaluating associations of glomerular number (Nglom) and glomerular volume with hypertension and kidney disease.
Important findings: The association of low Nglom with hypertension and renal insufficiency was described in the 1930s. Many investigators have noted loss of glomeruli with age, with most disappearing entirely, and have proposed that hypertension follows. In a recent German study, hypertensive patients had fewer glomeruli and larger mean glomerular volumes than nonhypertensive people. Among the 10-fold range of Nglom in our multiracial autopsy series, the lowest were in Australian Aborigines, who have the highest rates of renal failure. Nglom fell with age. There was a five-fold range in mean glomerular volume and considerable heterogeneity in individual glomerular volumes within a patient. Larger mean glomerular volume and greater individual glomerular volume heterogeneity correlated with lower Nglom, larger body size, hypertension, and black race. Hypertension increased with age and was marked by glomerular enlargement, intimal thickening and higher rates of glomerulosclerosis. In whites and Aborigines, but not in US blacks, lower Nglom was associated with hypertension, while robust numbers were highly protective.
Summary: Higher mean glomerular volume and individual glomerular volume heterogeneity mark glomerular stress. Low Nglom is an important determinant of hypertension and renal disease. Many 'missing' nephrons have probably been lost during life, leaving little trace. Additional factors contribute to high rates of hypertension in blacks.