Postoperative decline in renal function after rectal resection and all‐cause mortality: a retrospective cohort study

Abstract Aim Fluid loss, dehydration and resultant kidney injury are common when a diverting ileostomy is formed during rectal cancer surgery, the consequences of which are unknown. The aim of this retrospective single‐site cohort study is to evaluate the impact of sustained postoperative renal dysfunction after rectal resection on long‐term renal impairment and survival. Method All patients with rectal adenocarcinoma undergoing resection between January 2003 and March 2017 were included, with follow‐up to June 2020. The primary outcome was impact on long‐term mortality attributed to a 25% or greater drop in estimated glomerular filtration rate (eGFR) following rectal resection. Secondary outcomes were the long‐term effect on renal function resulting from the same drop in eGFR and the effect on long‐term mortality and renal function of a 50% drop in eGFR. We also calculated the effect on mortality of a 1% drop in eGFR. Results A total of 1159 patients were identified. Postoperative reductions in eGFR of 25% and 50% were associated with long‐term overall mortality with adjusted hazard ratios of 1.84 (1.22–2.77) ( p = 0.004) and 2.88 (1.45–5.71) ( p = 0.002). The median survival of these groups was 86.0 (64.0–108.0) months and 53.3 (7.8–98.8) months compared with 144.5 (128.1–160.9) months for controls. Long‐term effects on renal function were demonstrated, with those who sustained a >25% drop in renal function having a 38.8% mean decline in eGFR at 10 years compared with 10.2% in controls. Conclusion Persistent postoperative declines in renal function may be linked to long‐term mortality. Further research is needed to assess causal relationships and prevention.