they can be defined as aneurysmal dilatation of intra- and extra - hepatic ducts and are classified according to the involved segment of the biliary tree .
the incidence of choledochal cysts is increasing due to the improvements in imaging techniques and choledochal cysts of adults get clinical attention due to various complications such as cholangitis , bile stasis , and malignancies of the biliary tree . at times , choledochal cysts may grow very large and differentiation from other cystic masses of the abdomen can be challenging . the correct diagnosis of choledochal cysts in pre - operative patients is essential since reconstruction of the biliary trees is mandatory in these patients . here , we discuss the imaging features and correlate them to gross specimen in a young female with type 1a giant choledochal cyst , which manifested as a huge cystic mass in the abdomen of unclear etiology .
a previously healthy , 19-year - old female patient presented to the emergency room with intermittent abdominal pain and jaundice .
ultrasound ( us ) images showed a large septated cystic and tubular structure in the abdomen [ figure 1a ] . computed tomography ( ct )
scan was performed and it revealed a large , convoluted tubular and cystic structure in the right upper quadrant with associated dilated intrahepatic ducts [ figures 1b  d ] .
the long diameter of the cystic structure was over 23 cm with associated dilatation of intrahepatic ducts .
no solid , enhancing components were noted in the wall of this cystic mass . because of
the compressive effect by this mass , the pancreatic head was not clearly seen and relationship between this mass and pancreatic duct was unclear .
19-year - old female with intermittent abdominal pain and jaundice diagnosed with type 1a giant choledochal cyst .
( a ) ultrasound scan axial view shows a large cystic mass ( * ) and dilated bile ducts ( b ) .
the mass was very large and the relationship of the biliary tree to the mass was not clear on ultrasound .
( b ) computed tomography ( ct ) scan , axial view of portal venous phase demonstrates dilated intrahepatic ducts ( b ) .
( c ) computed tomography scan axial view at a lower level than 1b shows a large cystic mass ( * ) at the porta hepatis .
( d ) coronal reformatted computed tomography image delineates a huge cystic mass in right upper quadrant ( * ) .
magnetic resonance cholangiopancreaticography ( mrcp ) demonstrated a huge septated cystic mass appearing to communicate with the intrahepatic ducts [ figure 2a ] .
differential diagnoses include gallbladder hydrops , duplication cyst , mesenteric or peritoneal cyst , and a huge choledochal cyst . in view of biliary dilatation
19-year - old female with intermittent abdominal pain and jaundice diagnosed with type 1a giant choledochal cyst .
a ) axial and b ) coronal heavily t2-weighted images show a large cystic mass ( * ) , gallbladder ( g ) and intrahepatic ducts ( b ) .
roughly 2.5 l of bilious fluid was aspirated with subsequent decompression of the biliary tree .
explorative laparotomy was scheduled and performed and severe dilatation of common bile duct and relatively small - sized gallbladder was found on surgery .
intraoperative finding was a massive , thick walled cystic lesion measuring over 20 cm in maximum dimension arising from the common bile duct .
the cystic lesion involved entire extra - hepatic ducts and there was no stricture or soft - tissue masses .
the gross specimen and histopathological examination confirmed the diagnosis of a giant choledochal cyst , type ia according to todani classification [ figure 3 ] .
a schematic diagram shows the location of the cystic mass and its relationship to surrounding structures [ figure 4 ] .
19-year - old female with intermittent abdominal pain and jaundice diagnosed with type 1a giant choledochal cyst .
a ) the gross specimen obtained after excision of the cystic mass shows a massive , thick walled cystic lesion ( arrows ) measuring over 20 cm in maximum dimension arising from the left hepatic duct and confirms the diagnosis of a giant choledochal cyst .
( b ) h and e stained tissue ( 400 ) , shows the dilated bile duct with columnar epithelial lining , and dense fibrous wall ; scattered smooth muscle and elastic fibers are present ( arrows ) ; mild infiltration of chronic inflammatory cells are also seen ( arrowheads ) .
there is no evidence of dysplasia or malignancy schematic diagram shows the location of the choledochal cyst and resection margin ( dotted lines ) .
choledochal cysts are very rare lesions seen in people in western countries . in asian population
the incidence is increasing due to the use of the state - of - the - art imaging techniques such as multidetector ct ( mdct ) or mrcp .
patients with choledochal cysts can have several complications and are considered as a high risk group for cholangiocarcinomas and surgical excision of the entire cyst is recommended .
us is the primary imaging tool for evaluation , however , this modality has its limitations .
evaluating the entire biliary tree is difficult due to limited field of view and poor overview when compared with cross - sectional imaging modalities .
therefore , for accurate diagnosis , cross - sectional imaging modalities with a larger field of view are superior to us .
mdct can obtain volumetric data sets and multiplanar reformations ( mpr ) are readily available .
furthermore , mrcp is the preferred imaging modality for the correct diagnosis of biliary anomalies .
mrcp is non - invasive and can be obtained without the use of contrast agents .
2d or 3d mrcp images clearly delineate biliary anomalies . in adults patients , differential diagnosis for cystic masses at porta hepatis other than choledochal cysts include hepatic cysts , biliary cystadenomas , duplication cysts of the duodenum and colon , mesenchymal and peritoneal cysts and pseudocysts or cystic tumors from the pancreas .
. however , huge masses can compress adjacent structures and therefore intrahepatic ducts can be dilated simply due to mass effect . in those cases
, mrcp can also be helpful to make a correct diagnosis because mrcp can delineate the relationship between cystic masses and adjacent structures .
the most common type of choledochal cyst is type i and accounts for more than 75% of all choledochal cysts .
type i cysts involve the extrahepatic bile ducts and can be divided into three subtypes ; ia ( cystic ) , ib ( segmental ) and ic ( fusiform ) .
type i cyst should be differentiated from type iva cysts which involve both intra- and extra - hepatic ducts .
, there was no stricture between intra- and extra - hepatic ducts and intrahepatic duct dilatation was continuous to the dilated extra - hepatic duct .
furthermore , after percutaneous transhepatic biliary drainage ( ptbd ) insertion , intrahepatic ducts are seen collapsed and the diagnosis of type ia choledochal cyst can be made .
one of the strongly suggested etiologies is reflux of pancreatic juice into the common bile duct and anomalous pancreaticobiliary ductal union ( apbdu ) can facilitate this phenomenon .
actually , strong association of presence of apbdu and choledochal cysts was reported by many authors . however
, a case report of choledochal cyst in a 15-week - old fetus may refute this theory ; i.e. , 15-week - old fetus does not have pancreas tissue with exocrine function .
however , high incidence of choledochal cysts in patients with apbdu can not be ignored .
though endoscopic retrograde cholangiopancreaticography was considered as the gold standard for diagnosing abnormalities of the biliary tree and pancreatic ducts , mrcp is also excellent , non - invasive imaging modality for delineating and diagnosing congenital anomalies of pancreatic ducts and biliary trees including apbdu .
however , in our case , apbdu was not clearly demonstrated on mrcp because the choledochal cyst was too large and pancreas head was markedly compressed .
direct cholangiography via ptbd was not helpful also because the cystic mass was too large and filling of the pancreatic duct with contrast material was nearly impossible .
therefore , mdct might be the primary imaging modality for huge cystic mass in the abdomen and mrcp can be a problem - solving tool .
as mentioned above , adult patients with choledochal cysts have a higher risk of cholangiocarcinomas and other complications are commonly encountered in these patients . therefore , entire excision of choledochal cysts is recommended treatment option in most cases . in our case ,
mrcp or mdct also can be helpful for the planning of surgical excision and essential to pre - operative evaluation .
we report a giant , type ia choledochal cyst presenting with a massive septated cystic mass in the abdomen in a young adult patient .
state of the art cross - sectional imaging with mdct or mrcp can help to reach the correct diagnosis and formulate a robust surgical plan .
 choledochal cysts are uncommon congenital anomalies of the biliary tree , commonly presenting in infancy , generally in the 1st year of life . 
 presentation in adult life is less common , accounting for 20% of cases . a 19-year - old female patient presented to the emergency department with severe abdominal distension , a palpable abdominal mass , mild jaundice and low grade fever . 
 ultrasound , computed tomography ( ct ) and magnetic resonance imaging of the abdomen showed a massive septated cystic lesion filling the entire abdomen with a significant mass effect on surrounding structures . 
 origin of the lesion was unclear and diagnosis included a giant mesenteric or duplication cyst , massive gallbladder with hydrops , biliary cystadenoma and giant choledochal cyst , among others . 
 final diagnosis was a type ia choledochal cyst with massive asymmetric cystic dilatation of the extra - hepatic segments of the left hepatic duct with asymmetric dilatation of the right hepatic duct . 
 patient had an uneventful recovery after resection of the entire extrahepatic cyst and roux - en - y hepaticojejunostomy at the level of the hilum . in this article , we correlate ct and mri findings to gross and histopathological findings of this giant todani 's type ia choledochal cyst . 
INTRODUCTION
RADIOLOGIC FEATURES
PATHOLOGIC FEATURES
DISCUSSION
CONCLUSION