Since first being reported in 1723, congenital biliary dilatation, or choledochal cyst (CC), has been shown to have a female preponderance and is more common in Asia compared with western countries. Despite its exact etiology remaining unclear, CC can be treated correctly based on what is known. Surgical intervention is effective because of astute diagnosis and comprehensive preoperative/perioperative management and innovative strategies including minimally invasive techniques.
Classification
CC has been classified in various ways ; however, the Todani classification is most widely accepted, and involves five types ( Fig. 42.1 ). Type I CC predominates and 90% are either I or IVa. From experience, classifying CC according to the presence or absence of pancreaticobiliary malunion (PBMU) ( Fig. 42.2 ) would seem to be more relevant clinically, as signs/symptoms and anatomy/structure can be attributed directly to PBMU, and surgical strategies can be planned based on PBMU. As a result, CC with PBMU are type A: cystic dilatation of the common bile duct (CBD); type B: fusiform dilatation of the CBD; or type C: forme fruste CC with minimal or no dilatation of the CBD or common channel syndrome. CC without PBMU are type D: cystic diverticulum of the CBD; type E: choledochocele (diverticulum of the distal CBD); or type F: polycystic segmental dilatation of intrahepatic bile duct (IHBD) (Caroli’s disease).
Todani classification of choledochal cyst.
Choledochal cyst is classified into five types, I (a–c), II, III, IV-A and-B, V.
Classification of choledochal cyst (CC) by pancreaticobiliary malunion (PBMU).
Associated with PBMU : (a) Cystic CC. (b) Fusiform CC. (c) Form fruste CC (including nondilatation CC). Not associated with PBMU : (d) Cystic diverticulum of the common bile duct. (e) Choledochocele (diverticulum of the distal common bile duct). (f) Intrahepatic bile duct dilatation (Caroli’s disease).
Etiology
Numerous theories have been postulated, but none can explain all the types of CC seen clinically. A genetic basis is suspected because of female preponderance and different incidence rates around the world, and a recent report using “trio-based” exome-sequencing of 31 patients with CC found they shared 13 recurrently mutated genes.
CC would seem to be either congenital or acquired. Congenital CC develop during fetal life appearing to be associated with a structural defect of the bile duct. , When “acquired” or developing later in life, a long common biliopancreatic channel is widely accepted to be implicated. Conventionally, the terminal CBD and pancreatic duct unite to form a short common channel, which is completely surrounded by the Sphincter of Oddi. If this common channel is long, or part of it is not surrounded by a normal sphincter, pancreatic secretions may reflux into the biliary tree, and pancreatic proteolytic enzymes are activated causing epithelial and mucosal damage that induces structural weakness and dilatation of the choledochus.
This “long common channel theory” would appear to be a reasonable concept because anatomically almost all CC have PBMU, but the hypothesis that weakness of the choledochal wall is due to reflux of pancreatic fluid is not supported by extremely mild responses of the CBD to experimentally induced pancreatic fluid reflux in puppies performed by one of the coauthors. In addition, there are a number of patients with PBMU and high gallbladder amylase levels with no dilatation of the CBD. Although Babbit stressed that pancreatic fluid was the most likely factor causing edema, weakness, and eventual fibrosis of the distal CBD, neonates are not capable of secreting active fully functional pancreatic enzymes, and CC can actually be diagnosed antenatally as early as 15–20 weeks’ gestation, at which time the pancreas is definitely too immature to function. The authors believe that congenital stenosis of the common channel and PBMU may disrupt bile flow that could induce CC, at least in perinatal and young infants, rather than weakness of the duct wall caused by reflux of pancreatic fluid. Both PBMU and stenosis are associated with abnormal development of the ventral pancreatic duct and biliary duct system.
Clinical Features
Cystic CC usually present as an upper abdominal mass without jaundice and can be quite large in neonates and young children, whereas fusiform CC are more commonly associated with abdominal pain; CC diagnosed antenatally are more likely to be cystic. In young children, presenting symptoms can be divided roughly into two patterns: a right upper quadrant mass with intermittent jaundice due to biliary obstruction, seen in patients with cystic CC, and abdominal pain due to pancreatitis, typical of fusiform CC. By adolescence and early adulthood, CC has often been asymptomatic and not identified, or misdiagnosed as cholelithiasis, cirrhosis, portal hypertension, hepatic abscess, or biliary carcinoma. Surgery can be complicated by chronic inflammation that is not seen in younger children, and the incidence of postoperative complications can be high, even after primary excision. Biochemical liver function tests may be entirely normal or reflect hepatic functional deterioration due to biliary obstruction. Amylase and lipase levels are usually elevated during episodes of abdominal pain in fusiform CC or forme fruste CC, suggestive of active pancreatitis. Although rare, if blood clotting is prolonged secondary to chronic cholestasis, parenteral vitamin K should be prescribed.
Diagnosis
Preoperative Imaging
Ultrasonography (US) is the most effective investigation to perform when CC is suspected. The first CC diagnosed by prenatal US was reported in 1980, and numbers have been increasing annually. US can also delineate IHBD clearly and can evaluate the state of the liver parenchyma. Improvements in US technology and magnetic resonance imaging (MRI) have resulted in choledochal dilatation and cysts smaller than 20 mm being reported as early as 18–20 weeks of gestation. ,
Magnetic resonance cholangiopancreatography (MRCP) can provide excellent visualization of the pancreaticobiliary ducts, allowing detection of narrowing, dilatation, and filling defects with medium-to-high degrees of accuracy. MRCP is noninvasive and can be useful for delineating the pancreatic and biliary ducts proximal to an obstruction. However, in children younger than 3 years old, MRCP may not visualize the pancreaticobiliary ductal system because of their small caliber, and sedation is necessary. Nevertheless, MRCP is recommended for all CC patients preoperatively to provide the best imaging available to plan surgery accurately ( Fig. 42.3 ). Contrast-enhanced computed tomography (CT) may be indicated in some patients with pancreatitis or if an associated tumor is suspected clinically ( Fig. 42.4 ).
Preoperative MRCP: type-Ia.
Preoperative assessment focuses in particular on the size of the cyst, the presence or absence of intrahepatic bile duct dilatation, the location of the confluence of the cystic duct, and the course of the pancreatic duct. Strategy for dissecting the pancreatic side of a CC and the level for hepaticojejunostomy anastomosis can by planned accurately.
Preoperative CT: type IV-A.
CT allows the area surrounding a CC to be confirmed. In this case, anastomosis to the dilated intrahepatic bile duct ( arrowheads ) was also considered.
Preoperatively, endoscopic retrograde cholangiopancreatography (ERCP) can accurately visualize the configuration of the pancreaticobiliary ductal system in fine detail. However, as ERCP is invasive, unsuitable for repeated use, and contraindicated during acute pancreatitis, it has been replaced by MRCP at most centers. Other investigations that are available and reported to be useful for diagnosing CC (but considered obsolete) include percutaneous transhepatic cholangiography, especially for patients with IHBD dilatation and severe jaundice, intraductal US for delineating the distal CBD and pancreatic duct, and a radio-isotope scan (99mTc-DISIDA) to determine baseline liver function and impairment of biliary excretion as a marker of the severity of liver cirrhosis.
Intraoperative Cholangiography
With improvements in preoperative imaging, such as MRCP or CT, the entire biliopancreatic ductal system, including the intra- and extrahepatic bile ducts and pancreatic duct, can be visualized reliably in detail in most patients, so intraoperative cholangiography is unnecessary. Thus, it is beneficial only when sufficient information is otherwise not available for safe surgical intervention. When a CC is large, intraoperative cholangiography via the gallbladder or directly via the CBD cannot generate enough pressure for contrast to spread effectively and must be performed separately for the IHBD and distal CBD by selective techniques as required, during excision.
Timing of Surgery
Some pediatric surgeons recommend primary excision soon after diagnosis, but in most cases, the CC is not the cause of acute symptoms; rather associated pancreatitis is the etiology, and the patient should be stabilized clinically before surgery. From experience, , complete excision (CE) need not be performed hastily if jaundice is absent; rather, patients should be investigated/assessed thoroughly, and surgery planned strategically. In cases of bile peritonitis following perforation, severe cholangitis, poor general condition, or a hugely dilated CBD in neonates, external biliary drainage is recommended, followed by delayed primary excision once fully stabilized, 2–3 months later.
The timing of surgery in neonates is highly controversial because there are very few reports about the management of asymptomatic CC detected on prenatal US or after birth. In neonates suspected of having CC, normal pigmented stools should be confirmed after meconium is passed and unconjugated jaundice levels monitored and confirmed to decline. At this stage, the most important concern is biliary patency, and this can be confirmed either clinically, biochemically, or by radio-isotope scanning. Although some surgeons recommend early surgery soon after diagnosis for CC, as mentioned earlier, for asymptomatic prenatally detected CC or asymptomatic CC detected after birth, surgery will usually be deferred for 3–6 months or until the infant weighs more than 5 kg. However, if serum bilirubin is raised, the authors believe that neonates should be treated by early surgery to exclude biliary atresia and prevent biliary and hepatic complications, such as liver fibrosis that can progress rapidly in cases of biliary obstruction, , reverse fibrosis, reduce the risk for cholangitis, prevent accumulation of biliary sludge, relieve obstructive jaundice, as well as prevent cyst perforation. The results of surgical intervention for CC in neonates are generally excellent but can vary depending on underlying pathology.
Surgical Planning
Complete excision (CE) is the aim of surgical intervention for CC and involves removal of all potentially affected or suspicious tissue because of high morbidity/risk for carcinoma associated with cystoduodenostomy or internal drainage, a common treatment performed in the past. Cystoduodenostomy and cystojejunostomy were abandoned as definitive treatments due to known risks for cholangitis, stone formation, and malignant transformation. CE for cystic/fusiform CC involves diverting bile from the dilated CBD away from contact with pancreatic juice in the pancreatic duct with proximal restoration of bile flow from the liver to the intestine. The authors’ procedure of choice for biliary reconstruction is Roux-en-Y hepaticojejunostomy (HJ), but hepaticoduodenostomy (HD) and other biliary reconstructive procedures are still performed elsewhere. Forme fruste CC is somewhat controversial with some surgeons performing cholecystectomy without excising the CBD as is commonly performed for adult CC patients. The authors recommend that pediatric forme fruste cases be treated the same as cystic/fusiform CC cases (i.e., by CE of the CBD and Roux-en-Y HJ) after experiencing several cases of CC treated by cholecystectomy alone (elsewhere) developing recurrent postoperative pancreatitis and eventually requiring further surgery to excise the CBD.
Primary Curative Surgery
Open Approach
General anesthesia is induced conventionally; endotracheal intubation is standard, an orogastric tube is placed, and a urinary catheter is inserted. Epidural analgesia can provide excellent postoperative pain relief. Broad-spectrum intravenous antibiotics are best given at induction of anesthesia and continued for 3–5 days postoperatively.
Transecting the Distal/Pancreatic Side of a CC
CE is much easier in neonates and young infants, because the wall of the dilated CBD is generally thin and there are few adhesions to surrounding structures, such as the portal vein , ( Fig. 42.5 ). Aspiration of the CC prior to dissection makes surgery easier if the CC is large. If dissection is difficult or becoming tedious, the anterior wall of the CC may be incised transversely to expose the posterior wall for direct inspection from the inside. It is recommended that the CC be incised in the middle portion closer to the duodenum, because there is often an anomalous opening of the hepatic duct. By incising the anterior wall, the CC can be freed from surrounding tissues including the portal vein and hepatic artery more easily and safely than by dissecting without incising the anterior wall ( Fig. 42.6 ). In older children, there are usually more adhesions between a cystic CC and surrounding vital structures, compared with infants or younger children. If CE of the distal portion is difficult due to inflammation or adhesions, mucosectomy of the distal portion of the CC is recommended, to avoid damage to the pancreatic duct, hepatic artery, and portal vein, and also to prevent leaving any epithelium from the distal portion of the CC behind because there is a risk for CC tissue to undergo malignant transformation. Mucosectomy is rarely indicated in neonates because there is little inflammation around the CC.
Complete excision of a cyst. Complete/full-thickness excision of a cystic CC (Left, arrowhead ).
Appropriate tension is crucial during dissection and ligation of cystic CC. Complete/full-thickness excision of a fusiform CC (Right, arrowhead ). Confirming the location of the orifice of the pancreatic duct using intraoperative endoscopy is imperative for preventing damage to the pancreatic duct during dissection and ligation.
Anterior wall incision of CC .
Prior to commencing or during dissection of a cystic CC, the anterior wall is incised transversely to facilitate dissection of the posterior wall and enhance safety. This maneuver is highly effective and should be used whenever dissection is becoming difficult, as it ensures safe surgery.
Intraoperative Endoscopy
Since 1986, the authors have routinely performed intraoperative endoscopy (IE) ( Fig. 42.7 ) of the common channel ( Fig. 42.8 ), the orifice of the pancreatic duct, and IHBD ( Fig. 42.9 ) to examine the duct system directly for stone debris and duct stenosis, and to remove stone debris by irrigation with normal saline using a pediatric cystoscope or fine fiberscope with a flush channel at CE. , There was a high incidence of IHBD debris not detected by preoperative imaging and debris could be present in the absence of IHBD dilatation, although debris was more common when IHBD dilatation was present. A long-term follow-up review of IE patients found the incidence of postoperative stone formation was lower than reported in the literature.
Intraoperative endoscopy.
Intraoperative endoscopy of the distal common bile duct on the pancreatic side. A pediatric ureteroscope with a flush channel is inserted through an opening made in the cyst ( arrow ).
Intraoperative endoscopy for ducts on the pancreatic side.
Pancreatic side duct: Protein plugs seen in the lumen (Left, arrowhead ). Lumen after removal of a protein plug causing obstruction (Middle). Arrow : Pancreatic duct orifice. Duodenal lumen, confirming that the lumen to the duodenum can be opened without obstruction (Right).
Intraoperative endoscopy for intrahepatic bile ducts.
Intrahepatic duct: Debris ( arrowheads ) can be irrigated from an intrahepatic duct (Left). After irrigation, the lumen is free of debris and can be inspected for anatomic issues that could cause complications at the anastomosis such as stenosis or leakage.
Transecting the Common Hepatic Duct
The common hepatic duct is usually transected at the level of distinct caliber change. Because residual CC mucosa has been implicated in malignant transformation, care must be taken to ensure no CC tissue remains unintentionally after CE ( Fig. 42.10 ), especially in older children. Suturing at the anastomosis will be easier when the lumens to be sutured are larger, but in pediatric CC without IHBD dilatation, and cystic CC in particular, lumens tend to be narrow the younger and smaller the patient. In contrast, when IHBD dilatation exists, the anastomosis may seem easier because the dilated IHBD can be sutured directly during HJ.
Transection of the common hepatic duct.
In cystic CC without intrahepatic bile duct dilatation, complete removal of a cyst will leave a very small anastomotic opening.
Another option is to widen the lumen at the anastomosis by using scissors to incise the anterior wall of the narrow common hepatic duct longitudinally toward the hepatic hilum, then everting the right and left sides of the incised anterior wall of the common hepatic duct and anchoring them to the hepatic parenchyma. HJ can be performed in a single layer with interrupted sutures using a larger lumen ( Fig. 42.11 ).
Hilar hepatic ductoplasty.
After the anterior wall of a narrow common hepatic duct is incised toward the hepatic hilum, the center and right and left sides of the incised anterior wall of the common hepatic duct are everted, and anchored to the hepatic parenchyma before hepaticojejunostomy is performed.
If the lumen of the common hepatic duct at the HJ anastomosis is 4 mm or less in younger patients with cystic CC, a Carrel patch with 2–3 mm of CC wall can be used to increase the diameter at the anastomosis to 6–7 mm ( Fig. 42.12 ), because a larger lumen is easier to anastomose technically, especially when CC is not associated with IHBD dilatation. A study of CC specimens excised from young pediatric patients who have been followed up on for some 20 years with no evidence of malignant transformation as adults also found no evidence of premalignant lesions. While malignant transformation has been reported as a late complication in older or adult CC cases, no pediatric cases have been identified by the authors after years of extensive experience; CE at younger ages with IE will further contribute to preventing malignant transformation. Hepaticoenterostomy (HJ or HD) at the hepatic hilum, similar to a Kasai hepatoportoenterostomy, may be indicated in specific cases, such as in patients with dilated IHBD with stenosis in the common hepatic duct at the porta hepatis or adolescent patients with severe inflammation and fibrosis of the common hepatic duct. In such cases, larger lumens may facilitate surgery, but careful follow-up is mandatory because of IHBD dilatation.
Carrel patch anastomosis.
Carrel patch anastomosis: Carrel patch with 2–3 mm of cyst wall can be used to increase the diameter at the anastomosis to 6–7 mm.
The Anastomosis
An end-to-end anastomosis of the jejunum to the cephalad remnant of the CBD is recommended if the diameters of the CBD and the proximal Roux-en-Y jejunum are similar, but in most cases, an end-to-side anastomosis is performed because the CBD is too small. The anastomosis should be as close as possible to the closed end of the jejunal limb because an end-to-side anastomosis farther from the closed end of the proximal jejunum will allow a blind pouch to form as the child grows. Bile stasis in the blind pouch can lead to intrahepatic stone formation, especially if there is IHBD dilatation.
The authors seldom perform other procedures such as hepaticoenterostomy at the hilum or valved jejunal interposition hepaticoduodenostomy to prevent reflux of digested food into the IHBD, because while they may seem appealing theoretically, there is no significant difference in morbidity. Hepaticoenterostomy at the hepatic hilum is more difficult than conventional hepaticoenterostomy, particularly in neonates and young infants without IHBD dilatation, and valved jejunal interposition hepaticoduodenostomy is a complicated procedure. The Roux-en-Y limb is created by identifying the ligament of Treitz, exteriorizing jejunum about 15 cm distal from the ligament, and performing a Roux-en-Y jejunojejunostomy with customization and approximation of the Roux limb to prevent the Roux-en-Y jejunal limb from becoming unnecessarily long and redundant with growth, especially when CE is performed when patients are very young. Some surgeons predetermine the length of the Roux-en-Y jejunal limb without considering the size of the child, and customizing by using the length to the xiphoid process as a guide is recommended. Redundancy of the Roux limb leads to bile stasis in the limb itself that, in turn, can contribute to cholangitis or stone formation.
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