Impact of Visceral Fat Area in Colorectal Surgery

Many studies have demonstrated a close relationship between body fat distribution and the occurrence of metabolic syndrome; an excess of abdominal adipose tissue, especially intra-abdominal visceral fat, leads to obesity-related complications [1]. Visceral obesity is closely related to the development of colorectal cancer, as well as other metabolic complications [2], and the distribution of adipose tissue also seems to be important in the pathogenesis of colorectal cancer [3]. Therefore, analytical morphometric assessment has recently been proposed to improve preoperative risk stratification, and the body mass index (BMI) has been widely used to express the degree of obesity, although it does not always adequately reflect the degree of visceral fat [4]. Accordingly, several other body composition parameters, such as the visceral fat area (VFA), have been assessed by using preoperative staging computed tomography in patients undergoing various surgical procedures [5]. Some cutoff values of the VFA in the Korean population have been reported for use as a diagnostic criterion of abdominal obesity, and the value of the VFA associated with an increased risk of obesity-related disorder in Korea was reported to be 103.8 cm [6]. Also, Oka et al. [7] more recently reported cutoff levels of the VFA in the Japanese population, with VFA >130 cm in men and VFA >90 cm in women indicating obesity. Many reports state that obese patients have unfavorable surgical outcomes, including longer operative time, increased postoperative complication rate, increased conversion rate, prolonged hospital stay [8] and shorter disease-free survival [9] after resection for colorectal cancer. A meta-analysis revealed high BMI to be associated with higher risks of infectious complications, including surgical site infections and pulmonary infection [10]. Recently, however, Yu et al. [11] investigated the distribution of the VFA and general obesity in the Korean population, and they concluded that visceral obesity had no influence on intraoperative difficulties, postoperative complications, and postoperative recovery in patients with sigmoid colon or rectal cancer. They did not clearly state the reason obesity did not influence the operative outcomes in their research, although they presumed the cutoff value of the VFA would affect their results. The associations between obesity and gastrointestinal disease are of variable strength, and the underlying mechanisms are incompletely understood, but obesity and metabolic syndrome clearly have a significant, potentially avoidable, and often underrecognized, impact on the population burden of gastrointestinal disease [12]. No doubt, visceral obesity plays a strong role in the development of metabolic syndrome; however, some controversy still remain and needs to be resolved between the relationship of visceral obesity and postoperative complications. To clarify the correlation between visceral obesity and operative outcome, we need further investigation to identify more accurate predictors, such as BMI, body surface area and VFA/subcutaneous fat area ratio, for the outcomes of colorectal surgery.