Middle segment pancreatectomy: a useful tool in the management of pancreatic neoplasms.

Small, benign, or low-grade malignant tumors located in the neck of the pancreas are usually treated with enucleation. However, if enucleation is too risky because of possible damage of the main pancreatic duct, standard pancreatic resections are performed. Such operations can lead to impaired long-term exocrine-endocrine function. Middle segment pancreatectomy consists of a limited resection of the midportion of the pancreas and can be performed in selected patients affected by tumors of the pancreatic neck. Middle segment pancreatectomy is a safe and feasible procedure for treating tumors of the pancreatic neck; in experienced hands it is associated with no mortality but with high morbidity, even if the rate of "clinical" pancreatic fistula is about 20%. Moreover, it allows a surgeon to preserve pancreatic parenchyma and consequently long-term endocrine and exocrine pancreatic function.

Introduction

Whereas neoplastic lesion located in the pancreatic head or body-tail are usually resected by pancreaticoduodenectomy or distal pancreatectomy, tumors in the neck represent a real challenge for a surgeon. In these cases, standard or extended pancreatectomies performed for benign or borderline cases can determine the loss of a great amount of glandular tissue, significantly increasing the risk of diabetes, impaired exocrine function, and splenic loss.1–6

Enucleation would be an adequate alternative for small, benign, and low-grade malignant tumors, such as endocrine and cystic neoplasms of the pancreas. Unfortunately this conservative procedure cannot be always applicable. When the neoplastic lesion measures up to 2 cm or more, or it is encased within the pancreatic gland, enucleation is associated with a high risk of Wirsung’s duct damage; moreover in the case of tumors with uncertain biological behavior this approach should be avoided because of the risk of tumor recurrence1–5.

Letton and Wilson7 reported for the first time in the English literature in 1959 two cases of traumatic midpancreatic transection followed by a reconstruction with a Roux-en-Y jejunal loop anastomized to the distal part of the gland. Dagradi and Serio,8 from our own Department of Surgery, were the first in 1984 to propose middle pancreatectomy with an “oncological” indication, treating a pancreatic insulinoma. Subsequently, other authors reported cases of resection of the middle pancreas, of varying extent, using various terms such as “central pancreatectomy,” “middle segment pancreatectomy,” “segmental pancreatectomy,” and “intermediate pancreatectomy.”9–13 The underlying indications for surgery ranged from chronic pancreatitis to benign, uncertain behavior, or low-grade malignant exocrine and endocrine neoplasms1–19. Different techniques were adopted for gastrointestinal reconstruction, including jejunal anastomosis of both the proximal and distal stump, or of only the distal stump, with pancreaticoduodenal or pancreaticogastric anastomosis.1–21

Surgical Technique

The abdomen is entered through a midline incision. The gastrocolic ligament is opened, preserving the gastroepiploic vessels, and the pancreatic gland is exposed. The posterior peritoneum along the superior and inferior margin of the pancreas is incised. The superior mesenteric vein and the portal vein must be identified and their surfaces cleared below the gland. The plane between the superior mesenteric and portal vein should be teased apart. The splenic artery and vein are dissected free and separated from the gland. Some venous tributaries to the portomesenteric axis and some minor collaterals of the splenic artery can be ligated. Then, the posterior surface of the pancreatic neck is isolated from the portomesenteric axis and a ribbon is passed behind the gland to elevate it. Sutures are placed along the superior and inferior margins to indicate where the proximal and distal transection should be performed and to ligate those vessels running along the margins. The segment of the pancreas with the tumor is subsequently transected through a knife or a stapler to the left and to the right of the lesion. The cephalic stump is sutured with interrupted stitches after elective ligation of the Wirsung’s duct or by means of a stapler. A small stent is placed in the main pancreatic duct while performing pancreojejunostomy or pancreogastrostomy; the stent can be left in place, even if in our experience we have never done it. Two closed-system suction drains are used to drain the cephalic stump of the gland and the pancreaticojejunostomy/pancreaticogastrostomy.

Discussion

It has been shown that standard pancreatic resections are nowadays associated with low mortality and morbidity if performed in high-volume centers by experienced surgeons.22–24 It is remarkable that this type of surgery can lead to long-term complications, such as diabetes, exocrine insufficiency, and late postsplenectomy infection25,26.

The incidence of postoperative exocrine and endocrine impairment is not predictable in patients with apparently “normal pancreas.” Factors such as fibrosis of the remnant, Wirsung’s duct obstruction, preexisting chronic pancreatitis, benign or malignant disease, and subclinical diabetes may play a role as “risk factors.”1–3 After standard left-sided resection there is an increased incidence of endocrine impairment and onset of diabetes reported from 17 to 85% of patients; it is reasonable that the extent of the resection is strictly related to the incidence of endocrine–exocrine long-term insufficiency27–31.

For all these reasons, more conservative surgical techniques have been advocated for small, benign, or low-grade malignant tumors located in the neck of the gland, aimed for sparing, as much as possible, pancreatic parenchyma. Whenever neoplastic lesions are not small and superficial enough to be simply enucleated, middle segment pancreatectomy should be considerated.1–6

Middle segment pancreatectomy accounts for only 3% of the pancreatic resections performed at our institution and about 100 cases have been reported in the English literature1–21,32–34: this means careful selection of patients. In fact, the small number of patients who underwent this type of operation is related to different factors: specific localizations of the neoplasm, well-selected indications (benign or low-grade malignant tumors), and a distal pancreatic stump of at least 5 cm in length.

Some authors1,3 have reported that this operation can be performed only in the case of small tumors (<5 cm in diameter); in our experience, although the mean diameter of the resected lesions was 27.4 mm, we have safely performed middle segment resection for tumor measuring more than 5 cm, harboring from the anterior face of the pancreas.

Middle segment pancreatectomy was also occasionally used for malignant disease: two islet cell carcinomas, one vipoma who subsequently developed hepatic metastases, one cystadenocarcinoma, and one carcinoma in situ2,3,10–12.

In the past we have also performed this operation for malignant tumor but we had pancreatic recurrence of the tumor in two patients (one affected by metastasis and one by intraductal papillary mucinous neoplasms [IPMN] with in situ carcinoma); moreover, two patients with adenoma and borderline main duct IPMN had a tumor recurrence in the pancreatic gland. Thus, we believe that in patients affected by primary or metastatic malignant tumor, a standard resection would be more appropriate. Moreover, middle pancreatectomy in our experience should also be avoided in patients affected by IPMN, especially main duct type because of their potential malignity and the possibility to have different degrees of dysplasia along the Wirsung’s duct in the same patients.

The surgeon must be sure to achieve tumor-free proximal and distal resection margins after performing middle segment pancreatectomy and, for this reason, frozen section examination is mandatory.

Middle segment pancreatectomy is a meticulous procedure. There is the possibility of leaks from both the closed cut edge of the head and the pancreaticojejunostomy, considering that in most patients we are dealing with a normal soft pancreatic texture with a small Wirsung’s duct. Thus, not only great care must be taken in selecting the patients who will benefit from this operation, but also an experienced pancreatic surgeon working in a high-volume center is required for performing the procedure.1–4,6,32,33

Median pancreatectomy is reported to be associated with no mortality but with a high postoperative morbidity, above all consisting of pancreatic fistula.6 In our experience the “clinical” pancreatic fistula rates after pancreaticoduodenectomy and left pancreatectomy are 10 and 20%, respectively.23,35–37 Between January 1990 and December 2005 61 patients underwent middle segment pancreatectomy at our institution. The incidence of pancreatic fistula—according to the International Study Group on Pancreatic Fistula definition22—was 51%. It is remarkable that most patients complained of Grade A fistula, which is a “biochemical” fistula without any clinical impact, whereas 13 patients (21%) developed a grade B or C fistula, which required prolonged in-hospital stay. In almost all patients the conservative management was successful; no one underwent reoperation and in four cases intraabdominal collections were treated with ultrasound-guided drainage. The mortality rate was zero.

The risk of developing a pancreatic fistula must be taken into account in the preoperative decision making; we believe that this risk is acceptable when the procedure is performed in a high-volume center and for patients with a long-life expectancy, such as young or middle-aged people affected by benign or low-grade tumors.

The most important advantage of middle segment pancreatectomy is the good endocrine and exocrine long-term function.1–6,10 Iacono et al.1 in a series of 13 patients demonstrated that postoperative oral glucose tolerance, pancreaticolauryl and fecal fat excretion were normal in all cases and they studied six patients pre- and postoperatively with oral glucose tolerance test showing no significant differences before and after surgery. Moreover, Sperti et al.3 showed, in a review of the literature, no case of impaired endocrine function in 59 evaluable patients whereas exocrine function was reported to be normal in 56 out of 59.

Another advantage of this procedure is the possibility to preserve the spleen, preventing the risk of postsplenectomy sepsis and hematologic disorders, which is low but exists in an adult.38,39

In conclusion, middle segment pancreatectomy is a safe and technically feasible surgical approach for removing pancreatic neck tumors in well-selected patients; in experienced hands it is associated with no mortality but with high morbidity. Most of the complications do no require reoperation or prolonged in-hospital stay and can be successfully managed conservatively. Moreover, it allows the surgeon to preserve pancreatic parenchyma and consequently long-term endocrine and exocrine pancreatic function.