POPF is the most common major complication after pancreatic resection and may cause secondary intra-abdominal abscess formation, septic and hemorrhagic complications, and death (9, 10). POPF remains significant morbidity even in high-volume pancreatic centers. Therefore, it is very important to prevent or diagnose PF early. Many studies have been carried out to identify risk factors in this regard, and various strategies have been proposed and tested to prevent its development. However, no single method has been proven to be suitable for all patients.
The prevalence of pancreatic fistulas after PD prompted the International Study Group of Pancreatic Fistula (ISGPF) to develop a standardized grading system, which classified the fistulas into grades A, B, or C. Grade A fistulas were reclassified as biochemical leaks (BLs), while grade B and C fistulas were accepted as high-output postoperative pancreatic fistulas (CR-POPFs) (11, 12). These definitions have been validated and well accepted in clinical practice (13, 14). The most validated predictive model is the fistula risk score (FRS), which uses pancreatic duct diameter, gland texture, intraoperative blood loss, and pathology to stratify patient risk (15, 16). Microchannel presence along with main pancreatic duct diameter and pathology were the parameters examined in the present study.
A recent study revealed that normal drain fluid levels of amylase on the first and third postoperative days had a negative predictive value for POPF (17). This, in turn, allows for the earlier removal of postoperative intra-abdominal drains. The same study could not demonstrate any significant relationship between pancreatic duct diameter, pancreatic softness, pancreatic stent placement, octreotide use, and POPF for pancreaticojejunostomy in 126 patients (17). However, that study compared clinical POPF patients (grades B-C) with others. In the present study, we aimed to reach more specific findings by comparing biochemical leaks with three times higher drain fluid amylase (grade A) and those with normal levels. Although some studies do not recommend the routine use of intraoperative drains (18), most surgeons support the routine use of intraoperative drain placement in the pancreatic region. In the present study, drain was placed routinely.
The characteristics of the pancreatic parenchyma are determinants of the development of PF after PD. Numerous studies have identified soft pancreatic tissue as a significant risk factor for PF (8, 19–21). However, the present study did not assess pancreatic density. It is widely accepted that a fibrotic pancreas facilitates anastomosis, while a soft pancreas complicates anastomosis. When suturing and knotting a soft pancreas, the risk of damage to the pancreatic parenchyma and fine pancreatic duct is higher, leading to an unsafe pancreatic anastomosis and pancreatic leakage (22). It has been reported that the quality of the pancreas is associated with the pancreatic duct diameter and pancreatic juice secretion (23). A soft pancreas is usually accompanied by a small pancreatic duct (20, 24) and abundantly secreted pancreatic juice (25, 26). The pancreatic duct diameter was found to be correlated with PF (27).
A small pancreatic main duct may present a technical challenge to surgeons during the reconstruction of pancreatojejunostomy. Some studies have suggested that a pancreatic duct diameter of < 5 mm is associated with an overall higher risk of developing POPF (28, 29). In one study, every 1 mm increase in the diameter of the pancreatic duct was found to be associated with a 28% reduction in the probability of POPF (30). Various studies have reported that placing a stent in the main pancreatic duct in pancreaticojejunal anastomosis is an effective method to reduce the rate of POPF after PD (31, 32). In the present study, a stent was placed in the pancreatic anastomosis as standard in all patients.
The review of the literature identifies a few studies investigating postoperative factors, unlike many studies focusing on preoperative factors for POPF. Among these, the two most similar studies to our study are the studies by Nahm et al. (33) and Umezaki et al. (34). The common result of both studies was that pancreatic acinar cell density on the cross-sectional surface was significantly associated with POPF. The study by Umezaki et al. on 121 patients identified POPF in 23 patients. Male gender, high blood loss volume, soft pancreas, pancreatic duct width, and pancreatic acinar cell density on the cross-sectional surface were found to be associated with POPF. Male gender and acinar cell density were found to be independently associated with POPF. Nahm et al., in turn, demonstrated that acinar cell density at the pancreatic resection margin was significantly associated with POPF for all pancreatic resections (33).
Histomorphological characteristics of the pancreatic remnant may play an independent role as a risk factor for POPF. A simple histological score based on frozen sections may predict the risk of developing POPF intraoperatively. In fact, the present study observed that the presence of microchannels other than the Wirsung on the cross-sectional surface might be associated with POPF. It was thought that the inability to perform a special anastomosis of the microchannels and the inability to include them in routine pancreaticojejunostomy had a direct effect on this increase.
Among the limitations of this study were the limited number of patients from a single center and the non-exclusion of those with a history of diabetes. Grade B and C POPFs could not be evaluated as a separate group in this study.
This study concluded that a main pancreatic duct diameter of < 3 mm, and the presence of microchannels on the pancreatic cross-sectional surface might increase the risk of fistula. Due to the lack of a standard algorithm to reduce the risk of POPF, innovative ideas may be needed for surgical techniques and perioperative management in high-risk groups. Effective results can be obtained if the presence of microchannels is added to the risk factors for POPF and studies are conducted in larger patient groups.