The course and insertion of the cystic duct are clinically relevant to endoscopic and surgical biliary procedures. Although the cystic duct usually joins the extrahepatic bile duct from the right, its length, trajectory, and insertion site vary considerably. Low insertion, medial insertion, and a prolonged parallel course may obscure the relationship between the cystic duct and the main extrahepatic duct, complicating image interpretation and procedural orientation [1]. In an MRCP study of 198 patients, Sarawagi and colleagues identified low cystic duct insertion in 9% and a parallel course in 7.5% [2]. These represent study-specific frequencies rather than universal prevalence estimates, a separate MRCP study from Shiraz reported lower frequencies of these variants [3].

        Magnetic resonance cholangiopancreatography (MRCP) provides noninvasive delineation of biliary anatomy and can demonstrate cystic duct variants relevant to intervention. Taourel and colleagues showed its value in identifying anatomical configurations that may increase the risk of bile duct injury during laparoscopic cholecystectomy [4]. Nevertheless, low medial insertion can remain difficult to recognize when the cystic duct closely parallels or overlaps the main bile duct. A reported case of insertion just proximal to the ampulla illustrates how an unusually long cystic duct can complicate anatomical interpretation [5].

        Endoscopic retrograde cholangiopancreatography (ERCP) is a principal therapeutic procedure for choledocholithiasis, allowing stone extraction and biliary drainage. However, its therapeutic benefits must be considered alongside its recognized adverse events [6]. Temporary biliary stenting is recommended in selected circumstances, including irretrievable common bile ductstones requiring drainage [7]. In patients with low cystic duct insertion, accurate identification of the ductal junction and confirmation of the guidewire and stent trajectory are particularly relevant because entry into the cystic duct may be mistaken for access to the main biliary channel [1,8]. Biliary stent malposition within a low-inserting cystic duct has been documented previously. George and colleagues described a 62-year-old man in whom multidetector computed tomography demonstrated inadvertent placement of a biliary stent into the cystic duct, with subsequent operative confirmation [8]. Recognition of such anatomy is also relevant during cholecystectomy, where misidentification of biliary structures is an established mechanism of injury [9]. The multisociety safe cholecystectomy guideline emphasizes reliable anatomical identification and recommends intraoperative biliary imaging when anatomy is uncertain or bile duct injury is suspected [10]. The present report describes a separate patient whose malpositioned biliary stent was discovered unexpectedly during elective laparoscopic cholecystectomy following ERCP for choledocholithiasis. Its educational focus is the operative finding and the subsequent reinterpretation of the available MRCP, highlighting the importance of correlating preoperative imaging with intraoperative anatomy when an unexpected ductal configuration is encountered.

Case Presentation

Presentation and Diagnostic Assessment: A 62-year-old patient attended a gastrointestinal clinic with jaundice of five days’ duration. The supplied clinical account describes investigations consistent with obstructive jaundice. MRI and MRCP demonstrated a stone in the lower common bile duct, associated dilatation of the intrahepatic and extrahepatic biliary system, and gallbladder calculi. Patient sex, examination findings, laboratory values, stone dimensions, and measured duct diameters were not provided.

Endoscopic Intervention

Following preparation, ERCP was performed. The distal common bile duct stone was extracted, and duct sweeping and irrigation were undertaken because sludge was observed. A 7-Fr plastic biliary stent was deployed. Stent length, configuration, guidewire trajectory, sphincterotomy status, and the final cholangiographic appearance were not available in the supplied documentation. Subsequent ultrasound was reported to show multiple small gallbladder stones, a common bile duct of normal diameter, and a stent in situ. The report did not document the full course of the stent.

Operative Findings and Treatment

Approximately two weeks after ERCP, the patient attended Al-Shaab Teaching Hospital for elective laparoscopic cholecystectomy. A history of cardiac disease prompted cardiac and anaesthetic assessment. The specific cardiac diagnosis, medication regimen, and perioperative risk classification were not supplied. Under general anaesthesia, a four-port laparoscopic approach was used. According to the operating surgeon, the critical view of safety was achieved and the cystic artery was clipped. The cystic duct was wide, and application of conventional clips was difficult. A haemostatic clip was subsequently applied. The description of a “stone-passer” duct is treated here as an operative impression of a wide duct, rather than proof that a calculus had traversed it. Opening or division of the cystic duct exposed a plastic biliary stent within its lumen, extending toward the gallbladder cavity (Figure 1). Clips were removed to facilitate extraction (Figure 2), and the stent was removed through the cystic duct opening (Figure 3). The remaining steps of cholecystectomy were completed successfully according to the supplied account. The final method of cystic duct stump closure, completeness of the extracted stent, use of intraoperative cholangiography, and assessment for bile leakage require confirmation from the operative record.

Figure 1: Stent Encountered Within the Cystic Duct

Figure 2: Exposure of the Stent After Clip Removal

Figure 3: Extraction of the Plastic Stent

Outcome and Retrospective Imaging Review

The postoperative course was reported as uneventful. Discharge timing, postoperative liver function tests, histopathology, and duration of follow-up were not provided. Consequently, the report cannot establish longer-term freedom from bile leak, retained duct stones, or biliary stricture. After surgery, the MRI and MRCP were reviewed with a radiologist. The treating team interpreted the images as showing low cystic duct insertion with a prolonged closely apposed course alongside the main extrahepatic duct (Figures 4 and 5). The original description suggested a junction near the ampulla of Vater. The exact insertion level and length of any shared distal segment cannot be established from the supplied photographed screenshots and should be confirmed on the original MRCP dataset. This description does not establish a pancreaticobiliary maljunction Table 1.

Table 1: Clinical Timeline

Figure 4: MRCP Anterior View of the Biliary Tree (Arrow Indicate Low Insertion Cystic Duct)

Figure 5: Additional MRCP Posterior View (Arrow Clearly Revelated Low Insertion Cystic Duct)

The principal finding in this case was the direct observation of a plastic biliary stent within the surgically opened cystic duct. Low cystic duct insertion provides a plausible anatomical explanation, as this configuration may permit a guidewire and subsequently a stent to enter the cystic duct rather than the intended main biliary channel. The clinical relevance of low insertion and a parallel course has been described in anatomical imaging studies and in a previous report of cystic duct stent malposition [1-3]. Nevertheless, the proposed sequence in the present patient remains an inference. Without the original ERCP fluoroscopic images or documented final stent position, initial malposition cannot be distinguished confidently from subsequent displacement. Migration is a recognized complication of plastic biliary stents. Observational studies have identified associations with underlying biliary disease, stent characteristics, and duration of placement [4-5]. These findings support consideration of migration as an alternative explanation for an unexpectedly positioned stent, but they do not establish that migration into the cystic duct occurred in this patient. Accordingly, the most defensible description is an intraoperatively identified stent within the cystic duct, with uncertainty concerning when and how it reached that position. The anatomical interpretation also requires precision. Low insertion should be described according to the demonstrable junction between the cystic duct and the main extrahepatic bile duct. A long parallel segment may appear closely apposed or overlapping on projection images, making the actual confluence difficult to identify. MRCP studies demonstrate substantial variation in cystic duct course and insertion, while individual reports describe unusually distal junctions near the ampulla [2,6–8]. However, proximity alone does not establish a shared lumen or an ampullary insertion. In the present case, any definitive description of a common channel or insertion immediately adjacent to the ampulla would require review of the complete source images and the formal radiological assessment. George and colleagues provide a directly relevant published precedent [3]. They described a 62-year-old man in whom multidetector computed tomography demonstrated a biliary stent inadvertently positioned within a low-inserting cystic duct, with subsequent surgical confirmation. In contrast, recognition in the present account occurred during laparoscopic cystic duct division and prompted retrospective review of the preoperative MRCP. The educational distinction therefore concerns the sequence of recognition and the operative response. The present case should not be described as the first report of this complication, and the clinical measurements, treatment details, and outcomes of the published patient must remain separate from those of the current patient. The postoperative ultrasound description of a stent “in situ” did not establish which duct contained its proximal segment. Similarly, the reported normal common bile duct diameter after stone extraction did not independently confirm correct stent placement. In this setting, the relevant anatomical question concerns the entire stent trajectory and its relationship to the cystic duct junction. MRCP can delineate biliary variants, and the earlier report demonstrates the value of cross-sectional imaging in localizing an abnormal stent course [3,7]. Nevertheless, the available screen captures in the present account cannot substitute for assessment of the complete imaging study. Retrospective interpretation should therefore acknowledge the limitations imposed by projection, image quality, and incomplete access to the source sequences. The finding should also be considered within the broader context of therapeutic ERCP. The ASGE guideline addresses ERCP-based treatment of choledocholithiasis, while the ESGE guideline recommends temporary plastic biliary stenting for irretrievable stones when drainage is required [9,10]. Broader ESGE guidance further emphasizes that stent selection and use depend on the underlying biliary indication [11]. These recommendations support appropriate use of biliary stents but do not establish correct positioning in an individual patient. Documentation of the indication, deployment images, final stent position, and subsequent removal or exchange plan would improve interpretation of an unexpected operative finding. The operating surgeon reported achievement of the critical view of safety. However, the available still images do not independently establish that all its components were demonstrated. The critical view requires clearance of the hepatocystic triangle, separation of the lower gallbladder from the cystic plate, and confirmation that only two structures enter the gallbladder [12]. This approach addresses identification of the cystic duct and artery before division, an important consideration given the established role of anatomical misidentification in bile duct injury [13]. It does not, by itself, map the distal cystic duct insertion or confirm the trajectory of an intraluminal stent. Identification of the structures entering the gallbladder and assessment of the distal ductal anatomy are therefore complementary questions.

The multisociety safe cholecystectomy guideline supports the critical view of safety for anatomical identification and recommends intraoperative biliary imaging when anatomy is uncertain or bile duct injury is suspected [14]. The WSES guidelines similarly emphasize safe anatomical identification and selective use of intraoperative imaging when clarification is required [15]. In a comparable unexpected stent finding, pausing further division to reassess the anatomy and determine whether additional imaging is needed would be consistent with these principles. The present account does not establish whether intraoperative cholangiography or another imaging method was performed. Consequently, the favourable reported recovery represents an individual outcome and should not be interpreted as evidence that stent extraction without further anatomical assessment is generally sufficient.

Strengths and Limitations

The principal strength is the visual documentation of an unexpected intraductal foreign body and its extraction, supported by retrospective multidisciplinary imaging review. Limitations include incomplete clinical records, absence of ERCP fluoroscopy, uncertain exact ductal confluence, and unspecified postoperative surveillance. This single case cannot quantify the risk associated with low insertion or establish a preferred treatment strategy. Reporting has been organized around CARE domains, with missing elements explicitly identified [4].

A plastic biliary stent was encountered within the cystic duct during elective laparoscopic cholecystectomy after ERCP for a distal common bile duct stone. Retrospective MRCP review was interpreted as showing low cystic duct insertion. The case emphasizes correlation of the full stent course with biliary anatomy and careful reassessment when operative findings differ from the expected anatomy. The exact distal junction and the mechanism of malposition remain to be confirmed from the original imaging and procedural records.

1. Turner, M.A. and A.S. Fulcher. “The cystic duct: normal anatomy and disease processes.” Radiographics, vol. 21, no. 1, 2001, pp. 3–22. https://doi.org/10.1148/radiographics.21.1.g01ja093.
2. Sarawagi, R. et al. “Anatomical variations of cystic ducts in magnetic resonance cholangiopancreatography and clinical implications.” Radiology Research and Practice, vol. 2016, 2016, article 3021484. https://doi.org/10.1155/2016/3021484.
3. George, R.A. et al. “Low insertion of a cystic duct into the common bile duct as a cause for a malpositioned biliary stent: Demonstration with multidetector computed tomography.” Singapore Medical Journal, vol. 50, no. 7, 2009, p. e246.
4. Arhan, M. et al. “Migration of biliary plastic stents: Experience of a tertiary center.” Surgical Endoscopy, vol. 23, no. 4, 2009, pp. 769–775. https://doi.org/10.1007/s00464-008-0067-x.
5. Kawaguchi, Y. et al. “Risk factors for proximal migration of biliary tube stents.” World Journal of Gastroenterology, vol. 20, no. 5, 2014, pp. 1318–1324. https://doi.org/10.3748/wjg.v20.i5.1318.
6. Taghavi, A.R. et al. “Anatomic variations of the cystic duct in magnetic resonance cholangiopancreatography in Shiraz: A cross-sectional study.” Iranian Journal of Medical Sciences, vol. 47, no. 1, 2022, pp. 48–52. https://doi.org/10.30476/IJMS.2021.88447.1918.
7. Taourel, P. et al. “Anatomic variants of the biliary tree: Diagnosis with MR cholangiopancreatography.” Radiology, vol. 199, no. 2, 1996, pp. 521–527. https://doi.org/10.1148/radiology.199.2.8668805.
8. Yu, J.J. et al. “A case report on a rare anatomic variant of cystic duct insertion.” Journal of Surgical Case Reports, vol. 2017, no. 7, 2017. https://doi.org/10.1093/jscr/rjx131.
9. ASGE Standards of Practice Committee et al. “ASGE guideline on the role of endoscopy in the evaluation and management of choledocholithiasis.” Gastrointestinal Endoscopy, vol. 89, no. 6, 2019, pp. 1075–1105.e15. https://doi.org/10.1016/j.gie.2018.10.001.
10. Manes, G. et al. “Endoscopic management of common bile duct stones: European Society of Gastrointestinal Endoscopy (ESGE) guideline.” Endoscopy, vol. 51, no. 5, 2019, pp. 472–491. https://doi.org/10.1055/a-0862-0346.
11. Dumonceau, J.M. et al. “Endoscopic biliary stenting: Indications, choice of stents, and results: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline—Updated October 2017.” Endoscopy, vol. 50, no. 9, 2018, pp. 910–930. https://doi.org/10.1055/a-0659-9864.
12. Strasberg, S.M. and L.M. Brunt. “Rationale and use of the critical view of safety in laparoscopic cholecystectomy.” Journal of the American College of Surgeons, vol. 211, no. 1, 2010, pp. 132–138. https://doi.org/10.1016/j.jamcollsurg.2010.02.053.
13. Strasberg, S.M. et al. “An analysis of the problem of biliary injury during laparoscopic cholecystectomy.” Journal of the American College of Surgeons, vol. 180, no. 1, 1995, pp. 101–125.
14. Brunt, L.M. et al. “Safe cholecystectomy multi-society practice guideline and state of the art consensus conference on prevention of bile duct injury during cholecystectomy.” Annals of Surgery, vol. 272, no. 1, 2020, pp. 3–23.
15. 15. de’Angelis, N. et al. “2020 WSES guidelines for the detection and management of bile duct injury during cholecystectomy.” World Journal of Emergency Surgery, vol. 16, 2021, article 30. https://doi.org/10.1186/s13017-021-00369-w.