Adult choledochal cysts: current update on classification, pathogenesis, and cross-sectional imaging findings

Imaging of Biliary Tree Abnormalities

Pathologic conditions of the biliary system, although common, can be difficult to diagnose clinically. Challenges in biliary imaging include anatomic variants and the dynamic nature of the biliary tract, which can change with age and intervention, blurring the boundaries of normal and abnormal. Choledochal cysts can have numerous appearances and are important to diagnose given the risk of cholangiocarcinoma potentially requiring surgical resection. Choledocholithiasis, the most common cause of biliary dilatation, can be difficult to detect at US and CT, with MRI having the highest sensitivity. However, knowledge of the imaging pitfalls of MRI and MR cholangiopancreatography is crucial to avoid misinterpretation. Newer concepts in biliary tract malignancy include intraductal papillary biliary neoplasms that may develop into cholangiocarcinoma. New paradigms in the classification of cholangiocarcinoma correspond to the wide range of imaging appearances of the disease and have implications for prognosis. Accurately staging cholangiocarcinoma is imperative, given expanding curative options including transplant and more aggressive surgical options. Infections of the biliary tree include acute cholangitis or recurrent pyogenic cholangitis, characterized by obstruction, strictures, and central biliary dilatation. Inflammatory conditions include primary sclerosing cholangitis, which features strictures and fibrosis but can be difficult to differentiate from secondary causes of sclerosing cholangitis, including more recently described entities such as immunoglobulin G4-related sclerosing cholangitis and COVID-19 secondary sclerosing cholangitis. The authors describe a wide variety of benign and malignant biliary tract abnormalities, highlight differentiating features of the cholangitides, provide an approach to interpretation based on the pattern of imaging findings, and discuss pearls and pitfalls of imaging to facilitate accurate diagnosis. ©RSNA, 2024 Supplemental material is available for this article.

Novel 3D morphological characteristics for congenital biliary dilatation diagnosis: a case-control study

BACKGROUND

Congenital biliary dilatation (CBD) necessitates the timely removal of dilated bile ducts. Accurate differentiation between CBD and secondary biliary dilatation (SBD) is crucial for treatment decisions, and identification of CBD with intrahepatic involvement is vital for surgical planning and supportive care. This study aimed to develop quantitative models based on bile duct morphology to distinguish CBD from SBD and further identify CBD with intrahepatic involvement.

MATERIALS AND METHODS

The retrospective study included 131 CBD and 209 SBD patients between December 2014 and December 2021 for model development, internal validation, and testing. A separate cohort of 15 CBD and 34 SBD patients between January 2022 and December 2022 was recruited for temporally-independent validation. Quantitative shape-based (Shape) and diameter-based (Diam) morphological characteristics of bile ducts were extracted to build a CBD diagnosis model to distinguish CBD from SBD and an intrahepatic involvement identification model to classify CBD with/without intrahepatic involvement. The diagnostic performance of the models was compared with that of experienced hepatobiliary surgeons.

RESULTS

The CBD diagnosis model using clinical, Shape, and Diam characteristics showed good performance with an AUROC of 0.942 (95% CI: 0.890-0.994), AUPRC of 0.917 (0.855-0.979), accuracy of 0.891, sensitivity of 0.950, and F1-score of 0.864. The model outperformed two experienced surgeons in accuracy, sensitivity, and F1-score. The intrahepatic involvement identification model using clinical, Shape, and Diam characteristics yielded outstanding performance with an AUROC of 0.944 (0.879-1.000), AUPRC of 0.982 (0.947-1.000), accuracy of 0.932, sensitivity of 0.971, and F1-score of 0.957. The models demonstrated generalizable performance on the temporally-independent validation cohort.

CONCLUSIONS

This study developed two robust quantitative models for distinguishing CBD from SBD and identifying CBD with intrahepatic involvement, respectively, based on morphological characteristics of the bile ducts, showing great potential in risk stratification and surgical planning of CBD.

Biliary Duct Dilatation: AJR Expert Panel Narrative Review

Biliary duct dilatation is a common incidental finding in practice, but it is unlikely to indicate biliary obstruction in the absence of clinical symptoms or elevated levels on liver function tests (LFTs). However, the clinical presentation may be nonspecific, and LFTs may either be unavailable or difficult to interpret. The goal of this AJR Expert Panel Narrative Review is to highlight a series of topics fundamental to the management of biliary duct dilatation, providing consensus recommendations in a question-and-answer format. We start by covering a basic approach to interpreting LFT results, the strengths and weaknesses of the biliary imaging modalities, and how and where to measure the extrahepatic bile duct. Next, we define the criteria for biliary duct dilatation, including patients with prior cholecystectomy and advanced age, and discuss when and whether biliary duct dilatation can be attributed to papillary stenosis or sphincter of Oddi dysfunction. Subsequently, we discuss two conditions in which the duct is pathologically dilated but not obstructed: congenital cystic dilatation (i.e., choledochal cyst) and intraductal papillary neoplasm of the bile duct. Finally, we provide guidance regarding when to recommend obtaining additional imaging or testing, such as endoscopic ultrasound or ERCP, and include a discussion of future directions in biliary imaging.

Diagnosis and management of choledochal cysts

BACKGROUND

Choledochal cysts (CCs) are rare cystic dilatations of the intrahepatic and/or extrahepatic bile ducts. We review the pathophysiology, diagnosis, and management of CCs.

METHODS

MEDLINE/PubMed and Web of Science databases were queried for "choledochal cyst", "bile duct cyst", "choledochocele", and "Caroli disease". Data were synthesized and systematically reviewed.

RESULTS

Classified according to the Todani Classification, CCs are generally believed to arise secondary to reflux of pancreatic enzymes into the biliary tree due to anomalous pancreaticobiliary duct union. Complications of CCs include abdominal pain, jaundice, cystolithiasis, cholecystitis, pancreatitis, liver abscess, liver cirrhosis and malignant transformation (3-7.5%). Radiological and endoscopic imaging is the cornerstone of CC diagnosis and full delineation of cyst anatomy is imperative for proper management. Management is generally guided by cyst classification with complete cyst excision necessary for CCs with high potential of malignant transformation such as types I and IV. 5-year overall survival after choledochal cyst excision is 95.5%.

CONCLUSION

Most CCs should undergo surgical intervention to mitigate the risk of cyst related complications such as cholangitis and malignant transformation.

Hepatobiliary mucinous cystic neoplasms and mimics

This review will provide an overview of hepatobiliary mucinous cystic neoplasms and their mimics such as complex appearing benign cysts, intraductal papillary neoplasm of bile ducts, choledochal cysts, infectious cysts, and other cystic neoplasms. Preoperative imaging, particularly abdominal MRI with MRCP, plays a key role in differentiating these entities which differ widely in management. Familiarity with the differentiating imaging features of mucinous cystic neoplasms and their mimics allows radiologists to provide management-guiding reports.

Clinical Features and Surgical Management of Bile Duct Cyst in Adults

Objectives

Bile duct cyst (BDC) is a rare congenital biliary malformation with 20% of cases initially diagnosed during adulthood. Although the incidence of BDC in adults is increasing worldwide, the clinical features of adult BDC remain unclear. The present study was aimed at characterizing the demographic and clinical features of this rare disease.

Methods

We constructed a retrospective database and analyzed records of 106 patients (mean age, 41.0 ± 14.8 years; 18 men (17.0%)) with BDC treated at our institution from May 2012 to October 2018. Data collected included demographic characteristics, clinical manifestations, surgical patterns, and prognoses. We compared the characteristics of patients undergoing their primary BDC resection against those of patients undergoing reoperation. Risk factors for bile duct infection (BDI), a common complication of BDC, were identified using univariate and multivariate analyses.

Results

Abdominal pain was the most common preoperative symptom, but 12 patients (11.3%) were asymptomatic. Ninety-nine patients underwent their primary BDC resection, and 7 patients received reoperation at our hospital. There was no significant difference in the postoperative complication rate between the two groups. Ninety-four patients were followed up for 37.8 ± 23.8 months, and BDI occurred in 33 patients (35.1%). Hilar anastomosis was an independent risk factor for BDI (odds ratio = 3.561; 95%confidence interval = 1.101, 11.517; and p = 0.034).

Conclusion

BDC was more frequent in women and abdominal pain was the most common preoperative symptom. The primary reason for reoperation was anastomotic stenosis. Reoperation had similar outcomes to primary resection and may be considered safe and acceptable if performed by a skillful surgeon. BDI was the most frequent postoperative complication with hilar anastomosis being the only independent risk factor. This highlights the importance of proper bile duct flow for surgical outcomes of BDC.

Congenital Cystic Lesions of the Bile Ducts: Imaging-Based Diagnosis

Congenital cystic lesions of the bile ducts represent a spectrum of liver and biliary system lesions, resulting from abnormal embryologic development of the ductal plate. These disorders include Caroli disease, choledochal cysts, autosomal dominant polycystic liver disease, congenital hepatic fibrosis, and biliary hamartomas. Each disorder carries a peculiar clinical presentation, prognosis, and risk of complications. Knowledge of radiological findings of fibropolycystic liver diseases is crucial for their appropriate detection and for differential diagnosis with other similar hepatic cystic lesions, in order to avoid relevant misdiagnosis. The aim of this review is to provide an illustrative summary of the most relevant imaging findings of these conditions as encountered on ultrasound, computed tomography, and magnetic resonance imaging, and provide pearls for imaging-based differential diagnosis.

Diverticulum of common hepatic duct leading to obstructive jaundice, a case report

Choledochal cyst is a dilation of the intrahepatic and/or extrahepatic biliary tree. The pathogenesis is unknown and potentially is multifactorial. In 1977, Todani classified the cysts under five different types according to their morphology, number and distribution along the biliary tree. Presenting symptoms of Choledocal cysts which include upper abdominal pain, acute cholangitis and jaundice, although often they are clinically silent and discovered as an incidental finding. Biliary complications include cholangitis, biliary stones, pancreatitis, portal hypertension and cholangiocarcinoma. We describe a case of a rare Type II Todani cyst located on the right side of the common hepatic duct characterised by a clinical presentation similar to that observed in Mirizzi Syndrome. The treatment of a Type II choledochal cyst consists in cystic excision.

A large choledochocystolithiasis mimicking Mirizzi syndrome

An 18-year-old man presented with spontaneous severe epigastric pain, progressing and radiating to back since 3 days. It was associated with epigastric tenderness, bilious vomiting and jaundice. He had been intermittently experiencing these symptoms for the last 1 year. No known comorbid. Ultrasound showed a poorly visualised heterogeneous focus at porta hepatis; considering poor visualisation, this might represent an enlarged calcified lymph node or cystic duct calculus causing extrinsic compression or a large sludge ball within the common bile duct (CBD), leading to dilatation of common hepatic duct and intrahepatic biliary system. Subsequent magnetic resonance cholangiopancreatography revealed a focal saccular dilatation of middle part of CBD, a type I-B choledochal cyst, large heterogeneous focus seen within it representing choledochocystolithiasis. Later, CT was performed for further characterisation of surrounding anatomy and pathology, which confused the appearance of choledochocystolithiasis for Mirizzi syndrome. Later, surgery and histopathology confirmed type I-B choledochocystolithiasis and chronic cholecystitis.

Biliary Anomalies in Patients With HNF1B Diabetes

CONTEXT

The clinical spectrum of organogenetic anomalies associated with HNF1B mutations is heterogeneous. Besides cystic kidney disease, diabetes, and various other manifestations, odd cases of mainly neonatal and posttransplantation cholestasis have been described. The biliary phenotype is incompletely defined.

OBJECTIVE

To systematically characterize HNF1B-related anomalies in the bile ducts by imaging with magnetic resonance imaging (MRI) or magnetic resonance cholangiopancreatography (MRCP).

SETTING AND PATIENTS

Fourteen patients with HNF1B mutations in the catchment area of the Helsinki University Hospital were evaluated with upper abdominal MRI and MRCP. Blood samples and clinical history provided supplemental data on the individual phenotype.

MAIN OUTCOME MEASURE(S)

Structural anomalies in the biliary system, medical history of cholestasis, other findings in abdominal organs, diabetes and antihyperglycemic treatment, hypomagnesemia, and hyperuricemia.

RESULTS

Structural anomalies of the bile ducts were found in seven of 14 patients (50%). Six patients had choledochal cysts, which are generally considered premalignant.

CONCLUSIONS

Structural anomalies of the biliary system were common in HNF1B mutation carriers. The malignant potential of HNF1B-associated choledochal cysts warrants further studies.

Primary Epidermoid Cyst of Biliary Duct Presenting as Choledochal Cyst

Choledochal cyst is a cystic dilation of the biliary tree that can increase the risk of malignancy in bile ducts and the gallbladder. These are usually lined by bile duct epithelium, which may undergo intestinal and squamous metaplasia. This is the first report of clinically diagnosed type II choledochal cyst that is entirely lined by metaplastic stratified squamous epithelium, unlike most other cysts, which are histologically lined by bile duct epithelium. This observation can potentially explain the underlying pathogenic mechanism of rare reports of squamous cell carcinomas arising in bile duct systems.