Pancreaticobiliary Maljunction

Pancreaticobiliary Maljunction and Variations of the

Pancreatico-Choledocho-Ductal Junction

Pancreaticobiliary maljunction (PBM) is a form of congenital anomaly in which the junction of the pancreatic and biliary ducts is located outside the duodenal wall. The configuration of the junction varies and is occasionally complex. This type of anomaly is almost always seen in patients with choledochal cyst or congenital biliary dilatation [1], and is also sometimes found in patients with congenital biliary atresia [2]. PBM, however, may occur independently of any other developmental changes in the common bile duct.

Fig. 1. Autopsy findings of choledochal cyst. a A huge choledochal cyst in an autopsy case (25-year-old man) with a polypoid carcinoma (arrow) in the posterior cyst wall and a metastatic nodule in the liver. b Pancreatico-choledochal-ductal junction (arrow) situated external to the propria muscularis of the duodenum. CBD = Common bile duct; MPD = main pancreatic duct; PV = papilla of Vater. From [30] with permission.

Fig. 1. Autopsy findings of choledochal cyst. a A huge choledochal cyst in an autopsy case (25-year-old man) with a polypoid carcinoma (arrow) in the posterior cyst wall and a metastatic nodule in the liver. b Pancreatico-choledochal-ductal junction (arrow) situated external to the propria muscularis of the duodenum. CBD = Common bile duct; MPD = main pancreatic duct; PV = papilla of Vater. From [30] with permission.

In the presence of PBM, pancreatic juice may flow freely into the extrahepatic bile duct and also the gallbladder, because the intraductal pressure of the pancreatic duct is usually higher than that of the biliary tract [3, 4]. Babbitt [1] postulated therefore that this influx of pancreatic juice into the common bile duct may be a factor causing cystic dilatation. As previously indicated, however, maljunction is not always associated with cystic dilatation, and the role of maljunction in the development of congenital cystic dilatation of the bile duct remains controversial.

Patients with PBM frequently develop neoplastic changes in the biliary tract [5, 6], regardless of cystic dilatation of the bile duct. The percentage of concomitant malignancy in the biliary tract is reported to be significantly high [7-9].

Figure 1 shows a huge choledochal cyst, 15 cm in diameter, in an autopsy case (25-year-old man), associated with a polypoid carcinoma, which had arisen in the posterior cyst wall with metastasis to the liver. The junction of the main pancreatic duct (MPD) and the common bile duct (CBD) was situated external to the muscularis propria of the duodenum, a condition which is referred to as PBM, thus forming an extended common channel [10, 11].

Tokuyama [12] classified the manner in which the CBD and MPD open into the duodenum into three types as follows: Type I: separate openings, Type II: one opening without a common channel, and Type III: common channel

Pancreatic duct

Pancreatic duct

Common bile duct

Common bile duct

Fig. 2. Common channel formation type (Type III). a Junction in the submucosal layer (Type IIIa). b Junction below the propria muscularis (Type IIIb). From [2] with permission.

formation. Type III was subdivided into two variations: the junction in the submucosal layer (a) and the junction below, or external to, the muscularis propria of the duodenum (b), designated PBM as described above, according to our previous study [2] as shown in figure 2. PBM was found in 18 (13.8%) of 130 autopsy and surgical cases of biliary tract carcinoma [10], including the case shown in figure 1, but in none of 199 control cases.

Mechanism of Pancreatic Juice Reflux into the Biliary Tract in PBM

The reason why PBM is abnormal is possibly explained more clearly by our reconstruction study [2], as shown in figure 3. In the controls, the CBD and MPD penetrate the muscularis propria of the duodenum obliquely and parallel to each other, and form a junction in the submucosal layer just before opening into the duodenum. The angle of the ductal junction is therefore very sharp. The sphincter of Oddi, which surrounds both ducts and the common channel, normally consists of three sections: the sphincter choledochus, the sphincter pan-creaticus and the sphincter ampullae [13]. Of these, the sphincter muscle at the distal end of the choledochus (sphincter choledochus) is the best-developed. It regulates the outflow of bile and prevents free communication between the bile and pancreatic ducts.

In cases of PBM, however, the junction of the ducts is situated external to the muscularis propria of the duodenum, thus forming an extended common channel [10, 11], as described above. The angle of the ductal junction is less sharp in these patients than in control cases. The well-developed sphincter muscle is situated in the submucosal layer, as in the control, but it mainly surrounds the common channel (sphincter ampullae), and the sphincter chole-dochus is extremely hypoplastic. These anatomical findings suggest the

Pancreaticobiliary Maljunction
Fig. 3. Sphincter muscle in PBM. A diagram showing the sphincter muscle at the end of the common bile duct and the MPD in controls (a) and in patients with PBM (b). From [2] with permission.

possibility of free communication between the ducts in cases of PBM. As the intraductal pressure of the pancreatic duct is normally higher than that of the bile duct [3, 4], reflux of pancreatic juice may occur into the bile duct and could lead to non-suppurative chronic inflammation of the bile duct.

Location ofJunction of Pancreatic Duct and Terminal

Bile Duct in PBM

Suda et al. [14] reported that in two specimens with a 'narrowed duct segment' distal to the cyst in patients with choledochal cysts a minute orifice was found macroscopically in the segment and was identified microscopically as a small duct from the pancreatic parenchyma, and that these small pancreatic

Fig. 4. One of the anatomical locations of junction of pancreatic duct and terminal bile duct in a case of PBM with congenital choledochal dilatation and carcinoma of the gallbladder (a 50-year-old woman). a ERCP showing a choledochal cyst (asterisk) and maljunction (arrow). Note narrow segment of the common bile duct between cyst and maljunction. b Postoperative preparation of the case with PBM (small arrow) and a choledochal cyst (large arrow). DPD = Dorsal pancreatic duct; SD = duct of Santorini; VPD = ventral pancreatic duct. From [14] with permission.

Fig. 4. One of the anatomical locations of junction of pancreatic duct and terminal bile duct in a case of PBM with congenital choledochal dilatation and carcinoma of the gallbladder (a 50-year-old woman). a ERCP showing a choledochal cyst (asterisk) and maljunction (arrow). Note narrow segment of the common bile duct between cyst and maljunction. b Postoperative preparation of the case with PBM (small arrow) and a choledochal cyst (large arrow). DPD = Dorsal pancreatic duct; SD = duct of Santorini; VPD = ventral pancreatic duct. From [14] with permission.

ducts were derived from the ventral pancreas, based on the distribution of islets with pancreatic polypeptide cells (PP islets) [14], as shown in figure 4.

From anatomical and radiological analyses of the junction of the pancreatic duct with the bile duct, there are variations in the location of the union of the terminal bile duct with ventral pancreatic duct system [15], as shown in figure 5.

0 0

Post a comment