Burr cells are red blood cells (RBCs) with 10-30 uniform, short, blunt projections distributed evenly around the circumference of the cell, giving the red cell surface a serrated appearance. The red blood cells retain central pallor. They are found in uremia, and to a lesser extent post splenectomy. Cells resembling burr cells (called crenated RBCs) occur when blood is stored too long in EDTA-containing tubes.