Congenital Bile Duct Cystic Dilatation

　　Congenital bile duct cystic dilatation can occur at any part of the intrahepatic and extrahepatic bile ducts, except for the gallbladder. Its causes include congenital and acquired factors, and the specific etiology is as follows:

　　1. Congenital Factors

　　1. Theory of Abnormal Proliferation of Bile Duct Epithelium

　　In 1936, Yotsuyanagi proposed the theory of congenital factors, which was accepted by most people. He believed that during the process of bile duct development in the embryonic period, the abnormal proliferation of epithelium led to uneven rates of epithelial proliferation in different parts of the bile duct and narrowing of the lower segment entering the duodenum, increasing bile duct pressure and causing the dilatation of the upper bile duct in the poorly developed area.

　　2. Theory of Abnormal Pancreatic and Bile Duct Communication

　　People have found through various means that the disease almost always exists with abnormal communication between the pancreatic and bile ducts. Miyano indirectly proved the abnormal communication by detecting the abnormally high amylase levels in bile during bile duct dilation.

　　3. Theory of Abnormal Nerve Development

　　In 1943, Shallow pointed out that the occurrence of congenital bile duct cysts has a defect in nerve cells, similar to the changes in Hirschsprung's disease. Yang Hongwei and others found through histological research on the nerve distribution at the distal end of the common bile duct in normal children and fetuses that the abnormal decrease in nerve distribution in the distal narrowed segment of congenital bile duct cysts is a primary lesion. Spastic stricture at the distal end of the bile duct is one of the causes of the disease, which is a congenital developmental abnormality. Abnormal communication between the pancreatic and bile ducts may coexist with the abnormal development of nerve endings at the distal end, resulting in spastic stricture. The pressure of pancreatic juice secretion is higher than the pressure within the bile duct, leading to persistent reflux, destroying the bile duct wall, and the combined action of both forms bile duct cysts. In recent years, some scholars believe that viral infections of bile duct epithelium, such as hepatitis B antigens, can also cause luminal obstruction or weakened bile duct walls, leading to cystic deformities, bile duct atresia, and other conditions.

　　2. Acquired factors

　　Some scholars believe that bile duct cysts, especially adult-type bile duct cysts, are mainly due to complete or incomplete obstruction of the bile duct, leading to bile stasis, infection, and fibrosis of the bile duct wall, resulting in loss of elasticity. When the pressure within the bile duct increases, secondary proximal bile duct dilatation occurs, gradually forming cysts. The cause of obstruction is often cholangitis, bile duct stones, tumors, or secondary to injury. In addition, pregnancy, enlargement of the hilar lymph nodes, pancreatic tumors, visceral prolapse, and duodenal papillary adenomas can also cause obstruction at the distal end of the bile duct, leading to this disease. Whether it can be denied that these acquired factors lead to cystic dilatation lesions is based on the existence of potential congenital abnormal factors, which needs to be further discussed.

　　3. Congenital factors combined with acquired factors

　　Kozloff et al. reported a case of an adult who had a normal bile duct during the first laparotomy but found a common bile duct cyst during the second operation. Kato et al. excised the bile duct mucosa locally in young dogs and adult dogs, ligated the distal end of the bile duct, and found that only young dogs developed bile duct cysts, while adult dogs did not have this result. This experiment also shows that bile duct cysts are caused by congenital weakness of the bile duct wall, supplemented by acquired bile duct obstruction factors. The formation of bile duct cysts generally requires two conditions, namely, narrowing of the wall and increased bile duct pressure factors, the latter of which is necessarily based on obstruction at the distal end of the bile duct.

　　In this disease, when there is abnormal convergence of bile duct lesions, the pressure within the pancreatic duct is higher than that within the bile duct, causing activated pancreatic juice to reflux into the bile duct, leading to various lesions when it stagnates with infected bile.

　　1. Hyperamylase bile:The amylase concentration can reach 100,000 U. For children under 2 years old, due to the immaturity of pancreatic cells, it may be lower than the normal level. At this time, if trypsin I and lipase show high values, it indicates reflux of pancreatic juice.

　　2. Bile duct dilatationThe common bile duct can be dilated in cystic and lobulated (cylindrical) types. The former usually occurs at a younger age, but can occur at any age, with 1/4 occurring in children under 1 year old, and about half are complicated with intraphepatic bile duct dilatation. The latter often occurs after 1 year of age, while it is rare for children under 1 year old to develop it, and it is easily detected by ultrasound. Abnormal convergence is the main cause of bile duct dilatation, but not the only cause.

　　3. Cholangitis:It is related to the activation of enzymes in bile stasis and refluxed pancreatic juice. It can often cause cholangitis, pancreatitis, suppurative cholangitis, and in severe cases, may be complicated with liver abscess and sepsis. Clinical manifestations may include fever, abdominal pain, jaundice, and increased white blood cell count, and may be accompanied by hyperamylasemia.

　　4. Gallstones: Local dilatation of the bile ducts accompanied by bile stasis, all of which become conditions for the formation of gallstones. Yamaguehi analyzed 1433 cases of congenital bile duct cystic dilatation, of which 80% of patients had gallstones, and most were gallbladder stones, some had intracystic stones, and a few had pancreatic duct stones.

　　5. Bile duct obstruction:This disease has varying degrees of distal obstruction, which can eventually lead to biliary cirrhosis and portal hypertension.

　　6. Bile duct cyst perforation: It may be related to the proteolytic enzymes in the retrograde pancreatic juice, and it often occurs after intense physical activity. It is more common in children and almost always occurs with malunion. Perforation can lead to diffuse peritonitis, and in severe cases, it can threaten life. The condition is better when there is an aseptic bile ascites, and jaundice can appear after absorption.

　　7. Carcinoma: Since Irwin et al. reported the carcinogenesis of congenital bile duct cysts in 1944, various scholars have successively reported some cases, with an incidence rate of 2.5% to 16.7%, adenocarcinoma accounting for about 77.9% to 95%, regressive carcinoma 21%, squamous cell carcinoma 9%, and occasionally reported undifferentiated carcinoma, acinar carcinoma, grape-like tumor, etc.

　　8. Liver cirrhosis: It can appear in infants aged 1 to 2 months, and is often related to combined bile duct atresia and congenital liver fibrosis. It often occurs with portal hypertension, and the prognosis is poor.

　　9. Portal hypertension: Due to liver cirrhosis, compression of bile duct cysts, and abnormal development of portal vein.

　　10. Hepatic vitamin D deficiency disease: Long-term persistent jaundice, reduced bile in the intestines, and fat absorption disorders lead to vitamin A deficiency, resulting in rickets and osteoporosis.

　　The typical clinical manifestations of this disease are abdominal pain, jaundice, and abdominal mass, but it is very rare to have typical triad symptoms in clinical practice, and most patients do not have specific clinical manifestations.

　　1. Abdominal pain:It is generally manifested as recurrent episodes of paroxysmal dull pain, bloating, or colicky pain in the upper abdomen, upper right abdomen, or around the umbilicus. During the attack, the child is very painful, and after the attack, it is as normal as a child. Sometimes, high-fat or large amounts of food can trigger the occurrence of abdominal pain, and young children are often misdiagnosed because they cannot describe their symptoms. Some abdominal pain recurs repeatedly, lasting for several months to several years, and the pain attacks are often accompanied by jaundice, and can be accompanied by symptoms such as nausea, vomiting, and anorexia. If the abdominal pain becomes persistent and is accompanied by fever and jaundice, it suggests the presence of symptoms of cholangitis. If there is an acute onset of abdominal pain with peritoneal irritation symptoms, it is common to have a perforation of the common bile duct, followed by peritonitis.

　　2. Abdominal mass:There is a cystic mass in the upper right abdomen or the right side of the abdomen, usually covered by the liver edge, with varying sizes. Sometimes, due to the regression of inflammation and edema at the lower end of the common bile duct or the flap-like action of the valvular folds at the end of the bile duct, the bile excretion decreases, resulting in the reduction of the cyst size and the gradual disappearance of jaundice. Therefore, the change in the size of the cyst has high reference value in the diagnosis of the disease. In the case of small choledochal cysts and fusiform dilatation of the bile ducts, abdominal masses cannot be palpated.

　　3. Jaundice:Due to the narrowing of the distal part of the common bile duct in most cases, the distal mucosa becomes edematous during cholangitis, making the lumen even narrower, resulting in obstructive jaundice. The appearance and deepening of jaundice indicate that the bile duct is obstructed at the distal end, causing poor bile drainage. This may be due to concurrent intracystic infection or pancreatic juice reflux. When the inflammation improves, edema subsides, and bile drainage is smooth, jaundice can be relieved or disappear. Therefore, intermittent jaundice is a characteristic. Most cases have this symptom, and the intervals between the onset of jaundice vary. Severe jaundice may be accompanied by skin itching and general discomfort. When the jaundice of some children worsens, the color of feces becomes lighter even white clay-like, and the urine becomes deep yellow at the same time.

　　In addition to the three main symptoms, fever may occur when there is infection in the cyst, with body temperature up to 38-39°C. Nausea and vomiting may also be caused by inflammation. Long-term obstructive jaundice can cause liver and pancreatic dysfunction, affecting digestion and absorption, leading to malnutrition and absorption disorders of fat-soluble vitamins, causing bleeding tendency.

　　The etiology of this disease is not yet clear, and it may be related to environmental factors, genetic factors, dietary factors, and emotional and nutritional factors during pregnancy. Therefore, it is not possible to prevent the disease directly by targeting the etiology. Early detection, early diagnosis, and early treatment are of great significance for indirect prevention of the disease. Paying attention to adequate intake of folic acid during pregnancy and regular physical examinations can play a certain role in early detection and prevention of the disease.

　　The purpose of the laboratory examination of this disease is to understand the patient's condition, which is not of great diagnostic significance for congenital bile duct cystic dilatation itself. In addition to laboratory tests, auxiliary examinations can also be taken, which are conducive to improving the diagnostic rate. The specific situation of these examinations is as follows:

　　1. Liver function test Used to determine the presence of jaundice, bile duct obstruction, liver function status, and the presence of liver cirrhosis.

　　2. Blood amylase Used to understand the possibility of pancreatitis in patients, elevated amylase can also indicate the existence of abnormal convergence of bile and pancreatic ducts. Normal amylase does not mean that the patient has no abnormal convergence of bile and pancreatic ducts, which needs to be paid attention to in clinical practice.

　　3. Tumor marker detection Carcinoembryonic antigen, CEA, CA19-9, are helpful for the detection of patients with tumors in older patients with longer disease duration.

　　4. Ultrasound, CT examination Non-invasive and effective examination methods can better determine the size and location of cysts, with a high diagnostic rate, and can differentiate between liver abscesses and liver tumors. Especially the inexpensive and effective ultrasound, can be used as the first choice of examination method. If ultrasound finds thickening of the cyst wall or nodular changes in the suspicious bile duct cyst, one should be vigilant for cancerous changes.

　　5, Abdominal X-ray examination When the cyst is large, the shadow consistent with the cyst can be found on the plain film, and the image of the compressed gastrointestinal tract with air can be seen. Barium meal examination of the upper gastrointestinal tract or barium enema can more accurately reflect the situation of the enlarged cyst compressing surrounding organs. During the barium meal examination of the upper gastrointestinal tract, the C-shaped loop of the duodenum can be seen to increase and shift downward and forward. If the cyst is located in the duodenum at the level of the ampulla of Vater, the duodenum can be deformed or have a shadow of filling defect. During barium enema, the liver area of the colon can be seen to shift downward and forward.

　　6, Pyelography It can detect the expansion and deformation of the renal pelvis caused by the compression of the enlarged cyst on the ureter, and it is also conducive to distinguishing kidney tumors, malformations, and retroperitoneal tumors.

　　7, Selective celiac artery angiography It can detect shadow of avascular mass.

　　8, Endoscopic retrograde cholangiopancreatography (ERCP), percutaneous transhepatic cholangiography (PTC) It can not only show the location and type of the cyst, but also understand the whole bile duct system. It is especially beneficial for checking for stones, tumors, and malformations of the pancreaticobiliary ductal union, such as ERCP. In cases of severe jaundice cholangitis or failed ERCP, PTC examination can be performed. If PTC is performed under ultrasound guidance, it is safer and more reliable. When used together, they are especially valuable for diagnosing patients without typical triad or difficult cases.

　　9, 131I rose red scanning It can be used for the examination of pediatric bile duct diseases.

　　10, Intra-venous cholangiography Due to the poor concentration ability of the gallbladder in children, and the large amount of bile in the dilated gallbladder, it is not fully visible, so if 5% glucose 50ml is added to 1g of methylene blue dextran for intravenous drip in children, the cholangiography effect is better.

　　11, 99mTc-HTDA scintigraphy It can show the anatomical structure and functional status of the bile duct.

　　12, Cholangiography during surgery It can greatly improve the diagnostic rate of the disease and understand the whole pathological changes of the bile duct.

　　13, MRI and magnetic resonance cholangiopancreatography (MRCP) The latest technology at present, with diagnostic value comparable to ERCP, can clearly show the intrahepatic and extrahepatic bile ducts, gallbladder, pancreatic duct, and bileopancreatic duct junction, without the concern of inducing acute cholangitis and acute pancreatitis, especially for patients who are not suitable for ERCP, the diagnostic value is evident, such as those with severe jaundice complicated with pancreatitis, and patients who have undergone bile-enteric anastomosis in the past.

　　The diet of patients with this disease should be light, with attention to reasonable dietary matching to ensure comprehensive and balanced nutrition. Eat more vegetables and fruits, and eat less spicy and刺激性 food.

　　It is considered futile to treat congenital bile duct cystic dilatation with conservative treatment alone; only surgical treatment is the fundamental and effective method.

　　1. External Drainage:In cases where the general condition is extremely poor, such as severe bile duct infection, severe jaundice, rupture of the cyst complicated with diffuse peritonitis, accompanied by toxic shock, or if it is temporarily not suitable for complex surgery due to other reasons, it may be considered as an emergency procedure. Long-term external drainage can cause the patient to lose a large amount of bile, leading to water and electrolyte imbalance and acid-base imbalance, so a second-stage operation is still required after the condition improves. Before the second operation, retrograde cholangiography should be performed to understand the situation of intrahepatic and extrahepatic bile duct dilation, whether the cyst has decreased in size, and its communication with the duodenum.

　　2. Internal Drainage：Anastomosis between the cyst or gallbladder and the digestive tract, which was a commonly used first-line procedure before the 1960s. The bypass surgery using the gallbladder was abandoned due to its failure to relieve bile stasis and even worsen it, as well as the high risk of retrograde biliary tract infection. The anastomosis between the cyst wall and the stomach was also rarely used due to significant reflux and retrograde infection. Cyst duodenal anastomosis was first used clinically by Bakes in 1907 and can be selected for infants and young children with clear diagnosis and obvious symptoms, especially those who are weak and critically ill and not suitable for major surgery. It is particularly practical for bile duct cysts localized to the posterior part of the duodenum, but the incidence of reflux cholangitis and anastomotic stenosis is relatively high, so it should be selected with caution.

　　3. Cystectomy and Bile Duct Reconstruction：It is a type of surgery that is widely used at present. The most commonly used one is the hepatic duct jejunum Roux-Y anastomosis. This procedure was established by McWhorter in 1924 and was abandoned for a period due to its large surgical scope, excessive bleeding, and significant trauma. It was later recommended by Kasai and Alonson-Lej and applied to clinical practice, and it has been continuously improved, especially the surgical method of cyst wall resection introduced by Lelly in 1979, which can effectively prevent the injury to large blood vessels adherent to the posterior wall of the cyst.

　　4. Hepatectomy：For simple left or right intrahepatic bile duct cystic dilation, it is advisable to perform partial hepatectomy, eliminating the basis of canceration. For patients with bilateral intrahepatic cystic bile duct dilation, left hemihepatectomy and right bile duct jejunostomy should be performed. For patients with intrahepatic and extrahepatic cystic bile duct dilation, treatment is more difficult, and it may be necessary to resect the extrahepatic cystic dilated bile duct and consider performing bile duct jejunostomy at the hilum.