In the present study, the relationship between the anatomic location of the pancreas and the incidence of POPF was evaluated on a CT image with a sagittal view in the patients who underwent LG or OG. We found that PLH and P-A length were significantly longer in patients with POPF compared with those without POPF in patients who underwent LG. In the multivariate analysis, PLH ≥12.4 mm and P-A length ≥ 45 mm were extracted as an independent predictor for POPF after LG. The D-Amy levels on PODs 1 and 3 after LG were also significantly higher in patients with a PLH of ≥12.4 mm compared with those with a PLH of < 12.4 mm. These findings indicate that PLH and the P-A length can be a predictor of POPF after LG. However, in patients who underwent OG, the length of PLH and P-A length were not correlated with the frequency of POPF or D-Amy levels on PODs 1 and 3.
The incidence of POPF after LG is reported to be 1.7 to 7.2% [4, 7, 11, 25, 26], and it was reported to be higher compared with after OG [7, 13,14,15]. POPF is thought to be caused by several factors, including direct damage to the pancreas or lateral thermal injuries by surgical instruments. In addition, blunt pancreatic injury during suprapancreatic lymph node dissection was recently shown to be a cause of POPF in LG [27]. Depending on the anatomic location of the pancreas, compression or retraction of the pancreas by an assistant’s forceps may be required to provide a good surgical view. LG tends to cause excessive pancreas compression because of the restricted instrument axis and lack of delicate tactile sensations. Ida et al. showed pancreatic juice leaking after pancreatic compression using fluorescence imaging with a chymotrypsin probe in a swine laparoscopic gastrectomy model. This suggests that pancreatic compression using the assistant’s forceps can contribute to POPF [28].
Although the measurement method differed in each study, the anatomic position of the pancreas that was evaluated using a preoperative CT image is a predictor of POPF occurrence in LG patients [17, 18]. In the current study, we measured PLH and PLD focusing on the distance between the root of the left gastric artery and the level of the pancreatic body surface. In addition, we investigated the P-A length, a predictor of POPF, reported by Kumagai et al. [18]. Our results showed that long PLH and P-A length were independent predictive factors for POPF in LG, and the odds ratio of PLH (4.19) was higher compared with the P-A length (4.06). It has been well documented that for safe and effective suprapancreatic dissection, it is important to keep the “outermost layer,” meaning the outside of the autonomic sheath around the artery [29]. The anatomical landmark to approach outermost layer is the junction of common hepatic, splenic, and left gastric artery, and the root of the left gastric artery is most useful for recognizing the junction of these arteries on CT images. On the other hand, the nerves sheaths and ganglia surrounding the celiac artery are not usually divided to expose the root of celiac artery located anterior to the aorta in radical gastrectomy. In other words, the depth of the root of celiac artery is not precisely the same as the depth of the outermost layer. Therefore, in theory, the PLH, defined by the distance between the root of the left gastric artery and pancreas, may more accurately represent the depth of the suprapancreatic dissection than the P-A length, defined by the distance between the root of the celiac artery and pancreas. Because CT is a modality that is routinely used for pretreatment diagnosis of gastric cancer in clinical practice, we can easily evaluate the risk of POPF before surgery by measuring PLH in the single slice in the sagittal position.
Another highlight of this study is that it is the first to reveal one of the reasons of the higher incidence of POPF in LG than in OG in the real world. Several authors have indicated the potential risk of pancreatic trauma owing to anatomical location of the pancreas in LG. On the other hand, no previous reports have investigated the relationship between anatomical location and POPF in OG. In the current study, we examined both LG and OG cases during the same period at the same institution, and our results showed the anatomical location of the pancreas in open surgery was not a risk factor for POPF. OG involves less limitation on forceps mobility, and gentle compression or retraction of the pancreas using the human hand could avoid excessive pancreatic parenchymal damage. Therefore, our results indicate that the risk factors for POPF after LG may differ from those after OG. To the best of our knowledge, this is the first report that clearly showed that the anatomic location of the pancreas may be a specific risk factor for POPF after LG.
Several preventive measures for patients who are at high risk for POPF in LG, such as those with a long PLH, were reported to be useful in improving the surgical view, such as additional ports, increasing the pneumoperitoneum pressure, and extreme rotation of the operating table. The best way to avoid pancreas injury is to avoid touching it during the procedure. Tsujiura et al. reported a significant decrease in the incidence of POPF when there was no direct compression of the pancreas during suprapancreatic lymph node dissection in LG patients [27]. Another measure to prevent POPF may be to use a surgical robot, which was developed to overcome several disadvantages that were identified in conventional laparoscopic surgery. Surgical robots provide surgeons with more degrees of freedom through their articulating surgical instruments. Suda et al. reported a single institutional retrospective cohort study, which demonstrated that the incidence of POPF after robotic gastrectomy (RG) was significantly lower compared with that in LG patients (0% vs. 4.3%, p = 0.029) [30]. In addition, a multi-institutional prospective study from Japan showed that RG significantly reduced the morbidity rate from 6.4% after LG to 2.45% after RG (p = 0.0018), and the incidence of all-grade POPF was only 5.8% [33]. Although further trials are needed, RG may, therefore, reduce the damage and injury to the pancreas and prevent POPF compared with LG and OG.
There were some limitations to the present study. First, this study was a nonrandomized retrospective study. Since some parts of the patient’s background between OG and LG were significantly different, in particular, the OG group contained significantly more cases of advanced stage and those who had undergone TG or D2 dissection, which are risk factors for POPF, than the LG group. Therefore, propensity score matching (PSM) analysis should be considered to eliminate these selection bias, but it is not appropriate to perform PSM owing to the small sample size in this study. Examining the correlation between the anatomic pancreatic position and POPF in advanced gastric cancer patients who undergo LG is required as a next step. Second, diagnostic modalities for POPF may be a concern. The diagnostic criteria for POPF have not been uniformly defined in gastric cancer surgery. Therefore, the definition of POPF after gastrectomy varied with each previous study. The ISGPF criteria were applied in the present study, because these criteria were considered to be more objective compared with other criteria, and they have been used extensively in the field of pancreatic surgery. Although the incidence of POPF in this study was high (24.9%) compared with our daily clinical experience. The incidence of grade B or higher POPF with clinically relevant changes was 4.4%, which was equivalent to that in previous reports [7, 13,14,15]. However, it is controversial whether patients with BL on ISGPF can be considered as those with POPF, because BL is deemed to be a potential POPF with no clinical impact. In this study, we included BL as one of the diagnostic criteria of POPF owing to the small number of events of grade B or higher POPF. Although several reports have shown that high D-Amy levels are closely correlated with POPF after gastrectomy, further studies with large patient population are required to investigate the relationship between PLH and “true POPF” of grade B or higher.