| disease | Biliary Duct Dilatation |
Biliary dilatation is a relatively common congenital biliary malformation. Previously, it was considered a lesion confined to the common bile duct and was thus referred to as a congenital choledochal cyst. The first case was reported by Vater in 1723, and Douglas provided a detailed description of its symptomatology and pathology in 1852. Over the past century, as understanding of this condition has deepened, recent biliary imaging has revealed that dilated lesions can occur in any part of the intrahepatic or extrahepatic bile ducts. There are various types based on location, morphology, and number, and the clinical manifestations also differ accordingly.
bubble_chart Epidemiology
This disease has a relatively high incidence in Asia and can occur at any age, with cases reported from newborns to the elderly. However, 75% of cases are diagnosed before the age of 10. It is more common in females, with a female-to-male ratio of 3:1. According to statistics from the Pediatric Hospital of Shanghai Medical University, the number of cases accounts for approximately 1:1000 of the total hospital admissions.
There are numerous theories regarding the cause of the disease, and no definitive conclusion has been reached so far. Most believe it is a congenital condition, while others argue that acquired factors also play a role in its formation. There are three main theories:
(1) **Congenital Anomaly Theory** It is proposed that during embryonic development, primitive bile duct cells proliferate into a solid cord-like structure, which later gradually hollows out and becomes patent. If certain epithelial cells overproliferate, excessive cavitation occurs during the hollowing and patency process, leading to dilation.
Some scholars believe that the formation of bile duct dilation requires the combined involvement of congenital and acquired factors. The congenital factor is the weakened development of the bile duct wall due to excessive proliferation and cavitation of bile duct epithelial cells during the embryonic period. Acquired factors, such as obstruction of the distal common bile duct secondary to pancreatitis or inflammation of the ampulla, along with subsequent increased intraductal pressure, ultimately lead to bile duct dilation.(2) **Abnormal Pancreaticobiliary Duct Junction Theory** This theory suggests that during embryonic development, the common bile duct and the main pancreatic duct fail to separate normally, resulting in an abnormally long common channel far from the ampulla of Vater. Additionally, the junction angle between the main pancreatic duct and the common bile duct is nearly perpendicular. Consequently, the pancreaticobiliary duct junction occurs outside the duodenal wall, where no sphincter exists, leading to the loss of sphincter function and mutual reflux of pancreatic juice and bile. When pancreatic secretion increases and pressure rises, the bile duct dilates. Recent endoscopic retrograde cholangiopancreatography (ERCP) studies have confirmed pancreaticobiliary duct junction in 90–100% of cases, along with elevated amylase levels in the dilated bile ducts. Animal experiments have shown that after pancreatic juice enters the biliary tract, the activity of amylase, trypsin, and elastase increases, which may be the primary cause of bile duct injury.
(3) **Viral Infection Theory** This theory proposes that biliary atresia, neonatal hepatitis, and bile duct dilation share the same etiology, being the result of inflammatory infections in the hepatobiliary system. Following viral infection, the liver undergoes giant cell transformation, and bile duct epithelial damage leads to lumen occlusion (biliary atresia) or weakened duct walls (bile duct dilation). However, support for this theory has declined in recent years.
Bile duct dilation can occur in any part of the intrahepatic or extrahepatic bile ducts, primarily presenting in two forms: cystic dilation and fusiform dilation. The common type is cystic dilation of the common bile duct, where the intrahepatic bile ducts are either not dilated or exhibit multiple cystic dilations, while the bile ducts distal to the dilation are significantly narrowed, with a diameter of only 1–2 mm. The site of bile duct stenosis is at the transition between the extra-pancreatic free common bile duct and the intra-pancreatic common bile duct. Due to obstruction, the increased pressure in the proximal bile duct leads to cystic dilation and thickening of the duct wall, with the confluence pattern being the bile duct → pancreatic duct type. In cases of fusiform dilation of the common bile duct, the intrahepatic bile ducts dilate toward the peripheral ducts, gradually tapering. The stenosis occurs at two sites: the confluence of the two ducts and the transition within the duodenal wall of the common pancreaticobiliary duct. Obstruction leads to grade I dilation of the common duct and fusiform dilation of the common bile duct, with the confluence pattern being the pancreatic duct → bile duct type. At the onset of the disease, bile duct dilation is pronounced, and symptoms alleviate slightly as the dilation diminishes.
Depending on the duration of the disease, the dilated duct wall may exhibit varying histopathological changes. In early cases, the duct wall shows reactive epithelial hyperplasia and thickening, composed of dense fibrotic inflammatory tissue with scarce smooth muscle and little or no intraluminal membrane coverage. The size of cystic dilation varies, with luminal fluid ranging from tens to over a thousand milliliters. The color of the bile within the cyst depends on the degree of obstruction; the bile may be viscous or thin and pale green. The bile may be sterile, but if infection occurs, it is often caused by Gram-negative bacteria. Rapid progression of inflammatory changes may even lead to perforation of the duct wall. Small pigmented stones may be found within the cyst. The malignancy rate increases with age, being less than 1% in pediatric cases but as high as 15% in adults. Histopathological studies confirm that adenocarcinoma is the most common type, and research on cyst wall tissue and immunohistochemistry has revealed that biliary epithelial metaplasia is associated with carcinogenesis.
Classification: There are multiple methods for classifying bile duct dilation. In 1959, Alonso-Lej proposed the first classification, which at the time was considered a condition limited to the common bile duct, dividing it into three types: cystic dilation of the common bile duct, diverticulum of the common bile duct, and terminal cystic dilation of the common bile duct. In 1971, Longmire et al., recognizing that the disease could involve the intrahepatic biliary system, further classified it into five types, adding multiple cystic dilations of the intra- and extrahepatic bile ducts and fusiform dilation of the intra- and extrahepatic bile ducts. Currently, the condition can be classified into three major types based on the location of dilation: intrahepatic, extrahepatic, and combined intra- and extrahepatic. It can also be classified by the number of dilations (single or multiple) and by the morphology of dilation (cystic, fusiform, diverticular, etc.). Associated abnormalities such as pancreatic duct anomalies, hilar stenosis, and stones can also be indicated. For example, multiple cystic dilations of the intrahepatic bile ducts with stones, fusiform dilation of the common bile duct with anomalous pancreaticobiliary junction, etc.
bubble_chart Clinical Manifestations
The initial symptoms of most cases occur between the ages of 1 and 3, but the final diagnosis is often delayed much later. The cystic type accounts for nearly one-quarter of cases within the first year of life, with the main clinical symptom being an abdominal mass, while the fusiform type mostly develops after the age of 1, primarily presenting with abdominal pain and jaundice.
Abdominal mass, abdominal pain, and jaundice are considered the classic triad of symptoms for this condition. The abdominal mass is located in the right upper quadrant, below the costal margin, and in large cases, it may occupy the entire right abdomen. The mass is smooth, spherical, and may have a distinct cystic elasticity. When the cyst is filled with bile, it may feel solid, resembling a tumor. However, the size often fluctuates; the mass enlarges during infection, pain, or an attack of jaundice and may slightly shrink after symptoms subside. Small bile duct cysts, due to their deep location, are difficult to palpate. Abdominal pain occurs in the mid-upper abdomen or right upper quadrant, varying in nature and intensity. Sometimes it manifests as persistent distending pain, while other times as colicky pain. Patients often adopt a knee-chest position and refuse food to alleviate symptoms. The onset of abdominal pain indicates obstruction at the bile duct outlet, increased pressure in the common duct, and possible reflux of pancreatic juice and bile, leading to symptoms of cholangitis or pancreatitis. Clinically, this is often accompanied by fever and sometimes nausea and vomiting. During symptom episodes, blood and urine amylase levels often rise. Jaundice is mostly intermittent and is often the main symptom in young children. The severity of jaundice is directly related to the degree of biliary obstruction. Mild cases may show no clinical jaundice, but with the onset of infection or pain, temporary jaundice may appear, with stools turning pale or gray and urine darkening. All these symptoms are intermittent. Due to poor drainage at the distal bile duct outlet, pancreaticobiliary reflux can trigger clinical episodes. When bile flows smoothly, symptoms alleviate or disappear. The intervals between episodes vary; some occur frequently, while others remain asymptomatic for long periods.
The classic triad of symptoms was once thought to be a definitive feature of this condition, but this is not the case. In early cases, the three major symptoms rarely appear simultaneously. Recent reports indicate that with increasing early diagnoses, more fusiform dilations are being detected, and fewer than 10% of cases exhibit the triad. Most cases present with only one or two symptoms. According to various reports, 60–70% of cases involve a palpable abdominal mass, and 60–90% involve jaundice. Although jaundice is clearly obstructive, many patients are initially misdiagnosed with hepatitis and only confirmed after repeated episodes. Abdominal pain also lacks typical manifestations, making it easy to misdiagnose as other abdominal conditions. Intra- and extrahepatic multiple bile duct dilations generally present symptoms later, only becoming apparent when intrahepatic cysts become infected.
Caroli's disease: Caroli first described cases of multiple cystic dilatations of the intrahepatic peripheral bile ducts in 1958. Hence, congenital intrahepatic bile duct dilatation is also known as Caroli's disease. It is classified as a congenital hepatic cystic fibrosis sexually transmitted disease, believed to be autosomal recessive, predominantly affecting males, and primarily seen in children and young adults. Early reported cases were not associated with hepatic fibrosis or portal hypertension. However, subsequent reports indicated that two-thirds of cases were accompanied by congenital hepatic fibrosis and often involved various renal pathologies, such as polycystic kidney disease. Advanced stage cases may progress to cirrhosis and portal hypertension. According to Sherlock's classification, it is divided into four categories: congenital hepatic fibrosis, congenital intrahepatic bile duct dilatation, congenital choledochal cyst, and congenital hepatic cyst, collectively referred to as hepatobiliary fibropolycystic disease. The hepatobiliary system may exhibit one or more of these conditions simultaneously. The disease is characterized pathologically and clinically by intrahepatic bile duct dilatation and gall fel stasis leading to cholangiolitis and stone formation. However, due to often atypical clinical symptoms, it can manifest at any age, with recurrent episodes of right upper abdominal pain, fever, and jaundice. During acute episodes, the liver is markedly enlarged but typically shrinks rapidly once infection is controlled and symptoms improve. Liver function impairment does not correlate proportionally with clinical symptoms. In the initial stage [first stage], the condition is frequently misdiagnosed as cholecystitis or liver abscess. If combined with congenital hepatic fibrosis or extrahepatic bile duct dilatation, among other fibrocystic sexually transmitted diseases, the symptoms become more complex, potentially including signs of cirrhosis, extrahepatic biliary obstruction, or urinary tract infections. Diagnosis is often delayed and usually confirmed only through surgical intervention. In recent years, the application of diagnostic methods such as ultrasound imaging and various cholangiography techniques has enabled accurate identification of intrahepatic lesions, leading to an increase in reported cases. However, this has also led to the inclusion of secondary biliary dilatations caused by other compressive factors, thereby complicating the conceptual definition of Caroli's disease.
The diagnosis of this disease can be considered based on the three main symptoms that intermittently appear from childhood, namely abdominal pain, abdominal mass, and jaundice. If the symptoms recur, the likelihood of diagnosis increases significantly. In cystic cases, the primary symptom is an abdominal mass, with an earlier onset age, and the diagnosis can be made through palpation combined with ultrasound examination. In fusiform cases, the main symptom is abdominal pain, and in addition to ultrasound examination, ERCP or PTC is required for an accurate diagnosis. Jaundice symptoms show no significant difference between the two types and can occur in both.
(1) Biochemical tests: Measurement of blood and urine amylase should be considered routine during episodes of abdominal pain, as it aids in diagnosis. It may indicate the possibility of concurrent pancreatitis or suggest abnormal pancreaticobiliary ductal junction, where high-concentration pancreatic amylase refluxes into the bile duct and directly enters the blood through the bile capillaries, leading to hyperamylasemia. Simultaneous measurements of total bilirubin, 5′-nucleotidase, alkaline phosphatase, and transaminase levels are elevated but return to normal during the stage of remission. In cases with a prolonged course, there may be hepatocellular damage, while asymptomatic cases show normal test results.
(2) B-mode ultrasound imaging: This method offers advantages such as direct visualization, tracking, and dynamic observation. When biliary obstruction leads to dilation, it can accurately detect the location and extent of fluid content, the degree and length of bile duct dilation, with a diagnostic accuracy rate exceeding 94%. It should be used as a routine diagnostic method.
(3) Percutaneous transhepatic cholangiography (PTC): This procedure is more likely to succeed in cases of biliary duct dilation, clearly displaying the intrahepatic bile ducts and their flow direction, and confirming the presence and extent of bile duct dilation. In cases of jaundice disease, it can differentiate the cause or site of obstruction and observe pathological changes in the bile duct wall and its interior, identifying the cause of obstruction based on imaging characteristics.
(4) Endoscopic retrograde cholangiopancreatography (ERCP): Using a duodenoscope, a contrast agent can be directly injected into the bile and pancreatic ducts via the papillary opening to determine the extent of bile duct dilation and the site of obstruction, as well as to visualize the length and abnormalities of the common pancreaticobiliary channel.
(5) Gastrointestinal barium meal examination: In cases of significant cystic dilation, it may show displacement of the duodenum to the left front, enlargement of the duodenal frame, and an arc-shaped indentation. Its diagnostic value has been largely replaced by ultrasound examination.
(6) Intraoperative cholangiography: During surgery, injecting a contrast agent directly into the common bile duct can display the entire imaging of the intra- and extrahepatic biliary system and the pancreatic duct, helping to understand the extent of intrahepatic bile duct dilation and the reflux between the pancreatic and bile ducts, which aids in selecting surgical methods and postoperative management.
Among the various examination methods mentioned above, ultrasound and generation and transformation tests are generally performed first in clinical practice. If an abdominal mass is palpated clinically, the diagnosis can be confirmed. If no mass is palpated but ultrasound suggests a suspected diagnosis, ERCP is required. If limited by equipment or age, PTC is performed, supplemented by other methods if necessary.
bubble_chart Treatment Measures
For the treatment of the symptomatic stage of attack, fasting for 2–3 days is adopted to reduce the secretion of gallbladder bile and pancreatic juice, thereby alleviating the pressure within the bile ducts. The use of antispasmodics to relieve pain, antibiotics for 3–5 days to prevent and control infection, along with corresponding symptomatic treatment, often achieves the goal of symptom relief. Given its frequent recurrence and various complications, timely surgical intervention is advisable.
(1) External drainage: Applied in select severe cases, such as severe obstructive jaundice accompanied by liver cirrhosis, severe biliary tract infection, or spontaneous bile duct perforation. Intermediate-stage [second-stage] management is performed after the condition improves.
(2) Internal drainage between the cyst and the intestine: For example, cystoduodenostomy, which has been associated with numerous complications such as recurrent cholangitis, anastomotic stricture, and stone formation. This has led to the adoption of cystojejunostomy with Roux-en-Y anastomosis, incorporating various anti-reflux designs in the intestinal loop. However, the issue of pancreaticobiliary maljunction persists, resulting in postoperative cholangitis or pancreatitis symptoms, sometimes necessitating reoperation. Additionally, there have been frequent reports of cyst wall carcinogenesis post-surgery, making this method rarely used today.
(3) Resection of the dilated bile duct and biliary reconstruction: In recent years, the preferred radical approach involves resecting the dilated bile duct segment and reconstructing the biliary tract to eliminate the lesion and achieve pancreaticobiliary diversion. Physiological biliary reconstruction can be performed by interposing the jejunum between the hepatic duct and duodenum, optionally adding an anti-reflux valve, or employing hepaticojejunostomy with Roux-en-Y anastomosis or hepaticoduodenostomy. These methods yield good results, provided the anastomosis is sufficiently large to ensure adequate gallbladder bile drainage.
As for the treatment of intrahepatic bile duct dilation secondary to extrahepatic bile duct dilation, the cylindrical dilation often resolves postoperatively. However, in cases of cystic dilation (mixed type), even with extrahepatic bile duct drainage, regardless of anastomosis size, intrahepatic bile duct stasis, infection, stone formation, or carcinogenesis may still occur. Therefore, most experts advocate partial hepatectomy for localized cystic intrahepatic dilation.
Treatment of Caroli disease: The primary approach involves prevention and management of cholangitis, with long-term use of broad-spectrum antibiotics, though outcomes are generally unsatisfactory. Due to the extensive nature of the disease, surgical treatment often fails. If the lesion is confined to one lobe, lobectomy may be performed, though reports indicate resectability in fewer than one-third of cases. The long-term prognosis is extremely poor.
Even after radical surgery for bile duct dilation achieves pancreaticobiliary diversion, some cases still frequently exhibit clinical manifestations of cholangitis or pancreatitis, such as abdominal pain and elevated serum pancreatic amylase. This is related to intrahepatic bile duct dilation and pancreatic duct abnormalities. Symptoms can be alleviated with fasting, anti-inflammatory therapy, antispasmodics, and cholagogues. Over time, the intervals between episodes gradually lengthen. Long-term follow-up shows satisfactory outcomes in 80% of cases.
The poor drainage or even obstruction of bile flow caused by cystic dilation of the affected area and relative stenosis of the distal bile duct is the root cause of complications. The main complications include recurrent ascending cholangitis, biliary cirrhosis, bile duct perforation or rupture, recurrent pancreatitis, stone formation, and ductal wall carcinogenesis.
In infancy, it should primarily be differentiated from biliary atresia and various types of hepatitis, and ultrasound examination can aid in diagnosis. In older children, it should be distinguished from chronic hepatitis. Often, during the first episode of jaundice, it may be misdiagnosed as epidemic hepatitis, especially for fusiform bile duct dilation or cases where a palpable mass is unclear. Longer-term observation and repeated ultrasound examinations along with generation and transformation measurements can often clarify the diagnosis.
