Surgical site infections (SSI) pose a common challenge in the field of surgery. Current evidence and literature do not provide clear consensus whether the use of subcutaneous drainage will help reduce the incidence of SSI in patients who underwent abdominal surgery, especially in wounds that are categorized as contaminated (class 3) or dirty/infected (class 4).

The objective of this clinical study is to compare the rate of surgical site infection in contaminated and dirty/infected surgical wounds among patients whose wounds are inserted with subcutaneous drainage and patients who are not inserted with subcutaneous drainage.

This study is a randomized, controlled and open study, where participants who undergo abdominal surgery will be randomly allocated into two groups: (i) patients whose wounds are inserted with subcutaneous negative pressure drain and (ii) patients whose wounds are not inserted with subcutaneous negative pressure drain.

The participants in this study will know the details about the presence of their drain placement after the operation. If the patient was assigned to the drain group, the drain will be placed for five days or until there are no content observed in the drain. The primary outcome of this study is the occurrence of SSI, which will be tracked up to 30 days post-operation. The patient in both groups will also be evaluated by the surgeons at day 3, 5, 7, 14 and 30 post-operation for signs and complications of SSI. In situation where the patients are discharged prior to the date of evaluation, the patients will be scheduled for evaluation during the follow-up visits.

If SSI is detected in the drain group prior to removal, the drain will be removed and the patient will be treated with wet dressing combined with antibiotics. Complications of SSI will also be noted. Patient's data on demographic, medical history, clinical presentation, details of operation, and other laboratory findings will also be collected to investigate for risk factors for development of SSI between each group.

Inclusion Criteria:

• Age equal or over 18 years old
• Admitted to Queen Savang Vadhana Memorial Hospital
• Receive abdominal surgery and were classified as class 3 or 4 wound

Exclusion Criteria:

• Patients who undergo operation for ostomy
• Patients who do not receive appropriate antibiotics
• Patients who undergo operation before full recover of prior operation
• Patients who undergo laparoscopic operation
• Pregnant women
• Patients who had history of prior radiation therapy at abdomen
• Patient with immunocompromised status
• Patient with chronic skin disease