The purpose of this study is to determine which drug (chlorhexidine gluconate vs. povidone iodine) as a preoperative antisepsis in clean-contaminated abdominal surgery (liver, hepatobiliary, small or large bowel, stomach) is effective.

Inclusion Criteria:

1. Resection of following organs (clean-contaminated open surgery)

   • Liver, Pancreas, Bile duct, Duodenum
   • Stomach
   • Colon, Small bowel

2. Aged 20 - 85 years old

3. Use Prophylactic antibiotics

4. Use Preoperative bowel preparation

5. Elective operation

6. ASA classification 1-2 ASA I : no known systemic disease ASA II : single systemic disease & mild or well controlled ASA III : multiple systemic diseases or moderately controlled systemic disease ASA IV : poorly controlled systemic diseases

7. adequate organ functions defined as indicated below:

   • WBC 3000 ~ 12 000/mm3
   • > Hb 8.0 g/dl
   • > Plt 100 000/mm3
   • < Cr 1.2 mg/dl

Exclusion Criteria:

1. allergy to chlorhexidine or povidone
2. clean surgery or contaminated surgery
3. patients who cannot be followed up during 1 month
4. patients taking immunosuppressant drugs or chemotherapy agents
5. emergent surgery and reoperation
6. uncontrolled diabetes, BMI > 30 kg/m2
7. vulnerable patients