Risk Factors for Postoperative Pulmonary Complications in Patients Undergoing Colorectal Surgery for Malignancy at Dhaka Medical College Hospital: A Prospective Observational Study

Background: Postoperative pulmonary complications (PPCs) are important causes of morbidity after major abdominal surgery. Patients undergoing colorectal surgery for malignancy may be particularly vulnerable owing to advanced age, smoking, respiratory disease, comorbidities, poor nutritional status, and open surgical approaches. Aim: This study evaluated the incidence and risk factors for PPCs among patients undergoing colorectal surgery for malignancy at Dhaka Medical College Hospital (DMCH). Methods: A prospective observational study included 200 adult patients undergoing colorectal surgery for malignancy at DMCH from January 2024 to December 2025. Demographic, clinical, laboratory, anaesthetic, and operative variables were recorded prospectively. PPCs included pneumonia, treated atelectasis, respiratory failure, pleural effusion requiring intervention, treated bronchospasm, or unplanned postoperative mechanical ventilation. Univariate associations were assessed using appropriate statistical tests. Variables with P<0.10 were entered into multivariable binary logistic regression. Adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were calculated, and ROC analysis assessed model discrimination. Results: Among 200 patients, 32 (16.0%) developed PPCs. Pneumonia occurred in 15 (7.5%), atelectasis in 12 (6.0%), and respiratory failure in 7 (3.5%). PPCs were associated with older age, smoking, chronic respiratory disease, ASA physical status ≥III, hypoalbuminaemia, and open surgery. Multivariable analysis identified age ≥65 years (aOR 2.74, 95% CI 1.17–6.42; P=0.020), smoking (aOR 2.31, 95% CI 1.01–5.30; P=0.047), chronic respiratory disease (aOR 3.21, 95% CI 1.19–8.65; P=0.021), ASA ≥III (aOR 2.86, 95% CI 1.25–6.53; P=0.012), and open surgery (aOR 2.68, 95% CI 1.15–6.24; P=0.022) as independent risk factors. Conclusion: PPCs affected approximately one-sixth of patients. Advanced age, smoking, chronic respiratory disease, higher ASA physical status, and open surgery were independently associated with PPCs. Early risk identification may support targeted respiratory optimization and closer postoperative surveillance.