Twin-glomeruli and duplication of glomerular capillary tuft in human kidneys

Since the turn of this century the term twin-glomeruli (TG) designates a pair of glomerular capillary tufts supplied by a single afferent arteriole. Screening for TG has been performed in a series of kidney slides from 200 unselected consecutive autopsy cases with 21 (10.5%) positive results. Serial sectioning of 21 TG-positive and 10-TG-negative kidneys revealed the frequency of TG = 0.48% (71 among 15035 glomeruli) in the first group and 0.38% (32 TG among 8241 glomeruli) in the second. In individual cases the frequency ranged from zero up to 1.73% of all glomeruli. Three types of TG could be distinguished according to the distance between glomerular hili and the degree of Bowman's capsules coalescence. A complicated spatial relationship between the glomerular vessels and surrounding tubules was demonstrated by plastic reconstructions. TG are believed to be of a variety of renal architecture probably occurring in every human kidney. On the other hand, the glomeruli with two, mostly incomplete capillary tufts, which are occasionally found in the kidneys of newborns and children with multiple malformation syndromes and kidney dysplasias, are supposed to give evidence of a disturbed development of the kidneys.