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Choledochal cysts are rare, congenital, and less commonly acquired cystic dilations of the extrahepatic or intrahepatic biliary tree, most often associated with an anomalous pancreaticobiliary junction that permits pancreatic enzyme reflux and chronic ductal inflammation. Progressive weakening of the bile duct wall leads to cystic dilation, bile stasis, and recurrent injury. Female sex and East Asian ancestry are recognized risk factors. Clinical manifestations vary by age and range from abdominal pain, jaundice, and a palpable right upper quadrant mass to nonspecific symptoms or complications such as cholangitis, pancreatitis, and stone formation. Diagnostic evaluation relies on ultrasonography and magnetic resonance cholangiopancreatography to define biliary anatomy and guide classification. Definitive management requires complete cyst excision with biliary reconstruction, typically Roux-en-Y hepaticojejunostomy, to reduce risks of cirrhosis and cholangiocarcinoma. This activity strengthens the clinician’s ability to evaluate, diagnose, and manage choledochal cysts using evidence-based strategies. Participants review etiology, risk factors, pathophysiology, clinical features, imaging modalities, and surgical principles, emphasizing timely referral and long-term surveillance. Emphasis on collaboration with surgeons, radiologists, gastroenterologists, nurses, and other interprofessional team members highlights coordinated perioperative planning, complication prevention, and structured follow-up, all of which enhance patient safety and optimize outcomes. Objectives: Differentiate choledochal cysts from other biliary disorders based on clinical presentation, laboratory findings, and imaging characteristics. Implement best practices for managing choledochal cysts and mitigating their potential complications. Improve awareness in patients and families about symptoms, long-term risks, and the role of surgery and follow-up in choledochal cyst management. Collaborate with all members of the interprofessional team, including specialists such as gastroenterologists, pathologists, and surgeons, to provide efficient, comprehensive, and coordinated care for individuals with choledochal cysts. Access free multiple choice questions on this topic.

Choledochal cysts, also known as biliary cysts, are rare anomalies characterized by 1 or more areas of dilation of the extrahepatic or intrahepatic bile ducts. In 1959, Alonso-Lej et al first classified choledochal cysts into 3 types based on the site of biliary duct dilation.[1] In 1977, Todani et al expanded this system by adding 2 additional types.[2] This 5-category anatomical classification remains the most widely used by clinicians, with each type demonstrating distinct natural history, complications, and management considerations. A classification emphasizing pathogenesis rather than solely ductal anatomy has been proposed to better reflect differences in clinical course, complications, and treatment strategies among the 5 types.[3] Certain choledochal cyst types are premalignant, while others follow a more indolent course. Clinical presentation is frequently nonspecific. High suspicion for choledochal cysts is essential in patients presenting with jaundice, abdominal pain, or a palpable abdominal mass. Imaging studies are critical for accurate diagnosis since physical findings and symptoms may be subtle or nonspecific. Timely identification and appropriate surgical management optimize outcomes and long-term prognosis.

The exact etiology of a choledochal cyst remains unknown, prompting multiple proposed theories. The most widely accepted is the Babbitt theory, which suggests that choledochal cysts arise from an anomalous pancreaticobiliary junction (APBJ). This abnormality occurs when the biliary and pancreatic ducts converge 1 to 2 cm proximal to the sphincter of Oddi. The resulting long channel lacks sphincter protection, permitting biliopancreatic reflux and activation of pancreatic enzymes. Elevated intraductal pressure subsequently causes ductal dilation, inflammation, epithelial injury, dysplasia, and malignant transformation of the biliary tree.[4] Support for this theory includes the presence of high concentrations of amylase, trypsinogen, and phospholipase A2 in choledochal cyst fluid, with results from multiple studies demonstrating elevated phospholipase A2 and trypsinogen levels in bile.[5][6] Experimental animal models with surgically created APBJ develop biliary duct dilation and cyst formation, further corroborating this mechanism.[7] However, the Babbitt theory is challenged by reports indicating APBJ in only 50% to 80% of cases and the absence of reflux in antenatally diagnosed choledochal cysts. Neonatal pancreatic acini may also be incapable of producing sufficient enzyme activity to induce ductal injury.[8] Alternative theories advocate a purely congenital etiology for choledochal cysts. Kusunoki et al observed a reduced number of ganglionic cells in the distal common bile duct (CBD) of patients with choledochal cysts compared with controls. The absence of ganglionic cells results in dilation of the proximal CBD, analogous to the pathogenesis of achalasia and Hirschsprung disease.[9] These theories primarily apply to type I and type IV choledochal cysts. Type II choledochal cysts, or true CBD diverticula, are thought to arise from biliary duplication cysts, whereas type III choledochal cysts, or choledochoceles, may result from biliary or duodenal duplication cysts.

Alternative theories advocate a purely congenital etiology for choledochal cysts. Kusunoki et al observed a reduced number of ganglionic cells in the distal common bile duct (CBD) of patients with choledochal cysts compared with controls. The absence of ganglionic cells results in dilation of the proximal CBD, analogous to the pathogenesis of achalasia and Hirschsprung disease.[9] These theories primarily apply to type I and type IV choledochal cysts. Type II choledochal cysts, or true CBD diverticula, are thought to arise from biliary duplication cysts, whereas type III choledochal cysts, or choledochoceles, may result from biliary or duodenal duplication cysts. Obstruction at the ampulla of Vater has also been proposed to account for distal intramural bile duct dilation localized to type III cysts.[10] The etiology of Caroli disease, classified as type V choledochal cyst, is presumed to result from incomplete remodeling of the ductal plates. Caroli disease may be associated with biliary atresia due to a shared ductal plate malformation pathogenesis and is also linked to autosomal recessive polycystic kidney disease and, less frequently, autosomal dominant polycystic kidney disease.[11]

A clear regional variation exists in the incidence of choledochal cysts, with approximately two-thirds of reported cases occurring in Japan. This condition predominantly affects the Asian population, with an incidence of 1 in 1000 live births, compared with 1 in 100,000 to 150,000 live births in Western populations. Although uncommon in Western populations, incidence in the United States and Australia has been reported as 1 in 13,500 and 1 in 15,000 live births, respectively.[12] The female-to-male ratio is 4:1.[13] The underlying factors responsible for Asian and female predominance remain unknown. Most choledochal cysts are diagnosed during childhood, while only 25% of cases are discovered in adults, a proportion that has been increasing in recent years.[14]

As mentioned, multiple schemes for classifying choledochal cysts have been proposed (see Table. Todani Classification of Choledochal Cysts). However, the Todani modified classification, introduced in 1977 and encompassing 5 types of choledochal cysts, remains the most widely used by clinicians (see Image. Todani Classification of Choledochal Cysts).[15][16] Table Table. Todani Classification of Choledochal Cysts. APBJ, anomalous pancreaticobiliary junction; CBD, common bile duct

Histopathologic features of choledochal cysts vary according to patient age. In pediatric individuals, the cyst wall demonstrates lymphocytic infiltration and is lined by columnar epithelium. Dense collagenous tissue and smooth muscle bundles may be present, indicating cyst wall fibrosis. In adults, cysts more commonly exhibit mucosal inflammation and epithelial hyperplasia.[18][19] Histologic appearance also differs among choledochal cyst types. Type I and some type IV cysts may show poorly formed, atrophic, or denuded biliary mucosa. Metaplasia and dysplasia within the cyst lining increase with advancing age, conferring a higher risk of malignant transformation. Cholangiocarcinoma development follows a multistep process, typically beginning with KRAS and TP53 mutations, followed by inactivation of the tumor suppressor gene, DPC4. Type II choledochal cysts resemble gallbladder duplication histologically but arise from the extrahepatic bile duct. Type III cysts are usually lined by duodenal mucosa and less frequently by biliary mucosa. Type V choledochal cysts demonstrate bile duct proliferation accompanied by periportal and bridging hepatic fibrosis.[20]

Approximately 85% of choledochal cysts are asymptomatic, whereas 15% present with clinical manifestations. In adults, symptoms most frequently include right upper quadrant (RUQ) abdominal pain, while children more commonly present with jaundice.[21] The classic triad of choledochal cysts—abdominal pain, a palpable RUQ mass, and jaundice—is observed in only 20% of cases. Among children, 85% present with both an abdominal mass and jaundice, compared with 25% of adults. Infants younger than 12 months may exhibit jaundice, acholic stools, and vomiting. When abnormalities are present, physical examination most commonly reveals RUQ tenderness or a palpable mass.

Laboratory evaluation alone cannot establish the diagnosis of choledochal cysts. The imaging modalities used for detection, along with their expected findings, are outlined below. Ultrasonography Prenatally, choledochal cysts may be detected on abdominal ultrasonography as a cystic structure in the region of the porta hepatis.[22][23] Postnatally, ultrasonography is generally the preferred initial imaging modality. Sensitivity for detecting choledochal cysts ranges from 71% to 97%, and the examination provides valuable information regarding cyst location, hepatic echotexture, and portal structures. However, when CBD dilation is observed, ultrasonography fails to determine the underlying cause in approximately 1 in 3 patients and cannot reliably identify the presence of an APBJ.[24] Computed Tomography Cholangiography Computed tomography (CT) cholangiography more accurately delineates intrahepatic ductal dilation, distal CBD, and pancreatic duct anatomy compared with ultrasonography, making it particularly useful for type IV and type V choledochal cysts. Sensitivity for diagnosing choledochal cysts is 90%, whereas characterization of the pancreatic duct is achieved in 64% of cases. Visualization of intraductal dilation and its extent aids surgical planning, including consideration of segmental hepatic resection. Technetium-99 Hepatobiliary Iminodiacetic Acid Scan Technetium-99 hepatobiliary iminodiacetic acid (HIDA) scanning can differentiate choledochal cysts from biliary atresia in neonates. Sensitivity for diagnosing type I choledochal cysts is 100%, but it decreases to 67% for type IVa choledochal cysts due to limited detection of intrahepatic duct dilation. This modality is also valuable for identifying spontaneous rupture of choledochal cysts, as extravasation of tracer into the peritoneal cavity indicates perforation.[25] Endoscopic Retrograde Cholangiopancreatography

Technetium-99 hepatobiliary iminodiacetic acid (HIDA) scanning can differentiate choledochal cysts from biliary atresia in neonates. Sensitivity for diagnosing type I choledochal cysts is 100%, but it decreases to 67% for type IVa choledochal cysts due to limited detection of intrahepatic duct dilation. This modality is also valuable for identifying spontaneous rupture of choledochal cysts, as extravasation of tracer into the peritoneal cavity indicates perforation.[25] Endoscopic Retrograde Cholangiopancreatography Endoscopic retrograde cholangiopancreatography (ERCP) demonstrates the highest diagnostic accuracy for choledochal cysts. The use of this imaging modality is limited by potential complications, including cholangitis, acute pancreatitis, bleeding, and perforation. The invasive nature of ERCP and the ionizing radiation delivered to patients further limit its clinical application. Patients with long common pancreaticobiliary channels, sphincter of Oddi dysfunction, or dilated ducts are at higher risk for ERCP-associated adverse events. ERCP offers both diagnostic and therapeutic capabilities, which are particularly relevant for type III choledochal cysts, for which endoscopic sphincterotomy can be performed.[26] Magnetic Resonance Cholangiopancreatography Magnetic resonance cholangiopancreatography (MRCP) is considered the gold standard for diagnosing choledochal cysts, with a sensitivity of 90% to 100%. The noninvasive nature, absence of ionizing radiation, and minimal procedural risk associated with this imaging technique have increased its use over time. MRCP also allows identification of APBJs, cholangiocarcinoma, choledocholithiasis, and spatial relationships of choledochal cysts to surrounding structures.[27] Limitations include reduced ability to detect minor ductal abnormalities or small type III choledochal cysts.[28][29]

Management of choledochal cysts depends on cyst type and the extent of hepatobiliary involvement. All cysts should be resected to mitigate the risk of complications, including cholangitis and cholangiocarcinoma, and to restore bile flow (see Image. Resected Choledochal Cyst Specimen). Early surgical excision is recommended. Results from a randomized clinical trial demonstrated that neonatal patients diagnosed antenatally with choledochal cysts who underwent surgical excision before 1 month of age had a lower risk of hepatic fibrosis and faster normalization of liver function tests compared with controls.[30] Historically, treatment consisted of external or internal drainage with cholecystectomy. Complete cyst excision is now preferred because partial drainage procedures do not eliminate the risk of malignancy or other complications, including pancreatitis, cholangitis, and biliary stenosis. Type I choledochal cysts are managed with complete excision of the entire extrahepatic biliary tree and restoration of bile flow via Roux-en-Y hepaticojejunostomy. Pancreaticoduodenectomy may be required in cases with extension of the cyst into the pancreatic head. However, complete excision without pancreatic resection is often feasible to reduce surgical morbidity. Hepaticoduodenostomy was previously performed but is no longer recommended due to the increased risk of biliary and gastric malignancy from pancreatic fluid reflux into the biliary tree.[31] Management of type II choledochal cysts is determined in part by the size of the connection between the cyst and the bile duct. Simple closure or ligation of the connection is sufficient when the cyst neck is small. Larger connections may require excision of the cyst with or without resection of the adjacent bile duct segment, followed by Roux-en-Y hepaticojejunostomy and closure over a T-tube. Evidence remains inconclusive regarding whether hepaticojejunostomy provides superior outcomes in these cases.[32]

Management of type II choledochal cysts is determined in part by the size of the connection between the cyst and the bile duct. Simple closure or ligation of the connection is sufficient when the cyst neck is small. Larger connections may require excision of the cyst with or without resection of the adjacent bile duct segment, followed by Roux-en-Y hepaticojejunostomy and closure over a T-tube. Evidence remains inconclusive regarding whether hepaticojejunostomy provides superior outcomes in these cases.[32] Symptomatic type III choledochal cysts or cysts in young asymptomatic individuals are typically treated with biliary sphincterotomy or sphincteroplasty during ERCP due to the low risk of malignancy. Biopsy of the cyst epithelium is performed to exclude dysplasia and determine epithelial type, as biliary mucosal lining carries a higher risk of malignancy. Large cysts may undergo marsupialization during ERCP or transduodenal surgery.[33] Complete resection would require pancreaticoduodenectomy, which carries significant morbidity and is rarely justified for this lesion. Type IV choledochal cysts are managed similarly to type I cysts, with interventions guided by cyst location and extent. Patients with intrahepatic ductal stenosis or dilatation, hepatolithiasis, or parenchymal atrophy are at increased risk for cholestasis, hepatic abscesses, recurrent cholangitis, and malignancy.[34] When only 1 hepatic lobe is affected, the preferred surgical approach is partial hepatectomy with excision of the extrahepatic bile ducts and reconstruction via Roux-en-Y hepaticojejunostomy. Patients with risk factors for malignancy derive the greatest benefit from partial hepatectomy. Excision of the dominant extrahepatic disease appears to reduce the risk of cancer since malignancy most commonly arises in the extrahepatic biliary tree.[35] Concurrent transduodenal sphincteroplasty is indicated in patients with a choledochocele as part of the disease spectrum.

When only 1 hepatic lobe is affected, the preferred surgical approach is partial hepatectomy with excision of the extrahepatic bile ducts and reconstruction via Roux-en-Y hepaticojejunostomy. Patients with risk factors for malignancy derive the greatest benefit from partial hepatectomy. Excision of the dominant extrahepatic disease appears to reduce the risk of cancer since malignancy most commonly arises in the extrahepatic biliary tree.[35] Concurrent transduodenal sphincteroplasty is indicated in patients with a choledochocele as part of the disease spectrum. A 1-year retrospective analysis demonstrated that adults have significantly higher rates of postoperative biliary strictures compared with children. Adults who underwent resection of the extrahepatic bile ducts alone exhibited higher incidences of biliary strictures, choledocholithiasis, and the need for repeat surgery than those who also underwent liver resection. Malignancy developed in 5 adult patients, whereas all pediatric specimens were benign.[36] Management parallels that of the extrahepatic component of type IVa choledochal cysts, with excision of the extrahepatic bile ducts and reconstruction via Roux-en-Y hepaticojejunostomy. Concurrent transduodenal sphincteroplasty is performed for lesions containing a choledochocele component. Management of type V choledochal cysts depends on the extent of the disease. For localized or unilobar involvement, segmental hepatic resection is the preferred approach. In cases of diffuse or bilobar disease with symptoms, orthotopic liver transplantation should be considered, although nonoperative management of cholangitis and optimization of liver function remain priorities.[37] External biliary decompression or internal drainage via approaches such as choledochoduodenostomy or hepaticojejunostomy provides only limited benefit. Results from a multicenter study comparing liver resection and transplantation reported that 69% of patients had disease confined to a single hepatic lobe, while the remainder exhibited bilobar involvement. Five-year survival rates were 97% following partial hepatectomy and 89% after liver transplantation.[38]

RUQ abdominal masses or cystic lesions may represent hepatic cysts, biliary hamartomas, pancreatic pseudocysts, duodenal atresia, mesenteric or omental cysts, gastric, duodenal, or intestinal duplication cysts, gallbladder duplication or distension, or ovarian cysts. Recurrent cholangitis should also be considered in the differential. Dilated bile ducts in adults or children may result from impacted cholelithiasis, Mirizzi syndrome, post-ERCP biliary strictures, cholecystectomy, or liver transplantation, primary sclerosing cholangitis, chronic pancreatitis with secondary biliary stricture, or acute pancreatitis with transient ductal dilation. In infants or neonates presenting with an RUQ cyst or cholestasis, differential diagnoses include biliary atresia, cystic biliary atresia, and inspissated bile syndrome.

A meta-analysis of 2904 cases of choledochal cysts reported that 11% of patients developed malignancy. Prognosis in those with cancer is poor, with a 5-year survival rate of approximately 5%. The risk of malignancy is 4 times higher in patients who underwent surgical drainage without cyst excision compared with those who received complete cyst excision. Median age at diagnosis of cholangiocarcinoma is 49.5 years in patients with choledochal cysts, compared with 65 years in patients without choledochal cysts. These findings support the recommendation for complete surgical excision of choledochal cysts in asymptomatic adult patients.[39] Excision of choledochal cysts generally yields excellent outcomes, with an 89% event-free rate and an overall 5-year survival rate of 95.5%.[40] Postoperative morbidity and mortality are uncommon in children but occur more frequently in adults. Type IVa choledochal cysts exhibit the highest complication rates, including intrahepatic ductal stones and anastomotic strictures.

Malignancy The overall risk of malignancy in choledochal cysts is approximately 5% and increases with advancing age. The risk in pediatric individuals is very low.[41] Drainage of a choledochal cyst without resection does not reduce the likelihood of malignant transformation. Even after complete cyst excision, residual risk of malignancy persists, necessitating long-term postoperative surveillance.[42] Neoplasms predominantly occur in type I choledochal cysts and the extrahepatic ducts of type IV cysts, and are uncommon in types II, III, and V. Preceding genetic events include KRAS and TP53 mutations, observed in approximately 60% of carcinomas, followed by inactivation of the DPC4 gene.[43][44] APBJs, which facilitate pancreatic juice reflux and hepatocellular injury, are associated with carcinogenesis and represent a risk factor for cholangiocarcinoma even in the absence of a choledochal cyst.[45] Inducible nitric oxide synthase may also contribute to mucosal hyperplasia and carcinogenesis.[46] Stricture Postoperative stricture formation is associated with many complications, including bile stasis, stone formation, ascending cholangitis, acute pancreatitis, mucosal chronic inflammation, fibrosis, and malignancy.[47] A wide surgical anastomosis reduces the risk of postoperative stricture formation by allowing free, unobstructed biliary drainage.[48] Ascending Cholangitis Ascending cholangitis is a common complication of choledochal cysts resulting from pancreaticobiliary reflux. Postoperative anastomotic strictures or residual debris within dilated intrahepatic ducts can lead to bile stasis, stone formation, and recurrent cholangitis.[49] Intraoperative choledochoscopy reduces the risk of cholelithiasis and cholangitis by facilitating the removal of intrahepatic stones.[50] Sludge and Stone Formation

Ascending cholangitis is a common complication of choledochal cysts resulting from pancreaticobiliary reflux. Postoperative anastomotic strictures or residual debris within dilated intrahepatic ducts can lead to bile stasis, stone formation, and recurrent cholangitis.[49] Intraoperative choledochoscopy reduces the risk of cholelithiasis and cholangitis by facilitating the removal of intrahepatic stones.[50] Sludge and Stone Formation Sludge and stone formation may develop years to decades after surgical intervention due to anastomotic stricture formation or residual debris within dilated hepatic ducts.[51] When postoperative anatomy permits, bile duct stones are typically removed via ERCP. Intrahepatic stones are managed using endoscopic ultrasound–guided hepaticogastrostomy, with a reported success rate of approximately 90%. Percutaneous transhepatic cholangioscopy is employed when endoscopic ultrasound–guided hepaticogastrostomy is not feasible. However, this approach requires external drainage, which poses particular challenges in pediatric patients. Surgical intervention is rarely necessary when neither endoscopic nor percutaneous approaches are possible.[52]

Choledochal cysts are rare anomalies with premalignant potential. Diagnosis is often challenging due to the nonspecific clinical presentation. High clinical suspicion is required when evaluating patients presenting with jaundice, abdominal pain, or a palpable abdominal mass. Imaging studies are essential to establish the diagnosis because physical findings and symptoms are frequently vague. Choledochal cysts are associated with multiple complications, including cholangitis, pancreatitis, cirrhosis, and cholangiocarcinoma. Surgical excision has demonstrated excellent outcomes, supporting the recommendation for early diagnosis and prompt management. Patient and family education regarding the potential risks and benefits of surgical intervention is necessary, even in asymptomatic cases.

Accurate identification of signs and symptoms combined with comprehensive radiological assessment is critical for the initial management of choledochal cysts. Treatment is almost exclusively surgical, and most patients require long-term postoperative monitoring for the development of malignancy. Optimal outcomes depend on an interprofessional team comprising gastroenterologists, surgeons, pathologists, radiologists, and nursing staff. Oncologists are included if malignancy is detected. Pediatricians, internists, family practitioners, nurse practitioners, and physician assistants contribute to ongoing medical care and surveillance for complications.