Congenital bile duct cysts

　　One, the cause of the disease

　　It is still unclear, and there are many hypotheses. Most cases are considered to be caused by congenital maldevelopment. Congenital factors have two aspects:

　　1. The bile duct wall is thin, and some believe that there is a congenital defect in the supporting tissue of the duct wall, or there is ectopic pancreas tissue, causing the duct wall to be in a low tension state.

　　2. The distal obstruction of the common bile duct leads to increased intraductal pressure, thereby causing dilation.

　　The cause of obstruction can be congenital atresia, or abnormal hyperplasia of epithelial cells during the period of bile duct development, resulting in stenosis; some believe it is due to an imbalance of the autonomic nervous system at the distal end of the common bile duct, causing spasm, or due to neuromuscular coordination disorders of the Oddi sphincter; some believe it is due to the angulation of the bile duct duodenal junction, forming a valve-like structure, causing obstruction. The acquired lesions that cause bile duct cystic dilation may include inflammatory scars, stones, bile duct or surrounding tumors, and enlarged lymph nodes. Neonatal hepatitis can cause damage to bile duct epithelium, leading to bile duct obstruction and surrounding fibrosis. When the secretory pressure of the pancreas is greater than the pressure of the liver to secrete bile, pancreatic juice can easily reflux into the common bile duct, causing inflammation; pancreatitis or ampullitis is a common cause of distal obstruction of the common bile duct. In summary, it is generally believed that bile duct cysts are the result of the combination of weakened wall and distal obstruction.

　　Secondly, the pathogenesis

　　The classification methods of bile duct cysts vary, but most tend to be divided into 3 types:

　　1. The common type is the most common, accounting for over 80%, with the common bile duct showing a spindle-shaped or aneurysmal dilation, ending in a stricture. The intrahepatic bile ducts are usually in a normal state, and the gallbladder and cystic duct are generally included within the cyst, or can be limited to the cystic dilation of the bile duct below the cystic duct.

　　2. The diverticulum type is less common, with a diverticulum-like cyst appearing on one side of the bile duct wall from the superior margin of the duodenal ampulla to the inferior end of the cystic duct, while the rest of the bile ducts are normal or slightly dilated.

　　3. Prolapse of the common bile duct in the duodenum. Also known as the duodenal bile duct cyst or Vater壶腹囊肿, it is a rare condition.

　　The cyst is round, located in part or all of the common bile duct, with varying sizes, inner diameter of 2-25cm, and capacity ranging from several ml to over ten thousand ml, with the largest capacity reaching 13340ml. The cyst wall may thicken due to inflammation, with a thickness of 1-10mm. Generally, the wall lacks complete epithelium and is composed of fibrous connective tissue, with scattered columnar epithelial cells, elastic fibers, and smooth muscle fibers visible. Inflammation is often present, and there may be bleeding spots or even ulcers. The distal bile duct may narrow or become angular due to compression by the cyst. The cyst contains thin brown fluid, usually sterile; when completely obstructed, due to poor liver function, bile may become white; after secondary infection, the color becomes deeper and turbid, and Escherichia coli can be cultured. Stones are occasionally seen within the cyst, but they are less common than imagined; and in cases of bile duct cysts with cancer, the incidence is 2.5%, much higher than the incidence of bile duct cancer in those without cysts (0.007% to 0.041%), and the average age of onset is younger, averaging 32 years, with an average survival time of 8 and a half months after diagnosis. The gallbladder is usually smaller than normal and can also become larger. Intrahepatic bile ducts can be normal or slightly dilated, and some may have intrahepatic bile duct cysts with liver fibrosis. The liver may become cholestatic and enlarged due to distal obstruction of the common bile duct, even leading to biliary cirrhosis, thus causing portal hypertension. Portal hypertension may also occur due to direct compression of the portal vein by the cyst. Cyst infection can cause intrahepatic cholangitis, even multiple liver abscesses, and Escherichia coli sepsis. Cyst rupture, or leakage due to exploratory puncture, can cause diffuse peritonitis.

　　The most common is jaundice, which is often the first noticed in children and can be intermittent or progressive. Severe jaundice can cause skin itching, grayish stools, and dark urine, indicating bile. Newborns and infants usually manifest as abdominal masses, obstructive jaundice, and whitish stools. In cases of severe obstruction, they can manifest symptoms similar to biliary atresia, such as severe jaundice and white stools, some with large upper abdominal masses without jaundice. Older children usually manifest typical triad symptoms, i.e., abdominal pain, abdominal mass, and jaundice, with abdominal pain being the main symptom, and fever and vomiting also occur. Abdominal pain is similar to the symptoms of recurrent pancreatitis, and a portion of cases are accompanied by high concentrations of amylase in the serum.

　　Symptoms usually appear in children and adults. According to statistics, 25% of cases are diagnosed within the first year of life, 60% before the age of 10, and 23% after the age of 40. The oldest case was 78 years old. The clinical manifestations are intermittent upper abdominal pain, right upper quadrant mass, and jaundice, known as the triad of choledochal cyst. However, it only accounts for 1/3 of the total number. 55% to 60% of cases have abdominal pain, 60% to 75% have masses, and 65% to 80% have jaundice, with quite different clinical manifestations. They can be completely painless, or the upper abdomen can tolerate dull pain, or even severe sharp pain in the right upper quadrant. Jaundice is the most common symptom, often the first noticed in children, and can be intermittent or progressive. Progressive jaundice in infants should be considered as congenital bile duct atresia. Severe jaundice can cause pruritus, grayish stools, and dark urine, which are manifestations of bile. The degree of jaundice is directly related to the degree of bile duct obstruction and infection. Masses can be palpated in the upper abdomen or right hypochondrium, with large ones occupying the entire right abdomen, feeling cystic, fixed and inactive. Small cysts can move slightly. After infection, there is marked tenderness and rebound pain. If it is a duodenal choledochal diverticulum, there are also symptoms of duodenal obstruction. In addition, nausea, vomiting, anorexia, diarrhea, and weight loss may occur. Infection may cause chills, fever, and an increased white blood cell count.

　　Congenital choledochal cyst seriously affects patients' daily lives, so it should be actively prevented. However, there is currently no effective preventive method for this disease, so early detection and early treatment are of great significance for the treatment of the disease.

　　1. Liver function tests:

      Determining the nature of jaundice is also necessary for preoperative diagnosis. The majority of patients show obstructive jaundice in blood, urine, and stool tests, and a series of tests for obstructive jaundice are all abnormal, including significantly elevated serum bilirubin, mainly direct bilirubin, elevated alkaline phosphatase and gamma-glutamyl transpeptidase, and varying degrees of acute liver dysfunction. A few patients may have basically normal indicators in all tests, and inflammatory changes such as increased peripheral blood leukocyte count and neutrophils may be seen in patients with infected cysts.

　　A considerable number of cases of this disease, especially those in the fusiform shape, are found to have elevated levels of pancreatic amylase in blood and urine during the course of the disease and are misdiagnosed as simple acute pancreatitis. In clinical practice, there are indeed cases with concurrent pancreatitis, but the majority of cases are due to abnormal pancreaticobiliary reflux, where pancreatic juice refluxes into the bile duct, even into the intrahepatic bile ducts, and pancreatic amylase in the capillary bile ducts can reflux into the blood circulation through the hepatic venous sinus, which is usually not true pancreatitis.

　　2. X-ray examination:

　　It is of great help to the diagnosis. The upper abdominal plain film shows a dense mass shadow, and gastrointestinal X-ray barium meal or hypotonic duodenal barium meal shows that the stomach is compressed and shifted to the left anterior position, the duodenum is shifted to the left anterior-inferior position, the duodenal flexure is enlarged, and the X-ray barium enema examination shows that the colon hepatic flexure is shifted to the anterior-inferior position. Cholecystography often fails. When the serum bilirubin is greater than 3mg/dl, there is no possibility of contrast enhancement by oral or intravenous contrast medium; only before jaundice appears, intravenous cholangiography may still be valuable, and small cysts may be visible. Large cysts do not show up due to dilution of the contrast medium, and percutaneous liver puncture for bile duct造影 may confirm the cystic dilatation of the choledochus, but there is a concern about leakage of bile. Retrograde cholangiography through a fiberoptic duodenoscope, if successful, is of the greatest value for the diagnosis of choledochal cyst, but 50% of the cases have elevated amylase levels postoperatively, and some cases may die due to induced pancreatitis. Intraoperative cholangiography is the most effective, as it can outline the contour of the cyst and the condition of the intrahepatic bile ducts, providing a favorable basis for the decision of the treatment plan.

　　3. Ultrasound examination:

　　A constant liquid level segment can be found, and the computed tomography scanner can reliably show the location and size of the abdominal cyst. Liver radionuclide scanning helps identify the condition of the intrahepatic bile ducts, as well as the location and size of the choledochal cyst. Selective abdominal aortic angiography shows a large area of avascular region, suggesting the location of the cyst.

　　I. Diet

　　1. Change daily dietary habits and reduce the fat content and total calorie intake of food.

　　2. Pay attention to rest and avoid overexertion.

　　3. Engage in appropriate physical exercise to enhance physical fitness.

　　4. Vitamin A, B vitamins, vitamin C, vitamin B6, and vitamin E can reduce the risk of liver cyst development and can be taken in moderate amounts.

　　5. Diet should be light, reduce alcohol consumption, change daily dietary habits, avoid spicy, greasy, and irritating foods with high fat content, and reduce the fat content and total calorie intake of food.

　　I. Treatment

　　1. Treatment during the inflammatory attack period.

　　(1) Fasting and gastrointestinal decompression can reduce the secretion of bile and pancreatic juice, and relieve the pressure in the bile duct.

　　(2) Antibiotics should be used to control infection. Common bacteria in biliary tract infection are Gram-negative intestinal aerobic and anaerobic bacteria, mainly bacilli, and cephalosporins and metronidazole can be selected.

　　(3) Anticholinergic drugs can be used to relieve spasm in patients with significant abdominal pain.

　　(4) Severe patients with acute suppurative cholangitis, severe obstructive jaundice, and early liver failure can be treated first with percutaneous transduodenal nasobiliary drainage or percutaneous liver puncture bile duct drainage. After preliminary reduction of jaundice and control of infection, surgical treatment can be selected.

　　(5) Patients with elevated serum amylase levels should be treated according to pancreatitis.

　　(6) Actively prevent and treat shock, including blood transfusion, fluid replacement, correction of water, electrolyte, and acid-base imbalances, and monitoring vital signs.

　　(7) Strengthen liver protection and nutritional support therapy. Supplement various fat-soluble vitamins (A, D, K, etc.) to maintain good nutritional status.

　　2. Once a diagnosis is made, surgical treatment should be adopted immediately. Surgery mainly involves drainage and resection. In principle, resection should be used as much as possible for diverticulum and duodenal choledochoceles; only for the common type, due to the large cyst, resection is difficult, it may damage surrounding important tissues, or in the acute infection stage, only drainage can be adopted. Drainage techniques include external drainage and internal drainage. External drainage is prone to hypotonic dehydration, acidosis, and electrolyte disorders, so it is only in unavoidable situations, such as severe infection or poor overall condition, that emergency surgery is performed by inserting a catheter through the gallbladder or performing a cystic bag suture. After the overall condition improves, bile-enteric pathways are established. Internal drainage techniques include cysto-jejunal anastomosis, cystogastric anastomosis, and cysto-ileal anastomosis, but they are prone to cause retrograde reflux of gastrointestinal contents, leading to ascending cholangitis. Therefore, some people advocate using the greater curvature of the stomach to form a tube and then anastomose it with the cyst; more commonly, a Roux cysto-jejunal Y-shaped anastomosis is performed, using a 30cm long, defunctional intestinal segment to anastomose with the cyst end-to-end. 70% to 80% of cases can achieve satisfactory efficacy. After cysto-intestinal anastomosis, if ascending cholangitis occurs, it often causes stenosis at the anastomosis site, and it is also prone to stone formation, and can also lead to malignant transformation due to inflammatory stimulation, often requiring reoperation. This indicates that initial cyst resection is ideal. However, the mortality rate of resection is high, so some authors advocate that only the inner layer of the cyst wall be resected at the important structural site, while retaining a thin outer membrane of the cyst wall, performing a complete cyst resection, and then anastomosing the proximal bile duct with the Y-shaped branch of the jejunum, or performing end-to-end bile duct anastomosis and adding a sphincteroplasty. Even if complete cyst resection cannot be achieved, at least most of the cyst wall should be resected to reduce postoperative complications. The mortality rate of internal drainage surgery is lower, but the postoperative disease rate is high; the disease rate after complete cyst resection is low, and the mortality rate has decreased from 50% to about 5%. The higher the preoperative correct diagnosis rate, the lower the mortality rate of surgery. In 1933, the preoperative correct diagnosis rate was only 3%, but it has now increased to 70% to 80%, so the safety of surgery has significantly improved. The development of liver transplantation has improved the prognosis of extrahepatic and intrahepatic biliary atresia.

　　II. Prognosis

　　With the improvement of the technology for correct diagnosis, the mortality rate of this disease has been greatly reduced. The development of liver transplantation has improved the prognosis for biliary atresia both inside and outside the liver.