Thermographic mapping of the abdomen in healthy subjects and patients after enterostoma

Objective: Heat is a sign and symptom of surgical wound infection in wound assessment criteria but there is currently no diagnostic tool being used in clinical practice to assess the skin temperature of surgical wounds. Using thermal imaging, the objective of this study was to map the temperature of the healing surgical wound and to provide confirmatory data of: a) optimum IR imaging distance from skin temperature target field of view (FOV) b) body composition effects on abdominal skin surface temperature readings c) thermal mapping characteristics of infected versus non-infected wounds post stoma-closure.

Method: The abdominal skin surface temperature of healthy, afebrile subjects was measured under controlled, ambient conditions in a small (240cm × 320cm) clinical room. Subject standing positions were 30cm, 60cm and 100cm from the IR camera. Abdominal skin surface temperature and thermal imaging maps were acquired in a population of surgical patients before and after closure of enterostoma.

Results: Subjects (30) aged 19-52 (median=29) years were recruited. At a distance of 100cm, each of nine anatomical regions showed a decrease in mean temperature as BMI increased. Subjects with BMI >25 had lower mean abdominal temperatures. Statistically significant differences were observed for right hypochondrium (p=0.022), left lumbar region (p=0.009), right lumbar region (p=0.010) and the umbilical region (p=0.021). Half of patients (5/10) developed surgical wound infection.

Conclusion: Within the operating distances investigated, no significant effect on abdominal temperature readings was observed. With increasing BMI, lower abdominal temperatures were noted. The thermal pattern of abdominal surgical wounds reveals some differences between the healing and infected wound. Healing wounds showed changes in the thermal 'map'; an increase in temperature on the first post-operative day, and 'warming' over the subsequent five days. 'Cold spots' emerged on the thermogram of the surgical wounds which subsequently were shown to be infected. Within the setting of a clinical environment, distances up to 100cm did not significantly alter skin temperature readings within the FOV. There is a suggestion that body composition influences skin temperature. Infected surgical wounds appear 'colder' than healing wounds.

Declaration of interest: The authors have no conflict or interest.The work was supported by a grant from the SingHealth Foundation.