Figure 7.1 Geographical variation in CM.

Figure 7.2 Relationship of choledochal pressure to morphology. Stepwise increase in Types 1F, 1C and 4 CCM.

Figure 7.3 (a) Relationship of choledochal pressure to epithelial abnormality. Stepwise increase in choledochal pressure is associated with more abnormal choledochal epithelial lining (epithelial lining/mural score [ELMS]). (b) Relationship of bile amylase to epithelial abnormality. High levels of bile amylase levels (used here as a surrogate of pancreatic reflux) are associated with normal epithelial lining (ELMS).

Figure 7.4 King’s classification of congenital CM.

Figure 7.5 Giant cystic CM (Type 1C). MRCP of 2-month-old infant with a palpable mass, although not jaundiced. Intraoperative pressures were >20 mmHg, with minimal bile amylase content. (Courtesy of Brice Antao.)

Figure 7.6 Fusiform CM (Type 1F). Schematic showing common channel blocked with debris and contrast refluxing into a dilated pancreatic duct and exiting via the accessory pancreatic duct.

There have been later additions to this broad classification, particularly in trying to harmonise it with the various forms of pancreaticobiliary malunion [27], but they have not really been widely adopted by the surgical community. There is also an abnormal angle of insertion of the CBD into the pancreatic duct, and a variable degree of proximal bile duct stenosis. In Type 1C, this proximal part is very obviously stenotic, and in the younger ones almost diaphanous.

Type 2 CM are rarely reported [28] and may indeed be an acquired pathology arising as a healed perforation of the CBD. There has also been recent debate on whether Type 3 CM or choledochoceles should be included at all in any classification of CM. Thus, Ziegler et al. from Indianapolis [12] report a large series of adults and children with CM, including 28 with choledochoceles. There were so many differences in terms of clinical features and age at presentation that they suggested they were not really congenital malformations at all. Certainly, the progression from simple common channel to dilatation, stone formation and actual choledochocele perhaps related to ampullary stenosis is easily conceptualised.

7.5.1  Common pancreatobiliary channel

Wong and Lister [29] showed that the pancreatobiliary ductal junction in early fetal life invariably lies outside the duodenal wall and sphincter muscle complex. By the time of birth, however, the union comes to lie within the wall and the choledochal sphincter, and it is failure of this final phase that leads to what we perceive as an anatomical common channel. Therefore, whether such malunion is simply an expression of disordered, more proximal biliary development (and incidental) or the actual cause of later biliary pathology is a moot point. It is unarguable that such anomalies form an intrinsic part of the CM complex, being present in >90% when looked for. They are seen in Types 1C, 1F and 4 malformations, but not in Types 2 and 5. Similarly, a common channel is also seen in about 50% of cases of biliary atresia if looked for [30].

The prevalence of common channel in an adult North American study of 2847 patients subjected to endoscopic retrograde cholangiopancreatography (ERCP) for symptoms was 3.5% [31]. None of these had a defined choledochal dilatation, but many had recurrent abdominal pain and specifically recurrent pancreatitis which resolved on extended endoscopic sphincterotomy. The association of symptoms particularly in children and again typically recurrent pancreatitis with a defined common channel probably deserves the epithet common channel syndrome, first used by Okada et al. in 1981 [32]. This should be defined by ERCP ideally, as protein plugs in the CC are often the precipitating factor [33], with biliary diversion being the surgical goal. It should always be defined by the absence of biliary dilatation and a common channel, as those with abnormal bile duct diameters are comfortably within the Type 1F spectrum [34].

Box 7.1 considers further the concept of forme fruste choledochal cyst [35] or choledochal cyst sans cyst [36].

7.5.2  Caroli’s disease and syndrome

Jacques Caroli,^* a French gastroenterologist and prolific author, described a number of intrahepatic biliary pathologies, which carry his name [37,38]. The term Caroli disease is usually applied to ectasia or segmental dilatation of the larger intrahepatic ducts (typically the left hepatic duct system) without any other extrahepatic manifestation and is usually sporadic. This needs to be distinguished from Caroli syndrome, which is a genetic condition in which there are multiple, discrete, small yet saccular dilatations of the intrahepatic bile ducts with almost invariably hepatic fibrosis and usually renal disease (Figure 7.7). This is generally inherited in an autosomal recessive manner [39–41] with overlap to congenital hepatic fibrosis and polycystic kidney disease (both autosomal dominant and recessive types).

Figure 7.7 Jacques Caroli (1902–1979) and ERCP-diagnosed Caroli’s syndrome. Note the normal extrahepatic duct and absence of a common channel.

The surgical treatment of Caroli’s syndrome is controversial. If the dilated ducts are unilobar in distribution and there has been obvious complications and symptoms such as stone formation and cholangitis, then hepatic resection is indicated. Bilobar disease is more challenging and transplantation is sometimes performed [41]. Fortunately, most complications occur during adulthood and intervention during childhood is rare.

7.6    CLINICAL FEATURES

7.6.1  Antenatal detection

Antenatal detection of a choledochal cyst was first reported by Dewbury in 1980 [42] and has become an increasingly important mode of presentation, making up about 15% of our CM series since 2000. The differential diagnosis is, however, quite wide during fetal life and might also include duodenal duplication, duodenal atresia, parenchymal liver cysts and, most importantly, cystic biliary atresia [43,44]. Those that do indeed have a CM are almost invariably choledochal cysts (i.e. Type 1C), rather than fusiform malformations, and most are detected from 18 to 20 weeks of gestation, being fairly static thereafter. No further fetal intervention is warranted at this stage, and certainly no attempts at aspiration.

After birth, the US scan should be repeated and will now be more diagnostic due to increased accuracy outside the uterus. Normal pigmented stools should be confirmed after passage of meconium and the invariable early unconjugated jaundice level is monitored and seen to decline. The key element in these infants is to demonstrate biliary patency (clinically, biochemically or occasionally using a radioisotope scan), and then an elective operation can be planned. Some surgeons, even in these infants, do advocate very early surgery, but most will defer it to 3–6 months. By comparison, in those that are demonstrably obstructed or cannot be distinguished from cystic BA, early operation is mandatory.

7.6.2  Postnatal features

The classical clinical triad was always held to be jaundice and fever occurring in a child with a palpable right upper quadrant abdominal mass. Unfortunately, this classical picture only occurs in about 15% of all those with CM [9].

CM can present at any age, but more than 90% will do so within the first decade. Clinical manifestations do differ according to the age of presentation. So, the typical presenting features in the newborn period will mimic biliary atresia and specifically cystic biliary atresia with obstructive jaundice, acholic stools and hepatomegaly, depending on the degree of obstruction. Older infants and toddlers tend to present with jaundice due to obstruction and sometimes are found to have an upper abdominal mass; most of these will have a Type 1C lesion. If obstructive features are ignored, then biliary cirrhosis is possible, although seemingly not as common as was reported in some older series [9]. Our recent experience suggests that it is only seen now in <2% of children.

Recurrent abdominal pain becomes a feature later on, and this may be due to an obstructed high-pressure system or actual recurrent pancreatitis. The latter is usually mild and short-lived, and diagnosed as such because of the hyperamylasaemia. Although a generalisation, this scenario seems to be more usually associated with Type 1F CM. Sometimes, investigation will simply show a common channel, a history of definite pancreatitis but not much in the way of biliary dilatation.

7.6.2.1  CHOLEDOCHAL PERFORATION

Perforation of a high-pressure system is uncommon (5%) in most series, and in these, the clinical scenario may mimic spontaneous biliary perforation in infancy (see Chapter 11) or appendicitis in the older child. Here, bile leakage is usually confined to the retroperitoneum, which then tracks down the paracolic gutter, leading to right-sided guarding and tenderness.

Considering the degree of dilatation of some CM, stone formation is perhaps surprisingly uncommon. It is obviously a manifestation of stasis and can be pigment or cholesterol-based within the bile duct. Debris (also known as protein plugs) is relatively commonly observed in the common channel, and probably more to do with the pancreatic juice than bile flow.

7.6.2.2  PANCREATITIS

The association of pancreatitis and choledochal cyst has been noted since the 1960s [45]. Since then, it has become one of the most common modes of presentation in both children and adults. The mechanism is believed to be reflux of bile into the pancreatic duct, possibly precipitated by obstructing protein plugs in the common channel. It certainly seems more evident in those with Type 1F CM than the cystic variant [21,46], and there are certainly higher on-table bile amylase levels [19], although there is overlap.

Fictitious pancreatitis was a term used to describe the association of hyperamylasaemia with not much in the way of clinical symptoms of actual pancreatitis. It was believed to be caused by absorption of refluxed amylase through the denuded epithelium of a choledochal cyst [47].

7.6.3  Diagnosis and investigation

An accurate diagnosis of CM should be established preoperatively in virtually all cases of CM. The current standard is US followed by magnetic resonance cholangiopancreatography (MRCP) (ideally obtained using a 3.0 T MR scan), and this should define most elements of key biliary and pancreatic anatomy. The degree of common duct and intrahepatic dilatation can be precisely measured, together with the presence or absence of luminal content. The grey area unfortunately in both US and MRCP is within the head of the pancreas and the definition of the common channel (presence, length or dilatation) [48]. Delineation can be deferred to the operative cholangiogram in most cases if the other elements are diagnostic.

ERCP may be needed for diagnosis in some children with suspected common channel syndrome presenting with recurrent pancreatitis and only borderline biliary dilatation. Occasionally, ERCP and preoperative stenting may need to be done for obstructed CM in older children, although the jaundice in most who do present in this way is usually transient.

Biochemical liver function tests may be entirely normal or show evidence of biliary obstruction. Amylase levels may be elevated during episodes of abdominal pain, suggestive of actual pancreatitis. A prolonged international normalised ratio (INR) secondary to chronic cholestasis should be corrected with parenteral vitamin K.

A radioisotope scan (99mTc-DISIDA) will be able to show baseline liver function and impairment of biliary excretion if there is doubt in borderline fusiform cases. It can also be useful in the acute situation if perforation is suspected.

7.7    SURGICAL MANAGEMENT OF CHOLEDOCHAL MALFORMATION

Relatively simple internal drainage procedures (e.g. cystduodenostomy) were once the recommended treatment during a large part of the twentieth century, with more radical excision of the cyst and biliary reconstruction only replacing it during the 1970s. These early operations that left the cyst in situ, if followed up for long enough, were plagued by complications such as cholangitis, stone formation (sump syndrome) and ultimately malignant change or cirrhosis [49]. Most CM will now come to surgery with the aim of excision of the abnormal part of the biliary tract, diversion of bile away from the pancreatic duct and proximal restoration of bile flow from the liver into the intestine. In most cases of Types 1F and 1C CM, this is straightforward and involves excision of the extrahepatic duct and gallbladder and preferentially an hepaticojejunostomy (HJ) using a Roux loop or, more controversially, an HD (vide infra).

Some centres have reported ERCP and sphincterotomy alone as definitive treatment for mild fusiform dilatation (or a least a common channel), although their long-term prognosis is not known, given that they do not abolish the pancreatic reflux [50].

7.7.1  Choledochal excision and biliary reconstruction (hepaticojejunostomy)

See Figure 7.8a–c and Box 7.2.

7.8    SURGICAL CONTROVERSIES

7.8.1  Type 4 choledochal malformation

The appropriate surgical response to the combination of intra- and extrahepatic biliary dilatation is to be flexible. In children, one should accept that it may be appropriate and safe to leave parts of a dilated biliary tract in situ. Dilatation in some is simply a product of increased biliary pressure, and following surgical relief by HJ, the dilatation diminishes [51]. Hill et al. [52] report 20 children from our King’s series with Type 4 CM. We have consistent US-based follow-up in these children and showed that intrahepatic dilatation was equally distributed between right and left, and that there was a return to normal intrahepatic bile duct diameters in half the series. All the others showed significant diminution (Figure 7.9).

Figure 7.8 Operative steps: excision and reconstruction CM. (a) Schematic cystic CM. (b) Division at common hepatic duct. Dissection within head of pancreas to junction with common channel. (c) Reconstruction using hepaticojejunostomy.

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