Preoperative anaemia did not alter complication rates (50.6% vs. 45.6%, p = 0.392) but patients with complications were more likely to be anaemic at discharge (88.9% vs. 74%, Hb 112 g/L ± 12 vs. 117 g/L ± 14, Hb < LLN 18 ± 14 g/L vs. 11 ± 11, all p < 0.001) and have longer LoS (9 [6–18] vs. 7 [5–9] days, p = 0.001). This evidence concerns the gene GSTM1 and anemia (phenotype).