Stratifying surgical wounds based on the level of contamination

The United States Centers for Disease Control and Prevention classify wounds, including surgical wounds, according to the degree of contamination.

• Clean surgical wounds are uninfected operative wounds in which no inflammation is encountered and the respiratory, gastrointestinal, genital or urinary tracts are not entered. In addition, clean wounds are primarily closed and, if necessary, drained with closed drainage. Operative incisional wounds that follow nonpenetrating (blunt) trauma should be included in this category if they meet the criteria.
• Clean–contaminated surgical wounds are operative wounds in which the respiratory, gastrointestinal, genital (including female and male reproductive tracts), or urinary tracts are entered under controlled conditions and without unusual contamination. Specifically, operations involving the biliary tract, appendix, vagina, and oropharynx are included in this category, provided no evidence of infection or major break in technique is encountered.
• Contaminated surgical wounds occur if there are major breaks in sterile technique (eg open cardiac massage), there is gross spillage from the gastrointestinal tract, or the incision encounters acute, nonpurulent inflammation (including necrotic tissue without evidence of purulent discharge). Open, fresh or accidental wounds are also included in this category.
• Dirty or infected wounds are those that involve existing clinical infection or perforated viscera, as well as old traumatic wounds with retained devitalised tissue. This definition suggests that the organisms causing postoperative infection were present before the operation [NB1].