Although the incidence of POPF has dropped over the past decade with the development of surgical techniques, the clinical POPF rate after DP is still high.[1] Pancreatic factors are considered to be important aspects of POPF after DP. Most studies assessed pancreatic factors by intraoperative subject judgement. Multiphasic CT is essential for the preoperative assessment before DP. Few studies have reported the prediction of POPF development after DP via preoperative CT evaluation of pancreatic factors. The results of the present study revealed that the occurrence of POPF after DP was not affected by any clinicopathological characteristics and surgical features other than pancreatic factors evaluated by CT imaging. Our study demonstrated that TPC was an independent predictor of clinical POPF following DP; however, PI and MPD dilation were not associated with clinical POPF. Furthermore, we found that patients with thick pancreatic cut-line and dilated MPD were more likely to develop a clinical POPF.
The controversy regarding pancreatic stump closure is hotly debated, with three recent RCTs on the topic. [1, 16, 17] None of the RCTs revealed which closure technique showed greater advantage over the other two. Our study found that clinical POPF did not differ between the stapler and hand-sewn closure (15/68 vs. 7/20; P = 0.378) groups. Thus, we suspected that the occurrence of the clinical POPF may not be solely dependent on the proper closure technique, but more on pancreatic factors.
There are three pancreatic factors that can be easily detected before surgery with a CT scan: TPC, pancreatic texture using PI, and MPD dilation. In 2011, Eguchi et al.[11] first showed that the thickness of pancreatic parenchyma in the remnants was an independent risk factor for PF after DP. Subsequently, Okano et al.[12] and Mendoza et al.[13] emphasized the role of pancreatic thickness in POPF after DP. Ecker et al.[4] tried to identify a clinical POPF risk score from 2026 patients following DP, and found that POPF occurrence cannot be reliably predicted, but pancreatic thickness was not included in their clinical POPF risk score. A thicker pancreatic cut-line means a larger-cut area[8] and more transected branches of the pancreatic duct. Thus, it is not surprising that a thicker cut-line is associated with a higher clinical POPF rate. In our study, all four patients with thick pancreatic cut-line and dilated MPD developed clinical POPF. A dilated MPD means that when MPD is obstructed, there is an increase in pressure on the transected branches of the pancreatic duct, which increases the possibility of POPF.[7] Therefore, when a thick pancreatic cut-line occurs along with a dilated MPD, clinical POPF is more likely to develop.
A major limitation of this widely used criterion (pancreatic texture) is intraoperative subjective assessment. It needs to be kept in mind that palpation-based determination is subjective and pancreatic texture was not accrued with palpation in laparoscopic cases. There are some objective preoperative evaluations introduced in published studies: CT,[18, 20, 22] MRI,[24] intraoperative ultrasound elastography,[25] and durometer[26]. Even though there is no research regarding which preoperative evaluation of pancreatic texture is the most accurate, preoperative CT is a reliable, critical, and convenient method. Several studies have revealed that a lower pancreas/spleen density ratio measured with CT scan represents a soft pancreas. [18, 20]
Pancreatic texture has long been considered an important factor in the occurrence and severity of POPF. Multiple studies about PD have identified that soft pancreatic texture poses a significantly higher risk of POPF than does hard pancreatic texture.[18, 19] Pancreatic texture in the upstream gland in a PD depends on the pathologic abnormality and is secondary to the MPD obstruction, while in the vast majority of cases, the abnormal area in DP has been resected so the remnant pancreas is mostly a soft, normal texture. Therefore, it is less probable that pancreatic texture plays the same significant role in PF after DP compared with PD.[10] A recent meta-analysis[14] showed that soft pancreatic texture (OR, 1.80; 95%CI, 1.08–3.02, P = 0.03) increased the risk of POPF in DP. Mendoza et al.[13] reported that although pancreatic texture alone was not a significant risk factor for PF, a soft thick pancreas may increase the likelihood of PF owing to the staplers used in laparoscopic DP. Our study failed to show that pancreatic texture evaluated with PI can affect the clinical POPF rate whether it is a thick or thin pancreatic cut-line. Further studies about combined pancreatic texture and thickness of the cut-line in different closure technique are needed.
Regarding thick pancreatic cut-lines, several studies reported that staple use can increase clinical POPF rate after DP.[12, 27] Kawai et al.[17] reported that pancreaticojejunostomy tended to be associated with a decreased incidence of clinical POPF in patients with a thick pancreas. Currently, no RCT or prospective study has verified which closure is suitable for a thick pancreas. Since staplers are the most commonly used surgical method in DP, determining how to improve staple use in a thick pancreas is very important. Prolonged peri-firing compression[21] can be helpful to reduce pancreatic tears, especially in a thick pancreas. It may be necessary to perform additional procedures to ensure better sealing of the pancreatic remnant when a stapler is used, such as additional running sutures or fibrin glue.
Furthermore, the selection of staple cartridge based on the thickness of pancreatic cut-line has drawn the attention of researchers. In 2013, Sugimoto et al.[8] first introduced a “compression index”, which was defined as the ratio between the height of staple cartridge over the thickness of pancreatic cut-line, and was also a risk factor for POPF. This finding indicated that a thicker pancreas should be transected using a greater height of staple cartridge; however, there is little research on the selection of cartridges in DP according to pancreatic thickness.
A systematic review[28] supported the strategy of selective drainage and early drain removal after pancreatic resection in low-risk patients, but mostly PD. Behrman et al.[29] found that drainage following DP was associated with a higher POPF rate and did not reduce intra-abdominal septic morbidity, nor the need for postoperative therapeutic intervention. There is only one study focused on the relationship between drainage and pancreatic thickness in DP. Chang et al.[30] reported that drainage following DP could be selectively indwelled in patients with a pancreatic thickness ≥ 17.3 mm. Data on this topic are currently limited. Definitive evidence regarding the necessity and indication for the use of drain in DP is needed, especially for a thick pancreas.
This study has several limitations. First, our data are limited by a small sample size and confounding variables, such as type of staple cartridge used. Second, as this was a retrospective study, subgroups were not randomly assigned, and the surgical decision varied depending on the surgery period. Finally, our study defined 15.35 mm as the cutoff value, but a true cutoff value still remains to be determined. Furthermore, the value of PI can be influenced by spleen lesions, such as splenic cyst, which may cause errors in the results. However, few studies have focused on the evaluation of pancreatic factors for POPF after DP using preoperative CT. Our findings may be helpful for evaluating the preoperative patients with CT scan, regarding risk stratification for POPF and postoperative management.