Association of pre-operative chronic kidney disease and acute kidney injury with in-hospital outcomes of emergency colorectal surgery: a cohort study.

BACKGROUND: Pre-operative kidney function is known to be associated with surgical outcomes. However, in emergency surgery, the pre-operative kidney function may reflect chronic kidney disease (CKD) or acute kidney injury (AKI). We examined the association of pre-operative CKD and/or AKI with in-hospital outcomes of emergency colorectal surgery. METHODS: We conducted a retrospective cohort study including adult patients undergoing emergency colorectal surgery in 38 Japanese hospitals between 2010 and 2017. We classified patients into five groups according to the pre-operative status of CKD (defined as baseline estimated glomerular filtration rate < 60 mL/min/1.73 m2 or recorded diagnosis of CKD), AKI (defined as admission serum creatinine value/baseline serum creatinine value ≥ 1.5), and end-stage renal disease (ESRD): (i) CKD(-)AKI(-), (ii) CKD(-)AKI(+), (iii) CKD(+)AKI(-), (iv) CKD(+)AKI(+), and (v) ESRD groups. The primary outcome was in-hospital mortality, while secondary outcomes included use of vasoactive drugs, mechanical ventilation, blood transfusion, post-operative renal replacement therapy, and length of hospital stay. We compared these outcomes among the five groups, followed by a multivariable logistic regression analysis for in-hospital mortality. RESULTS: We identified 3002 patients with emergency colorectal surgery (mean age 70.3 ± 15.4 years, male 54.5%). The in-hospital mortality was 8.6% (169/1963), 23.8% (129/541), 15.3% (52/340), 28.8% (17/59), and 32.3% (32/99) for CKD(-)AKI(-), CKD(-)AKI(+), CKD(+)AKI(-), CKD(+)AKI(+), and ESRD, respectively. Other outcomes such as blood transfusion and post-operative renal replacement therapy showed similar trends. Compared to the CKD(-)AKI(-) group, the adjusted odds ratio (95% confidence interval) for in-hospital mortality was 2.54 (1.90-3.40), 1.29 (0.90-1.85), 2.86 (1.54-5.32), and 2.76 (1.55-4.93) for CKD(-)AKI(+), CKD(+)AKI(-), CKD(+)AKI(+), and ESRD groups, respectively. Stratified by baseline eGFR (> 90, 60-89, 30-59, and < 30 mL/min/1.73 m2) and AKI status, the crude in-hospital mortality and adjusted odds ratio increased in patients with baseline eGFR < 30 mL/min/1.73 m2 among patients without AKI, while these were constantly high regardless of baseline eGFR among patients with AKI. Additional analysis restricting to 2162 patients receiving the surgery on the day of hospital admission showed similar results. CONCLUSIONS: The differentiation of pre-operative CKD and AKI, especially the identification of AKI, is useful for risk stratification in patients undergoing emergency colorectal surgery.