| Category | Example | Prophylactic Antibiotic |
| Clean | Hernia Varicose vein Breast Prosthetic Vascular Orthopaedic | Needed specially in prosthetics |
| Clean-contaminated | Elective cholecystectomy | Needed |
| Contaminated | Elective colorectal operations | Needed |
| Dirty | Abscess drainage Faecal peritonitis | Needed and continued after operation |