Risk Assessment of Abdominal Wall Thickness Measured on Pre-Operative Computerized Tomography for Incisional Surgical Site Infection after Abdominal Surgery

Assanee Tongyoo MD, FRCST*, Putipan Chatthamrak MD*, Ekkapak Sriussadaporn MD, FRCST*, Palin Limpavitayaporn MD, FRCST*, Chatchai Mingmalairak MD, FRCST*

Affiliation : * Department of Surgery, Faculty of Medicine, Thammasat University, Pathumthani, Thailand

Background : The surgical site infection (SSI) is a common complication of abdominal operation. It relates to increased hospital stay, increased healthcare cost, and decreased patient’s quality of life. Obesity, usually defined by BMI, is known as one of the risks of SSI. However, the thickness of subcutaneous layers of abdominal wall might be an important local factor affecting the rate of SSI after the abdominal operations.
Objective : The objective of this study is to assess the importance of the abdominal wall thickness on incisional SSI rate. Material and Method: The subjects of the present study were patients who had undergone major abdominal operations at Thammasat University Hospital between June 2013 and May 2014, and had been investigated with CT scans before their operations. The demographic data and clinical information of these patients were recorded. The thickness of subcutaneous fatty tissue from skin down to the most superficial layer of abdominal wall muscle at the surgical site was measured on CT images. The wound infectious complication was reviewed and categorized as superficial and deep incisional SSI following the definition from Centers for Disease Control and Prevention (CDC) guidelines. The significance of each potential factors on SSI rates was determined separately with student t-test for quantitative data and χ2-test for categorical data. Then all factors, which had p<0.10, were included into the multivariate logistic regression analysis and were analyzed with significance at p<0.05.
Results : One hundred and thirty-nine patients were included in this study. They all underwent major abdominal surgery and had had pre-operative CT scans. Post-operative SSI was 25.2% (35/139), superficial and deep types in 27 and 8 patients, respectively. The comparison of abdominal wall thickness between patients with and without infection was significantly different (20.08.4 mm and 16.07.2 mm, respectively). When the thickness at 20 mm was used as the cut-off value, 43 of 139 patients had abdominal wall thickness ≥20 mm. The incidence of SSI of the thickness ≥20 mm group was 37.2% (16/43) and of the less thickness group was 19.8% (19/96), with p<0.05. The univariate analysis revealed that abdominal wall thickness ≥20 mm, body weight ≥60 kg, and wound classification were the important factors related to SSI after the abdominal operation. However, only abdominal wall thickness and wound classification were still significant by multivariate analysis.
Conclusion : The findings of this study confirmed the significance of the subcutaneous thickness of abdominal wall at the surgical site on the incidence of incisional SSI. The thickness ≥20 mm had an effect on increasing post operative SSI rate especially in contaminated operations. These findings could be helpful in making healthcare providers fully aware and thus exercise special attention in wound care or even develop new modalities to prevent SSI in patients with the aforementioned risks.

Keywords : Subcutaneous abdominal wall thickness, Surgical site infection, Wound infection

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