AIM: To examine the impact of body mass index (BMI) on outcomes following pancreatic resection in the Chinese population.

METHODS: A retrospective cohort study using prospectively collected data was conducted at the Cancer Hospital of the Chinese Academy of Medical Sciences, China National Cancer Center. Individuals who underwent pancreatic resection between January 2004 and December 2013 were identified and included in the study. Persons were classified as having a normal weight if their BMI was < 24 kg/m² and overweight/obese if their BMI was ≥ 24 kg/m² as defined by the International Life Sciences Institute Focal Point in China. A χ² test (for categorical variables) or a t test (for continuous variables) was used to examine the differences in patients’ characteristics between normal weight and overweight/obese groups. Multiple logistic regression models were used to assess the associations of postoperative complications, operative difficulty, length of hospital stay, and cost with BMI, adjusting for age, sex, and type of surgery procedures.

RESULTS: A total of 362 consecutive patients with data available for BMI calculation underwent pancreatic resection for benign or malignant disease from January 1, 2004 to December 31, 2013. Of the 362 patients, 156 were overweight or obese and 206 were of normal weight. One or more postoperative complications occurred in 35.4% of the patients following pancreatic resection. Among patients who were overweight or obese, 42.9% experienced one or more complications, significantly higher than normal weight (29.6%) individuals (P = 0.0086). Compared with individuals who had normal weight, those with a BMI ≥ 24.0 kg/m² had higher delayed gastric emptying (19.9% vs 5.8%, P < 0.0001) and bile leak (7.7% vs 1.9%, P = 0.0068). There were no significant differences seen in pancreatic fistula, gastrointestinal hemorrhage, reoperation, readmission, or other complications. BMI did not show a significant association with intraoperative blood loss, operative time, length of hospital stay, or cost.

CONCLUSION: Higher BMI increases the risk for postoperative complications after pancreatectomy in the Chinese population. The findings require replication in future studies with larger sample sizes.

Over the past 20 years, overweight and obesity rates have increased dramatically in China[1-3]. The national survey showed that the prevalence of overweight and obesity in Chinese adults was 39.6% in 2009[1]. Body mass index (BMI), an indirect measure of adiposity, has been linked to an increased risk of chronic pancreatitis and pancreatic cancer[4-8]. For both conditions, pancreatectomy is imperative.

The influence of BMI on post-surgical complications after pancreatectomy remains controversial. Several studies have reported a positive association between BMI and risk of postoperative complications[9-15], including increased length of hospital stay[9-12], blood loss[13,14], and surgical site infection[15]; whereas others found no association[16-18]. Moreover, a majority of these studies were conducted in Western countries. Because body fat distribution, genetic predisposition to obesity, and background lifestyle factors are different between Caucasians and Asians[19], it is possible that the associations between BMI and postoperative complications following pancreatectomy may differ by ethnic group. Thus, a retrospective study of Chinese patients was conducted to examine the associations between BMI and complications after pancreatectomy.

Pancreatectomy is recognized as a highly invasive surgery. Despite recent advances in surgical technique, devices, and perioperative care, pancreatectomy is associated with a mortality of approximately 5% and a morbidity of 35%-60%[22-24]. Several studies suggested that the mortality after pancreatic surgery in most high-volume centers should be < 3%[25-27]. The present study was performed in a tertiary care and academic institution having the aforementioned prerequisites and resulted in a mortality rate (1.4%) that was in accordance with experienced centers. During the past six years, the annual caseload has increased to more than 40 resections, which might be partially responsible for the improved outcome. Moreover, operative time and blood administration were comparable to other series because of the high volume. Our study is consistent with others that have found comparable mortality in the control and overweight/obese group[16-18]. Analysis of the cause of mortality in our study revealed that pancreatic fistula with subsequent hemorrhage was responsible for 100% (5/5) of the deaths.

Several studies have consistently reported a greater risk for postoperative complications in the obese population as compared to lean subjects[9-15]. However, many recent reports seem to challenge this long-held opinion[16-18]. Morbidity after pancreatectomy in the present study was 35.4%, and the most frequent causes for morbidity were pancreatic fistulas resulting from pancreatic anastomotic insufficiency, bile leak resulting from biliary anastomotic insufficiency, surgical site infection, and delayed gastric emptying. Among patients who were overweight or obese, 42.9% experienced one or more complications, and this is significantly higher than normal weight individuals (29.6%). The results of the present study add to the growing debate over whether BMI increases complications after pancreatectomy.

Sledzianowski et al[28] identified obesity as an additional risk factor for leakage after distal pancreatectomy, and the study by Noun et al[12] highlights the increased risk after pancreaticoduodenectomy. The results of the present study are consistent with these studies that found higher bile leakage in the overweight/obese group. Pancreatic fistula is the factor most strongly linked with death in the majority of case series and remains the leading cause of morbidity after pancreatectomy. Noun et al[12] reported a significant association between BMI and pancreatic fistula after pancreatectomy. In this study, however, BMI did not show a significant association with pancreatic fistula. One potential explanation for this conflicting result is that there were only 92 cases included in their study.

In this study, an increased risk of delayed gastric emptying was observed in the overweight/obese group. In contrast, two earlier studies from American medical centers suggested that BMI was not significantly associated with delayed gastric emptying after pancreaticoduodenectomy[29,30]. One potential explanation for these conflicting results is that the association between BMI and delayed gastric emptying following pancreatectomy may differ by ethnic group. Additionally, the study by Sfarti et al[31] revealed that higher BMI correlated with delayed gastric emptying in type 1 diabetic patients, which might responsible for the phenomenon.

The influence of obesity on the operative difficulty of several abdominal procedures has previously been reported and has translated into increased blood loss and longer operating times than in normal-weight individuals[32,33]. In the present study, however, intraoperative difficulty was not significantly altered by intraoperative variables (blood transfusion, blood loss, and operative time) in the overweight/obese group. No one can ignore the fact that performing pancreatectomy in obese patients is more challenging and hazardous. There was no significant difference in the length of hospital stay between the two groups, which is consistent with many other studies[16,18].

There are several limitations of the current study. The retrospective nature of this study can be associated with selection bias as well as increased risk of differential misclassification bias. In addition, all patients were analyzed from a single institution, so the findings may not be generalizable to other settings. The limited sample size makes it difficult to adequately adjust for all potential confounding factors. There was an insufficient number of patients to perform subcategory analysis by BMI. Additionally, the relatively small sample size made it impossible to evaluate anything other than the overall complication rate on multivariable analyses. Although the majority of patients were tracked in a prospective database, a proportion required retrospective chart analysis.

In conclusion, the data show that pancreatectomy can be performed safely in overweight/obese patients, although with somewhat higher postoperative complications, bile leak, and delayed gastric emptying rate. However, the positive results in this study need to be replicated in studies with larger sample sizes with greater power.

We sincerely thank Zhihan Zou (McGill University) and Francine Foss (Yale University) for language proofreading.