Historically, choledochal cysts have been classified according to the descriptions published in 1959 by Alonso-Lej [4], with subsequent modifications. Alonso-Lej identified 3 types of choledochal cysts: the first type was a segmental cystic dilation of the common bile duct (CBD), the second a solitary CBD diverticulum, and the third a bulbous dilation of the distal-most portion of the CBD within the ampulla of Vater (choledochocele). This classification system has been modified by numerous investigators, including Longmire and colleagues [5] in 1971 and Todani and colleagues [2] in 1977. Todani’s modifications included subdividing type I cysts into (1) saccular, (2) segmental, and (3) diffuse. In addition to types I, II, and III, Todani also included type IV choledochal cysts, which are multiple and usually involve the intrahepatic and extrahepatic biliary system, and type V, intrahepatic bile duct cysts or Caroli disease (Fig. 1).

Fig. 1 (A–E) Choledochal cysts according to Todani’s modification of Alonso-Lej’s original scheme.

(Data from Todani T, Watanabe Y, Narusue M, et al. Congenital bile duct cysts: classification, operative procedures, and review of thirty-seven cases including cancer arising from choledochal cyst. Am J Surg 1977;134(2):263–9; and Alonso-Lej F, Rever W, Pessango D. Congenital choledochal cyst, with a report of 2, and analysis of 94 cases. Int Abstr Surg 1959;108(1):1–30.)

Since the time of Todani’s modifications, numerous surgical series have been published describing choledochal cysts, along with their relative frequencies, pathophysiology, and propensity for malignant degeneration. Choledochoceles (type III choledochal cysts) are only rarely included in these series because they comprise only 1% to 4% of all reported choledochal cysts [3,6]. Thus the natural history of choledochoceles has not been well characterized. Our group recently collected a combined surgical and endoscopic series of 146 patients with choledochal cysts including 28 choledochoceles, the largest single-institution Western series published to date [7]. In this series, choledochoceles were compared with choledochal cysts in terms of patient demographics, presenting symptoms, radiologic studies, associated abnormalities, and surgical and endoscopic procedures, as well as outcomes. Our analysis suggested that choledochoceles may have a discrete natural history compared with choledochal cysts.

Choledochoceles are dilatations of the distal CBD within the ampulla of Vater (Fig. 2). Choledochoceles are the rarest type of choledochal cysts, representing 1% to 4% of all reported cases [3]. The term choledochocele first appeared in a 1940 report from Wheeler [8], who described a case of biliary obstruction secondary to a dilated intraduodenal portion of the CBD, likening this situation to a similar phenomenon in the ureter (ureterocele). Only 4 choledochoceles were included in the publication of 94 choledochal cysts by Alonso-Lej in 1959 [4]. Even then, he questioned “as to whether or not it (choledochocele) originates from the same etiologic factors (as other choledochal cysts).” Subsequent investigators continued to question the relationship between choledochoceles and other choledochal cysts, including Trout and Longmire in 1971 [9], and many others over the following decades [10–16]. Choledochoceles continue to be a rare and poorly understood entity, with fewer than 200 cases reported in the English literature [15,17–19].

Fig. 2 Endoscopic view of choledochocele (type III choledochal cyst).

(From Ziegler KM, Pitt HA, Zyromski NJ, et al. Choledochoceles: are they choledochal cysts? Ann Surg 2010;252(4):683–90; with permission.)

The cause of choledochoceles and choledochal cysts is incompletely understood. The concept that choledochal cysts types I, II, IV, and V are congenital in nature is generally accepted. In contrast, several investigators have suggested that choledochoceles may be acquired [12,13,18,20]. In addition, choledochoceles may be lined with duodenal mucosa, and the potential for malignancy is reported to be significantly lower than in other types of choledochal cysts [15,19–21]. This decreased risk of biliary malignancy in combination with their accessible anatomic location has led to a shift in the management of choledochoceles from surgical to endoscopic therapy [17,19,22–25]. Some investigators have noted these dissimilarities between choledochoceles and choledochal cysts [12–16], but until recently, large series of surgical and endoscopic patients with choledochoceles have not been available.

Several theories exist regarding the cause of the various types of choledochal cysts. The fact that choledochal cysts are often diagnosed in infants supports the hypothesis that they are congenital in nature [26–28]. However, choledochal cysts are also postulated to be the result of another congenital anomaly, the anomalous pancreatobiliary duct junction (APBDJ). The anatomy of the biliopancreatic ductal system is notoriously variable. An APBDJ has been defined as insertion of the bile duct greater than 15 mm proximal to the ampulla of Vater (Fig. 3). The relationship between APBDJ and choledochal cyst formation was first described by Babbitt in 1969 [29]. He postulated that reflux of pancreatic juice into the CBD resulted in the cystic dilation of the duct. Embryologic data published by Wong and Lister [30] suggest that APBDJ results from failure of inward migration of the choledochopancreatic junction, leading to weakness in the wall of the bile duct. Since this time, the association between APBDJ and choledochal cysts has been well documented by several investigators [26,31,32]. APBDJ has generally not been observed in choledochoceles, which are less frequently associated with congenital biliopancreatic duct junction abnormalities [15,16].

Fig. 3 (A) APBDJ. (B) Magnetic resonance cholangiopancreatography image illustrating APBDJ (white arrow).

In our series, 83% of choledochal cysts were associated with an APBDJ. In contrast, only 5 junction abnormalities were described in the 28 patients with choledochocele, and this description may have been referring to the cystic dilation of the choledochocele itself, which often contains the termination of the bile duct and thus creates an abnormal-appearing common channel [7]. Although not occurring in conjunction with APBDJ, an increased incidence of pancreas divisum was seen in patients with choledochoceles in our series compared with those with choledochal cysts (37% vs 7%, P<.05), which is a unique observation. The low incidence of pancreas divisum in choledochal cysts has been reported [33–37], but limited data on pancreas divisum in patients with choledochoceles are available [19,34–38].

Another clue in determining the pathophysiology of choledochoceles, in contrast to choledochal cysts, is the observation that choledochoceles are seen with increased frequency in patients who have undergone previous cholecystectomy [19,39,40]. Our recent series showed that 44% of patients had previously had a cholecystectomy [7], similar to other reports from combined case series [12,40]. The finding that choledochoceles often occur in the setting of increased sphincter pressure brings into question the pathophysiology of their development. Thus, whereas choledochal cysts are generally accepted as congenital anomalies, many investigators postulate that choledochoceles may be acquired [12,18,20,23,25].

The method of presentation differs significantly between choledochoceles and choledochal cysts. Classically, choledochal cysts are found most commonly in female children; in contrast, patients with choledochoceles are more likely to be older and are more frequently male [11,39,40]. Our recent series showed the average age at presentation to be significantly greater in patients with choledochoceles compared with other cyst types (50.7 years vs 29 years). We did not observe the typical female predominance (57% vs 81% female) [7]. A review of all the Japanese and Western patients with choledochocele in 1994 (n = 109) also reported a lack of gender prevalence and older average age [18].

Patients with choledochal cysts typically present with pain and biliary tract symptoms, such as jaundice or cholangitis. The classic triad of abdominal pain, jaundice, and right upper quadrant mass is of historical importance, but is infrequently documented in modern series [3,41]. Several investigators have observed that symptoms also differ depending on the patient’s age at presentation: adults are more likely to present with pain, cholangitis, and/or malignancy, and children more likely to present with jaundice and/or abdominal mass [6,32,42]. Compared with those with choledochal cysts, patients with choledochoceles are more likely to present with pancreatitis and less likely to present with biliary tract symptoms [18,23,25,43]. Among patients with choledochoceles, Sarris and Tsang [40] reported a pancreatitis rate of 38%, as did Masetti and colleagues [17] in a large review. Our series of 146 patients showed a 48% rate of pancreatitis in patients with choledochoceles compared with only 24% in patients with choledochal cysts [7]. Conversely, the incidence of cholangitis was zero in patients with choledochoceles, whereas 21% of patients with choledochal cyst had cholangitis.

The diagnosis of choledochal cysts and choledochoceles has evolved over time. The increased use of abdominal imaging as well as the widespread availability of endoscopic evaluation have both improved our ability to characterize these lesions. In the early twentieth century, cystic biliary lesions were commonly identified by open surgical exploration [4,8]