Pictorial Essay
Abdominal Imaging
December 2006

Congenital Anomalies and Normal Variants of the Pancreaticobiliary Tract and the Pancreas in Adults: Part 1, Biliary Tract

Abstract

OBJECTIVE. The purpose of this article is to highlight the imaging features of congenital anomalies and normal variants of the biliary tract with contemporary imaging techniques such as MR cholangiopancreatography (MRCP), MRI, and helical CT.
CONCLUSION. Recognizing findings of congenital anomalies and normal variants of the biliary tract at MRCP, MRI, and helical CT, and knowledge of the clinical significance of each entity, are important for establishing a correct diagnosis and in guiding appropriate clinical management.

Introduction

Congenital anomalies and normal variants of the biliary tract may be clinically significant. For instance, aberrant or accessory biliary ducts may predispose patients to inadvertent ductal ligation at laparoscopic cholecystectomy [1] and may complicate surgeries, such as living donor right lobe liver transplantation [2]. Recent advances in MRI, MR cholangiopancreatography (MRCP), and MDCT have improved image quality greatly and have contributed to the increased recognition of these entities. Congenital anomalies and normal variants involving the biliary tract include aberrant or accessory biliary ducts, aberrant cystic duct insertion; bile duct cysts, alterations of the biliary tract associated with situs anomalies, and anomalous junction of the common bile duct with the pancreatic duct. Recognition of these entities as anomalies and normal variants may avoid diagnostic errors, aid in surgical planning, and prevent inadvertent ductal injury.

Aberrant Biliary Ducts

Anatomic variations of the biliary tract occur commonly [3] (Fig. 1). Normally, the right and left hepatic ducts converge at the portal hepatis to form the common hepatic duct. The right hepatic duct has two major branches—an anterior or ventrocranial branch, and a posterior or dorsocaudal branch. The left hepatic duct also has two major branches—medial and lateral. A right dorsocaudal branch draining into the left hepatic duct, also known as a crossover anomaly, is a common anomaly of the biliary system (Figs. 1C, 2, and 3). This branch drains the posterior segment of the right lobe of liver and joins the left main, rather than the right main, hepatic duct. An aberrant or accessory right hepatic biliary duct emptying into the common hepatic duct or cystic duct (Figs. 1D, 1E, 2, and 4) is also common; it is seen in 7.4% of patients undergoing cholangiography [3]. MRCP, mangafodipir trisodium-enhanced MRCP, CT cholangiography, and ERCP readily detect accessory and aberrant biliary ducts. Failure to recognize these anatomic variants may result in inadvertent ductal ligation, biliary leaks, and strictures, especially at laparoscopic cholecystectomy and living donor right lobe liver transplantation [1, 2].

Aberrant Cystic Duct Insertion: Low Insertion into Distal Common Bile Duct and Insertion into Right Hepatic Duct

Currently, laparoscopic cholecystectomy is performed far more frequently than open cholecystectomy in the treatment of patients with gallstone disease. Detection of anatomic variants that may increase the risk of bile duct injury during cholecystectomy has become more relevant with the advent of the laparoscopic approach [1]. MRCP has proven to be accurate in the diagnosis of anatomic variants of the biliary tree. Low insertion of the cystic duct into distal common bile duct (Fig. 5) occurs in 9% of all individuals. Cystic duct insertion into the right hepatic duct (Fig. 6) is a rare variant of the cystic duct. Failure to recognize these variants may lead to misidentification of the common bile duct (CBD) or right hepatic duct (RHD) for the cystic duct, and may result in inadvertent ligation or severance of a portion of CBD or RHD.
Fig. 1 Normal and variant biliary ducts. A, Normal biliary tree. B, Trifurcation of biliary duct (arrow). C, Right dorsocaudal branch (arrow) draining into left hepatic duct. D, Aberrant right hepatic duct (arrow) emptying into common hepatic duct. E, Aberrant right hepatic duct (arrow) draining into cystic duct.
Fig. 2 51-year-old man imaged for liver donor work-up. Coronal thick-slab MR cholangiopancreatography reveals dorsocaudal branch of right hepatic duct (arrows) draining into left hepatic duct (arrowhead). Aberrant right hepatic duct (open arrow) drains into common hepatic duct. Common bile duct (CBD), cystic duct (curved arrow), pancreatic duct (P), duodenum (D), and biliary bifurcation (bif) are noted.

Bile Duct Cysts

A bile duct cyst is a relatively rare congenital cystic dilation of the biliary tree that most commonly involves the extrahepatic bile duct. According to the Todani system, there are five types of bile duct cysts (Figs. 7A, 7B, 7C, 7D, 7E, and 7F).

Type 1: Choledochal Cyst

Type 1 bile duct cysts account for 80% to 90% of all bile duct cysts and are characterized by fusiform dilation of the extrahepatic bile duct (Fig. 7A). It is theorized that choledochal cysts form as the result of reflux of pancreatic secretions into the bile duct via an anomalous junction of the common bile and pancreatic ducts. The classic triad of jaundice, abdominal pain, and mass is not commonly seen in adult patients. Because the cyst should be resected completely to prevent associated complications, such as ascending cholangitis, cystolithiasis, and malignant transformation [4], accurate determination of the length of the extrahepatic bile duct involved by the cyst is crucial in surgical planning. MRCP is an effective imaging technique for diagnosis and preoperative evaluation of bile duct cysts [5] (Figs. 8A and 8B). On initial imaging, obstructive biliary dilation should be excluded. In contrast to obstruction that results in dilation of the intra- and extrahepatic bile ducts, type 1 bile duct cysts show dilation of the extrahepatic bile duct with little, if any, dilation involving intrahepatic ducts. The caliber of the duct located above and below the cyst is usually normal.

Type 2: Diverticulum

Type 2 bile duct cysts account for 3% of all bile duct cysts and represent a true diverticulum. At imaging, type 2 bile duct cysts are seen as saccular outpouchings arising from the supraduodenal extrahepatic bile duct or the intrahepatic bile ducts (Fig. 7B).

Type 3: Choledochocele

Choledochoceles account for 5% of all bile duct cysts and represent protrusion of a focally dilated, intramural segment of the distal common bile duct into the duodenum (Fig. 7C). Although choledochoceles may manifest in adults with episodic abdominal pain, jaundice, nausea, and vomiting, many are detected incidentally in patients without symptoms referable to the biliary tract. MRCP and direct cholangiography reveal a bulbous dilation of the intramural portion of the bile duct bulging into the duodenum (Figs. 9A, 9B, and 9C). Choledochoceles may be successfully managed with endoscopic sphincterotomy, surgical excision, or both, in symptomatic patients.
Fig. 3 46-year-old woman undergoing surgery for liver donor transplantation. Intraoperative cholangiogram reveals dorsocaudal branch (arrows) of right hepatic duct emptying into left hepatic duct. Common bile duct (CBD), duodenum (D), and biliary bifurcation (bif) are noted.
Fig. 4 57-year-old woman with abdominal pain. Coronal thick-slab MR cholangiopancreatography shows right aberrant biliary duct (open arrows) draining into common hepatic duct. Cystic duct remnant is noted (curved arrow). Common bile duct (CBD), pancreatic duct (P), duodenum (D), and biliary bifurcation (bif) are noted.
Fig. 5 44-year-old woman with chronic pancreatitis. Coronal thick-slab MR cholangiopancreatography shows cystic duct (arrows) with low insertion (arrowhead) into distal common bile duct (cbd). Gallbladder (GB) is noted.
Fig. 6 40-year-old woman with bile leak after cholecystectomy. ERCP image shows cystic duct remnant (arrows) insertion into aberrant right hepatic duct (open arrows). Biliary bifurcation (bif) and common bile duct (CBD) are noted.
Fig. 7A Classification of bile duct cysts. Type 1, fusiform dilation (arrows) of common bile duct.
Fig. 7B Classification of bile duct cysts. Type 2, diverticulum (arrows) originating from common bile duct.
Fig. 7C Classification of bile duct cysts. Type 3, choledochocele (arrows).
Fig. 7D Classification of bile duct cysts. Type 4A, fusiform dilation of extrahepatic bile duct (arrows) and cystic dilation of intrahepatic biliary ducts (open arrows).
Fig. 7E Classification of bile duct cysts. Type 4B, multiple cystic dilations involving only extrahepatic bile duct (arrows).
Fig. 7F Classification of bile duct cysts. Type 5, cystic dilation (arrows) of the intrahepatic bile ducts only (Caroli's disease).

Type 4: Multiple Communicating Intraand Extrahepatic Duct Cysts

Type 4 biliary cysts represent the second most common type of bile duct cysts (10%) and are subdivided into subtypes A and B (Figs. 7D and 7E). Type 4A is characterized by fusiform dilation of the entire extrahepatic bile duct with extension of dilation of the intrahepatic bile ducts (Figs. 10A and 10B). Type 4B cysts are extremely rare and are seen as multiple cystic dilations involving only the extrahepatic bile duct.
Fig. 8A 50-year-old woman with jaundice. Coronal thick-slab MR cholangiopancreatography shows large type 1 bile duct cyst of extrahepatic bile duct (arrows). Right and left hepatic ducts are slightly distended (open arrows). Gallbladder (GB) and duodenum (D) are noted.
Fig. 8B 50-year-old woman with jaundice. Percutaneous transhepatic cholangiogram of same patient shows large type 1 bile duct cyst of extrahepatic bile duct containing contrast material (arrows). Slightly distended left and right hepatic ducts are noted (open arrows). Percutaneous needle (Perc), gallbladder (GB), and duodenum (D) are noted.
Fig. 9A 30-year-old man with periampullary mass seen on CT performed at another institution. Coronal oblique, thin-slab MR cholangiopancreatography (MRCP) image reveals oval-shaped high-signal-intensity contour (arrows) of distal common bile duct (CBD) protruding into duodenum (D), which represents choledochocele. Pancreatic duct (P) is noted.
Fig. 9B 30-year-old man with periampullary mass seen on CT performed at another institution. Axial T2-weighted image shows fluid-filled structure (arrows) protruding into duodenum (D). Pancreas (P) is noted.

Type 5: Caroli's Disease

Caroli's disease is a rare form of congenital biliary cystic disease manifested by cystic dilations of intrahepatic bile ducts that may diffusely involve the right and left hepatic ducts [6]. There is an association with benign renal tubular ectasia and other forms of renal cystic disease. ERCP and MRCP are used to establish the diagnosis. The primary cholangiographic feature of Caroli's disease is cystic dilation of the intrahepatic bile ducts seen in conjunction with a normal extrahepatic bile duct (Figs. 11A and 11B). This finding can also occur in association with intrahepatic bile duct strictures, stones, abscess, and manifestations of cirrhosis.
Fig. 9C 30-year-old man with periampullary mass seen on CT performed at another institution. ERCP image shows contrast-filled and oval-shaped structure (arrows) of distal common bile duct (CBD) protruding into duodenum (D), which represents choledochocele seen at MRCP and MR.
Fig. 10A 54-year-old man with abdominal mass and pain. Sonogram shows aneurysmal dilation of extrahepatic bile duct (arrows). Dotted line between arrows represents measurement line of sonogram.
Fig. 10B 54-year-old man with abdominal mass and pain. Coronal oblique, thin-slab MR cholangiopancreatography shows marked dilation of extrahepatic bile duct (solid arrows) and left main intrahepatic duct (open arrow).

Biliary Abnormalities Associated with Situs Anomalies

In situs inversus, the bile ducts are reversed— right to left—as are the other abdominal organs (“mirror image”) [7] (Figs. 12A and 12B). In situs ambiguous with polysplenia, the stomach and multiple small spleens usually lie in the right upper quadrant of the abdomen, and the gallbladder and the liver lie close to midline (Fig. 13). It is important to be aware of these entities because situs anomalies may create a confusing clinical and imaging picture, especially in the setting of diseases such as acute cholecystitis [7].
Fig. 11A 70-year-old woman with jaundice. Coronal oblique, thin-slab MR cholangiopancreatography shows multiple cystic dilations of intrahepatic bile ducts (arrows) consistent with Caroli's disease. Common bile duct (CBD), duodenum (D), and pancreatic duct (P) are noted.
Fig. 11B 70-year-old woman with jaundice. Coronal T2-weighted image shows multiple fluid-containing foci (arrowheads) in papillae of kidneys, indicating renal tubular ectasia (medullary sponge kidney). Saccular dilations of intrahepatic bile ducts (arrows) are noted.
Fig. 12A 65-year-old man with hepatitis B. Coronal thick-slab MR cholangiopancreatography shows situs inversus with gallbladder (GB), common bile duct (CBD), and second portion of duodenum (D) in left upper quadrant, and pancreatic duct (P) coursing toward right. High signal intensity focus in right upper quadrant (S) represents fluid in stomach.
Fig. 12B 65-year-old man with hepatitis B. Axial CT shows gallbladder (GB) and liver (L) located in left upper abdomen, and stomach (S) and spleen (Sp) in right upper abdomen. Splenic vein (v) is noted.
Fig. 13 42-year-old woman with polysplenia syndrome. Axial CT scan shows two spleens (Sp) to right of midline. Gallbladder (GB) is near midline and stomach (S) is on right. Pancreas is foreshortened (P).
Fig. 14A 49-year-old woman with pancreatitis. Coronal oblique, thin-slab MR cholangiopancreatography shows 2.4-cm-long common channel (double arrows) distal to union of distal common bile duct (CBD) and pancreatic duct (P). Major papilla (open arrow) and duodenum (D) are noted. Mid common bile duct is focally dilated, which is consistent with type 1 bile duct cyst (Cyst).
Fig. 14B 49-year-old woman with pancreatitis. Schematic of A. The double arrows represent long common channel from orifice of papilla (open arrow) to union of distal common bile duct (CBD) and pancreatic duct (P). Mid common bile duct is focally dilated, which is consistent with type 1 bile duct cyst (Cyst). Duodenum is noted (D).

Anomalous Junction of the Biliary Ductal System with Pancreatic Duct

Anomalous junction of the pancreaticobiliary ductal system is usually defined as a union of the distal common bile duct and the pancreatic duct proximal to the duodenum whose length is greater than 1.5 cm [8]. Anomalous junction of the pancreaticobiliary ductal system has been reported in association with cholangiocarcinoma, gallbladder carcinoma, choledocholithiasis, and chronic pancreatitis. In this entity, pancreatic secretions can reflux into the common bile duct and can result in the development of a bile duct cyst (type l) [4, 5] (Figs. 14A and 14B).

Footnote

Address correspondence to J. Yu.

References

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Suhocki PV, Meyers WC. Injury to aberrant bile ducts during cholecystectomy: a common cause of diagnostic error and treatment delay. AJR 1999; 172:955-959
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Marcos A. Right lobe living donor liver transplan tation: a review. Liver Transpl 2000; 6:3-20
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Huang TL, Cheng YF, Chen CL, Chen TY, Lee TY. Variants of the bile ducts: clinical applica tion in the potential donor of living-related he patic transplantation. Transplant Proc 1996; 28:1669-1670
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Visser BC, Suh I, Way LW, Kang SM. Congenital choledochal cysts in adults. Arch Surg 2004; 139:855-860; discussion 860-862
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Irie H, Honda H, Jimi M, et al. Value of MR cho langiopancreatography in evaluating choledochocysts. AJR 1998; 171:1381-1385
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Levy AD, Rohrmann CA, Murakata LA, Lonergan GJ. Caroli's disease: radiological spectrum with pathologic correlation. AJR 2002; 179:1053-1057
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Fulcher AS, Turner MA. Abdominal manifestations of situs anomalies in adults. RadioGraphics 2002; 22:1439-1456
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Nomura T, Shirai Y, Sandoh N, Nagakura S, Hatakeyama K. Cholangiographic criteria for anomalous union of the pancreatic and biliary ducts. Gastrointest Endosc 2002; 55:204-208

Information & Authors

Information

Published In

American Journal of Roentgenology
Pages: 1536 - 1543
PubMed: 17114548

History

Submitted: May 5, 2005
Accepted: August 31, 2005

Keywords

  1. biliary system
  2. congenital
  3. CT
  4. developmental anomalies
  5. MRI

Authors

Affiliations

Jinxing Yu
All authors: Department of Radiology, VCU Health Systems, Virginia Commonwealth University, 1250 East Marshall St., Richmond, VA 23298.
Mary Ann Turner
All authors: Department of Radiology, VCU Health Systems, Virginia Commonwealth University, 1250 East Marshall St., Richmond, VA 23298.
Ann S. Fulcher
All authors: Department of Radiology, VCU Health Systems, Virginia Commonwealth University, 1250 East Marshall St., Richmond, VA 23298.
Robert A. Halvorsen
All authors: Department of Radiology, VCU Health Systems, Virginia Commonwealth University, 1250 East Marshall St., Richmond, VA 23298.

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