Accumulation of morphologically altered RBCs during storage. (A) Panoramic (×2000) (i) and detailed (×5000) (ii) views of short-stored RBC sample (day 12 of storage) containing a majority of discocytes (D) and type I (EI) or II echinocytes (EII), and panoramic (×2000) (iii) and detailed (×5000) (iv) views of long-stored RBC sample (day 41 of storage) containing abundant EIII, spheroechinocytes (SE), and spherocytes (S). (B) Representative scanning electron images of RBC shapes observed during storage in SAGM: D, EI, EII, EIII, SE, and S; numerically zoomed regions from 2000× acquisitions. Red square highlights morphologically altered RBCs defined as SMEs. Scale bars = 2 μM.