Thirty-six domestic piglets of both sexes, weighing 19-21 kg, were obtained from the Animal Center of Zhejiang University. All animals were treated humanely according to the national guidelines for the care of animals. The experiment was approved by the Animal Experiment Committee of the University of Zhejiang. The animals were fasted for 24 h before the experiment and allowed food and water ad libitum after the operation. The piglets underwent a preliminary sterile laparotomy under general anesthesia with 25 mg/kg sodium pentobarbital. The main pancreatic duct draining the body and tail was carefully separated and ligated with 1/0 silk thread, which produced total obstruction, and left the duodenal vascular arcade intact, as described by Pitkaranta et al[24]. This was then relieved by one of three methods at a second operation. For both operations, the animals were fasted the night before surgery. Intravenous cannulation and endotracheal intubation were performed after anesthetic induction. Animals received 1 L of normal saline during each procedure. Penicillin G benzathine in aqueous suspension (4 MU) was administered intramuscularly before the operation and continued the following day. The operation was performed under strict aseptic conditions. The controls underwent laparotomy only.

Four weeks after ligation of the main duct, laparotomy was performed again. After resection of the pancreatic head (5 cm), the diameter of the duct at the cut surface was measured, and the pigs underwent sequentially one of three types of pancreatico-intestinal anastomosis, or were kept as controls. The management of the pancreatic stump was: (1) end-to-end pancreaticojejunostomy invagination (EEPJ) to a Roux-Y loop in nine piglets, using two layers (1/0 silk interrupted inner and outer layer); (2) end-to-side duct-to-mucosa sutured anastomosis to a Roux-Y loop (ESPJ) in nine piglets, using two layers (1/0 silk interrupted inner and outer layer), completed by a second layer between the pancreatic capsula and jejunal seromuscular wall; or (3) binding pancreaticojejunostomy (BPJ) in nine piglets. The surgical techniques have been described previously[21–23]. The main procedure was as follows. End-to-end duct-to-mucosa sutured (1/0 silk interrupted) anastomosis to a Roux-Y loop was performed, the pancreatic duct and jejunal mucosa were sutured, and the stitch was only inserted to the submucosal layer of the jejunal wall (Figure 1A). This procedure was slightly modified from those previously described. Finally, a piece of unabsorbable thread (7/0 silk) was used to bind circumferentially together the jejunal seromuscular sheath and pancreatic remnant (Figure 1B). The thread tie is just tight enough to allow the tip of a medium-sized hemostatic forceps to be passed underneath the ligature. No stent was used in any of the anastomoses. Roux-Y limbs of 45 cm were created using a standard side-to-side technique. After 2 d of water, the animals had free access to standard lab chow. Animals were kept in individual living quarters. Body weight was determined with a cage scale preoperatively and repeated at 2, 4, 6 and 8 wk during follow-up, until the third operation.

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Figure 1 A: Pancreatic duct and jejunal mucosa are sutured, and stitch is only inserted to the submucosal layer of the jejunal wall; B: A piece of unabsorbable thread (7/0 silk) is used to bind together circumferentially the jejunal seromuscular sheath and pancreatic remnant.

Eight weeks after the second operation, laparotomy was again performed. Intrapancreatic ductal pressure was measured in all animals. As described by Bradley[25], a No 21 scalp vein needle (attached to a short length of connecting tube, a three-way stopcock, a manometer, and a 2-mL syringe, all filled with saline solution) was introduced into the duct of Wirsung directly through the surface of the pancreas. Fluid aspirated from the pancreatic duct into the syringe to confirm the position of the needle was meticulously replaced from the syringe before pressure measurement. The saline manometer was arbitrarily zeroed at the level of the anastomotic site. Fluctuation in pressure was noted with respiration in most animals. All pressures were recorded in the duct of Wirsung before operative pancreatography and surgical manipulation.

The jejunal wall was incised. The anastomotic site was grossly examined, and the status of the pancreatic drainage flow at the anastomosis was inspected by direct visual observation. Pancreatic exocrine function was evaluated by the secretin test. After 30 min basal secretion collection, secretin was administered (2 U/kg iv bolus; Sigma, St. Louis, MO, USA), and pancreatic juice at the anastomotic site was collected at intervals of 10 min for 60 min. Secretory volume, flow rate of pancreatic juice, and bicarbonate concentration were determined using standard laboratory techniques.

After resection of the remnant pancreas and jejunum en masse, pancreatography was performed immediately by inserting a catheter into the main duct at the tail of the pancreas. The contrast medium (meglumine diatrizoate) was instilled from a height of 10 cm to equalize the pressure as uniformly as possible. The extracted pancreas was placed on an X-Omat TL film ( Eastman Kodak, Rochester, NY, USA) for roentgenography at 300 mA, 26 kVp, 1.0 s and a film-focus distance of 88 cm. The maximum diameter of the main pancreatic duct was measured.

The pancreatic duct was examined for patency by cannulating the anastomosis distally, and testing to see if a catheter could be passed freely into the duct. Then, the anastomotic site and the long axis of the pancreatic duct of the body and tail were incised and examined macroscopically, and the specimens were fixed in 10% neutral formalin for 3 d. Sections containing the anastomotic site were prepared, embedded in paraffin, and stained with hematoxylin and eosin for histologic evaluation.

Data are presented as mean ± SD unless otherwise indicated. Statistical significance was assessed by analysis of variance or Student’s t test where appropriate. Results were considered significant at P < 0.05.

A percentage body weight change in relation to the preoperative value was determined for each animal. The postoperative weight gain for each group is shown in Figure 2. Duct-to-mucosa sutured anastomoses (ESPJ and BPJ) differed significantly from controls and EEPJ on postoperative week (POW) 2, 4, 6 and 8 (P < 0.05). The animals in the ESPJ and BPJ groups had a similar body weight gain, and these two types of anastomoses did not differ significantly from each other on POW 2, 4, 6 and 8 (P > 0.05). These mean body trends, however, suggested that the status of the anastomosis had some physiologic effect.

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Figure 2 Percentage weight gain in pigs undergoing three types of pancreatoenteric anastomosis and in control pigs.

All piglets recovered from the operation, and no fatality was encountered. Atrophy of the pancreatic parenchyma was shown in all animals in the three groups, and the main pancreatic duct at the cut surface of the pancreatic stump was markedly dilated at the end of POW 4 after the first operation (Figure 3, range 3.1-3.5 mm). At the end of POW 8 after the second operation, adhesion of the anastomotic portion to adjacent tissue was detected in all animals, the anastomotic site was healed completely, and no suture failure and intraperitoneal abscess formation around the anastomotic site were observed in any animal. None of the piglets showed anastomotic complications.

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Figure 3 Duct at the cut surface of pancreatic stump was markedly dilated at the end of POW 4 after ligation of the main pancreatic duct.

Intrapancreatic duct pressure on POW 8 is shown in Table 1. The levels were similar in ESPJ and BPJ, and no significance was found between the two procedures (P > 0.05). However, pressure in EEPJ was significantly higher than that in ESPJ and BPJ (P < 0.05).

The results of the secretin test for each group are summarized in Table 2. All three parameters, secretory volume, flow rate of pancreatic juice, and bicarbonate concentration, were significantly higher in ESPJ and BPJ compared to EEPJ (P < 0.05). However, the levels of the three parameters were similar in ESPJ and BPJ, with no significant difference between these two techniques (P > 0.05). These parameters suggested that the status of the anastomosis had some mechanical effect on pancreatic exocrine function.

Pancreatography performed after EEPJ revealed dilation and meandering of the main pancreatic duct, together with indistinct depiction of the secondary and tertiary bifurcation of the duct, and the anastomotic site exhibited a variable degree of occlusion (Figure 4A). The duct was partially blocked in one animal and completely blocked in another in the anastomotic region (Figure 4B). Pancreatography of both ESPJ and BPJ, however, showed normal ductal patency without stenosis at the anastomotic site and without ductal dilatation and meandering of the main pancreatic duct, but distinct secondary and tertiary bifurcations of the ducts (Figure 4C). In one animal only, a slight dilatation of the anastomosed duct was detected in BPJ. Macroscopically, cicatricial narrowing of the main pancreatic duct was not observed, which suggested effective pancreatic juice drainage. The maximum diameter of the main pancreatic duct is shown in Table 3. Significant differences were found in both the ESPJ and BPJ groups in comparison with the EEPJ group (P < 0.05). Main pancreatic duct diameters showed no significant differences between ESPJ and BPJ (P > 0.05).

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Figure 4 A: Anastomotic site was incompletely obstructed; B: Duct was blocked in the anastomotic region; C: Normal ductal patency without stenosis at the anastomotic site and without ductal dilatation proximal to it.

Macroscopically, in all specimens, there was firm union at the site of anastomosis, and the pancreas had an atrophic appearance. The specimens removed 8 wk after ESPJ and BPJ clearly showed complete mucosal continuity and good connective tissue union between the pancreatic duct and the jejunal lumen (Figure 5). The results were verified histologically, and microscopy showed that the intestinal mucosa had fused with that of the pancreatic duct, with gradual and continuous changes from one to the other (Figure 6). In contrast, in biopsies obtained in EEPJ, the portion of the pancreatic stump protruding into the jejunal lumen was largely replaced by cicatricial fibrous tissue in which concentric fibrous bands with scattered mononuclear inflammatory cells were seen, and no intestinal mucosa was observed to cover the remnant cut surface.

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Figure 5 Longitudinal specimen reveals good connective tissue union between the pancreatic duct and the jejunal lumen.

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Figure 6 Section showing that the intestinal mucosa had fused with that of the pancreatic duct, with gradual and continuous changes from one to the other. Original magnification × 100.

Resectional pancreatic surgery is carried out with increasing frequency for both malignant and benign diseases. However, no adequate studies appear to have been made of the pathophysiological changes following pancreaticoduodenectomy, particularly of anastomotic patency and function of the remnant pancreas. The most important factor affecting the function of the remnant pancreas is the patency of the pancreaticoenterotomy. In the present study, we attempted to examine anastomotic patency and postoperative pancreatic exocrine function in piglets after three different anastomotic methods using end-to-end pancreaticojejunostomy invagination (EEPJ), end-to-side duct-to-mucosa sutured anastomosis (ESPJ) and binding pancreaticojejunostomy (BPJ) (a new method).

There is little agreement about the best technique for pancreatic anastomosis of the gastrointestinal tract. The optimum technique is to secure a leakproof anastomosis that will not subsequently produce stenosis and exocrine deficiency. However, few clinical and experimental studies have focused on the postoperative pancreatic exocrine function. The main findings of this study were that the animals undergoing ESPJ and BPJ were much better than those undergoing EEJP, using several parameters of measurement, weight gain, intraductal pressure, secretory volume and flow of pancreatic juice, ductal patency and absence of duct dilatation.

As a new method of anastomosis, BPJ has been proven to be a safe, simple and efficient technique that avoids the primary complication of anastomatic leakage clinically and experimentally. The authors also confirmed that BPJ may effectively maintain anastomotic patency and preserve pancreatic exocrine function as well as ESPJ, and a mucosa-to-mucosa pancreaticojejunostomy is the best choice for anastomotic patency, when compared with EEPJ.

Our data were in accordance with those of previous studies that have reported better patency with mucosa-mucosa anastomosis when compared with EEPJ. According to our results, and taking into consideration the advantage of preventing anastomotic breakdown or pancreatic leakage and maintaining patency of the pancreatic duct by BPJ, we believe that this procedure will result in a more anatomically secure anastomosis than that with the standard method, and should decrease the morbidity and mortality of the operation, thus increasing its acceptability as the operation of choice for Whipple resection.

BPJ, a new method introduced to pancreatic surgery by Pen Shuyou et al, has increasingly been performed, especially in China, although other pancreaticojejunostomy techniques are also common. Clinical studies have revealed that the present technique is safe, simple and effective in fulfilling current demands on resectional pancreatic surgery. However, the anastomotic patency and residual exocrine pancreatic function after BPJ continues to require adequate evaluation.

The authors are to be commended on their excellent piece of research. There have been few clinical and experimental studies with a focus on the pathophysiological changes of pancreaticoenterotomy, particularly of anastomotic patency and function of the remnant pancreas. This is an interesting study, well designed and well performed. The discussions are to the point and not overstated. The authors’ findings certainly merit attention.