Choledochal Cyst

Background: Choledochal cysts are congenital anomalies of the bile ducts. They consist of cystic dilatations of the extrahepatic biliary tree, intrahepatic biliary radicles, or both. The first anatomic study of a choledochal cyst in the Western literature was published by Vater and Ezler in 1723. Douglas is credited with the first clinical report in a 17-year-old girl who presented with intermittent abdominal pain, jaundice, fever, and a palpable abdominal mass.

Alonso-Lej et al provided the first systematic description of choledochal cysts in 1959 based on the clinical and anatomic findings in 96 cases. The resultant system classified choledochal cysts into 3 types and outlined therapeutic strategies for each. The classification system for choledochal cysts was further refined by Todani et al and currently includes 5 major types (Todani, 1977).

For excellent patient education resources, visit eMedicine's Liver, Gallbladder, and Pancreas Center. Also, see eMedicine's patient education article Gallstones.

Pathophysiology: The pathogenesis of choledochal cysts is most likely multifactorial. Some aspects of the disease are consistent with a congenital etiology, others with a congenital predisposition to acquiring the disease under the right conditions.

The vast majority of patients with choledochal cysts have an anomalous junction of the common bile duct with the pancreatic duct (anomalous pancreatobiliary junction [APBJ]). An APBJ is characterized when the pancreatic duct enters the common bile duct 1 cm or more proximal to where the common bile duct reaches the ampulla of Vater. Miyano and Yamataka have demonstrated such APBJs in more than 90% of their patients with choledochal cysts.

The APBJ allows pancreatic secretions and enzymes to reflux into the common bile duct. In the relatively alkaline conditions found in the common bile duct, pancreatic proenzymes can become activated. This results in inflammation and weakening of the bile duct wall. Severe damage may result in complete denuding of the common bile duct mucosa.

From a congenital standpoint, defects in epithelialization and recanalization of the developing bile ducts during organogenesis and congenital weakness of the duct wall have also been implicated. The result is formation of a choledochal cyst.

Frequency:

• In the US: Choledochal cysts are relatively rare in the United States and Western countries. Reported rates range from 1 case per 2 million live births to 1 case per 100,000-150,000 live births.

• Internationally: Choledochal cysts are more prevalent in Asia than in the United States and other Western countries. More than 33% of all reported cases are from Japan, where Miyano and Yamataka have reported a prevalence of as high as 1 case per 1000 population.

Mortality/Morbidity: The morbidities associated with choledochal cysts are age dependent. Infants and children are frequently noted to develop pancreatitis, cholangitis, and histologic evidence of hepatocellular inflammation and damage.

The most worrisome complication of choledochal cysts is cholangiocarcinoma. The reported rate of this malignancy in patients with choledochal cysts is 9-28%.

Race: Persons of Asian ancestry, especially those of Japanese descent, may have a somewhat increased risk. No other ethnic or racial predilection has been well described.

Sex: Choledochal cysts are more prevalent in females. The female-to-male ratio is approximately 3-4:1.

Age: Most patients with choledochal cysts have some clinical manifestation of the disease in childhood. Approximately 67% of pediatric patients with choledochal cysts have signs or symptoms related to the cyst before they are aged 10 years. Note that a choledochal cyst may not become clinically apparent until the patient is an adult.

Anatomy: The following discussion of the pertinent anatomy of choledochal cysts is based on the Todani classification published in 1977.

• Type I choledochal cysts are most common and represent 80-90% of the lesions. Type I cysts are dilatations of the entire common hepatic and common bile ducts or segments of each. They can be saccular or fusiform in configuration. Type I cysts can be divided into 3 subclassifications, including type IA cysts, which are typically saccular and involve the entire extrahepatic bile duct (common hepatic duct plus common bile duct) or the major portion of the duct.

• Type II choledochal cysts are relatively isolated protrusions or diverticula that project from the common bile duct wall. They may be sessile or may be connected to the common bile duct by a narrow stalk.

• Type III choledochal cysts are found in the intraduodenal portion of the common bile duct. Another term used for these cysts is choledochocele.

• Type IVA cysts are characterized by multiple dilatations of the intrahepatic and extrahepatic biliary tree. Most frequently, a large solitary cyst of the extrahepatic duct is accompanied by multiple cysts of the intrahepatic ducts. Type IVB choledochal cysts consist of multiple dilatations that involve only the extrahepatic bile duct.

• Type V choledochal cysts are defined by dilatation of the intrahepatic biliary radicles. Often, numerous cysts are present with interposed strictures that predispose the patient to intrahepatic stone formation, obstruction, and cholangitis. The cysts are typically found in both hepatic lobes. Occasionally, unilobar disease is found and most frequently involves the left lobe.

Clinical Details: Some patients do not present until adulthood. In many adult patients, subclinical bile duct inflammation and biliary stasis have been ongoing for years. Adults with choledochal cysts can present with hepatic abscesses, cirrhosis, recurrent pancreatitis, cholelithiasis, and portal hypertension.

The clinical history and presentation of a patient with a choledochal cyst varies with the patient's age. Overt dramatic signs and symptoms are more common in infancy, whereas manifestations are more subtle and protean in adulthood.

Infants frequently come to clinical attention with jaundice and the passage of acholic stools. If this presentation occurs in early infancy, a workup to exclude biliary atresia may be initiated. Infants with choledochal cysts can have a palpable mass in the right upper abdominal quadrant; this may be accompanied by hepatomegaly.

Children in whom the condition is diagnosed after infancy present with a different clinical constellation, which includes intermittent bouts of biliary obstructive symptoms or recurrent episodes of acute pancreatitis. Children in whom biliary obstruction is present may also have jaundice and a palpable mass in the right upper quadrant. The correct diagnosis is occasionally more difficult in children with pancreatitis. Often, the only clinical symptoms are intermittent attacks of colicky abdominal pain. Eventually, an analysis of biochemical laboratory values reveals elevations in amylase and lipase levels. This leads to the proper diagnostic imaging workup.

Adults with choledochal cysts frequently complain of vague epigastric or right upper quadrant abdominal pain. Indeed, the most common symptom in adults is abdominal pain. A classic clinical triad of abdominal pain, jaundice, and a palpable right upper quadrant abdominal mass has been described in adults with choledochal cysts, although this is found in only 10-20% of patients. Cholangitis can be part of the clinical presentation in adult patients with biliary obstruction.

Choledochal cysts not appearing until adulthood can be associated with a number of serious complications resulting from long-standing biliary obstruction and recurrent bouts of cholangitis. These include cholelithiasis, severe pancreatitis, hepatic abscesses, hepatic cirrhosis, and portal hypertension.

Preferred Examination: According to Miyano and Yamataka, the preferred initial radiologic examination in the diagnostic workup of a choledochal cyst is abdominal ultrasonography (US). US is noninvasive, it involves no radiation exposure, and its findings are sensitive and specific for the diagnosis. Clinically, these features make sense as well. Patients with choledochal cysts most often have symptoms referable to the hepatobiliary system, and most US operators are familiar with the anatomy of this area.

Once a preliminary diagnosis is made using US, other supportive studies may be ordered, including abdominal CT, magnetic resonance (MR) imaging (MRI), or magnetic resonance cholangiopancreatographic (MRCP) examinations. These studies demonstrate the cyst with more precise anatomic detail. In addition, important anatomic relationships to surrounding structures are better defined than with other modalities.

Limitations of Techniques: US is an excellent choice for initial imaging, but it does have limitations, including operator experience; misinterpretation of cysts as the gallbladder or other structures; and decreased sensitivity in the presence of overlying bowel gas, pancreatitis, cholangitis, or other inflammatory processes. Differentiating a choledochal cyst from a hepatic cyst, hepatic abscess, acute fluid collection, or pancreatic pseudocyst may be difficult.

If the diagnosis is unequivocal with US, other supportive studies are usually required to adequately plan the surgical approach. If doubt remains despite sonographic evidence suggestive of the diagnosis, CT scanning or MRI/MRCP provides the details needed to confirm the diagnosis.

 

Choledochal Cyst

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

---

Clinical Presentation:
The classic clinical triad, which is seen in 25% of patients is jaundice, abdominal pain, and a right upper quadrant mass. Fifty percent of patients present by 10 years old.

Etiology/Pathophysiology:
A focal dilatation of the common and hepatic bile ducts of unknown etiology. Type 1 is the most common. Type 1A is dilation of the common bile duct below the cystic duct, Type 1B is dilation of the common and hepatic ducts. Type 2 is focal eccentric dilation of the common bile duct. Type 3 is a distal dilation of the common bile duct within the wall of the duodenum, a choledochocele. Caroli's disease, which is a cystic dilation of the intra and extrahepatic biliary ducts is sometimes classified as a Type 4 but is not really related to choledochal cyst. Complications include biliary cirrhosis and portal hypertension from prolonged extrahepatic obstruction, cyst rupture, stone formation, and cancer late in life.

Pathology:
Not applicable

Imaging Findings:
Ultrasound shows a large cystic lesion in the porta hepatis that is distinct from the gallbladder and communicates with dilated intrahepatic biliary ducts. DISIDA demonstrates normal hepatic extratction of tracer, excretion of tracer into the biliary system, and accumulation of tracer in the cyst.