This study revealed that obesity evaluated using %TFV and total or proximal gastrectomy was independently associated with postoperative complications. The %TFV may be a better parameter than BMI for the evaluation of the difficulty of gastrectomy and prediction of postoperative complications such as pancreatic fistula. These findings indicate that TFV may help to determine the necessity of drain management or frequent following up of blood tests and X-ray examination in the postoperative period and enable the early detection of each complication.
Excessive visceral fat poses difficulties during surgery, and obesity is associated with unfavorable surgical outcomes, including longer operative time, higher postoperative complication rates, lower number of resected lymph nodes, and prolonged hospital stay [4, 8, 22–24]. BMI is the most commonly used parameter for the evaluation of obesity. Several studies have shown that a higher BMI is associated with worse surgical outcomes [24, 25]. However, other studies revealed that BMI may not be a predictive factor of postoperative outcomes [3, 6–8]. This finding might be attributed to the fact that BMI is easy to assess. That is, it is calculated using height and weight. However, it does not directly reflect intra-abdominal fat volume [8, 26]. Whether obesity evaluated using BMI can be used to accurately predict operative risks remains controversial. Hence, VFA is used for the evaluation of obesity. It is measured on a cross-sectional CT scan and may directly reflect intra-abdominal fat. Several studies have shown that VFA is more accurate than BMI in predicting postoperative complications [3, 8, 27, 28]. Notably, VFA measurement is time-consuming and might not be suitable for clinical use. Thus, a simpler parameter is preferred in daily use. Besides, VFA is not always ideal as it is measured only on a one-slice CT scan.
In this study, we used %TFV obtained using BIA, which is increasingly used in recent studies [14, 15]. As expected, %TFV was found to be strongly correlated with BMI. However, theoretically, %TFV can only evaluate trunk fat mass, and BMI can assess whole body elements, including muscles and extremities. Therefore, the use of %TFV may be more suitable in predicting any difficulties encountered during surgery. Our results were consistent with this theory. Compared with VFA, %TFV cannot be utilized to distinguish subcutaneous fat from visceral fat, which is considered a disadvantage. However, its simplicity counteracts this detriment in daily clinical practice given that it can predict postoperative outcomes.
Preoperative exercise intervention has been reported to be beneficial, especially in obese patients [29]. When we conduct preoperative interventions, there is a concern about tumor progression, particularly in patients with advanced cancer. However, preoperative wait time up to 90 days has been reported not to affect survival even in cStage Ⅱ/Ⅲ gastric cancer patients [30]. Hence, obese patients might have the benefits of fewer complications by preoperative exercise. In this study, %TFV ≥ 150 was an independent risk factor for postoperative complications, and this population might be a good candidate for preoperative intervention, although further study is required for a firm conclusion.
In this study, pancreatic fistula and anastomotic leakage were more common in the TFV-H group than in the TFV-L group and this result was in accordance with that of a previous study [31]. Previous studies have reported the possible causes of poor outcomes among obese patients. High visceral fat may be associated with the misrecognition of anatomy and technical difficulty in achieving a good view of the surgical field. Occasionally, this causes excessive counter traction and over-compression in the pancreas during lymph node dissection [8, 25–28, 31]. These factors result in tissue trauma, a higher volume of blood loss, prolonged operative time, and pancreatic fistula. Excessive tension on the anastomosis site due to thick and heavy mesenteric fat may be a risk factor for anastomotic leakage [22, 27, 32]. In this study, pneumonia was more frequently observed in the TFV-H group, which was consistent with the result of a previous study [33]. Obesity is associated with decreased total lung capacity attributed to high intra-abdominal pressure or excessive subcutaneous fat around the thorax [34]. Difficulty in clearing airway secretions and delayed ambulation may be contributory factors for pulmonary complications, such as atelectasis and pneumonia. However, the number of patients who had each complication was extremely low in this study, and only the occurrence of pancreatic fistula showed a significant difference. Thus, further investigations should be conducted to accurately identify the occurrence of complications after surgery.
The current study had several limitations. First, this was a retrospective, single-center study. Hence, it was susceptible to selection and cognitive bias. Hence, a larger multicenter study should be performed to obtain a firm conclusion. Second, different surgeons performed gastrectomy during the study period. Hence, the differences in the ability of the surgeons might have affected the results. Although skilled surgeons supervised trainee surgeons who performed gastrectomy, the effect might still be significant. Third, the ideal TFV was derived from the median TFV-to-BFM ratio, which was obtained from data in this study because no previous studies have discussed the ideal distribution of body fat. However, this value should be determined based on the general population. Finally, TFV obtained using BIA represents both subcutaneous and visceral fat. Fat mass is more likely to accumulate in the visceral area in men than in women [6]. The surgical procedure is mainly affected by visceral fat [26], and whether the use of a similar %TFV threshold in both men and women is acceptable has not been confirmed. Thus, further studies should be conducted to identify the ideal threshold for each sex.