Congenital malformations of the biliary tract depict a key surgical challenge in the form of accurate diagnosis and safe operative intervention during the most frequent operation of the biliary tree, which is laparoscopic cholocystectomy. Their occurrence affects up to 47% of the general population.^[1] Among these, gallbladder duplication carries an estimated incidence of 1 in 4000 to 5000 births.^[2] From 1926 through January 2022, a total of 62 instances were reported, with only a few of them being diagnosed preoperatively.^{[3, 4]} Nevertheless, the rarest form of gallbladder duplication remains that of an accessory gallbladder emerging from the left hepatic duct. Thus, to our knowledge, this represents the fifth reported case in the international literature of the forenamed malformation.

Our case illustrates the importance of a high index of suspicion in patients with recurrent symptoms of cholelithiasis who have been subjected to cholecystectomy, as well as a comprehensive knowledge of the biliary tract’s anatomical variations, avoiding diagnostic and radiological imagining interpretations’ errors, as well as intraoperative bile duct injuries. The present case is reported in line with the Surgical Case Report (SCARE) guidelines.^[5]

A 40-year-old Caucasian female presented with recurring symptoms of upper abdomen pain. Past medical history was unremarkable. Clinical examination revealed tenderness in the epigastrium and the upper right quadrant. Laboratory examinations were within the normal range. An abdominal ultrasound (US) depicted a gallbladder containing stones and another anatomical entity that fell under the differential diagnosis of either a cystic structure or an accessory gallbladder. Afterwards an abdominal computed tomography (CT) was performed that revealed a duplicated gallbladder. A separate artery was seen arising from the left hepatic artery and supplying the cephalic gallbladder. The duplicated gallbladder was situated directly above the left hepatic artery, from which the accessory cystic artery arose providing its blood supply. A magnetic resonance cholangiopancreatography (MRCP) was performed, which confirmed the existence of an accessory gallbladder(Figs 1–3) , with its cystic duct originating from the left hepatic duct(Fig. 4) . Due to the mild clinical image and the lack of symptoms’ recurrence, no surgical intervention was scheduled. Conservative treatment with spasmolytics and lifestyle or dietary optimization was advised.

The first case of a duplicated gallbladder was reported in 1675 by Blasius et al., and Boyden et al. proposed the first classification of a gallbladder duplication.^[6]

During the gestational period, extrahepatic bile ducts develop from the distal part of the hepatocystic diverticulum. By the end of the 4th week, both the cystic duct and the gallbladder bud are developed. Moreover, by the 5th gestational week, the common bile duct and the hepatic ducts appear, while the duodenum rotates to the right and the developing common bile duct becomes displaced dorsally, taking its final anatomical position.

In the rare case of gallbladder anlage duplication, elements of multiple gallbladders enter the bile duct through the same cystic duct. Thus occurs the anatomical malformations septate, V-shaped, or Y-shaped gallbladder. The V-shaped gallbladder consists of two distinctive bodies that share the same cystic duct. In Y-shaped type, two distinctive gallbladders, with distinctive cystic ducts merge and end up as one structure in the bile duct.

In the cases of an accessory gallbladder, the main and the accessory cystic ducts join the bile duct separately. Likewise, cases of triple gallbladders have been observed.‌^{[7, 8]} To highlight the importance of our case, to date there have been reported 17 cases of triple gallbladder, and only 4 of an accessory gallbladder entering the left hepatic duct.^[9]

Based on the above embryological development, Harlaftis, proposed a double gallbladder classification into two groups: the split primordium (Vesica fellea divisum) and the accessory gallbladder (Vesica fellea duplex), with a third miscellaneous group reserved to the malformations that do not fall into the two above-mentioned categories, such as a triple gallbladder (Fig. 5).^[10] According to this classification, our case falls into the left trabecular group.

Numerous other classifications for gallbladder duplications have been proposed except from Boyden et al. Gross et al. proposed a new classification by A-F type^{[6, 11]}, while Mochizuki and Makita introduced a different classification based on types I-VI.^[12] Hence, our case corresponds to type H by Boyden et al., type E by Gross et al., and type VI by Mochizuki and Makita.

In addition, patients with gallbladder duplication are more likely to experience a higher incidence of gallbladder cancer.^[13]

In the differential diagnosis, entities that should be taken into consideration are choledochal cyst, focal adenomyomatosis, and gallbladder diverticula. The diagnostic algorithm, although not standardized, begins with abdominal ultrasonography, followed by MRCP, computed tomography, and/or endoscopic retrograde cholangiopancreatography (ERCP).^[14]

Due to its infrequent manifestation, there are no guidelines regarding the diagnosis and management of incidentally finding accessory gallbladders. Concurrent removal of both gallbladders at surgery is recommended, in order to minimize cholecystitis or biliary colic recurrence. The proposed treatment in symptomatic cases remains laparoscopic cholecystectomy with intraoperative cholangiography.^[15]

Thus, four more cases of a duplicated gallbladder with its accessory cystic duct arising from the left hepatic duct have been reported (Table 1). In most cases, ultrasonography raised the suspicion of an anatomical variation, yet failed to confirm the diagnosis. Subsequently, the definitive diagnosis was confirmed with either a laparotomy or ERCP. In all cases, cholecystectomy was performed. In our case, the diagnosis was confirmed with MRCP, and no ERCP or laparotomy was performed. Due to the non-recurrent character of the patient’s symptoms, a cholecystectomy was not advised

The aim of this rare case, is to shed light on anatomical variations or malformations of the biliary tree. Overall, the rarity of such cases may contribute to missed diagnosis. In order to depict biliary tree anomalies, imaging techniques that delineate the biliary anatomy of each case is of paramount importance.

To conclude, what is peculiar about duplicate gallbladder case reports is that it might be a risk factor for symptomatic or recurrent cholelithiasis. Preoperative knowledge of such biliary tract variations, can identify and thereby guide conservative or surgical decision with laparoscopic cholecystectomy. In case of surgical management, resection of both gallbladders is ideal to prevent recurrence of disease and avoid inadvertent complications such as hemorrhage or bile duct injuries.

The authors declare no conflict of interest.

L.B., D.C., and S.D.: conceptualization; L.B., D.C., D.F., and V.P.: manuscript writing, editing, and final revision; S.D., C.T., and L.B.: data collection; T.T., D.F., and V.P.: visualization and technical support; D.C. and T.T.: supervision. All authors approved the final draft of the manuscript.