Choledochal Cyst - Causes, Symptoms, and Treatment

Introduction

Bile is a yellow-green liquid produced and secreted by the liver. It comprises bile salts, phospholipids, conjugated bilirubin, cholesterol, electrolytes, and water. Bile is produced by the liver cells called hepatocytes and transported to the bile ducts present inside the liver. Then bile travels to the gallbladder through a larger duct called the common bile duct present outside the liver. The gallbladder stores the bile juice until required. The main functions of bile are to help in the absorption and digestion of fats and to remove waste products from the body. When the body needs bile for digestion, the gallbladder contracts and releases bile into the cystic duct, which then opens into the common bile duct and reaches the duodenum of the small intestine. The hormone cholecystokinin stimulates the release of bile from the gallbladder during digestion. The total volume of bile produced per day is 600 ml.

What Is a Choledochal Cyst?

A choledochal cyst is a congenital and rare anomaly of the bile duct that connects the liver to the gallbladder and the duodenum and transports bile. There are cystic (sac-like pockets of tissue filled with fluid, pus, or air) enlargements or dilations in the bile ducts outside and inside the liver. The cystic swelling prevents bile flow from the liver to the small intestine, causing the backflow of bile into the liver. This results in liver problems. It also blocks the bile transportation from the pancreas to the small intestine leading to inflammation of the pancreas called pancreatitis. Choledochal cysts are more common in females than males and occur in approximately 1 in 100,000 to 150,000 babies. Babies with choledochal cysts are at a higher risk of developing bile duct cancer during adulthood.

What Are the Causes of Choledochal Cysts?

There are several theories of the etiology of choledochal cysts, a few of which are:

• Anomalous Pancreaticobiliary Junction: It is a condition of the abnormal junction of bile and pancreatic ducts.

• Congenital: Some studies suggest that the cyst formation is simply congenital with no specific reason.

• Duplication Cysts: Some theories suggest that biliary duplication cysts are related to type Ⅱ cysts and biliary or duodenal duplication cysts are related to type Ⅲ cysts.

• Ductal Plate Malformation: Type Ⅴ cyst formation is linked to the abnormal remodeling of the ductal plates.

What Are the Signs and Symptoms of Choledochal Cysts?

Although choledochal cysts are present from birth, they may be diagnosed later. This is because the symptoms also start later from infancy or early childhood.

• Only 30% of patients with choledochal cysts exhibit a classical triad of symptoms that includes:

  • Palpable abdominal mass in the upper right region of the belly.

  • Intermittent abdominal pain in the upper right quadrant.

  • Jaundice (yellowish coloration of skin and eyes).

• Other symptoms include:

  • Nausea and vomiting.

  • Fever.

  • Cholangitis-inflammation of the bile duct.

  • Pancreatitis-inflammation of the pancreas.

  • Pale or clay-colored stools.

What Are the Types of Choledochal Cysts?

The location of the choledochal cyst can be either intrahepatic or extrahepatic. There are many classification systems for choledochal cysts. But the Todani classification done in 1977 is the most commonly and widely used classification by doctors. According to the Todani classification, there are five types of choledochal cysts which are listed below.

• Type Ⅰ - This type accounts for 50% to 80% of all cysts occurring in the common bile duct.

• Type Ⅱ - About 2% of cases are of this type, where diverticular dilation develops anywhere throughout the extrahepatic duct. Diverticular dilation is a small sac-like bulge formed on the outer wall of the duct.

• Type Ⅲ - It represents 1.4% to 4.5% of cysts, knowns as choledochocele. They are cystic dilation of the distal common bile duct inside the duodenum (first part of the small intestine).

• Type Ⅳ - This type accounted for 15% to 35% of all cysts present as multiple dilations and decided into two subtypes type ⅣA which involves cysts of both the intrahepatic and extrahepatic biliary ducts, and type ⅣB, which means cysts only extrahepatic ducts have cystic swellings.

• Type Ⅴ - This comprises 20% of cysts, which are cystic dilations of only the intrahepatic biliary ducts. This type is called Caroli’s disease.

How Is a Choledochal Cyst Diagnosed?

There are no specific laboratory tests for choledochal cysts. The major diagnostic methods include:

• Computerized Tomography Scan: The CT scan can identify cysts in the liver, pancreatic duct, and distal common bile duct more accurately than an ultrasound scan. It also helps in planning surgery such as segmental lobectomy.

• Ultrasonography: Some choledochal cysts can be identified during a prenatal ultrasound. But it can also be found during the postnatal ultrasound. So it is usually the initial imaging method.

• Endoscopic Retrograde Cholangiopancreatography: This is a combination of endoscopy and fluoroscopy used to both diagnose and treat bile duct and pancreatic duct cysts. But it is invasive, uses ionizing radiation, and leads to other complications. It can be used to perform endoscopic sphincterotomy.

• Magnetic Resonance Cholangiopancreatography: It is the gold standard method of diagnosis with the highest sensitivity rate of 90% to 100%. It has the advantages of being noninvasive, not using ionizing radiation, and not causing any associated complications. In addition, it can detect conditions like cholangiocarcinoma and choledocholithiasis (gallstones).

• Technetium-99 Hepatobiliary Iminodiacetic Acid Scan: This imaging procedure uses a radioactive tracer material that is injected into the bloodstream to identify how bile travels from the liver to the intestine and the associated structural abnormalities on its way. It has a high sensitivity rate while diagnosing type Ⅰ choledochal cyst. It can also detect the rupture of a cyst and its leakage.

What Is the Treatment of Choledochal Cysts?

The treatment of choledochal cysts depends on the type of cyst and its extent. Each cyst type has variations in treatment approaches. But as a thumb rule, all cysts are removed, and normal bile flow is restored.

• Early Surgical Excision: The cysts are removed in neonates to help early recovery and restoration of liver functions to avoid complications in later years.

• Roux-en-Y Hepaticojejunostomy or Hepaticoduodenostomy: It is a surgical procedure performed to bypass the bile duct and directly connect the liver to the jejunum or duodenum.

• Diverticulectomy: Type Ⅱ and Ⅲ cysts are treated by simple surgical removal of the cyst or the diverticulitis and blocking the diverticular attachment.

• Liver Surgery: Liver resection or liver transplantation is the treatment for type Ⅴ cysts.

What Are the Complications of Choledochal Cysts?

• Malignancy.

• Ascending cholangitis.

• Portal hypertension.

• Stricture formation.

• Pancreatitis.

• Cystolithiasis.

• Infection.

• Liver cirrhosis.

• Gastrointestinal obstruction.

• Stone and sludge formation.

Conclusion

A choledochal cyst is a precancerous lesion. It should be diagnosed early in life to lower the risk of cancer, and appropriate treatment with a proper investigation should be delivered. The prognosis of this cyst is excellent with complete cyst excision and poor with cancer development. Therefore, it is vital for an interprofessional approach of pediatricians, pediatric gastroenterologists, pediatric surgeons, pathologists, radiologists, and oncologists to treat the condition successfully.