Keywords
choledochal cyst - congenital choledochal malformation - hepaticojejunostomy - epidermoid
cyst
New Insights and the Importance for the Pediatric Surgeon
We describe two variants of choledochal malformations that do not fit the standard
classifications. One case appears unique consisting of a unilateral cystic dilatation
of the right-hepatic duct, surgically resected and anastomosed to a jejunal loop with
preservation of the left-sided biliary drainage. The cyst was lined with nonkeratinising
stratified squamous epithelium which is extremely rare in choledochal malformations.
Introduction
Congenital choledochal malformation (CCM) simply implies dilatation of the extra-
and/or intrahepatic biliary tract in the absence of obstruction. The actual pathogenesis
is not known for certainty, although most seem to be related to a degree of distal
stenosis leading to proximal dilatation.[1]
We have used our own Kings' College Hospital classification, which is a simplification
of Todani's classification, a modification of previous classifications. The commonest
are characterized as a cystic extrahepatic dilatation (type 1c), a fusiform extrahepatic
dilatation (type 1f), and the combination of either with intrahepatic duct dilatation
(type 4). In most of them, there is also an accompanying pancreaticobiliary junction
malformation and long common channel (CC) which has the potential for free intermixing
of bile and pancreatic juice.
We describe two patients with atypical morphology that did not conform to any of the
usual descriptions.
Case Reports
Case 1: the first case concerns a female infant of Iranian parentage born at term. Diagnosis
of a cyst at the porta hepatis was made on an antenatal scan just before birth after
arrival in the United Kingdom. Previous scans from abroad were not available. She
developed jaundice with a maximum total bilirubin of 380 µmol/L that settled spontaneously.
Alpha feto-protein (AFP) level was 756 kIU/L. Ultrasound and subsequent magnetic resonance
cholangiopancreatography (MRCP) showed a cyst with dimensions 20 mm × 16 mm at the
porta hepatis, without evidence of proximal intrahepatic biliary dilatation.
Surgical exploration and cholangiography was performed at 12 weeks and showed cystic
dilatation confined to the right-hepatic duct with an entirely normal left-hepatic
duct draped around and with a low insertion of a cystic duct into a normal-looking
common bile duct (CBD; [Fig. 1A]). Intraductal pressure was measured at 5 mm Hg (normal). There was no evidence of
a CC on the cholangiogram. Bile amylase was 4 IU/L and CA19-9 was 89,400 kU/L.
Fig. 1 Case 1: (A) schematic drawing of the choledochal malformation of the right-hepatic duct; (B) postoperative right-hepatic duct jejunostomy.
Following cholecystectomy, the cyst was detached from the CBD and the transected proximal
part with its draining segmental ducts anastomosed to a Roux's loop ([Fig. 1B]). The left duct and CBD were left intact. Histopathology showed a cyst lined by
nonkeratinising stratified squamous epithelium. Follow-up up to 1.5 years had been
unremarkable.
Case 2: The second case was a boy of Nigerian origin, born prematurely at 31 weeks, who
was presented with transient conjugated jaundice and was found to have a dilatation
(10 mm) of the proximal CBD. His mother was HIV + ve (low-risk retrovirus positive),
and he was treated with a nucleoside reverse transcriptase inhibitor since birth.
At birth, he had positive anti-HIV antibodies but DNA was not detectable. Images from
the preoperative MRCP and ERCP are shown in [Fig. 2].
Fig. 2 Case 2: preoperative MRCP (A) and ERCP (B) images of dilated proximal CBD. Note the normal distal CBD and absence of a CC.
CBD, common bile duct; CC, common channel; MRCP, magnetic resonance cholangiopancreatography.
Jaundice resolved but the dilatation persisted and increased over time, so he underwent
surgical exploration at the age of 2.6 years. This showed a cystic dilatation extending
proximally from the junction of cystic duct to the common hepatic bile duct (CHD).
Intracystic pressure was measured at 20 mm Hg (normal < 5 mm Hg). The remaining distal
CBD appeared normal and there was no evidence of a CC. Bile amylase was 5 IU/L and
CA 19.9 was 9,600 kU/L. Both cyst and gallbladder were resected and a hepaticojejunostomy
en-Roux performed. Histopathology showed a dilated bile duct lined by columnar type
biliary epithelium with mural fibrosis but with no significant inflammation.
He has had 2 years of follow-up with normal serial ultrasound scans.
Discussion
CCMs are rare with most infants and children (> 80%) presenting as types 1c, 1f, or
4. Most cases of extrahepatic dilatation are stereotypical with two basic morphologies.
The classical choledochal cyst (type 1c) involves the entire CBD, and CHD ending abruptly
in what can be a filamentous connection with the pancreatic duct. Alternatively, the
dilatation appears fusiform, of smaller diameter, with a more gradual termination
and junction with the pancreatic duct.
Unilateral cystic dilatation of the hepatic duct is exceptional with perhaps only
two reported cases in the literature. Prekop et al reported a 14-month-old boy with
a large “cystic malformation of the right-hepatic duct,” with little more clinical
detail including nature of epithelial lining.[2] Gidi et al reported a 56-year-old woman with cystic dilatation of the right-hepatic
duct who underwent a resection of the cyst with right hepatectomy to achieve complete
resection. Histopathology was similar to our own, although it was described as extensive
squamous metaplasia with areas of columnar epithelium rather than de novo stratified
squamous epithelium characteristic of ours.[3] As normal bile duct consists of vascularized, innervated fibrous tissue, lined by
a single layer of tall columnar epithelium, we feel that ours is likely to be congenital
rather than acquired metaplasia.[1]
The lining and situation in the porta hepatis in our first case do appear similar
to that of the squamous-lined cystic dilatation described by Chiu et al in a 6-month-old
boy.[4] This malformation was antenatally detected and, at operation, found to arise from
the common hepatic duct with separate entry of both right- and left-hepatic ducts.
Finally, Kwon et al described a diverticulum of the bile duct (type 2 CCM) with stratified
squamous epithelial lining in a 63-year-old man.[5] Metaplastic squamous lining often associated with recurrent infection and stones
can lead to malignant change.[6] Certainly, the age of our child implies a congenital rather than metaplastic origin
for the squamous nature of the epithelium.
The second case, while nominally a type 1c, is distinctly unusual with sparing of
the distal duct and no CC. The high-intracystic pressure of 20 mm Hg suggests an obstructive
etiology, and there was no suggestion of extrinsic compression as might be found with
a healed spontaneous perforation.[7] It is interesting to note that this child was delivered from an HIV + ve mother,
though it is difficult to find real evidence of cause and effect.[8]
We have previously reported a series of CCM where we measured CA 19.9 in bile to try
and identify a cohort who might have particular predisposition to dysplasia and perhaps
later malignancy.[9] We found that it was invariably raised and often in very-high concentration but
bore no relationship with simultaneous obtained bile amylase and choledochal pressure.
Indeed, it could be localized on staining to otherwise normal biliary epithelium.
CA 19.9 levels in both cases were raised, although whether that represents normal
biliary tract epithelium elsewhere or from the cyst is not known.
Surgical reconstruction was bespoke in case 1 with preservation of the left-sided
biliary drainage but more typical in case 2. Primary duct to duct anastomosis seemed
possible in that case but was rejected, as it was felt to be less safe than a standard
Roux's loop.
Conclusion
In conclusion, neither case fits comfortably into the standard CCM classifications
and both present different perspectives on possible etiological factors.[10]
