Table 1.

SSI risk factors and indication concepts for colorectal surgery.

Potential risk factors			SSI indications in clinical notes
Pre-operation	Intra-operation	Post-operation	Post-operation Medical Concept‡
age gender current smoker pre-op hospital stay diabetes anemia† BMI (>=30) prior operation§ steroid usage blood transfusion	ASA score* operation type wound classification duration of operation MIS** vs. others	anemia† ascites wound disruption abdominal tenderness† antibiotics†	wound infection cellulitis abdominal contamination purulent drainage fascial/wound dehiscence abdominal infection purposeful reopening of the incision pain/swelling/redness at the incision abscess infected fluid antibiotic treatment for infection

^{† ‡}extracted from clinical notes using NLP;

^‡each concept consists of a set of the corresponding keywords; the other variables were from ACS-NSQIP

^§surgical procedure within 30 days prior to the assessed operation

^*American Society of Anesthesiologists (ASA) physical status classification

^**Minimally Invasive Surgery