Congenital choledochal cyst in children

　　1. Etiology

　　The etiology of congenital bile duct cysts is still controversial. Over the past decade, with the progress of morphological, bile enzyme, and animal experimental research on this disease, a deeper understanding of its etiology has been achieved. Most scholars believe that the disease is related to congenital abnormal convergence of the bile pancreatic duct and distal obstruction of the common bile duct.

　　1. Congenital malformation of the pancreatic bile duct junction

　　The formation of abnormal convergence, which refers to the abnormal convergence of the pancreatic bile duct at the site of the duodenal papilla, and not in the extraduodenal wall or the morphological and anatomical congenital malformation of the convergence site. Since Babbitt proposed in 1969 that abnormal convergence of the pancreatic bile duct is the cause of common bile duct dilatation, in recent years, this theory has been emphasized even more. If the common bile duct and pancreatic duct cannot be normally separated during the embryonic period, it will lead to an abnormal connection between the distal end of the pancreatic duct and the common bile duct, with the common bile duct connected at an angle of 90° or less than 30°, which causes the normal pancreatic bile duct (less than 2-4mm) to extend abnormally to 20-35mm, resulting in increased intraductal pressure in the normal pancreatic duct (0.294-0.49kPa, 30-50mmH2O) and the bile duct (0.247-0.294kPa, 20-30mmH2O). This leads to the reflux of pancreatic juice into the common bile duct, causing recurrent inflammation and destruction of the elastic fibers of the bile duct wall, resulting in expansion of the wall, and some children may develop recurrent acute or chronic pancreatitis due to increased intraductal pressure.

　　2. Maldevelopment of the bile duct

　　In 1936, Yotsu-Yanagi first proposed that during the embryonic period, the proliferation of primitive bile duct epithelial cells is unbalanced. If there is excessive proliferation at the distal end, then during the process of canalization and vacuolization, the distal end will appear narrow and the proximal end will expand, forming this disease. The common bile duct wall lacks congenital elastic fibers, and it will gradually expand when the intraductal pressure increases, and there is no obstruction at the distal end.

　　3. Viral infection

　　In recent years, through changes in histopathology, it has been found that hepatitis B virus, cytomegalovirus, adenovirus, and other viruses can cause bile duct lumen obstruction or thinning of the bile duct wall, leading to malformations of the bile duct.

　　4. Abnormal nerve distribution

　　Some scholars have found that the nerve distribution in the common bile duct of infants and fetuses is compared with the distribution of nerve ganglion cells in the distal narrow segment of children with common bile duct dilatation, and the number of nerve fiber bundles and nerve ganglion cells in the narrow segment of the children with the disease is significantly reduced compared to the control group. Therefore, it is believed that the occurrence of common bile duct dilatation is related to the abnormal distribution of the distal nerve plexus and nerve ganglion cells of the common bile duct. However, the decrease in nerve ganglion cells and the abnormal development of the nervous system are congenital or secondary acquired lesions that require further study.

　　2. Pathogenesis

　　1. Pathological changes

　　Macroscopically, the common bile duct presents as a spherical cyst or fusiform dilatation, with varying degrees of dilatation, diameter ranging from 2 to 3 cm to 20 to 30 cm, and wall thickness from 2 to 3 mm to nearly 0.5 cm. The size of the mass is not proportional to the age of the child. The wall structure of the cyst often cannot maintain the mucosal and muscularis mucosae tissue of the common bile duct, showing changes such as mucosal desquamation and inflammatory infiltration, while the muscularis is mostly degenerative hypertrophic muscle fibers, mixed with a large amount of fibrous connective tissue. The cyst contains deep green, thick bile, and sometimes sandy-like stones. In some cases, the bile obtained during surgery has positive bacterial culture. Due to long-term chronic bile obstruction, varying degrees of cirrhosis can occur, with the liver appearing brownish green and harder. Generally, after surgical decompression (relieving 'back pressure'), cirrhosis improves within 2 to 6 months, and clinical symptoms also improve. However, if surgical treatment is not performed, recurrent infections can lead to chronic intrahepatic bile duct inflammation, resulting in progressive biliary cirrhosis, increased portal vein pressure, secondary splenomegaly, splenic hyperfunction, varices in the lower segment of the esophagus, and rupture of varices causing massive hematemesis and melena. Due to bile stasis and bacterial proliferation, biliary infections and stone formation can occur, and external bile ducts and cysts can also rupture, leading to bile leakage and the development of biliary peritonitis. Long-term recurrent infection can cause bile duct epithelial malignancy or acute and chronic pancreatitis. Therefore, according to its pathological changes, early and active surgical treatment should be adopted for the disease.

　　2. Classification

　　Congenital bile duct dilatation can occur in both intrahepatic and (or) extrahepatic bile ducts, with common bile duct cysts being the most common. However, with the development of imaging diagnostic technology, other types of lesions, especially cystic dilatation of intrahepatic bile ducts (Caroli disease), are more common than before, leading to a more complex and disordered classification. Flanigan's proposed classification method is relatively simple and practical:

　　(1) Cystic dilatation of the common bile duct: the most common, accounting for 77%, presenting with cystic or fusiform dilatation.

　　(2) Diverticulum-like dilatation of the common bile duct: it can be diverticulum-like dilatation of the common bile duct or gallbladder, mostly diverticulum-like dilatation of the lateral wall of the common bile duct, connected to the lateral wall of the common bile duct with a narrow base or short pedicle, accounting for 2% to 3.1%.

　　(3) Cystic dilatation at the distal end of the common bile duct: also known as bile duct diverticulum, the distal end of the common bile duct dilates and extends into the duodenum, accounting for 1%.

　　(4) Cystic dilatation of intrahepatic and extrahepatic bile ducts, including Caroli disease, accounting for 18.9%.

　　(5) Cystic dilatation of intrahepatic bile ducts, also known as Caroli disease.

　　1. Bile stasis

　　Due to bile duct obstruction, bile stasis leads to gradual enlargement of cysts, presenting cholestasis within the liver, which gradually develops into biliary cirrhosis, severely impairing liver function.

　　2、胆管炎

　　由于排胆不畅，局部抵抗力降低，易发生细菌感染，致急性胆管炎、肝内感染、甚至肝脓肿等。反复发作胆管炎常使胆管壁肿胀、肥厚、纤维化等，使远端胆管更狭窄，甚至闭塞。

　　3、胰腺炎

　　胰胆管接合部异常，可使高压的胆管内胆汁逆流入胰管，损害胰小管及腺泡，胰液渗入胰实质而引起胰组织自溶，并发胰腺炎。

　　4、囊腔内结石形成

　　因胆汁淤滞、胆道感染及胆管狭窄，胆汁成分可发生变化，有利于胆色素结石的形成。王长林报告1例13岁患者，从胆总管囊肿中取出大量的小颗粒状胆色素结石，且左右肝管内也有很多结石。我们有3例小儿胆总管囊肿病例也合并有胆色素结石。Yamaguchi总结1433例的病例，并发结石的占8.0％。

　　5、出血因胆道梗阻

　　致肝功能损害，加上胆盐不能进入肠道，脂溶性维生素吸收障碍，肝脏对凝血因子的合成发生障碍，可致出血，包括皮肤瘀斑、牙龈出血、消化道出血等。

　　6、囊肿穿孔或破裂

　　囊肿逐渐增大，囊内压力逐渐增加，在囊壁的薄弱处，易因腹压突然增加或上腹部的外伤而发生穿孔，引起急性胆汁性腹膜炎。中国台湾、日本和中国都有这方面的报告，占1.8％。

　　7、囊肿癌变

　　囊肿内长期胆汁淤滞、反复发作胆管炎及胰胆管汇合异常，胰液反流入囊腔等，可使胆管壁发生炎症、溃疡、再生或化生，在此基础上诱发癌变。癌变率占2.5％。

　　1、腹痛

　　再发性右上腹或上腹中部疼痛性质和程度不同，有时是绞痛，牵拉痛或轻微胀痛，继发感染时可伴有发烧，有时有恶心和有腹痛者约占80％～90％。

　　2、肿物

　　位于右上腹肋缘下，上界为肝边缘所覆盖，巨大者可超越腹中线，肿物表面平滑，呈球状囊性感，小的胆总管囊肿，由于位置深，不易扪到，在感染，疼痛，黄疸发作时，肿物增大，好转后又可缩小，以右上腹肿物就诊者约占70％左右。

　　3、黄疸

　　约50％病例有黄疸，黄疸的程度与胆道梗阻的程度有直接关系，黄疸一般为再发性，多合并感染及发热，以上症状多为间歇性发作，由于胆总管远端出口不通畅，内容物滞留，出现胆道感染，使症状发作，经过治疗几天后，内容物顺利引流，症状减轻或消失，有的患儿发作频繁，有些可几个月发作一次，除以上症状外，发作时可伴有恶心呕吐，黄疸时可出现白陶土样大便，尿色加深，个别患儿特别是婴幼儿发生囊肿穿孔时，即引起急性胆汁性腹膜炎症状，高热腹胀甚至发生休克。

　　Early and prompt diagnosis and timely surgical treatment are the key to preventing this disease. Various fat-soluble vitamins (A, D, K, etc.) should be supplemented to maintain good nutritional status. Pay attention not to eat or eat less spicy and irritating foods, such as chili, alcohol, and greasy foods. In summer, pay attention to easy-to-digest and nutritious diet, eat more vegetables, do not eat spoiled food, to prevent intestinal infectious diseases. Pay attention to rest, prevent overfatigue, and enhance the body's resistance. In summer, eat more watermelons and other fruits, which can cool down the body, replenish body fluids, prevent constipation, and achieve the purpose of preventing perianal abscesses.

　　One, Ultrasound

　　It is the simplest and most non-invasive examination method, which can obtain an initial diagnosis, and can see a clear low echoic area below the liver, which can determine the size of the cyst, the degree of stricture at the distal end of the bile duct, and can know the degree and extent of intraportal bile duct dilatation and whether there is dilatation within the bile duct. This method has the advantages of being non-invasive, non-radiative, convenient and easy to perform, low cost, and can be observed dynamically, and the accuracy of diagnosis can reach 94%.

　　Two, CT scan

　　It can clearly determine whether there is dilatation of bile ducts inside and outside the liver, the location, degree, and shape, position, the degree of stricture at the distal end of the common bile duct, and whether there is intraportal bile duct dilatation, the shape and location of dilatation, etc., which is helpful for the selection of surgical procedures. The lesions can be displayed by cross-sectional images, and it can be assisted by intravenous injection of iodinated contrast agents to show tubular structures, with high value for localization and quantification, similar to the role of ultrasound, but it can only cross-sectionally show the bile duct, cannot show the length of the obstructed bile duct, and has radiation, is expensive, and can be complementary to ultrasound.

　　Three, Retrograde Cholangiopancreatography Endoscopic Cholangiography

　　Using pediatric duodenal fiberoptic endoscopy, a catheter can be inserted through the duodenal papilla for angiography, which can show the full view of the pancreatic and bile ducts, especially for the abnormal convergence of the pancreatic and bile ducts, which can be clearly visualized, providing reliable evidence for the selection of treatment methods. ERCP has relatively less injury, children require general anesthesia, while adults only need mucosal infiltration anesthesia, with no significant organic injury, the angiography is easy to succeed, and it can achieve better diagnostic effects than PTC. Currently, in foreign countries, ERCP can also be successfully performed on newborns, and it is more effective for the diagnosis of pancreatico-biliary convergence abnormalities. Through the duodenoscope, contrast agents can be directly injected into the bile duct and pancreatic duct, directly showing the full view of bile duct cysts. In adults, this is a routine examination method, but for children, certain conditions and equipment are required, and it is more commonly used in older children.

　　Four, Percutaneous Transhepatic Cholangiography (PTC) examination

　　This examination can:

　　1. Understand the location of intraportal bile duct cystic dilatation, which can provide guidance for surgical selection.

　　2. Understand the presence of abnormal convergence of the pancreatic duct and pathological changes at the distal end of the bile duct.

　　3. Clarify the diagnosis and understand the degree of stenosis of the bile ducts at both ends.

　　4. Take bile for bacteriological examination. Before puncture, a prothrombin time test is required. If the coagulation mechanism is poor, this method is often not used. PTC uses a fine needle to directly inject contrast medium into the intrahepatic bile duct, through which the intrahepatic and extrahepatic bile ducts can be visualized, and the situation of biliary malformation can be directly observed. However, due to the fact that this examination method requires general anesthesia and has a large amount of damage, there is a risk of puncture failure, pneumothorax, bile leakage, and bleeding, and it is currently mostly replaced by ERCP.

　　Five, Radionuclide Liver and Biliary Scanning

　　Using 99mTc, it can directly dynamically observe the morphology and function of the liver and biliary system, and can also observe the position, size, shape, and excretion of the bile duct cyst.

　　Six, Upper Gastrointestinal Barium Meal Examination

　　It can be seen that the duodenal window is expanded, the anteroposterior diameter is flattened, and the lateral diameter is widened. In the lateral view, the descending part of the duodenum is forwardly displaced as shown in Figure 2, and it can be diagnosed.

　　Seven, Upper Gastrointestinal X-ray Contrast

　　When the cyst is large, a smooth, uniformly dense soft tissue mass can be seen in the upper right abdomen, and it can also show that the antrum and duodenum of the stomach are downward and to the left, the duodenal loop is expanded, forming an arc-shaped indentation; in the lateral view, the stomach and duodenum are compressed, the duodenal frame is expanded, and it is forwardly displaced. However, for the梭状形 bile duct dilation, it is difficult to diagnose with ordinary X-ray examination.

　　Eight, Cholangiography

　　Oral or intravenous cholangiography, due to the dilution of the contrast medium, the imaging is often unclear. It is not suitable to use when there is severe liver dysfunction. Currently, it is mostly replaced by more advanced examination methods, and it has been basically discontinued in clinical practice. Intraoperative cholangiography, the contrast medium is directly injected into the gallbladder or bile duct, showing the entire intrahepatic and extrahepatic bile ducts, understanding the nature and extent of the lesions, and is very helpful for diagnosis and determining the surgical method.

　　Nine, Magnetic Resonance Cholangiopancreatography (MRCP)

　　It is the latest cholangiography method at present, which does not require contrast medium. After computer processing, only the clear three-dimensional images of the bile duct and pancreatic duct remain. It is a high-tech non-invasive imaging technology that has matured and been applied in clinical practice since the 1990s. By using the special imaging technology of magnetic resonance, a clear imaging effect of the pancreatic and bile ducts can be obtained, and even it can be determined whether there is a malformation of the pancreaticobiliary union. Recent large-scale clinical studies have shown that the diagnosis of simple bile duct dilation alone is far from being able to guide surgery correctly.

　　1. Prefer

　　Onions, celery, carrots, radishes, green peppers, finger citron, winter melon, pumpkin, bamboo shoots, corn, tofu, ginger, apples, watermelons, walnuts, milk, a small amount of alcohol, vitamin C.

　　2. Taboo

　　Chicken, eggs, fatty pork, mutton, ghee, shrimp, crabs, high-fat foods, calcium supplements, antidiarrheal drugs, anticholinergic antispasmodics, tonifying and astringent herbs.

　　First, treatment

　　If the disease is not treated surgically, it is often due to recurrent infection, biliary cirrhosis, common bile duct perforation, or cancer and death. Therefore, when the child is diagnosed, surgery should be performed in a timely manner.

　　1. Principle

　　There are three requirements:

　　(1) The primary purpose of the surgery is to restore the drainage of bile into the intestines to prevent ascending cholangitis.

　　(2) Resect the dilated common bile duct to prevent cancer in the future.

　　(3) To prevent anastomotic stricture in the future.

　　2. Surgical methods

　　The currently commonly used surgical methods are:

　　(1) Cystectomy, hepatic duct jejunal Roux-Y anastomosis, and additional preventive reflux valve shaping surgery.

　　(2) Cystectomy, interposition of jejunum as a biliary tract, with a preventive reflux giant valve surgery.

　　(3) Cysto-duodenal anastomosis and cystectomy with hepatic duct duodenal anastomosis, this method is currently used less often due to the difficulty in preventing retrograde infection and anastomotic stricture.

　　II. Prognosis

　　Due to the frequent occurrence of cholangitis and the aforementioned various complications in this disease, early surgical intervention should be performed. Before the 1970s, cystoenteric anastomosis or partial cyst resection combined with enteric anastomosis was commonly used. With the increasing reports of malignant transformation of choledochal cysts, the rate is between 10% and 20% in foreign countries, and there are scattered case reports in China as well. The average age of primary cystic malignant transformation is 50 years old, but the average age of malignant transformation after cystoenteric drainage is 35 years old; the average age of patients at the time of internal drainage is 25 years old, so the average time from internal drainage to malignant transformation is about 10 years. The site of primary malignant transformation can be in the bile duct (53%) or in the gallbladder (46%), but after internal drainage, 85% of the malignant transformations occur in the residual cysts, and only 9% in the gallbladder. When performing partial cyst resection, the remaining part of the cyst wall can also undergo malignant transformation. The reason why cancer is more likely to occur after cystoenteric anastomosis may be that when there is an abnormal convergence of the bile duct and pancreatic duct, pancreatic juice is prone to flow into the cyst cavity, and the activation of pancreatic enzymes by enterokinase from the small intestine can exacerbate the inflammatory changes within the cyst and accelerate the occurrence of cancer. Therefore, internal drainage of the cyst and partial cyst resection with internal drainage are not advisable, and even for patients who have undergone such procedures, consideration should be given to resection of the cyst. The currently recognized surgical procedure for type I choledochal cyst is cystectomy, Roux-en-Y hepatic duct jejunal anastomosis, or hepatic duct-jejunal interposition anastomosis. In the 1950s, the mortality rate of this procedure was relatively high, around 30%, but it has significantly decreased in recent years, around 4%; Harbin Medical University Affiliated Second Hospital reported 41 cases in 1986, with no deaths. We have also performed nearly 30 cases so far, with no deaths. For type II choledochal cysts, cystectomy and bile duct-bile duct anastomosis are performed. If the pancreatic segment of the common bile duct has a diverticulum, the lateral posterior wall of the duodenum can be incised to find the pancreatic duct and protect it, resect part of the pancreatic head tissue, the pancreatic segment of the bile duct, and the diverticulum, and perform an interposition jejunal anastomosis between the bile duct and duodenum using the cut end of the bile duct and the incision of the duodenum. For type III choledochal cysts, the anterior lateral wall of the duodenum can be incised, and cystectomy or additional sphincterotomy of the Oddi's ampulla can be performed in the lumen, and then the pancreatico-biliary duct can be transplanted into the posterior wall of the duodenum. For type IV choledochal cysts, which are limited to a lobe of the liver, a local lobectomy of the liver can be performed. If there are extensive intrahepatic lesions, liver transplantation (liver transplantation) is required. And various forms of intrahepatic bile duct internal and external drainage are not effective.