A retrospective cohort study included 10,581 colorectal cancer patients treated at Shanghai Changhai Hospital in 2019–2023. The prevalence of baseline renal insufficiency (RI) was 32.4%, hematuria 31.2%, elevated cystatin C 2.4%, serum uric acid 8.7%, serum creatinine 4.3%, blood urea nitrogen (BUN) 3.5%, decreased estimated glomerular filtration rate (eGFR) 2.2%, chronic kidney disease diagnosed by ultrasonography 1.5%, and patient-reported 1.1%. About 47.2% of RI cases were caused by hematuria and other parameters complemented it in detection. Post-treatment renal insufficiency (PTRI) affected 20.3% of patients, of which 14.8% had a ≥25% change in BUN, 8.3% in cystatin C, 4.4% in creatinine, 3.9% in eGFR, and 0.2% in uric acid. Independent risk factors for baseline RI were age ≥65 years and cardiovascular disease; PTRI was predicted by open surgery, intestinal stoma, postoperative complications, and chemoradiotherapy. Both baseline RI and PTRI were independent predictors of disease-free survival and overall survival. A comprehensive assessment of RI including eGFR, hematuria, and proteinuria is clinically useful, with the need for early evaluation in high-risk patients.[1]