Periportal cholangioplasty is the use of the most rational surgical pathways and techniques to manage surgical diseases occurring in and around the first hepatic portal through accurate preoperative imaging evaluation. Periportal biliary surgery is a difficult and focal area of biliary surgery, bringing together a variety of difficult and complex biliary surgical conditions, such as hilar bile duct cancer, hilar bile duct cancer embolus, hilar bile duct stenosis, hilar bile duct cyst, hilar bile duct stones, and gallbladder cancer invading the hilar. Regardless of benign or malignant hilar biliary diseases, they are characterized by high surgical difficulty, easy intraoperative bleeding, many postoperative complications, high recurrence rate and high mortality rate. For example, the restenosis rate after bile-intestinal Roux-en-Y anastomosis for hilar bile duct stenosis is more than 10%. At present, the resection rate of hilar cholangiocarcinoma is only 45-66%, among which type IV hilar cholangiocarcinoma was once considered as a forbidden area for surgery, and it is very easy to recur after surgery. The application of perihilar surgery technique is based on the fine understanding of perihilar anatomy, and the core of perihilar surgery technique is hilar revealing, lesion resection and reconstruction of hilar bile duct. The introduction of the concept of precision surgery into the management of perihilar surgery diseases can greatly improve the success rate of surgery, and the application of correct perihilar surgery techniques can greatly improve the cure rate of complex and difficult biliary tract diseases. First, the complexity of perihilar surgery 1, anatomical variability The first hepatic hilar is the lateral part of the “H”-shaped groove of the liver surface, with the square lobe of the liver above and at the top of the hilar and the caudate lobe at the back. The first hepatic hilar brings together the bile ducts, hepatic artery and portal vein that enter the hepatic hilar, and the three ducts cross each other to form an intricate three-dimensional structure. However, in 12%-15% of patients, the right hepatic artery passes in front of the bifurcation of the hepatic duct, which is likely to cause bile duct stenosis and stones if the bile duct is compressed. The direction and convergence of the bile ducts, hepatic arteries and portal veins of the left and right hepatic hemispheres vary greatly from individual to individual, causing uncertainty and complexity in the treatment of perihilar disease. 2. The complexity of pathophysiology The hyperplasia and atrophy of the liver caused by different diseases often lead to rotation of the hilar position or obscured by the hyperplastic square or caudal lobes, resulting in a deeper hilar position and increasing the difficulty of anatomical exposure. In addition, when combined with portal hypertension, hypertrophy of connective tissue in the hilar, varices in the hilar veins, and even formation of portal vein spongiosis, can easily lead to intraoperative hemorrhage and embarrassing situation of intraoperative inching. Periportal disease is often accompanied by obstructive jaundice, which can easily cause intraoperative bleeding and postoperative liver insufficiency. Once the bile duct is completely obstructed, the tumor often invades along the duct wall and easily invades the accompanying hepatic artery and portal vein, making it impossible to resect or radical resection. Even in the case of inflammatory strictures formed by hilar stones, the chronic inflammation is likely to form dense adhesions with the vessels, and the adhesions caused by the inflammation are often more extensive and bleed more easily when touched. Multiple surgeries can also result in scarring closure of the hepatic hilum and loss of anatomical clearance, causing great surgical difficulties. II. Implementation steps of perihilar surgery Perihilar surgery includes preoperative evaluation and preparation, intraoperative management and postoperative management such as: postoperative liver function maintenance, nutritional support, abdominal and biliary drainage, etc. To improve the efficacy of perihilar biliary disease and reduce complications and mortality, it is necessary to pass a comprehensive and systematic perihilar imaging assessment, liver function assessment and master the correct perihilar operation techniques, including the correct anatomical pathway, correct lesion resection techniques and hilar bile duct reconstruction techniques. 1.Pre-operative yellowing reduction Because perihilar disease often starts with severe obstructive jaundice, and is often combined with different degrees of biliary tract infection before surgery, coupled with the fact that surgery often requires liver resection, pre-operative yellowing reduction is very important. Although there are controversies in academic circles regarding the criteria and duration of preoperative yellowing reduction, the author and most scholars agree that for portal liver surgery requiring extensive liver resection, long operation time, trauma and high difficulty, when TBil >200umol/L, yellowing reduction is still required to improve surgical safety and reduce the proportion of intraoperative blood loss and postoperative liver failure. Yellow reduction should be based on PTCD drainage, and stent reduction under ERCP is not advocated. As hilar disease often leads to separation of the left and right hepatic ducts, PTCD drainage of the left and right hepatic ducts with multiple bile ducts should be performed, at least to drain the bile ducts of the preserved side of the liver. For obstructive intrahepatic cholangitis caused by inflammatory stenosis of the hilar and hilar bile duct stones, preoperative drainage of the intrahepatic bile duct is also required to control biliary tract infection. In addition, contrast injection is not recommended after PTCD drainage, otherwise it will lead to cholangitis. 2. Three-dimensional imaging reconstruction techniques of the porta hepatis Thin-layer CT, MRI and MRCP are the imaging examinations that must be completed in every case of perihilar disease. Recently, the use of computer software for three-dimensional reconstruction of the image data of thin-layer CT can display the relationship between the lesion and the hilar vessels in a three-dimensional, all-round and multi-angle manner, which greatly improves the accuracy of preoperative resectability assessment and can make full use of individual anatomical differences to develop the most reasonable surgical plan. For example, I have encountered a patient with type IIIa hilar cholangiocarcinoma. Preoperative 3D image reconstruction revealed that the right posterior hepatic duct bypassed the posterior portal vein and merged with the left hepatic duct, the right anterior and right posterior branches of the portal vein merged with the left branch of the portal vein in a “trigeminal” pattern, and the right hepatic artery came from the superior mesenteric artery. According to the preoperative imaging evaluation, “radical resection of the right anterior lobe with preservation of the right posterior lobe for hilar cholangiocarcinoma” was planned. The intraoperative exploratory findings were completely consistent with the preoperative imaging examination, which not only achieved the goal of radical treatment, but also avoided sacrificing the innocent right anterior lobe of the liver. 3. Liver function assessment and preparation Most of the perihilar biliary tract diseases are combined with obstructive jaundice preoperatively, while extensive liver resection is required, and some patients may also be combined with chronic active hepatitis and fatty liver, so preoperative liver reserve function assessment and determination of residual liver volume are very important. The liver function tolerance criteria and assessment protocols for extensive liver resection can be operated according to the relevant guidelines established by the Chinese Medical Association Biliary Surgery Group, but when doing right-trilobar and left-trilobar resections of very large areas of the liver, we try not to challenge the 20% residual liver volume limit, even for seemingly normal livers. Because we tend to focus more on the harm of chronic viral hepatitis on liver function and ignore the potential harm of fatty liver, some patients with fatty liver will result in postoperative residual liver insufficiency after the limit volume resection of liver even if the preoperative liver function is normal. I have met a patient with type IV hilar cholangiocarcinoma without preoperative jaundice and completely normal liver function, who underwent an enlarged right hemicolectomy with less than 400 ml of intraoperative bleeding, no hilar block, and a residual liver volume greater than 25%, but postoperative liver failure still occurred. For patients with severe jaundice, if TB> 200 umol/L, preoperative reduction of yellowing must be required if a hemicolectomy is needed. If the DNA of hepatitis B virus is >105, antiviral treatment must be performed until the DNA is <103. 4. Anatomy and exposure of the hepatic hilar Depending on the location and confluence of the bile ducts, hepatic artery and portal vein bifurcations in the hepatic hilar and the extent of the hepatic hilar to be exposed surgically, different techniques of hepatic hilar dissection can be used. Patients with a low bifurcation of the hilar bile ducts can easily expose the hilar structures. When dissecting the hepatic hilum, it is important to pay attention to anatomic variation to prevent accidental injury to the bile ducts and vessels in the hilar region. ① Hepatic portal plate separation technique: This is the most commonly used technique to expose the hepatic hilum. The hilar plate is formed by the fusion of the Glisson sheath with the envelope of the square lobe of the liver and extends to the right as the gallbladder plate and to the left as the umbilical plate. There are no significant vessels directly in front of the bile ducts, which can be dissected between the Glisson sheath and the square lobe of the liver. Small amounts of bleeding can be stopped with electrocoagulation or pressure filling with hemostatic material. Under normal circumstances, about 50 px of extrahepatic bile duct tissue can be revealed. In patients with low biliary bifurcation, this approach can completely reveal the confluence of the left and right hepatic duct bifurcations. Since the gallbladder and hilar plates are continuous with each other, prior cholecystectomy helps to dissect the right hilar structures. In patients with high bile duct stenosis, the hepatic hilum is often closed by hyperplastic scar tissue. If the bile duct bifurcation is high and the hilar bile duct cannot be completely exposed by separating the hilar plate, the hepatic tissue can be split along the median hepatic fissure to completely open up the hilar plate. The median hepatic fissure is the dividing line between the left and right liver, in order to avoid damage to the median hepatic vein, the liver can be split along the left side of the median hepatic fissure in 1.0~37.5px section, the depth of incision is appropriate to fully reveal the hilar bile duct, the length of incision is generally 2/3 under the median hepatic fissure, the small hepatic vessels or bile ducts along the section should be properly ligated or sutured, the use of CUSA knife for fine dissection of intrahepatic bile ducts can reduce intraoperative bleeding The fine dissection of intrahepatic bile ducts with CUSA knife can reduce intraoperative bleeding. For patients whose tumors invade the hepatic hilar vessels, median hepatic fissure can also be used first to open the hepatic hilar before dealing with the involved hepatic hilar vessels can improve the surgical safety. The hyperplasia of the hepatic square lobe will obstruct the dissection of the hepatic hilar and make the hilar structure deeper. In this case, the top of the hepatic hilar can be opened after resection of the hepatic square lobe or the liver tissue above the transverse groove of the hilar (part of the right anterior segment of the liver) with CUSA knife. This allows complete exposure of the hepatic duct bifurcation and the transverse part of the left hepatic duct, and also provides space for biliary-intestinal anastomosis. ④ Lesion resection and revascularization The core of resection of lesions in the hilar region is the adequate exposure of the lesion, the separation of the hilar vessels and ensuring negative cut margins of the involved bile ducts. Invasion of vessels by malignant lesions is an important reason why lesions cannot be resected. Since the bile ducts are located anterior to the vessels, opening the portal plate and then dissecting the bile ducts first facilitates the treatment of the invaded vessels and is safer. Combined portal vein resection can significantly improve the prognosis of hilar cholangiocarcinoma. If the invasion of portal vein is less than 25 px, segmental resection of portal vein is feasible; for invasion of more than 25 px, grafting of additional veins is often required. When hepatic artery infiltration becomes the only obstacle to obtain R0 resection, combined hepatic artery resection should be considered to achieve radical resection of biliary malignancies in the hilar region; otherwise, the hepatic artery should be preserved. It is still controversial whether hepatic artery reconstruction should be performed for hilar cholangiocarcinoma, but the author believes that for patients with severe preoperative jaundice and long obstruction time and large resection area, the hepatic artery on the preserved side should be reconstructed to reduce the incidence of postoperative liver failure and biliary complications. Regardless of whether the anastomosis is reconstructed in the portal vein or the hepatic artery, attention needs to be paid to the direction of the vessel suture to prevent torsion and stenosis of the reconstructed vessel and to ensure that the anastomosis is tension-free. To avoid postoperative anastomotic thrombosis, especially for hepatic artery reconstruction, repeated pulling or clamping of the vessel and damage to the intima should be avoided when dissecting and separating the vessel, and the anastomosis should be closed with a 6-0 prolene suture with external rotation. In order to avoid ischemia of the residual liver during revascularization, the portal vein and hepatic artery can be dissected and reconstructed in steps without affecting the resection. In case of adhesion between benign lesions and blood vessels, a blunt push with a suction device or electric knife tip can be used, and a "small step-by-step" strategy should be adopted to carefully separate and avoid damage. In case of vascular injury, it should not be clamped blindly, and 5-0 or 6-0 prolene suture should be applied to stop the bleeding and ensure the vascular patency. ⑤ Biliary-intestinal anastomosis After the removal of perihilar disease lesions, bile duct plasticity and biliary-intestinal anastomosis is another difficult point. After removal of the lesion of hilar cholangiocarcinoma, many secondary and tertiary bile ducts often remain in the left and right half of the liver. The thin and slender walls of bile ducts and the surrounding blood vessels often accompany each other, coupled with the narrow space in the hilar region, make the surgery more difficult. In order to avoid missing the severed bile ducts, sutures should be used to mark each bile duct when it is severed. The right anterior and right posterior branches and the left internal and left external bile ducts can be combined into one opening and anastomosed with the intestine. If the two bile ducts are far apart, separate bile-intestinal anastomoses may also be performed. Mucosa-to-mucosa anastomosis of the bile duct mucosa to the jejunal mucosa should be performed to avoid postoperative strictures, except in a few extreme cases, where anastomosis of the hepatic portal tissue to the jejunum is not recommended. The sutures should be 5-0 or 4-0 PDS sutures according to the thickness and diameter of the bile duct wall. In addition, the author recommends that a continuous external anastomosis should be performed as much as possible when performing a biliary-intestinal anastomosis. When the bile duct is very slender, silicone tube can be implanted to support it, and the stenosis ring needs to be cut open and reshaped before doing large caliber bile-intestinal anastomosis. Specific application of perihilar technique 1.Hilar cholangiocarcinoma The comprehensive application of perihilar dissection technique can improve the radical resection rate of hilar cholangiocarcinoma, increase the safety of surgery and reduce postoperative complications. The invasion of hepatic hilar vessels is the main reason for the low resection rate and the increase of surgical risk and difficulty of hilar cholangiocarcinoma. For patients with Bismuth I and II types, if the following 4 points are met: (i) the extent of tumor invasion is between P and U points; (ii) the involved vessels can be resected and reconstructed; (iii) there is no atrophy in the liver lobe; (iv) a separate perihilar resection is feasible for those without intrahepatic metastasis to maximize the preservation of liver tissue and increase the volume of residual liver. For patients with Bismuth type III and IV, if the following 3 points exist: ① tumor invasion unilaterally exceeds P or U points; ② unilateral vascular invasion that cannot be resected and reconstructed exists; ③ unilateral intrahepatic metastasis, perihilar resection combined with lobectomy is feasible. Type IV hilar cholangiocarcinoma used to be considered to be beyond radical resection and only suitable for liver transplantation. However, with the application of CUSA knife precision hepatectomy technique and periportal dissection technique, for patients with Bismuth type IV, even if the tumor invades beyond P and U points unilaterally or combined with unilateral vascular invasion, radical resection can still be achieved by periportal resection combined with lobectomy. The surgical difficulty lies in the plastic collocation of multiple bile ducts in the residual liver and the mucosa-to-mucosa anastomosis of the jejunum. For type IV hilar cholangiocarcinoma that invades the portal vein of the resected liver lobe, the "cis-reverse" approach can be used: first the middle hepatic cleft opens the hepatic portal plate, cuts off the bile duct on the healthy side and then dissects the portal vein bifurcation and cuts off the involved portal vein to improve surgical safety. The author had a case of type IV hilar cholangiocarcinoma without jaundice and with right portal vein involvement. The tumor invaded the right anterior and right posterior lobe bile ducts as well as the transverse part of the left hepatic duct. During surgery, the hilar plate was carefully dissected with a CUSA knife, and after opening the hilar plate, the B4, B2, and B3 bile ducts were severed at the distal end of the confluence of the left internal and left external bile ducts, respectively, and then the severed right branch of the portal vein was treated, and the left internal, left external, and left caudate lobe bile ducts were combined into a common opening, and then a continuous mucosa-to-mucosa anastomosis of bile and intestine was performed to achieve radical treatment. For cholangiocarcinoma in the hilar region that cannot be cured, such as bilateral invasion of portal vein and hepatic artery, contracture of hepatoduodenal ligament and extensive lymph node invasion and metastasis, the technique of hepatic hilar plate separation can be used to dissect out the bile ducts above the obstruction plane and place a T-tube to perform T-tube jejunostomy bridge internal drainage, which has the advantages of simple surgery, less bleeding, smooth drainage, stable internal environment after surgery and can greatly improve the quality of life. 2.Hilar bile duct stenosis Injurious bile duct stenosis is often accompanied by scarring and inflammatory adhesions in the liver portal, and removal of the stenosed bile duct and reconstruction of the bile-intestinal pathway is the only cure. The difficulty of surgery lies in dissecting out the normal bile duct above the stenosis. For Bismuth I and II bile duct stenosis, the normal bile duct to the confluence of the left and right hepatic ducts can generally be dissected outside the liver by lowering the hepatic portal technique, and bile-intestinal anastomosis can be performed after resection of the stenotic segment. However, for bile duct stenosis of Bismuth type III or higher, it is often necessary to perform a mid-hepatic split or square lobe resection, complete resection of the stenotic segment of the bile duct and then perform a large diameter bile-intestinal anastomosis. For hilar bile duct stenosis combined with atrophy of one liver lobe or segment, the affected liver lobe or segment can be resected at the same time. 3. Hepatic hilar bile duct stones are usually removed by lithotripter or choledochoscope after bile duct incision. After stone extraction, stenosis ring incision and bile-intestinal anastomosis will be performed. However, if a huge stone is embedded in the hilar bile duct and lithotripsy and lithotripsy are ineffective, the intrahepatic bile duct at the site of stone impaction needs to be exposed by the perihepatic technique and the stone can be removed only by incision of the bile duct. In a patient with bilateral intrahepatic diffuse bile duct stones without hepatic atrophy, a 50px diameter stone was embedded in the left inner lobe opening extending to the confluence of the left and right hepatic ducts, and the opening of the left and right hepatic ducts was narrowed, and choledochoscopic extraction and lithotripsy were ineffective. The stone was then removed by choledochoscopy, and the rest of the bile duct stones were removed by choledochoscopy, and a large caliber mucosa-to-mucosa anastomosis of the hilar bile duct jejunum was performed after complete dissection of the hilar bile duct stenosis loop. 4.Hilar bile duct cyst The core of bile duct cyst treatment is to perform bile-intestinal anastomosis after complete excision of the cyst to achieve complete biliopancreatic diversion and prevent malignant transformation of the residual cyst wall. For bile duct cysts limited to the hilar region, it is impossible to achieve the surgical goal of complete resection of the lesion and reconstruction of the bile-intestinal pathway while preserving normal liver tissue without the perihilar technique. According to the new bile duct cystic dilatation typology proposed by Dong Jiahong, B2 type central hepatic duct type intrahepatic bile duct cystic dilatation (lesions involving both the main bile ducts of the bilateral liver lobes and the confluence of the left and right bile ducts) and D2 type intra- and extrahepatic bile duct dilatation (lesions involving both the central hepatic ducts of the bilateral liver lobes and the extrahepatic bile ducts) require the use of the perihilar surgical technique for complete resection of the cyst. Surgery requires segmental resection of the cystic lesioned hepatic ducts after opening the hilar plate through a median hepatic fissure or square lobectomy, and Roux-en-Y anastomosis of the bile duct jejunum after splicing and shaping of the right and left class II or higher hepatic ducts. For type B1 central hepatic duct intrahepatic bile duct cystic dilatation (unilateral central hepatic duct cystic dilatation in the liver lobe), a lobectomy or segmental resection is feasible, and for type D1 (lesion involving the central hepatic duct and extrahepatic bile duct in the unilateral liver lobe), a unilateral lobectomy + extrahepatic bile duct is feasible, and the residual hepatic bile duct is performed with a bile-intestinal Roux-en-Y anastomosis. Conclusion Periportal surgery is a difficult area of hepatobiliary and pancreatic surgery, full of challenges, risks, changes and uncertainties. Perihepatic portal surgery technique is a comprehensive technique involving preoperative, intraoperative and postoperative aspects. Using the concept of precision surgery, an optimal and personalized surgical plan is developed for each patient suffering from a perihilar biliary surgical condition. The use of the most rational anatomical pathways and the most precise surgical techniques, together with advanced surgical instruments and equipment, can greatly improve the cure rate of perihilar biliary diseases.