Endoscopic Ultrasound Diagnosis and ERCP Treatment of Type III Choledochal Cyst: A Case Report and Review of Literatures

Choledochal cyst (CC) is a rare congenital anomaly of the biliary tract characterized by cystic dilatation of the bile ducts, which usually manifests as recurrent epigastric pain, fever, and jaundice, and may potentially be complicated by recurrent acute pancreatitis. Once diagnosed, surgical intervention should be performed as soon as possible to reduce the potential risks of cholestatic cirrhosis and even biliary malignancy that result from chronic infection and obstruction of the biliary system. Clinical classification of CC is an evolving process. The Todani classification, first introduced in 1977, has been adopted in clinical practice worldwide because of its simplicity and practicality 1, though there are certain limitations. Anatomical classifications based on abnormal pancreaticobiliary junctions have also been proposed to elucidate the pathogenesis; however, so far, no unified standard has been established 2. According to the Todani classification, type III CC—defined as cystic dilatation located at the terminal intraduodenal segment of the bile duct—is the most rare form, accounting for less than 6% of all cases 3. Imaging examination alone, such as conventional abdominal ultrasound, also has difficulty in the evaluation of the lesions 4. Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive diagnostic approach that can clearly visualize the entire bile duct system and its relationship with the pancreatic duct, and has served as the optimal modality for CC diagnosis 5. Here we report a case with type III CC who was accurately diagnosed by using imaging examination with endoscopic ultrasound (EUS) and was successfully treated with biliary and pancreatic duct stenting plus cyst fenestration under endoscopic retrograde cholangiopancreatography (ERCP). A 44-year-old female patient was admitted to our hospital in August 2024, complaining of intermittent epigastric pain under the xiphoid process and the right upper quadrant of the abdomen for 6 years. Three days before admission, she experienced worsening epigastric pain accompanied by vomiting, heartburn, acid reflux, and hiccups, etc. The patient had a previous history of cholecystectomy for cholecystitis 5 years before her admission. Physical examination revealed mild tenderness in the middle and upper abdomen, in the absence of yellow dye of skin and sclera, rebound tenderness or muscle tension of the abdomen, or the Murphy's sign. Laboratory tests revealed mild leukocytosis (white blood cell count 14.3 × 109/L) and elevated C-reactive protein (CRP; 66.27 mg/L), indicating active inflammation. And liver function tests showed elevated bile acids (128.5 μmol/L), which was predominantly due to an increased direct bilirubin level (33.5 μmol/L). This was consistent with cholestasis. Abdominal computed tomography (CT) was then performed, showing dilatation of the common bile duct (CBD) after cholecystectomy. Gastroscopy showed chronic non-atrophic gastritis with erosions and a submucosal bulging in the descending part of the duodenum. Acute biliary pathology was initially considered based on the patient's epigastric pain, inflammatory markers, and cholestatic liver biochemistry. The subsequent contrast-enhanced CT did not demonstrate pancreatic enlargement, peripancreatic fat stranding, fluid collection, or necrosis, which was not consistent with acute pancreatitis. Empirical treatment including antibiotics, somatostatin, and proton pump inhibitor (PPI) was administered, which resulted in significant symptom relief. To further evaluate bile duct dilatation, MRCP was performed, which showed a CBD of up to 10 mm in diameter, with mild compensatory dilatation of the hepatic ducts. While the pancreas showed no definite morphological abnormality on MRCP. EUS demonstrated heterogeneous echogenicity at the pancreatic tail, and mild dilatation of the pancreatic duct at the head of the pancreas, suggesting possible inflammatory changes. In addition, a cystic lesion of about 2.5 cm was found on the duodenal wall, which communicated with the bile duct, leading to compression of the opening of the pancreatic duct. Also, lymph node enlargement in the hilar area of the liver was observed. The patient was finally diagnosed with type III CC and underwent ERCP, during which major duodenal papilla enlargement with the patulous papillary orifice protruding into the intestinal lumen was detected (Figure 1A,B). This was consistent with the cystic dilatation of the terminal segment of the CBD on previous MRCP (Figure 1C,D) and EUS (Figure 1E,F). The opening of the major duodenal papilla located at the posteroinferior aspect of the duodenal lumen, with a small amount of bile flowing out. The guidewire was probed upward through the opening of the papilla (Figure 1G,H) and entered the bile duct. Approximately 40 mL of yellow–green bile was aspirated. Extrahepatic bile duct was slightly dilated (about 1.0 cm) with enlargement of the terminal segment (about 1.2 cm in diameter). Therefore, papillotomy was performed. The dilated tip of the papilla was opened to about 0.6 cm with a needle knife for bile outflow, followed by the placement of one plastic stent (7-Fr; 9 cm) in the bile duct and the other (5-Fr; 7 cm) (both from Jiangsu Maggie Medical Technology Co. Ltd., Changzhou, Jiangsu Province, China) in the pancreatic duct (Figure 1I,J). The patient was discharged on the third day after surgery. Postoperatively, serum amylase increased markedly (peak value 679.52 U/L), but returned to normal limits within 2 days. This transient elevation was considered procedure-related, and the patient did not develop clinically evident post-ERCP pancreatitis. At the 6-month follow-up, she remained symptom-free. The incidence of CC has been estimated to be about 0.007% in the United States and around 0.1% in Asia 6, 7. The pathogenesis of CC is mainly due to cystic dilatation of the CBD, abnormal pancreaticobiliary duct junction, cholestasis and inflammatory response, and abnormal proliferation of bile duct epithelium. At the early stage of the disease, most patients present with mild, intermittent upper abdominal discomfort, which worsens after meals while relieves at night or fasting. As the disease progresses, bile duct obstruction gradually worsens with secondary infection. Moreover, persistent and intractable upper abdominal pain may occur, accompanied by systemic symptoms such as mild fever, poor appetite, and weight loss. The Todani classification divides CC into 5 types 1. Type I CC is the most common type, with cystic dilatation limited to the CBD, accounting for over 80% of all cases. Type II CC is the diverticular type, in which cystic dilatation is limited to a part of the CBD. Type III CC is the choledochocele type, with the bile duct being tubular or cystic. Types IVa and IVb CC affect the intrahepatic and extrahepatic bile ducts, respectively. And type V CC, also known as Caroli's disease, is characterized by multiple cystic dilatation of the intrahepatic bile duct. Among them, type III CC is closely associated with developmental malformation of the CBD. During embryonic development, CBD and the pancreatic duct are not completely separated, resulting in pancreaticobiliary maljunction (PBM) and reflux of pancreatic fluid into the bile duct. This further induces an inflammatory response and bile duct epithelial cell proliferation, and ultimately leads to cyst formation and subsequent bile duct dilatation that protrudes into the duodenal cavity. Law and Topazian have reported that choledochoceles possess distinctive intra-ampullary anatomic features and can be subclassified based on local morphology rather than pancreaticobiliary junction abnormalities, indicating that mechanisms other than PBM may also contribute to cyst formation 4. Consistently, a systematic review including data accessed from 1975 to 2015 demonstrated marked variability in the clinical and anatomical features of choledochocele, without uniform reporting of PBM across cases 7. Conventional ultrasound may easily misdiagnose CC as cholecystitis. Our patient reported recurrent abdominal pain and was considered to have cholecystitis and underwent cholecystectomy; however, her symptoms persisted even after the operation. She was then considered to have possible biliary pathology based on clinical presentations; however, imaging studies demonstrated the absence of definitive evidence of acute pancreatitis. This suggests that CC remains incompletely understood and is easily misdiagnosed. Moreover, the patient did not have obvious abnormalities in the bile–pancreatic confluence, and the formation of the duodenal wall cyst could be a congenital anomaly, which might be related to the abnormal bile excretion after cholecystectomy. EUS has recently become an important diagnostic modality for digestive diseases, especially unexplained CBD dilatation. It has an extremely high diagnostic value for PBM 8, with a high sensitivity due to its high-resolution imaging and real-time observation, which can precisely identify the presence of type III CC. In addition, as a noninvasive or minimally invasive method, EUS reduces pain during the procedure and the risk of complications. Real-time observation enables the physicians to accurately determine the location and size of CC, as well as its relationship with adjacent organs, which facilitates the establishment of surgical strategies. Furthermore, EUS has multimodal imaging and can be used in combination with fine-needle aspiration/biopsy (FNA/B) and other techniques to obtain histopathological evidence. Traditionally, type III CC is managed by cyst excision with Roux-en-Y hepaticojejunostomy. Nonsurgical treatment is often considered for elderly patients with poor general condition and high surgical risk, which mainly includes antibiotics and interventional endoscopic therapy; among them, ERCP in combination with pharmacological medication can be used as a palliative therapy. Compared with traditional surgery, minimally invasive endoscopic approaches have recently shown comparable efficacy but with less trauma and faster recovery 9, 10. During the operation, the CBD and the pancreatic duct opening need to be carefully explored to determine whether there is a PBM. If PBM is found, pancreaticojejunostomy should be performed to avoid postoperative pancreatic fluid reflux that may lead to anastomotic stenosis or recurrence of cysts 8, 9. In recent years, minimally invasive technology has also been widely adopted during the surgical treatment of CC. Compared to open surgery, laparoscopic resection of CC is associated with less trauma and faster recovery, and has become one of the mainstream surgical procedures for this disease. Robot-assisted resection of CC can further improve surgical accuracy and reduce the incidence of complications 10. EUS diagnosis followed by ERCP is a novel approach that is currently proposed, that is, after a confirmative diagnosis by EUS, biliary drainage and cyst decompression under ERCP is performed, or with further laparoscopic cyst resection and bile duct reconstruction 11, 12. This combined treatment integrates the advantages of two minimally invasive technologies, which can further avoid surgical trauma and accelerate patient recovery. In our case, EUS precisely identified a cystic dilatation of the distal bile duct protruding into the duodenal wall, and ERCP successfully achieved drainage through papillotomy and stenting, resulting in complete symptom relief. We thus performed a literature review for cases with type III CC that were accurately diagnosed by EUS and effectively managed with ERCP, covering all articles published over the past 20 years in the PubMed, Web of Science, and Scopus databases using the following search terms: (“type III choledochal cyst”) OR (“choledochocele”) AND (“endoscopic ultrasound”) AND (“ERCP”). The results are summarized in Table 1 5, 12-16. These findings highlight that the EUS–ERCP combination not only enables precise localization and characterization of cystic lesions but also provides a minimally invasive, single-stage therapeutic option. Compared with conventional open surgery, this approach offers a more economical and efficient management strategy with shortened postoperative recovery time and lower procedural morbidity. Abdominal ultrasound and upper abdominal enhanced CT scan only led to the diagnosis of cholecystitis in our case. While type III CC was confirmed using gastroscopy and EUS. ERCP was then performed, offering a reasonable, economical and efficient diagnosis and treatment strategy for the patients with type III CC. However, this was only a single-case experience with a relatively short follow-up period; our experience in diagnosing type III CC may not be generalized to other populations. In addition, the absence of long-term postoperative imaging follow-up limits the assessment of potential recurrence or delayed complications. Therefore, multicenter studies with larger sample sizes and longer follow-up periods are warranted to validate the diagnostic accuracy and therapeutic efficacy of the combined EUS–ERCP approach. In summary, EUS is characterized by its noninvasive or minimally invasive high-resolution multimodal imaging and real-time observation and scanning, showing a high sensitivity for the diagnosis and treatment of type III CC. With the application of emerging technologies such as artificial intelligence and big data analysis, an efficient and dynamic clinical decision-support system could be established for type III CC that facilitates physicians in formulating more optimized diagnostic and treatment strategies. Written informed consent was obtained from the patient for the publication of this case report and images. The authors declare no conflicts of interest. Data used to support the findings of this study are available from the corresponding author upon reasonable request.