Low preoperative haemoglobin is a risk factor for Clavien-Dindo grade IV-V and non-surgical complications in colorectal cancer surgery

BACKGROUND: Preoperative anaemia is common in patients undergoing colorectal cancer surgery, but the association between preoperative haemoglobin (Hb) and postoperative morbidity remains unclear. METHODS: This retrospective cohort study included all 2,374 patients who underwent elective colorectal segmental resection for colorectal cancer at Oulu University Hospital between 2014 and 2024. After exclusions for missing Hb data (n=49), procedures other than primary curative resection (n=735), missing complication data (n=117), and age under 18 years (n=1), 1,472 patients were analysed. Receiver operating characteristic analysis was used to determine the optimal Hb cut-off, and logistic regression was used to identify factors associated with Clavien-Dindo classification (CDC) grade IV-V complications. RESULTS: Preoperative anaemia was present in 444/859 (51.7%) men and 208/613 (33.9%) women. Overall, 758/1,472 (51.5%) patients developed a postoperative complication. Compared with non-anaemic patients, anaemic patients had higher rates of CDC grade IV-V complications (7.4% vs 2.6%, p<0.001) and non-surgical complications (31.4% vs 20.4%, p<0.001). The optimal Hb cut-off for CDC grade IV-V complications was 117.5 g/L. Low Hb was associated with severe complications in univariable (OR 3.02, 95% CI 1.79-5.10) and multivariable analyses (OR 1.76, 95% CI 1.01-3.05). CONCLUSIONS: Low preoperative Hb is an independent risk factor for severe postoperative complications, particularly non-surgical events, after colorectal cancer surgery. Data-driven Hb thresholds may improve preoperative risk stratification.