Quantitative measures of visceral adiposity and early postoperative complications following complex abdominal wall reconstructions.

Joshua S Winder, MD, Alexander J Shope, BS, Salvatore Docimo, Jr., DO, Eric M Pauli, MD. Penn State Milton S Hershey Medical Center

Introduction: Obesity is a risk factor for complications after hernia repair, but the contribution of visceral adiposity to perioperative hernia morbidity is unclear. Quantitative analysis of the visceral to subcutaneous fat ratio (VSFR) using computed tomography (CT) based measurements has been proposed to be a more effective means of assessing obesity related morbidity than simple body mass index (BMI) calculations alone. The objective of this study was to examine the effect of visceral obesity on post-operative morbidity in patients undergoing abdominal wall reconstruction.  

Methods: We performed a retrospective review of a prospectively maintained database of patients who underwent posterior component separation with transversus abdominis release (PCS/TAR) from 2012-2015.  All patients who had a CT scan of the abdomen and pelvis within 30 days of surgery were included in the study. Patient demographics, medical co-morbidities, operative details, complications and length of stay were recorded. Visceral and subcutaneous fat areas were obtained from postoperative CT scans using DICOM viewing software (Osirix 6.5, Pixmeo) from a single axial slice at L4-L5 intervertebral space and used to calculate the VSFR.  The CT attenuation level to delineate the regions of adipose tissue was set using -190 to -30 Hounsfield units.  An elevated VSFR, indicating a larger amount of visceral fat, was defined as ≥ 0.4.

Results: Thirty-nine patients were identified; median age 56 years, ASA score 2, BMI 32kg/m2, 60% female.  The median VSFR was 0.46.  Twenty-seven (69%) patients had VSFR ≥ 0.4.  When comparing baseline characteristics of gender, age, ASA, BMI, hernia grade, hernia area, and presence of comorbid conditions such as diabetes mellitus and pulmonary disease there was no significant difference between patients with elevated VSFR to those with normal VSFR.  When comparing postoperative complications including surgical site infections (superficial/deep), seromas, hematomas, skin-level dehiscence, organ space infections, venous thromboembolism, ileus, respiratory failure, cardiac events, and need for mechanical ventilation postoperatively, there was no significant difference between groups.  

Conclusions: Our results failed to show a significant difference in postoperative morbidity based on VSFR, although this may be due to our small numbers of patients or the lower rates of post-operative events after PCS/TAR. Interestingly, 69% of patients in the study had an elevated VSFR.  It is unclear whether this finding is due to the presence of a hernia or whether high VSFR is an independent predictor for hernia formation.

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