Opioid analgesics have many side effects. Quadratus lumborum (QL) block is one kind of regional nerve block that can reduce the side effects of opioid analgesics. The investigators hypothesize that QL block with local analgesics (ropivacaine) can significantly reduce pain intensity in comparison with placebo.

Opioid analgesics have been used to control the pain. However, many postoperative complication, such as nausea, vomiting, constipation, ileus, etc are related to opioid usage. Recently, local or regional pain nerve block, such as transversus abdominis plane block, wound infiltration, have been reported in several studies. Quadratus lumborum (QL) block was first introduced in the abstract of 2007 European Society of Regional Anesthesia. The effect is longer and more than that of transversus abdominis plane block because it works close to the spinal cord nerves. The QL block can be an effective pain control method for patients who underwent ileostomy closure. The aim of this study is to compare pain intensity after ileostomy closure between QL block (ropivacaine) group and placebo group (normal saline).

Inclusion Criteria:

• Aged 20-75 years, either sex
• Patients scheduled to undergo elective ileostomy repair surgery under general anesthesia.
• Patients underwent curative surgery and ileostomy due to colorectal cancer.
• Willingness and ability to sign an informed consent document

Exclusion Criteria:

• Allergies to anesthetic or analgesic medications
• Contraindication to the use of locoregional anesthesia
• Chronic opioid use
• Coagulopathy, Impaired kidney function, uncontrolled diabetes, psychiatric disorders, severe cardiovascular impairment or chronic obstructive lung disease
• Necessity of major resection other than colorectal, palliative surgery
• BMI above 35kg/m2
• American Society of Anesthesiologists (ASA) physical status above 3