Mulberry particles formed by red blood cells in human weddelite stones

In a series of electron microscopic studies of human urinary stones, mulberry shaped particles were observed in 5 out of 51 calcium oxalate dihydrate (COD) containing stones. The mulberries were crenation products of red blood cells which adhered to the surface of bipyramid COD crystals, followed by impregnation of the COD. The red cells appeared to participate in the crystal growth by creating foci of surface nucleation, or by formation of a layer of crust on the surface of the bipyramids which caused deposition of an additional layer of calcium oxalate. The lipid containing organic matrix seems to have a role in COD crystal growth.