Surgical wounds are classified into four main categories, known as the Altemeier system, to help predict the risk of infection. This classification guides surgical teams in planning procedures, choosing prophylactic antibiotics, and managing patient care.
Category 1: Clean Wounds (Class I)
This is the lowest risk category, representing a procedure where the surgical site is protected and there is no entry into an organ system that naturally harbors bacteria.
- Description:
- No infection is present.
- Only normal skin flora is present (the bacteria that naturally live on your skin).
- No hollow organs (like the respiratory, digestive, or genito-urinary tracts) are intentionally opened.
- Examples:
- Coronary Artery Bypass Grafts (CABG) and most other cardiac surgeries.
- Closed orthopedic procedures (e.g., hip or knee replacement).
- Most neurosurgical cases.
- Vascular surgery.
Special Note (Class ID): A sub-category exists for Class I procedures where a prosthetic device (like a heart valve, mesh, or breast implant) is inserted. The risk remains low, but the presence of foreign material requires special consideration.
Category 2: Clean-Contaminated Wounds (Class II)
These procedures carry a slightly elevated risk because a hollow organ containing some bacteria is opened, but under strict, controlled conditions.
- Description:
- Hollow organs that contain native bacterial flora (respiratory, digestive, or genito-urinary tracts) are opened.
- The procedure is performed under controlled circumstances with no significant spillage of contents into the surgical cavity.
- Examples:
- Uncomplicated appendectomy.
- Elective cholecystectomy (gallbladder removal).
- Elective gastrointestinal surgery (with a slightly higher risk for colorectal surgeries).
- C-Section and hysterectomy.
- Prostate surgery.
Category 3: Contaminated (Class III)
This category indicates a significantly elevated risk of infection due to the presence of fresh trauma, a major breach of sterile technique, or gross spillage of contents from an organ.
- Description:
- Open, “fresh” accidental wounds (often encountered early after the injury).
- Operations involving a major break in sterile technique (e.g., an uncontrolled spillage of bile or intestinal contents).
- Wounds given through inflamed but non-purulent tissue.
- Examples:
- Gunshot wounds to the abdomen with an acute presentation.
- Penetrating torso wounds.
- Ruptured appendix.
- Diverticulitis.
Category 4: Dirty (Class IV)
This is the highest risk category, defined by the existing presence of infection, necrotic (dead) tissue, or an uncontrolled source of bacteria.
- Description:
- Open, “old,” traumatic wounds with a significant delay in treatment and containing necrotic tissue.
- Wounds created to manage a perforated or ruptured viscus (organ).
- Wounds created in the presence of an overt clinical infection (i.e., pus/purulent material is already present).
- Examples:
- Incision and drainage of an abscess.
- Perforated bowel (especially the large bowel).
- Fecal peritonitis (widespread inflammation due to perforated diverticulitis).
- Necrotizing soft tissue infections.
Summary Table for Quick Reference
| Wound Class | Risk Level | Key Defining Feature |
| Clean (Class I) | Lowest | Elective incision; no infection; no entry into contaminated tract. |
| Clean-Contaminated (Class II) | Low/Medium | Controlled entry into a contaminated tract (e.g., GI, respiratory) with no spillage. |
| Contaminated (Class III) | High | Major breach in technique, fresh accidental wound, or gross spillage. |
| Dirty (Class IV) | Highest | Existing infection/pus, necrotic tissue, or presence of established contamination. |