CQ1: Is the narrow segment a reliable landmark for determining the distal (intrapancreatic) bile duct transection line?

A PubMed search using the terms “congenital biliary dilatation,” “narrow segment,” and “surgery” yielded 17 studies. Similarly, an Ichushi‐Web search using the same terms yielded nine studies.

According to the Japanese clinical practice guidelines for CBD published in 2017, resection of the pancreatic bile duct just above the pancreatic duct junction was recommended, leaving as little remnant as possible [2]. In cystic‐type CBD, a narrow segment at the end of the bile duct can be observed, making resection near the pancreatic junction relatively simple. However, in cases with fusiform‐type CBD, the narrow segment is obscure, creating a risk of pancreatic duct damage and becoming a source of postoperative pancreatic juice leakage, pancreatitis, or pancreatic duct stenosis. To prevent these complications, there are reports of confirmation using intraoperative cholangiography with a metal clip [3] or biliary endoscope [4]. There is a paucity of data regarding the management of the intrapancreatic portion of cysts and postoperative pancreatic complications. Complete excision of the intrapancreatic portion of the cyst is recommended for two reasons: (1) the residual cyst may contribute to stone formation and (2) carcinoma may arise from this residual cyst. However, this is a tedious job, with a chance of injury to the pancreas. Early complications of distal dissection include pancreatitis or pancreatic fistula due to damage to the pancreatic duct. To avoid pancreatic injury, many authors recommend intramural dissection of the cyst [5], partial excision leaving behind the intrapancreatic portion of the cyst [6], and intraoperative cyst endoscopy [4] to identify the location of the pancreatic duct so that as much of the distal bile duct as possible can be excised without pancreatic duct injury. Ando et al. recommended dissection outside the epicholedochal plexus to prevent pancreatic injury [3]. It is important to note that the narrow distal segment connecting the cyst and the main pancreatic duct is located not at the bottom of the cyst, but more proximally to the right ventral aspect of the cyst.

To investigate how the duodenal‐side bile duct is transected in clinical practice, a questionnaire survey regarding the resection line of the intrahepatic bile duct was conducted during the 71st General Meeting of the Japanese Society of Gastroenterological Surgery. Only 19.2% of respondents reported transecting the bile duct just above the pancreatic duct junction, corresponding to complete excision of the duodenal‐side bile duct. In contrast, 42.5% described transecting the hepatic‐side to the pancreatic duct junction, 19.2% reported transecting just inside the pancreatic parenchyma from the upper edge of the pancreas, and another 19.2% reported adjusting the resection line depending on whether the case involved a dilated or non‐dilated bile duct. These results suggest that only approximately 20% of institutions aim for the complete excision of the intrapancreatic bile duct, while the majority adopt resection lines that leave part of the intrapancreatic bile duct in situ [7].

Whether combined resection of the narrow segment surrounded by pancreatic parenchyma distal to the cyst is necessary is controversial. If the narrow segment is of pancreatic ductal origin, it should not be removed for prophylaxis.

CQ2: Where is the optimal resection line on the hepatic hilum side?

A PubMed search using the terms “congenital biliary dilatation,” “cyst excision,” and “hepatic hilum” yielded 26 studies. Similarly, an Ichushi‐Web search using the same terms yielded 8 studies.

According to the Japanese clinical practice guidelines for CBD published in 2016, the CQ of “When the dilated lesion includes the intrahepatic bile duct, to what extent should resection be made?” was raised. However, these guidelines do not provide a unified recommendation on this issue [2]. Although hepatectomy has been performed, hepatic resection should be considered in adult patients. However, in pediatric cases, it is generally regarded as excessively invasive. Furthermore, the 2024 edition of the clinical practice guidelines addresses the CQ: “Is hepatetomy recommended for Todani Type IV‐A?” The guidelines state that while hepatectomy may be considered in cases with hepatic atrophy or intrahepatic stones localized to one lobe, there remains no clear evidence that hepatectomy reduces the incidence of postoperative intrahepatic lithiasis or metachronous carcinogenesis. Therefore, it is suggested that even when biliary dilatation extends into the intrahepatic ducts, complete resection of all dilated segments is not necessarily required. Rather, in cases of biliary stenosis, relieving the stenosis and performing ductoplasty may be more important for preventing future strictures and intrahepatic stone formation.

Three studies specifically discussed the resection line of the bile duct on the hepatic side [8, 9, 10]. One of these studies compared 22 patients who underwent anastomosis at the common hepatic duct and 82 patients who underwent anastomosis at the hepatic hilum in Type IV‐A. Anastomotic stricture requiring reoperation occurred in nine patients in the common hepatic duct group, while only one patient in the hepatic hilum group who had primary intrahepatic bile duct stenosis required reoperation. The authors recommended bile duct resection at the hepatic hilum and ductoplasty for patients with Type IV‐A [8]. Two other retrospective observational studies have supported similar recommendations. Another study on adult patients recommended cyst excision for type I and resection of the hepatic hilum with ductoplasty for Type IV‐A [11]. Another study reviewed complications in 138 pediatric cases and found that anastomosis at the common hepatic duct or Type IV‐A disease was a risk factor for late complications. It also advocated for anastomosis and ductoplasty at the hepatic hilum [10].

Five studies focused on postoperative complications [10, 12, 13, 14, 15]. One study analyzing early postoperative complications in 173 pediatric cases reported a complication rate of 9.3% (16 cases), with bile leakage being the most frequent complication (10 cases). Four postoperative deaths (2.3%) were noted—three from bile leakage and one from liver failure [12]. Another study evaluated reoperations. Early complications caused by anastomotic failure and hemorrhage, and late complications caused by anastomotic strictures were the main reasons for reoperations. Persistent bile duct stenosis may be a potential risk factor for carcinogenesis [13].

One study evaluated the reduction in dilated bile ducts after surgery in pediatric cases [16]. With appropriate surgery, bile duct dilatation regressed within approximately 1.5 years. Persistent dilatation may indicate residual stenoses.

The risk of developing bile duct cancer after surgery for CBD is reportedly 120–200 times higher than that in the general population [17, 18]. One study summarizing 26 cases of cholangiocarcinoma arising from the hepatic bile ducts revealed a mean age of 51.8 years at cancer onset and a mean interval of 17.4 years from the initial surgery to cancer development. Notably, 53.8% of the cases were classified as Todani Type IV‐A [19].