The WISO trial: Subcutaneous fluid collections are no indication for surgical site infections

BackgroundWhether postoperative subcutaneous fluid collection increases the risk of surgical site infection (SSI) has not been elucidated. Therefore, the aim of this study was to investigate whether clinically asymptomatic subcutaneous fluid collection increases the risk of SSI by evaluating postoperative wounds using ultrasonography.MethodsAdults who underwent laparotomy with wounds at high-risk for SSI were included in this trial. Incision area was evaluated using ultrasonography on postoperative days 1, 2, and 4. Presence and volume of fluid collection, as well as occurrence of SSI were evaluated.ResultsA total of 59 patients were enrolled in this study. Of these, 5 were excluded as they underwent relaparotomy within 14 days. The primary endpoint (SSI) occurred in 18 (33.3%) of the 54 analyzed patients. There were no significant differences in baseline or intraoperative characteristics between patients with and without SSI. All patients received prophylactic antibiotics prior to incision. Subcutaneous fluid collection on at least one ultrasound was observed in 47 (87.0%) of 54 patients. There was no association between volume of fluid collection at all time points and occurrence of SSI. Furthermore, there was no association between change in volume of fluid collection at each time point and occurrence of SSI.ConclusionWe found no correlations between presence of subcutaneous fluid collection or its volume and occurrence of SSI. Furthermore, prediction of SSI using ultrasonography in the early postoperative stage seems unlikely.