ABSTRACT
Choledochal cyst(CDC) originating from the cystic duct (Type VI A) is uncommon. Dilatation of both the common bile duct (CBD) and cystic duct (Type VI B) is exceptionally rare in children, with only a handful of adult cases documented in medical literature to date. We report a case of a 1-year-old child who was diagnosed with a Type VI B CDC involving dilation of both the cystic and CBDs, confirmed by imaging and histopathology following cholecystectomy, cyst excision, and hepaticoduodenostomy. While recent medical literature has begun to explore Type VI CDCs, documented cases, particularly in pediatric patients, remain extremely scarce. This case report contributes to the emerging understanding of Type VI B CDCs, providing valuable insights into their clinical presentation, diagnostic approach, and surgical management outcomes.
KEYWORDS: Bile duct, choledochal cyst, magnetic resonance cholangiopancreatography, Type VI biliary cyst
INTRODUCTION
Choledochal cysts (CDCs) are rare congenital anomalies characterized by intrahepatic or extrahepatic biliary dilatation. The prevalence of this condition varies by region, with western countries reporting one case per 100,000–150,000 people, while certain Asian areas see a higher rate of one in 13,000. Initially, Alonso-Lej et al.[1] (1959) identified three types, which Todani et al.[2] later expanded into a five-variant classification system. A sixth variant was subsequently recognized, encompassing isolated cystic duct enlargement (Type VI A) and combined cystic and common bile duct (CBD) dilation (Type VI B), as reported by Serradel et al.[3] in 1991 and termed it as “Type VI biliary cyst.” Notably, only three to five reports of Type VI CDCs have been documented in medical literature. This report details the diagnostic journey and surgical intervention of a Type VI B CDC in a 1-year-old child, aiming to contribute to the strategic knowledge on managing this rare condition.
CASE REPORT
A 1-year-old girl was brought to our hospital with intermittent right upper quadrant pain exacerbated after a fatty meal lasting approximately 1 week per episode over the past year. The patient had no history of fever, jaundice, or weight loss. Physical examination revealed tenderness in the right upper quadrant but was otherwise unremarkable. Blood tests, including hemogram and chemistry, were normal. Abdominal ultrasonography (US) showed a normal gallbladder and a dilated CBD (6.3 mm). Further investigation with contrast-enhanced abdominal computed tomography and magnetic resonance cholangiopancreatography (MRCP) revealed dilation of both the cystic (10 mm) and CBDs (7.5 mm) with distal narrowing, consistent with Type VI B CDC [Figures 1 and 2]. No intrahepatic bile duct dilation, stones, sludge, or lymph node enlargement were observed. The gallbladder and intrahepatic bile ducts appeared normal, and no anomalous pancreaticobiliary ductal junction (APBDJ) was found. Intraoperative exploration confirmed the cystic dilation of both the CBD and cystic duct, supporting the Type VI B choledochal diagnosis [Figure 3]. Cholecystectomy along with excision of the CDC and hepaticoduodenostomy was carried out. The postoperative course was uneventful, and histopathological examination of the excised cyst confirmed the diagnosis. At the 6-month follow-up, liver function tests were normal, and ultrasound showed no intrahepatic bile duct dilation, and no residual cyst was present. A hepatobiliary iminodiacetic acid scan demonstrated patent biliary drainage without biliogastric reflux.
Figure 1.
Magnetic resonance cholangiopancreatography T2-weighted axial cut showing dilated cystic duct 10 mm (white arrow) and common bile duct 7.5 mm (yellow arrow)
Figure 2.
Magnetic resonance cholangiopancreatography reconstruction image showing dilated cystic duct 10 mm (white arrow) and common bile duct 7.5 mm (yellow arrow), common hepatic duct (star)
Figure 3.
Intraoperative image showing gallbladder, dilated cystic duct (yellow), and common bile duct (white)
DISCUSSION
In 1959, Alonso-Lej et al. initially categorized CDCs into three types.[1] Todani et al. later expanded this classification to include five variants.[2] Recently, a sixth variant, characterized by isolated cystic duct enlargement, was identified. Bode and Aust reported the first such case in 1983.[4] Serradel et al.[3] modified Todani’s classification to incorporate isolated cystic duct cysts, proposing a new Type VI CDC. In 2011, Yoon described imaging characteristics of CDCs involving the cystic duct in three cases, suggesting the inclusion of these variant anomalies in the classification. Michaelides et al., based on six cases, proposed classifying this type of CDC as a new subtype of Todani I cyst, termed type ID.[5] Bhoil et al. suggested further dividing Type VI cysts into Type VI A (isolated cystic duct dilatation) and Type VI B (combined cystic duct and CBD dilatation), which influences treatment decisions.[6] Sugumaran and Nag reported two cases initially diagnosed as Type I A and Type II CDC on MRCP, but intraoperative findings revealed Type VI A and B CDC, altering the management approach.[7] This highlights the importance of understanding these newer types and the need to expand the traditional classification. Most cystic duct lesions are symptomatic, with epigastric and/or right upper abdominal pain exacerbated by fatty meals being a common symptom, as observed in the present case. While the exact cause of these cysts remains unknown, an anomalous pancreaticobiliary ductal junction (APBDJ) can lead to ectasia of the CBD and cystic duct. Abdominal US is often the initial diagnostic tool, but MRCP is ideal for detailed biliary system anatomy visualization. Endoscopic retrograde cholangiopancreatography (ERCP) provides similar information to MRCP but is invasive. ERCP and Tc-99m hydroxyimino diacetic acid scans can diagnose but are not commonly used. Treatment for Type VI A involves simple cholecystectomy if the cystic duct opening into the CBD is narrow, which can be performed laparoscopically by clipping the cyst opening into the common hepatic duct. For wide openings, cyst and CBD excision along with hepaticoduodenostomy or Roux-en-Y hepaticojejunostomy is necessary. Despite the established classification, the recent identification of Type VI B CDC reveals gaps in our understanding of its pathogenesis, presentation, and optimal management strategies. This underscores the need for further research and documentation of Type VI B cases to refine diagnostic and treatment protocols. To date, very few cases of Type VI B CDCs in adults have been reported in the literature [Table 1].
Table 1.
Studies on Type VI choledochal cyst
| Study | Number of cases | Features | Classification given |
|---|---|---|---|
| Michaelides et al.[5] | 6 | Dilatation of the CHD, CBD, and dilatation of the central portion of the cystic duct | Not given |
| Yoon[8] | 3 | All three had involvement of cystic duct, and two had involvement of both the cystic and CBD | Not given |
| Bhoil et al.[6] | 1 | Combined dilatation of cystic duct as well as the CBD | Type VI B |
| Sugumaran and Nag[7] | 2 | 1 isolated cystic duct dilatation, 1 combined cystic and CBD dilatation | Type VI A and B, respectively |
| Joshi SV et al.[9] | 1 | Combined dilatation of cystic duct as well as the CBD | Type VI B |
CHD: Common hepatic duct, CBD: Common bile duct
CONCLUSION
Recent literature has begun to explore Type VI CDCs, although documentation, particularly in children, remains scarce. Accurate preoperative identification of Type VI CDCs is complex and necessitates thorough imaging studies. Distinguishing between Type VI A and Type VI B is essential, as treatment approaches vary. Current protocols for managing Type VI B CDCs, including deciding between cholecystectomy with cyst removal and hepaticoduodenostomy or Roux-en-Y hepaticojejunostomy, are founded on limited research. The absence of agreement and information on long-term surgical outcomes for Type VI B patients highlights a significant knowledge gap and the need for established treatment protocols.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
REFERENCES
- 1.Alonso-Lej F, Rever WB, Jr, Pessagno DJ. Congenital choledochal cyst, with a report of 2, and an analysis of 94, cases. Int Abstr Surg. 1959;108:1–30. [PubMed] [Google Scholar]
- 2.Todani T, Watanabe Y, Narusue M, Tabuchi K, Okajima K. Congenital bile duct cysts: Classification, operative procedures, and review of thirty-seven cases including cancer arising from choledochal cyst. Am J Surg. 1977;134:263–9. doi: 10.1016/0002-9610(77)90359-2. [DOI] [PubMed] [Google Scholar]
- 3.Serena Serradel AF, Santamaría Linares E, Herrera Goepfert R. Cystic dilatation of the cystic duct: a new type of biliary cyst. Surgery. 1991;109:320–2. [PubMed] [Google Scholar]
- 4.Bode WE, Aust JB. Isolated cystic dilatation of the cystic duct. Am J Surg. 1983;145:828–9. doi: 10.1016/0002-9610(83)90152-6. [DOI] [PubMed] [Google Scholar]
- 5.Michaelides M, Dimarelos V, Kostantinou D, Bintoudi A, Tzikos F, Kyriakou V, et al. Anew variant of Todani type I choledochal cyst. Imaging evaluation. Hippokratia. 2011;15:174–7. [PMC free article] [PubMed] [Google Scholar]
- 6.Bhoil R, Sood S, Sood RG, Singla G, Bakshi S. A variant of type VI choledochal cyst: Combined dilatation of cystic duct and common bile duct. J Ultrasound. 2016;19:71–2. doi: 10.1007/s40477-015-0186-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Sugumaran K, Nag HH. A new variant of choledochal cyst-type 6B. Cureus. 2021;13:e16273. doi: 10.7759/cureus.16273. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Yoon JH. Magnetic resonance cholangiopancreatography diagnosis of choledochal cyst involving the cystic duct: Report of three cases. Br J Radiol. 2011;84:e18–22. doi: 10.1259/bjr/77844300. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Bakhshi GD, Sable C, Dutt AS, Baligar SS, Jha MK, Joshi SV. Type VI B choledochal cyst – A rare entity. Int Surg J. 2022;9:1650–2. [Google Scholar]