Effective pain management after abdominal surgery is essential for recovery. This study compares two pain relief methods-intrathecal morphine (a single spinal injection) and continuous epidural analgesia-for patients undergoing open colorectal cancer surgery. The investigators expect intrathecal morphine to provide equal pain relief at rest 24 hours after surgery, while epidural analgesia may be more effective during movement. By 48 to 72 hours, both methods should offer similar pain control. The epidural group may require fewer additional pain medications but could experience more side effects, including a higher risk of low blood pressure and technical difficulties. Additionally, these patients may have a slightly longer hospital stay. In contrast, the intrathecal morphine group may have fewer overall side effects. Despite these differences, patient satisfaction, sleep quality, and recovery are expected to be similar in both groups. By evaluating these methods, this study aims to determine the most effective and safe approach to post-surgical pain management, improving comfort and recovery outcomes for patients.