What is Choledochal Cyst?
A choledochal cyst (CC), often considered a cystic expansion of the bile duct outside the liver, now has a broader meaning. It’s now referred to as a biliary cyst, which includes similar cysts found inside the liver. These cysts can appear in one or multiple portions of both the bile ducts inside and outside the liver. In 1959, researchers first grouped choledochal cysts into three types based on their location. By 1977, this classification was expanded to five types, which is the one used the most today. However, some experts argue over this classification, saying that each type of cyst behaves differently and is treated differently. They suggest a system based around how the cysts develop rather than simply their physical location.
Choledochal cysts are an unusual condition that might lead to cancer, adding to the complexity of their diagnosis. The symptoms are vague and could be diverse. Health professionals need to be alert for choledochal cysts when assessing patients complaining of yellow skin (jaundice), stomach pains, or any detectable lump in the belly region. Due to the unspecific nature of symptoms, the right imaging tests are vital for a accurate diagnosis. If the cyst is identified and removed on time, the outcomes are usually successful, with 89% of patients remaining problem-free and over 90% surviving for at least five years following the operation. Therefore, it’s essential to detect and manage the condition early on for the best outcome.
What Causes Choledochal Cyst?
The exact cause of a choledochal cyst, a type of digestive system cyst, is not clear, leading to a number of theories. One prevalent theory, proposed by Babbitt, suggests that the cyst develops from a faulty junction between the pancreatic and biliary ducts. When these ducts merge abnormally, it allows the pancreatic and biliary juices to mix and flow backward. This triggers pancreatic enzymes, causing increased pressure and leading to swelling, inflammation, and damage of the biliary ducts, which can potentially result in cancer.
Support for this theory comes from the evidence of high levels of amylase, a digestive enzyme, along with a few other enzymes identified in the bile within these cysts. Even some animal studies corroborate this theory by showing that artificially creating a faulty junction results in cyst formation. However, there are criticisms to this theory pointing out that this junction issue was found in only 50-80% of cases, and in some cases identified before birth, there was no evidence of backward flow. Plus, some suggest that newborns cannot produce enough pancreatic enzymes to cause this damage.
Another set of theories propose that these cysts are caused by inborn genetic issues. Similar to the development of conditions called achalasia and Hirschsprung’s disease, one theory states that having too few cells in the main bile duct can cause it to dilate or expand.
These theories mainly apply to types I and IV of choledochal cysts. For Type II and III, the probable cause leans more towards duplicated bile ducts or duplicated bile and duodenal ducts. A blockage at a digestive duct junction is speculated to cause localized expansion.
For type V, known as Caroli disease, it’s believed that the disease may occur due to a failure in the remodeling of ductal plates. It’s associated with a condition called biliary atresia, which may share a common cause related to the dysfunction of ductal plates. Caroli disease is also linked with a few types of genetic kidney diseases.
Risk Factors and Frequency for Choledochal Cyst
Choledochal cysts, or CCs, are more prevalent in certain regions, with two-thirds of cases in Asia happening in Japan. This disease is primarily seen in the Asian population, with around 1 in 1,000 babies born having it. However, in Western countries, the number drops dramatically to only 1 in 100,000 to 150,000 babies. Even though they are less common in countries like the United States and Australia, these places still report around 1 in 13,500 and 1 in 15,000 live births, respectively, being affected.
- Two-thirds of choledochal cyst cases in Asia occur in Japan.
- Approximately 1 in 1,000 babies born in the Asian population are affected.
- In western countries, the incidence drops to around 1 in 100,000 to 150,000 live births.
- In the United States and Australia, the numbers are around 1 in 13,500 and 1 in 15,000 live births respectively.
- The majority of CCs of type I and IV are seen in females, with a female to male ratio of 4:1 or 3:1.
The reason for the high incidence of these cysts in Asian populations and women remains unclear.
Signs and Symptoms of Choledochal Cyst
Choledochal cysts (CCs), are mostly diagnosed in children, with only 25% of cases being discovered in adults. It’s worth noting that the number of adults diagnosed with CCs has been growing recently. The characteristic trio of symptoms for CCs consists of abdominal pain, a noticeable abdominal lump, and jaundice (yellowing of the skin and eyes). However, these classic symptoms only occur together in about 20% of cases. In children, about 85% showcase two out of these three symptoms, usually the abdominal lump and jaundice. In contrast, only 25% of adults show this combination of symptoms. Babies under one year may exhibit symptoms like jaundice, pale stools, and vomiting. Among adults, abdominal pain is the most common symptom of CCs.
- Abdominal pain
- Bump in the abdomen
- Jaundice (yellowing of the skin and eyes)
- Pale stools (in babies below one year)
- Vomiting (in babies below one year)
Testing for Choledochal Cyst
There are no specific laboratory tests that can confirm the presence of choledochal cysts. Instead, doctors use several types of imaging tools to diagnose these cysts.
Ultrasound is often the first imaging method used. This painless, non-invasive technique can identify choledochal cysts in the region of the porta hepatis, which is located near the liver. While quite accurate at detecting these cysts, ultrasound may not determine their cause or identify their link to the pancreaticobiliary junction in all cases.
Another imaging tool that doctors might use is a computed tomography cholangiography, or a CT scan. This tool can provide a better look at areas that an ultrasound might miss, such as dilatation of intrahepatic ducts, the distal common bile duct, and the pancreatic duct. This permits it to be more accurate for certain types of cysts. It’s also helpful in surgical planning by identifying the extent of dilation.
A Technetium-99 Hepatobiliary Iminodiacetic Acid scan, or Technetium-99 HIDA scan, can differentiate between choledochal cysts and biliary atresia, a blockage in the ducts that carry bile from the liver, in newborns. It can also detect spontaneous rupture of the cysts.
Magnetic Resonance Cholangiopancreatography (MRCP) is known as the gold standard for diagnosing choledochal cysts. This method is especially popular because it doesn’t expose the patient to radiation, and it doesn’t come with risk factors like bleeding or perforation. Moreover, it can identify certain complications related to choledochal cysts. However, it might not be able to detect minor ductal abnormalities or small type III CCs.
Lastly, there is the Endoscopic Retrograde Cholangiopancreatography (ERCP), which provides the highest diagnostic accuracy for these cysts. It does come with certain risks due to its invasive nature and exposure to radiation. For this reason, its use is limited. Nontheless, it can also be used to provide treatment in specific situations, which makes it particularly significant.
Treatment Options for Choledochal Cyst
Choledochal cysts are treated depending on their type and the extent of liver and bile duct disease. Generally, all cysts should be removed and the flow of bile should be restored.
Early surgical removal of these cysts is advised. Based on a study, patients diagnosed with CCs and who had the cyst removed in their first month of life were found to have a lower risk of liver fibrosis and their liver functions returned to normal faster compared to those who undergo surgery at a later time.
For type I and type IV Cyst, the treatment involves fully removing the choledochus (bile duct) and restoring the flow of bile. This restoration can be done using either Roux-en-Y hepaticojejunostomy (HJ) or hepaticoduodenostomy (HD). There is ongoing debate over which restoration method is better, although several studies suggest a higher risk of stomach cancer due to bile reflux and bile duct cancer in HD compared to HJ cases. In fact, a review study noted a high rate of post-surgery reflux and gastritis in patients who underwent HD.
Previously, these cysts were treated by either external or internal drainage along with removal of the gallbladder. Now, it is recommended that these cases involve cyst excision due to the continued risk of cancer as well as other possible complications such as pancreatitis, inflammation of the bile ducts, and narrowing of the bile ducts.
The chance for type II and type III cysts transforming into cancer is lower. Type II cysts are managed by simply excising the cyst or wide removal of the diverticulum along with closure of the diverticular neck. For Type III cysts (choledochocele), treatment can be done in most cases by cutting the muscle controlling bile flow from the pancreas into the bile duct, especially in symptomatic or young patients without symptoms, along with a biopsy of the cyst lining to rule out abnormal growth and identify the type of lining the cyst has since cysts with biliary mucosal lining carry a higher risk of cancer. If the cyst is too large, it can be marsupialized during ERCP or through a transduodenal approach.
For Caroli disease (Type V CCs), management depends on the extent of the disease. If the disease is localized or affects one lobe of the liver, then a surgery to remove the affected liver segment is the best option. If the disease is widespread or affects both lobes and the patient has symptoms, then a liver transplant is recommended.
For patients with no cyst but an abnormal pancreatic-biliary junction, removal of the gallbladder is recommended due to the high risk for gallbladder cancer.
What else can Choledochal Cyst be?
There are different health conditions that can sometimes be mistaken for other diseases because they present similar symptoms. Some of these include:
- Liver cysts
- Duodenal atresia (a condition where the first part of the small intestine is not properly developed)
- Cysts in the mesentery or omentum (tissues that hold the abdominal organs in place)
- Duplication of the intestine (a condition where a part of the digestive tract is duplicated)
- Gallbladder duplication (a rare condition where there are two gallbladders)
- Ovarian cysts
It’s important for doctors to identify the exact condition to ensure proper treatment.
What to expect with Choledochal Cyst
A study by Ten Hove and his team revealed that out of 2904 cases of CC (choledochal cysts), 11% developed cancer. The outlook for patients who develop cancer is generally poor, with about 5% surviving after five years. It’s worth mentioning that the cancer risk in patients who only had a surgical drainage procedure, instead of removing the cyst entirely, was four times higher. This highlights the importance of early diagnosis and the right treatment for a better outcome.
On average, patients without a choledochal cyst developed cholangiocarcinoma (cancer) at an age of 65 years. In contrast, the average age was 49.5 years for those with a choledochal cyst. Therefore, it’s recommended that adults with symptom-free choledochal cysts should undergo complete surgical removal of the cysts.
The surgical removal of choledochal cysts generally portrays excellent results, with an 89% rate of no further complications and a 5-year survival rate above 90%. Post-surgery health issues and death are seen mostly in adults and are rare in children. Type IVA cysts show the highest rate of complications like stones in the liver ducts and scarring at the site of the surgical connection. Despite removing the cyst, the risk of developing cancer in bile ducts remains high, even after 15 years. Consequently, it is heavily advised to continuously monitor with blood tests and abdominal ultrasound scans.
Possible Complications When Diagnosed with Choledochal Cyst
Draining a choledochal cyst without surgical removal can potentially be dangerous because it has a high chance of leading to cancer. Even after the cyst is removed, there is a small risk of cancer, which means long term monitoring after the surgery is important. The likelihood of cancer after cyst removal is most common in types I and IV of choledochal cysts (CCs), while it’s less common in types II, III, and V.
Genetic changes that contribute to the development of bile duct cancer, including K-Ras and p53 mutations, are found in 60% of these cancers. People with an “abnormal pancreaticobiliary junction” (APBJ) might be at a higher risk, as the reflux of pancreatic juice leads to liver cell damage and can potentially trigger the growth of cancer cells. Another possible factor in cancer development is inducible nitric oxide synthase (iNOS), which might play a role in causing abnormal growth of the mucosal cells lining the bile ducts and thus lead to cancer.
Stricture
After surgery, there might be a narrowing of the bile duct, a condition known as a stricture. This could lead to various problems like bile stasis (stagnant bile), formation of gallstones, inflammation and infection of the bile duct, sudden inflammation of the pancreas (acute pancreatitis), long-standing inflammation of the mucosal lining (chronic mucosal inflammation), fibrosis (scar tissue), and, potentially, cancer. To lower the risk of stricture formation, during surgery, the surgeon ensures there is a sufficiently large opening (anastomosis) for smooth bile flow into the bowel.
Ascending Cholangitis
Ascending cholangitis, an infection of the bile duct, is a common complication of choledochal cysts. It happens due to the reflux of pancreatic juice and intestinal content into the bile duct. After surgery, the formation of a stricture or remaining debris in dilated intra-liver ducts can make bile stagnant, leading to gallstone formation and cholangitis. A choledochoscopy, an examination of the bile ducts, is performed during surgery to reduce the chances of gallstone formation and cholangitis by removing any stones from within the liver.
Sludge and Stone Formation
Formation of sludge (thickened bile) and gallstones can occur after surgery due to either a stricture or dilated liver ducts with leftover debris. It was found in past reports that post-surgery formation of gallstones within the bile duct (choledocholithiasis) happened in 25% of cases, while stone formation within the liver (hepatolithiasis) happened in 33% of cases.
Preventing Choledochal Cyst
A choledochal cyst is a rare, potentially cancerous abnormality that can be challenging to diagnose. This condition doesn’t always have clear symptoms, making it tricky for doctors to identify. Medical professionals should consider the possibility of a choledochal cyst when a patient experiences unexplained jaundice (yellowing of the skin and eyes), stomach pain, or a noticeable lump in the abdomen.
Because these symptoms can be somewhat vague and resemble other conditions, the correct imaging studies are vital for an accurate diagnosis. Complications linked with choledochal cysts include a wide range of issues, such as infections in the bile ducts (cholangitis), inflammation of the pancreas (pancreatitis), bile duct cancer (cholangiocarcinoma), and cirrhosis (scarring) of the liver and bile ducts.
Early detection and treatment of a choledochal cyst is important – removing the cyst has been shown to be highly effective. Therefore, if such a condition is suspected, it’s best to act promptly to confirm the diagnosis and commence treatment.