Multiple efferent arterioles of the human kidney glomerulus as observed by scanning electron microscopy of vascular casts.

About three thousand resin vascular casts of human renal glomeruli were examined with a scanning electron microscope, and two extremely rare glomeruli with quadruple or quintuple efferent arterioles were found. Each of these multiple efferent arterioles arose independently from the glomerular capillary tuft supplied by a single afferent arteriole. In addition, 34 glomeruli possessed double or triple efferent arterioles and two showed double afferent arterioles. In one of the former cases, one of the double efferent arterioles had a heterotopic origin near the urinary pole of the glomerulus. No glomerulus with triple or more afferent arterioles was noted.