CASE 9407 Published on 16.09.2011

Annular pancreas and choledochal cyst in an adult patient

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Ankur Arora, Shivendra Singh*, Amar Mukund, Shalini Thapar, Deepak Jain

Department of Radiodiagnosis and *Gastro-surgery, Institute of Liver and Biliary Sciences, New Delhi, India

Patient

32 years, male

Categories

Area of Interest Abdomen ; No Imaging Technique

No Procedure ; No Special Focus ;

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Clinical History

A 32-year-old male patient presented with mild gradually progressive jaundice. His total, direct and indirect bilirubin levels were 1.59, 0.71 and 0.88 mg/dl respectively. Alkaline phosphatase was elevated (294 IU/L) and albumin/globulin ratio altered (0.5). SGOT and SGPT were within the normal range.

Imaging Findings

In view of his laboratory parameters, abdominal ultrasonography was suggested to rule out choledocholithiasis. Ultrasonogram revealed marked dilatation of the common bile duct (CBD). No overt intraductal calculus was seen. Subsequent MRCP revealed marked fusiform dilatation of the extra-hepatic (supra-pancreatic) CBD with mildly prominent right and left hepatic ducts. Smooth tapering of the distal intra-pancreatic CBD was seen. No intra-ductal filling defect was evident. No obvious common channel of the distal common duct and main pancreatic duct (MPD) could be demonstrated on MRCP. MPD was normal in course and calibre. Additionally seen was a rind of pancreatic tissue completely encircling the second part of duodenum representing an annular pancreas. The duodenum above it showed sudden transition in calibre and was mildly dilated. MRCP, however, failed to reveal any duct encircling the duodenum.

Discussion

Annular pancreas is an uncommon congenital anomaly which can either present in neonatal period-early childhood, or may go unnoticed till adulthood. It has a reported incidence of 1 in 20,000 of the population. It is characterised by the presence of pancreatic tissue encircling either completely or incompletely the second-part of duodenum. The exact etiopathogenesis is debatable; however, as per the most widely accepted theory, it is the early division of the ventral pancreatic-anlage into 2-segments which is believed to be responsible. Complete annular pancreas most commonly presents as proximal small-bowel obstruction frequently during neonatal period which can be associated with other congenital anomalies such as Down syndrome, Hirschprung’s disease, oesophageal atresia. In contrast, incomplete or partial annular pancreas mostly remain asymptomatic till adulthood; and is mostly incidentally detected on abdominal imaging performed for other reasons. It is best seen on axial-fat-saturated T1-weighted MR images as rind of pancreatic parenchyma encircling the duodenum in a complete or incomplete/partial fashion. MRCP can in addition show associated with other pancreatobiliary anomalies such as pancreas divisum, anomalous junction of the pancreatic and common bile ducts or choledochal cyst.

Choledochal cyst is a relatively common congenital anomaly of the biliary tree characterised by cystic dilatation of the extrahepatic bile ducts, with or without dilatation of the intrahepatic biliary ducts. The most widely accepted aetiological explanation is an anomalous junction of the pancreatic and the distal common bile duct (CBD) resulting in reflux of pancreatic enzymes into the biliary-tree with resultant weakening, scarring and dilatation of the CBD wall. Choledochal cysts can remain clinically silent until adulthood or may manifest symptoms much later in life. The classic clinical triad of choledochal cyst described includes pain, jaundice and/or a palpable upper abdominal lump. As per the Todani et al classification there are 5 types of choledochal cysts. Type-I cyst represents 80-90% of all the choledochal cysts. Type-Ia refers to cystic dilatation of the CBD; type-Ib is focal segmental dilatation and type- Ic is fusiform dilatation of the duct. Type-II cysts are true diverticulae from the CBD. Type-III cysts refer to the cystic dilatation of the intraduodenal portion of the CBD (choledochocele accounting for 1 to 5%). Type-IV cysts (approximately 10%) are of two types. Type-IVA has multiple intra-aswell as extrahepatic cysts and type-IV B has only multiple extrahepatic cysts. Type-V cysts involve only the intrahepatic ducts and may be focal or diffuse (termed as Caroli's disease).

Differential Diagnosis List

Annular pancreas with choledochal cyst

Biliary stricture with upstream dilatation (DD of choledochal cyst)

Duodenal stenosis (DD of annular pancreas)

Final Diagnosis

Annular pancreas with choledochal cyst

References

[1] Mortelé KJ, Rocha TC, Streeter JL, Taylor AJ (2006) Multimodality imaging of pancreatic and biliary congenital anomalies. Radiographics 26:715-31 (PMID: 16702450)

[2] Martin-Hirsel A, Cantrell CJ, Hulka F (2004) Antenatal diagnosis of a choledochal cyst and annular pancreas. J Ultrasound Med 23:315-8 (PMID: 14992371)

[3] Benya EC (2002) Pancreas and biliary system: imaging of developmental anomalies and diseases unique to children. Radiol Clin North Am 40:1355-62 (PMID: 12479715)

[4] Yu J, Turner MA, Fulcher AS, Halvorsen RA (2006) Congenital anomalies and normal variants of the pancreaticobiliary tract and the pancreas in adults: part 1, Biliary tract. AJR Am J Roentgenol 187:1536-43 (PMID: 17114548)

[5] Yu J, Turner MA, Fulcher AS, Halvorsen RA (2006) Congenital anomalies and normal variants of the pancreaticobiliary tract and the pancreas in adults: part 2, Pancreatic duct and pancreas. AJR Am J Roentgenol 187:1544-53 (PMID: 17114549)

[6] Rizzo RJ, Szucs RA, Turner MA (1995) Congenital abnormalities of the pancreas and biliary tree in adults. Radiographics 15:49-68; quiz 147-8 (PMID: 7899613)

[7] Todani T, Watanabe Y, Narusue M, Tabuchi K, Okajima K (1977) Congenital bile duct cysts: classification, operative procedure and review of thirty seven cases including cancer arising from choledochal cyst. Am J Surg 134:263-9 (PMID: 889044)

Case information

URL:	https://www.eurorad.org/case/9407
DOI:	10.1594/EURORAD/CASE.9407
ISSN:	1563-4086

Figure 1

2D-MRCP

2D-MRCP reveals marked fusiform dilatation of the common duct with prominence of right and left hepatic ducts.

Marked fusiform dilatation of the common duct can be seen along with prominent right and left hepatic ducts. Abrupt but smooth tapering of the distal CBD is seen on this 2D-MRCP image.

Intra-pancreatic CBD shows abrupt but smooth tapering.

Figure 2

Coronal FIESTA MRI

Choledochal cyst can be well appreciated on this coronal T2-weighted FIESTA sequence. Pancreatic parenchyma can be seen on the right side of duodenum (arrow).

Pancreatic parenchyma can be seen on either side side of duodenum (arrow).

Pancreatic parenchyma can be seen encircling the duodenum (arrow).

Figure 3

Axial fat saturated T1-weighted MRI

Pancreatic parenchyma is seen encircling the second part of duodenum which is opacified with orally administered diluted gadolinium-based contrast medium.