Histological analysis of organs. Shown are representative H&E-stained sections of organ tissue harvested from rabbits in the heparin/protamine cohort (A) and the citrate/calcium cohort (B). No significant necrosis, hemorrhage, or parenchymal damage was identified in any of the brain or liver tissues in either cohort, regardless of treatment. There was uniform evidence of renal and liver venous congestion in the control and heparin-treated animals, regardless of treatment. Glomeruli (arrowheads) were generally intact without evidence of necrosis. Scale bars, 100 μm; original magnification ×100.