[Anatomy of the head of the pancreas and various limited resection procedures for intraductal papillary-mucinous tumors of the pancreas].

The surgical anatomy, as well as the results of anatomic investigation of the pancreas, are reviewed. Anatomic descriptions, which are useful not only for ordinary pancreaticoduodenectomy or distal pancreatectomy, but also for limited resection of the pancreas for low-grade malignancy such as mucin-producing tumors or cystic lesions of the pancreas, are also provided. The fusion fascia of the head of the pancreas is called the "fusion fascia of Treitz" and that of the body and tail of the pancreas is termed the "fusion fascia of Toldt." The fusion fascia is histologically composed of a loose connective tissue membrane. All of the important pancreaticoduodenal arcades of arteries and veins are situated on this membrane, i.e. between this membrane and the pancreatic parenchyma. The topography of the head of the pancreas shows that, after branching from the gastroduodenal artery, the anterior superior pancreaticoduodenal artery runs toward a point 1.5 cm below the papilla of Vater, then turns to the posterior aspect of the pancreas to join the anterior inferior pancreaticoduodenal artery. For preserving the duodenum, the artery toward the papilla is very important. The artery toward the papilla of Vater runs along the right side of the common bile duct after branching from the posterior superior pancreaticoduodenal artery. The gastrocolic trunk of Henle has been reported to be found in about 60% of individuals. It is possible that the gastroepiploic vein and anterior superior pancreaticoduodenal vein (ASPDV) can be divided at pancreaticoduodenectomy with preservation of the superior right colic vein if this area is free of carcinoma. The ASPDV and anterior inferior pancreaticoduodenal vein (AIPDV) form an arcade on the anterior surface of the pancreas. However, arcade formation was not found between the posterior superior pancreaticoduodenal vein (PSPDV) and posterior inferior pancreaticoduodenal vein (PIPDV) in many of the cases examined. The vein joined by the inferior mesenteric vein was also investigated. We termed the artery originating from the gastroduodenal (GD) or dorsal pancreatic (DP) arteries, located on the cranial side of the head of the pancreas, the supra-transverse pancreatic (supra-TP) artery. Surgeons should be aware of the presence of the supra-TP artery during pancreatic surgery. The type of procedure used for intraductal papillary-mucinous tumor (IPMT) of the pancreas is various. The standard operations, such as pancreaticoduodenectomy, pylorus-preserving pancreaticoduodenectomy, and distal pancreatectomy with splenectomy, are performed. In some cases, limited resection such as uncal resection, pancreatic head resection with segmental duodenectomy, duodenum-preserving subtotal resection of the head of the pancreas, and spleenpreserving distal pancreatectomy with conservation of the splenic artery and vein are also performed. However, the type of procedure to use for IPMT is unclear, since there are still many unanswered questions regarding IPMT. Those unanswered questions include how a differential diagnosis of benign or malignant can be made clinically, how the extent of tumorous spread can be determined clinically, and whether patients with this disease can be cured after the tumor apparently infiltrates. IPMT may show multicentric development, while ordinary duct cell carcinoma may easily develop in the pancreas with IPMT. The reasons why duodenum-preserving resection of the pancreatic head is not popular involve the above problems and other technical problems. With preservation of the residual pancreas to maintain the duodenum and/or bile duct, the cut end of the pancreas may more frequently be positive for tumor cells, and IPMT and/or duct cell carcinoma may develop more often in the residual pancreas. We face the problem of whether several types of limited resection of the pancreas are suitable for IPMT with surgical indications due to possible malignancy and/or considerable ductal spread of neoplastic epithelia. When the pancreas head is completely resected, the bile duct, the papilla of Vater, and/or part of the duodenum should also be resected, and the significance of function-preservation declines. Important points for the future development of duodenum-preserving resection of the pancreatic head include clarifying the unanswered questions about IPMT, solving technical problems through the accumulation of anatomic and basic studies, and reporting objective results obtained in successful duodenum-preserving procedures. On the other hand, distal pancreatectomy that preserves both the splenic artery and vein and the spleen is steadily gaining popularity. Although this procedure is somewhat complicated, it is not technically difficult and can be safely performed by any surgeon. This procedure is indicated for some cases with chronic pancreatitis and IPMT.