Choledochal Cyst

Introduction
Figure 1 shows what the normal bile duct system looks like. Bile, which is made by the cells of the liver, is collected in tiny ducts (tubes). It drains out of the liver in successively larger ducts to the point where one large duct drains each of the two lobes of the liver, finally emptying into the common bile duct, which empties into the upper intestine. When bile is made in the liver it is first stored in the gall bladder, which connects to the common bile duct, and the gallbladder empties when fat enters the intestine.

Bile contains digestive enzymes as well as the breakdown products of old red blood cells, which can no longer fulfill their function. When there is any disturbance in bile flow, liver damage may result. If there is a blockage, bile builds up in the blood and the patient becomes jaundiced with a yellow color to the eyes and skin.

Figure 1. The drawing shows the normal arrangement of the gallbladder and bile ducts below the level of the liver. This is in contrast to the drawing shown in figure 2.

If there is partial blockage, mild jaundice may result, as well as infection and inflammation, which is termed cholangitis. Repeated cholangitis leads to scarring within the liver, which is called cirrhosis, and eventually a bad outcome for the patient. Choledochal cyst is one of the common abnormalities that affect the biliary system of children who present with complaints of upper abdominal pain and jaundice.

Types of Choledochal Cysts
Figure 2 shows the five common types of choledochal cyst, but numerous variations and combinations of these types of cysts are also occasionally encountered. Type I, which is dilation (ballooning) of the common bile duct, represents 85 to 95 percent of cases. In this form of abnormality, the gallbladder usually enters the choledochal cyst itself, which is really a very dilated common bile duct. The right and left bile ducts and the ducts within the liver are usually normal in size in these instances, and the common duct itself is greatly enlarged.

Figure 2. These are the five common types of choledochal cyst malformations. The ability to show these clearly by cholangiography (injecting dye into the bile ducts) has made it possible to plan appropriate operative treatment

Type II choledochal cyst is a diverticulum (outpouching) abnormality, although the common bile duct itself is normal.

Type III choledochal cyst is a localized area of dilation within the duodenum or pancreas and the rest of the biliary tree is usually normal. There is almost always some degree of narrowing or blockage in these cases. Pain, in particular, is characteristic of type III choledochal cyst.

Type IV choledochal cyst is a variation of type I in which the ducts within the liver are enlarged. Type V choledochal cysts have a normal bile duct system outside the liver with dilation of the large ducts within the liver.

In general, when a choledochal cyst is diagnosed in the newborn, there is very little inflammation (reaction) of the bile ducts or the liver. However, in older children sufficient time has passed for there to have been repeated bouts of cholangitis, in which case there may be extensive inflammatory reaction within the entire biliary tree and the liver. Surgical correction is more difficult in the latter.

Stones have been seen in teenage and older patients within a choledochal cyst and the ducts within the liver, but usually only sludge has been noted in younger patients. Most infants have a complete blockage at the level of the duodenum, but older patients usually have an open common bile duct.

In like fashion, newborn infants with choledochal cyst have normal livers whereas older children may show signs of cirrhosis, which may in turn block venous blood flow coming from the intestine resulting in high pressure and sometimes serious bleeding, a condition referred to as portal hypertension. Additionally, in instances where patients have had portions of a choledochal cyst in place for long periods, 10 to 15 percent of patients may develop cancers.

Why Do Choledochal Cysts Develop?
The etiology of choledochal cyst in its various forms of presentation is not precisely known. However, the so-called “common channel theory” stands out as the most likely explanation.

Figure 3. A.) This shows the normal relationship between the common bile and pancreatic ducts as they join and pass through the wall of the duodenum (left) and the abnormal relationship (right) in which there is a common channel that permits destructive digestive pancreatic enzymes to enter and damage the common bile duct. B.) This dye injection of the bile and pancreas ducts shows the typical picture of an abnormal pancreaticobiliary duct junction in association with a choledochal cyst (arrow) (from O’Neill JA: Choledochal cyst. Curr Prob Surg 24:6, 1992)

Figure 3 shows a drawing of a normal entry point of the common bile duct and main pancreatic duct into the duodenum. In almost all instances of choledochal cyst there is an abnormal arrangement of the pancreatic and bile duct junction in which the junction is high above the level of the muscle in the wall of the duodenum which controls the direction of flow within these ducts.

With an abnormal pancreaticobiliary duct junction, there is free-flow of pancreatic juice into the common bile duct extending up to the level of the liver. In the fetus, certain of the digestive enzymes in pancreatic juice may damage the wall of the forming common bile duct resulting in duct dilation (enlargement) and a downstream blockage. The reason for the abnormal pancreaticobiliary junction seen in patients with choledochal cyst is likely to be based on genetic or hereditary factors as is noted below.

Typical Presentation
In all reported series, most of the patients with types I and IV choledochal cysts have been female with a ratio of four females to one male, but the number of males to number of females in types II, III and V has been noted to be equal. This large number of females is suggestive of a sex-linked genetic problem.

Additionally, choledochal cysts and bile duct abnormalities are much more common in Oriental than in other populations, another suggestion that hereditary factors are involved. On the other hand, these abnormalities do not tend to run in families from one child to the next, so multiple factors must be involved.

With regard to age at time of presentation, there are two distinct groups of patients. The first group is younger than six months of age and the choledochal cyst usually is found in the first month of age. These infants present with a clinical picture of complete bile duct blockage and jaundice. At other times, newborns have evidence that bile is flowing into the intestines, but this stops after three to six weeks of age, indicating that the blockage has increased over time. Infants usually present with jaundice (yellow skin and eyes), but pain is not usually evident. Numerous infants have been noted to have a choledochal cyst in utero on prenatal ultrasound, but following birth it appears that jaundice takes one to three weeks to become evident.

The so-called adult form of choledochal cyst presents in patients older than six months of age and usually older than two years. In the latter group of patients, the most common form of presentation has been abdominal pain and jaundice, and occasionally a soft mass can be felt in the right upper area of the abdomen. It is thought that the cause of abdominal pain in these patients is related to stretching of the dilated duct or to cholangitis. On rare occasions, patients present with signs of pancreatitis (inflammation of the pancreas), but this is usually associated with cholangitis.

Whereas the clinical picture is fairly clear cut in the newborn group, the picture is more confusing and difficult to interpret in older patients as the symptoms associated with choledochal cyst are similar to those ordinarily associated with gallstones. Since the introduction of laparoscopic cholecystectomy for gallstones, a number of patients with choledochal cysts have been discovered when routine x-rays with injection of dye (contrast) into the bile duct system have been taken at the time of operation. Since older patients show signs of increasing inflammation and liver damage with a choledochal cyst, it seems evident that the earlier a diagnosis is made and treatment undertaken, the better it is for the patient.

Diagnosis

Blood tests
No blood test is specific for the diagnosis of choledochal cyst; rather studies indicate the status of the patient and any possible complications. Since the most common sign of a choledochal cyst is jaundice, the main finding is an increase in bilirubin in the blood. At times, in cases of severe cholangitis or longstanding biliary blockage, patients may show signs of a decrease in blood clotting.

Radiology studies
The only sure way to diagnose a choledochal cyst is some form of radiology study. As mentioned previously, prenatal ultrasound frequently identifies a choledochal cyst that may be present in the fetus. Immediately following birth, the most helpful initial screening study is abdominal ultrasound since this study is capable of showing the entire bile duct system within and outside the liver, the gallbladder, and the pancreas.

Most people feel that in the newborn with jaundice and an enlarged biliary tree outside the liver shown on ultrasound, no further diagnostic studies are required preoperatively. In addition to ultrasound examination in the newborn, some physicians also like to obtain a nuclear medicine scan or a CT scan (Figure 4).

Figure 4. Choledochal cyst identified on CT scan. The bile duct (white with arrows) should be less than one tenth as large as it is.

Because of the subtle clinical presentation of most older patients, this age group may require additional studies, particularly because of the intermittent nature of jaundice seen in this age group. In older patients, injections of the bile duct system with dye (contrast) either through the skin or by means of a scope placed in the duodenum while performing x-rays or special MRI techniques may be needed.

Figure 5. A type I choledochal cyst during removal (arrows). Note the narrowing of the cyst near the bottom (arrow head)

In addition to demonstrating the common channel frequently seen in these patients, these studies are particularly useful for defining the precise anatomy so that planning an appropriate operation can be undertaken. At the time of operation, x-rays using a contrast injection directly into the bile duct system (operative cholangiogram) are usually performed in order to confirm all of the preoperative findings. It usually does not take very long to obtain all of the preoperative information necessary to plan operative correction. While diagnostic studies are being accumulated, measures are undertaken to make sure the patient is in the best possible preoperative condition. Antibiotics are usually a part of this preparation.

Treatment
The only effective approach to treatment is surgical correction (Figure 5, 6 and 7). Other measures only serve the purpose to maximize the patient’s condition before operation is.

Figure 6. A Type I choledochal cyst (arrow) at removal.

Figure 7. Choledochal cyst being removed showing the cyst and the gallbladder.

The treatment of choledochal cyst has changed through the years as information has been accumulated about how patients have fared following each given approach. Additionally, improved diagnostic techniques and surgical and anesthetic management as well as pre- and postoperative care have permitted approaches that were not possible many years ago.

Figure 8 shows the three surgical approaches that were used in the past as well as the one preferred today by all surgeons who deal with this problem. Cyst-duodenostomy or joining of the choledochal cyst, which was left in place, to the duodenum has been abandoned since long-term follow-up indicated that patients treated this way were not protected from cholangitis and subsequent cirrhosis

Figure 8: This drawing shows the various options available for the surgical management of choledochal cyst. The method shown on the right, complete cyst removal with drainage into a specially constructed limb of intestine is preferred.

Roux-en-Y cyst-jejunostomy or drainage of the cyst into a specially constructed intestinal arrangement for drainage of bile has worked long-term in a few patients while others have developed cholangitis. However, the long-term risk of cancer is still present as the cyst itself remains in place. Therefore, the operation is no longer performed.

The preferred procedure today is to completely remove (excise) the dilated duct system outside the liver and to drain the common bile duct as it exits the liver into a loop of intestine designed to prevent backflow of intestinal contents into the liver, thus protecting the patient from cholangitis. As long as no blockage occurs at the level of the suture line between the bile duct system and the intestine, these patients do very well long term.

Numerous variations of this procedure have been designed through the years, but in the end a simple joint (anastomosis) between the bile duct at the liver and an appropriately long limb of intestine to prevent the intestinal contents from regurgitating back up has stood the test of time. Patients with other forms of choledochal cyst are managed as the anatomy dictates but the principles are similar.

Does surgery make a difference?
The vast majority of patients treated for types I, II, III and IV choledochal cyst who do not have preexisting cirrhosis or portal hypertension appear to do well long-term. However this is dependent upon long-term follow-up of the patient to ensure that the site of drainage of the bile duct system into the intestine remains open and that any postoperative episodes of cholangitis are investigated thoroughly and appropriately treated. Ultrasound is a helpful study in this respect. Fortunately, there is little or no mortality associated with operative correction unless the patient has advanced liver disease at presentation. In the absence of complications, patients would appear to have a normal lifespan as well.