Anastomotic leakage (AL) is a severe complication after colorectal surgery, with incidence rates of 2-30%. This prospective, single-center observational cohort study aims to identify and quantify independent risk factors for AL, determine its incidence and impact on outcomes, and develop a predictive model. Approximately 430 patients undergoing colorectal resection with anastomosis will be enrolled from August 2025 to August 2026. Risk factors will be assessed preoperatively, intraoperatively, and postoperatively. AL will be defined and graded per the International Study Group of Rectal Cancer (ISGRC) criteria.

Anastomotic leakage (AL) remains a major complication after colorectal surgery, contributing to morbidity, mortality, prolonged hospital stays, and increased costs. Its etiology is multifactorial, involving patient, disease, and surgical factors. This study will prospectively evaluate risk factors in a single-center setting to minimize variability.

AL definition (per ISGRC): Defect at anastomotic site causing communication between intra/extraluminal compartments and luminal tract, diagnosed via clinical signs (e.g., peritonitis, fecal discharge), radiological evidence (e.g., CT showing extraluminal air/contrast or fluid collection), or operative verification.

Severity grading:

• Grade A: Asymptomatic/mild, no active treatment.
• Grade B: Requires intervention (e.g., drainage, antibiotics) but no reoperation.
• Grade C: Requires reoperation.

Risk factors categorized as:

• Preoperative: Demographics (age, sex, BMI), comorbidities (ASA score, diabetes....), lifestyle (smoking, alcohol), nutritional status (albumin, CRP), neoadjuvant therapy, medications, diagnosis (e.g., cancer, tumor location), and bowel preparation.
• Intraoperative: Approach (open/laparoscopic), resection type, anastomosis details (hand-sewn/stapled, level, perfusion assessment), peritoneal soiling, diverting stoma, operative time, blood loss/transfusion, drainage, surgeon experience, complications.
• Postoperative: AL diagnosis/severity/management, inflammatory response (CRP, WBC), anemia, complications (ileus, infection), hospital stay, nutritional support, mobilization, reoperation, ICU stay, mortality, pain management.Early detection of leak using inflammatory markers either in the serum or drain fluid. Drain fluid inflammatory markers (Drain Fluid Calprotectin(CP), Drain Fluid C-Reactive Protein (CRP), Drain Fluid Procalcitonin)and Serum inflammatory markers(Serum C-Reactive Protein (CRP), Serum Procalcitonin (PCT), Serum Lactate dehydrogenase (LDH)).

Data from electronic records, surgical notes, nursing charts, and follow-up. Statistical analysis includes descriptive stats, univariate/multivariate logistic regression for risk factors, subgroup analyses, and predictive model development/validation.

The study adheres to the Helsinki Declaration and Good Clinical Practice (GCP). Informed consent is required.

Inclusion Criteria:

• Aged ≥18 years
• Undergoing elective or emergency colorectal resection with primary anastomosis (e.g., ileocolic, colocolic, colorectal, coloanal)
• Providing written informed consent

Exclusion Criteria:

• Colorectal resection without anastomosis (e.g., end stoma)
• Inflammatory bowel disease (Crohn's, ulcerative colitis)
• History of previous colorectal surgery involving anastomosis
• Pregnancy
• Unable to provide informed consent or comply with follow-up

All eligible patients undergoing elective/emergency colorectal surgery with primary anastomosis (e.g., ileocolic, colocolic, colorectal, coloanal). No intervention; observational only. Risk factors and outcomes will be monitored prospectively.