Chapter 1 of 8 · Fundamentals
Definition & etiology
Definition, Epidemiology, and Etiology of Choledochal Cysts
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What the experts said
Choledochal cyst is a congenital cystic dilation of the biliary tree.
Incidence of choledochal cysts in the Western world is about 1 in 100,000.
In Eastern Asia, choledochal cyst incidence is 1 in 13,000.
Choledochal cysts are three to four times more likely in females than in males.
There is no genetic predisposition to choledochal cysts, but some genes including PKD1 have been identified in limited studies for type 5 choledochal cysts.
The most common classification system for choledochal cysts was developed by a surgeon named Tadani in Japan and includes five types.
For types 1 and 4 choledochal cysts, the etiology is likely embryologic, relating to pancreaticobiliary duct junction (pancreaticobiliary malunion), which creates a long common channel of the pancreaticobiliary duct.
Reflux of pancreatic enzymes from the head of the pancreas back into the biliary tree causes inflammation, degeneration, and epithelial changes in types 1 and 4 choledochal cysts.
In type 5 choledochal cysts, genetic mutation might predispose to more diffuse dilation of both the intra- and extrahepatic biliary trees.
Type 1 choledochal cyst is a dilation of the extrahepatic common bile duct only, which can be fusiform or saccular.
Type 2 choledochal cyst is a small diverticulum off of the common bile duct.
Type 3 choledochal cyst is a choledochocele affecting the portion of the common bile duct in the wall of the duodenum.
Type 4a choledochal cyst consists of multiple cysts in both the intra- and extrahepatic biliary tree.
Type 4b choledochal cyst consists of multiple cysts in the extrahepatic biliary tree only.
Type 5 choledochal cyst is intrahepatic only and diffusely throughout, called Caroli's disease, which can be diffuse or limited to one lobe or one hemi-liver.
In younger children such as infants, choledochal cysts are often diagnosed incidentally on axial imaging or ultrasound for other causes.
In children, choledochal cysts often present with symptoms consistent with cholangitis, such as jaundice or fever.
Patients with choledochal cysts can have a palpable right upper quadrant mass.
The triad of jaundice, fever, and palpable right upper quadrant mass (Charcot's triad) is incredibly uncommon as a presentation of choledochal cysts.
Giant choledochal cysts in small children can perforate and present with biliary ascites.
Giant choledochal cysts can be diagnosed prenatally on week 20 ultrasounds.
Prenatally diagnosed choledochal cysts require fetal consultation at a fetal surgery center for establishment of care and counseling, because cystic biliary atresia must be ruled out postnatally.
A recent citation demonstrated that if a choledochal cyst was diagnosed prenatally and was larger than 4.5 centimeters at the 20-week anatomy scan, there was a higher rate of postnatal symptomatology, suggesting these patients may benefit from earlier intervention.
Differential diagnosis for a one-year-old presenting with jaundice includes problems with the pancreatic or biliary tree, stone disease (choledocholithiasis, cholelithiasis), gallstone pancreatitis, and choledochal cyst.
A one-year-old with jaundice is a little old for biliary atresia, which is usually considered in an infant.
Physical exam findings to look for in suspected choledochal cyst include jaundice or scleral icterus and, in younger children, a palpable abdominal mass.
Labs to check for suspected choledochal cyst include liver function tests (total, direct, and indirect bilirubin levels) and possibly a CBC to look for evidence of cholangitis or infection.
The major initial screening imaging test for choledochal cyst is an abdominal ultrasound.
Liver biopsy is not typically needed for older patients with reliable ultrasound imaging, but becomes critical in neonates or newborns to rule out cystic biliary atresia variant.
CT scan is commonly used for choledochal cyst workup because of the ease with which young children can be scanned.
MRCP is useful for choledochal cysts with hilar or intrahepatic disease to understand the extent of cystic change and to identify variant biliary anatomy, which occurs in 15 to 20% of patients.
ERCP can be used for both diagnostic and therapeutic purposes in choledochal cysts, depending on prior scan findings and the type of cyst.
There are no non-surgical treatment options for choledochal cysts.
Choledochal cysts require surgery due to the risk of recurrent cholangitis from biliary stasis and superinfection.
Type 1 and type 4 choledochal cysts with pancreaticobiliary malunion carry approximately an 8% lifetime risk of hepatobiliary malignancy, most specifically cholangiocarcinoma and gallbladder cancer.
Studies estimate the lifetime risk of malignancy in choledochal cysts to be anywhere from 6% to 30%.
Even after surgical resection of choledochal cysts, some studies suggest there is still about a 4% lifetime risk of malignancy, requiring lifelong surveillance.
If a patient with choledochal cyst presents with active infection, pancreatitis, or cholangitis, the best approach is to cool the patient off and treat the underlying process before scheduling surgery after sufficient recovery.
For incidentally found choledochal cysts, surgery should be scheduled sooner rather than later, when it makes sense for the family schedule.
Preoperative workup for choledochal cyst surgery includes laboratory values to ensure no other disease process is impairing liver function, and imaging (ultrasound and CT scan are often sufficient).
MRCP is recommended preoperatively if there is any question about the patient's anatomy or if the patient has a very proximal choledochal cyst or dilation into the hepatic ducts.
The surgical goal for choledochal cyst repair is complete excision of the cyst.
For type 1 and type 4 choledochal cysts, the goal is to remove as much of the duct as possible, taking the duct all the way down behind or into the head of the pancreas to where it tapers, to avoid leaving remnant cyst.
For type 1 and type 4 choledochal cysts, biliary drainage reconstruction often includes a Roux-en-Y hepaticojejunostomy, but a hepaticoduodenostomy is also an option.
Type 2 choledochal cyst can be treated by simple removal of the diverticulum at its neck with repair of the common bile duct.
Type 3 choledochal cyst (limited choledochocele) can be treated with ERCP and sphincterotomy.
If type 3 choledochal cyst involves the wall of the duodenum, transduodenal resection options exist, and biopsy of the choledochocele mucosa is important because biliary epithelium exposed to intestinal secretions could become malignant.
Type 5 choledochal cyst (Caroli's disease) management depends on disease extent: if limited to an anatomic part of the liver, resection may be appropriate; if diffuse throughout the liver without adequate functional remnant, transplantation may be necessary.
For choledochal cyst surgery in children less than 2 years old, a transverse incision or right subcostal incision is preferred; for older children, an upper midline incision is a viable option.
During choledochal cyst dissection, hepatic arteries are medial and the portal vein is posterior to the cyst.
Dr. Bondock performs an intraoperative cholangiogram through the gallbladder to understand where the tapering of the distal cyst occurs to avoid leaving remnant cyst.
For Roux-en-Y hepaticojejunostomy reconstruction, Dr. Bondock goes about 15 to 20 centimeters distal from the ligament of Treitz, performs a two-layer jejunojejunostomy, and does a hepaticojejunostomy with interrupted 5-0 or 6-0 Maxon suture.
Dr. Bondock performs the Roux-en-Y limb retrocolic and closes the small bowel mesentery.
For type 2 choledochal cyst, once the cyst is tapered down to the common bile duct, the neck is resected and the common bile duct is repaired with interrupted absorbable suture without leaving a T-tube.
Type 3 choledochal cyst can be approached endoscopically with ERCP and sphincterotomy, but if the lesion is large and obstructing the common duct, a transduodenal approach is needed, sometimes with preoperative stents to separate it from the duodenum.
Type 5 choledochal cyst (Caroli's disease) can be addressed surgically with liver resection if cystic disease is limited to one hemi-liver with adequate liver remnant and preserved biliary outflow, but if diffuse throughout the liver, liver transplantation may be necessary.
Postoperative considerations for choledochal cyst surgery include enteric drainage and awaiting return of bowel function.
Dr. Bondock typically places an NG tube postoperatively because of the new jejunojejunostomy, but tries to remove it the day after surgery.
Drains are placed postoperatively to assess for biliary leaks from the new hepatoenteric anastomosis and are typically removed once the patient is tolerating a regular diet.
Institutionally, patients are placed on a choleretic like Actigall and cholangitis prophylaxis (daily Bactrim) for three to six months after choledochal cyst surgery.