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Year : 2015  |  Volume : 20  |  Issue : 3  |  Page : 128-132

Comparative analysis of spherical and fusiform choledochal cyst based on three-dimensional magnetic resonance cholangiopancreatography, biliary amylase, and histopathological examination

1 Department of Pediatric Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Pediatric Surgery, Advanced Pediatric Centre, Postgraduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Radiodiagnosis, Postgraduate Institute of Medical Education and Research, Chandigarh, India
4 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Date of Web Publication18-Jun-2015

Correspondence Address:
Dr. Prema Menon
Room No. 3103, Level 3-A, Department of Pediatric Surgery, Advanced Pediatric Centre, P. G. I. M. E. R., Chandigarh - 160 012
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0971-9261.159021

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Aims: The aim was to compare biliary amylase, common channel, and gall bladder/liver histopathology between spherical and fusiform choledochal cysts. Materials and Methods: Children undergoing cyst excision with Roux-en-Y hepatico-jejunostomy over a 17 months period were prospectively studied. The common channel was assessed by three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP). Results: Among 22 patients (spherical = 10, fusiform = 12), there was a higher incidence of spherical cysts in infants (5/7-71.4%) and fusiform cysts in older children (10/15-66.7%) (P = 0.09). Common channel identified in 14 (64%) cases was long (>10 mm) in 5 (38.2%) (one spherical, four fusiform [P = 0.5]) with associated high biliary amylase levels (>500 IU/L) in four (one spherical, three fusiform) (P = 0.05). Exact point of junction of common bile duct with pancreatic duct was visible with coronal half-Fourier-acquisition single-shot turbo spin-echo and 3D sampling perfection with application with optimize contrast using different flip angle evolution sequence using a reformatted plane of axis, particularly coronal, and coronal oblique orientation. Biliary amylase was raised (>100 IU/L) in 4 (40%) in the spherical group, compared to 8 (67%) in the fusiform group. Mean biliary amylase was similar in gallbladder and cyst in spherical but higher in gallbladder in fusiform cysts. Mean biliary amylase was <500 IU/L in 85.7% infants. Five out of 7 infants had liver fibrosis or cirrhosis on histopathology (P = 0.05). There were no dysplastic changes in the gallbladder epithelium. Conclusion: Three-dimensional MRCP delineated the common channel in two-third cases especially in coronal and coronal oblique orientation. The long common channel may have an etiological role in fusiform cysts. Spherical cysts, especially in infants, have a higher incidence of obstructive cholangiopathy.

Keywords: Biliary amylase, choledochal cyst, common channel, fusiform, spherical, three-dimensional magnetic resonance cholangiopancreatography

How to cite this article:
Aggerwal N, Menon P, Rao KN, Sodhi KS, Kakkar N. Comparative analysis of spherical and fusiform choledochal cyst based on three-dimensional magnetic resonance cholangiopancreatography, biliary amylase, and histopathological examination. J Indian Assoc Pediatr Surg 2015;20:128-32

How to cite this URL:
Aggerwal N, Menon P, Rao KN, Sodhi KS, Kakkar N. Comparative analysis of spherical and fusiform choledochal cyst based on three-dimensional magnetic resonance cholangiopancreatography, biliary amylase, and histopathological examination. J Indian Assoc Pediatr Surg [serial online] 2015 [cited 2023 Jun 1];20:128-32. Available from: https://www.jiaps.com/text.asp?2015/20/3/128/159021

   Introduction Top

Choledochal cysts (CC) are commonly either spherical (S) or fusiform (F) in shape with the former being more common in infants. [1] Very few studies have so far compared the morphology with associated abnormal union of the pancreatico-biliary junction (AUPBJ), biliary amylase levels and histopathological examination (HPE) of gall bladder (GB) epithelium. [2],[3] In this study, we compared these factors in these two types of CC and also assessed the role of three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) in the detection of the common channel.

   Materials and Methods Top

This was a prospective study of children below 12 years age diagnosed with CC presenting between August 2012 and December 2013. Clearance was taken from the Institute Ethics Committee. Patients were divided into two groups based on the anatomical shape of the CC (S/F) on ultrasonogram (USG) abdomen. Those with type II, III, and V CC based on Todani classification, [4] ruptured CC and those presenting with cholangitis requiring external drainage or endoscopic stent placement were excluded.

Patients underwent 3D MRCP as outpatients. This was performed on a 3-Tesla magnetic resonance system (Magnetom Verio; Siemens, Erlangen, Germany) with a phased-array body coil. Sequential thick slab coronal half-Fourier-acquisition single-shot turbo spin-echo (HASTE) images in upper abdomen, was followed by thin slab 3D respiratory triggered sampling perfection with application with optimize contrast using different flip angle evolution (SPACE) sequence. Contrast-enhanced study was done whenever indicated. Anatomical characteristics of the cyst including common channel, intrahepatic biliary radical dilatation (IHBRD), and pancreatic duct were assessed.

Complete hemogram, liver function tests (LFT), prothrombin index (PTI), and serum amylase were done on admission. At laparotomy, fluid from CC and GB were aspirated for estimation of amylase level before starting the dissection. Biliary amylase levels were classified as low (<100 IU/L), marginally high (100-500 IU/L) and high (>500 IU/L). [5] Total excision of the cyst (i. e., from just below the confluence above and intrapancreatic part below) and Roux-en-Y hepatico-jejunostomy was performed. The proximal and distal ducts were flushed with saline before excision. The distal duct was always ligated. Liver biopsy was studied for any obstructive changes, intra-hepatic biliary dilatation, and periportal fibrosis. GB and CC were also studied for dysplastic/metaplastic changes using periodic acid-Schiff stain. All patients were followed up till the end of the study period.

Statistical analysis was carried out using Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, version 15.0 for Windows). All tests were two-sided and were performed at a significance level of α = 0.05.

   Results Top

Over a period of 17 months, 10 patients with S (M:F = 1:1), and 12 patients with F CC (M:F = 2:1) (P = 0.4) were operated. The mean age at operation was 2.7 years ± 3.07 (range 4 months-10 years) in S group and 5.9 years ± 5.0 (range 9 months-12 years) in F group (P = 0.1). All patients were symptomatic. They presented with intermittent upper abdominal pain (5 S [50%] and 9 F [75%]), jaundice (8 [80%] S and 7 [58%] F), and large palpable abdominal mass (1 S). Four patients in each group had a past history of acholic stools and cholangitis (40% S, 33% F). Hepatomegaly (6 S [60%] and 2 F [16%] [P = 0.07]), splenomegaly (3 S [30%] and 1 F [8%] [P = 0.1]), as well as dilated abdominal veins with associated gastric varices (1 S) were noted. There was no statistically significant difference between the two groups.

The mean values of LFT in S and F groups were serum bilirubin (10.5 vs. 1.6 mg/dL), serum glutamic oxaloacetic transaminase (143 vs. 113 U/L), serum glutamic pyruvic transaminase (122 vs. 85 U/L), serum alkaline phosphatase (504 vs. 576 U/L), respectively (P > 0.05). PTI was significantly deranged in 3 (30%) patients in S group who also had a cirrhotic liver. Mean levels of serum amylase were 195 ± 418 U/L (S) and 109 ± 59 U/L (F). One patient in S group showed a marked elevation in preoperative serum amylase, which decreased significantly after surgery.

Choledochal cysts were identified in all patients on USG and MRCP. The mean diameter of CC in S and F group were 34.5 mm and 22 mm, respectively. Sludge/stone was identified in 50% patients. Pancreas and the pancreatic duct were found to be normal in all. Common channel was identified in 14 (64%) patients: 4 S (29%) and 10 F (71%) group (P = 0.7). The exact point of junction of the common bile duct (CBD) with the pancreatic duct was visible with coronal HASTE and 3D SPACE sequence using a reformatted plane of axis, particularly coronal and coronal oblique orientation [Figure 1]. Mild central IHBRD was seen in 7 S and 5 F CC.
Figure 1: Magnetic resonance cholangiopancreatography with maximal intensity projection of fusiform choledochal cyst joining main pancreatic duct to form common channel (a) Coronal anterior image (b) Coronal oblique image giving better visualization and (c) Coronal posterior image

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Intraoperatively, the shape of CC on MRCP was confirmed. In S group, one patient had an atretic GB, and three had ascites. Right accessory hepatic duct and inflamed, adherent CC was seen in one patient in each group.

Differences in length of the common channel, biliary amylase levels, and liver HPE between the two groups were analyzed [Table 1]. High biliary amylase level was seen in 4 (1 S, 3 F) out of five patients with the long common channel (P = 0.05). No statistically significant correlation was seen between raised preoperative serum amylase and raised biliary amylase in CC (P = 0.1) and GB (P = 0.1). HPE of CC in both groups showed fibrocollagenous wall and inflammatory infiltrates. There was no evidence of dysplasia, metaplasia or precancerous changes in the GB mucosa.
Table 1: Comparison of common channel length, biliary amylase, and liver histopathology between spherical and fusiform CC

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No wound infection, anastomotic leak or sub-acute intestinal obstruction was seen in either group. In S group, four infants developed sepsis with bleeding diathesis, among whom two (20%) with hepatic encephalopathy expired in the late postoperative period and another left against medical advice in view of poor prognosis (P = 0.1). All these patients had liver cirrhosis on HPE. There were no other complications during the follow-up period in any patient with a resolution of preoperative symptoms in all.

Differences between infants and the older children (>1-year) group were analyzed [Table 2]. Although HPE of CC and GB were similar, 3 out of 7 infants (2 S, 1 F) had cirrhosis compared to only one 2-year-old child (S) (6.6%) (P = 0.05) in the older age group. Porto-portal fibrosis was also milder in the latter group.
Table 2: Comparison of type of CC, biliary amylase and liver histopathology between infants and older children

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   Discussion Top

The incidence of CC in the Asian population is about 1 in 1,000 with two-thirds of cases reported from Japan. [5],[6] In spite of this high incidence and known association with AUPBJ, the etiopathogenesis is still not clear. [7] Some studies have described the association of common channel with particular forms of CC, pancreatic reflux (high biliary amylase) and biliary tract/GB malignancy. [3],[4],[5],[6] Very few have however compared all three aspects together between spherical and fusiform cysts.

In Japan, 60% CCs are diagnosed in patients <10 years old with a median age of 63 months. [3],[8] In our study, the mean age of presentation was 54 months with spherical dilatation presenting earlier at 2.7 years compared to fusiform dilatation (mean age: 5.9 years) (P > 0.05). Although literature search has shown a 3-4 times higher incidence in females, there was no major gender difference in our study (M:F ratio-1.5:1). [8],[9]

Magnetic resonance cholangiopancreatography plays a major role in the diagnosis of CC due to its noninvasive nature and ability to reconstruct structures without radiation. The pancreatic duct, as well as the CC is hyperintense on T2-weighted images, and are visible in most two-dimensional (2D) MRCP images. However, the common channel, normally 0.2-1.0 cm long, is not easily visualized on USG. It's length can be overestimated in conventional MRCP. [10] Komi et al. used endoscopic and intraoperative cholangiography to delineate the anatomy. [11] The CBD can join the main pancreatic duct at right angles, at an acute angle or as a complex network of ducts. Any injury during dissection of CC can predispose to postoperative pancreatitis. [10],[12] In our study, the exact point of junction of the CBD with the pancreatic duct was visible in 64% cases, with the length of the common channel varying from 5 mm to 18 mm. Coronal HASTE and a 3D SPACE sequence using a reformatted axis of the plane, particularly coronal and coronal oblique orientation were useful. Increased accuracy of common channel anatomy is probably the biggest advantage of 3D MRCP reconstructed images over 2D MRCP [Figure 1]. In nearly three-fourths patients where common channel was detected, fusiform dilatation (P > 0.05) was present, including the youngest, a 10-month-old infant. Suzuki et al. visualized AUPBJ in 53.3% (16/30) patients with a higher detection rate in fusiform compared to spherical dilatation (70% [14/20] vs. 20% [2/10]), the youngest a 26-month-old child with fusiform dilatation. [13]

The presence of AUPBJ can be strongly suspected when the biliary amylase is high. Bile acids are involved in the activation of pancreatic enzymes, which may induce chronic cholecystitis and later on mucosal hyperplasia in spite of the bile not coming into contact with the duodenum. [14] In infants, biliary amylase levels are usually very low, despite malunion due to the incomplete acinar growth of the pancreas. [8],[15] In our study also, the majority of infants had bile amylase <500 IU/L as compared to older children, which was statistically significant. Davenport et al. noted high levels of biliary amylase in spherical (2,700-28,000 IU/L) and fusiform (500-75,000 IU/L) types of dilatation. [16] In our study, patients with fusiform dilatation had relatively higher biliary amylase levels compared to the spherical group. Four of 5 patients who had long common channel had biliary amylase >500 IU/L (P = 0.05).Three of them had fusiform dilatation. This association of fusiform dilatation with AUPBJ may be the cause of the higher incidence of presentation with abdominal pain in our study. Pancreatitis and dysplasia in GB and CC are also therefore likely to be higher but were not corroborated in our study.

Ono et al. noted epithelial hyperplasia, chronic cholecystitis, and intramural fibrosis in GB irrespective of the type of dilatation. [17] A significantly higher incidence of mucosal hyperplasia in the fusiform than in the spherical type has been reported. [8],[18] Although not statistically significant, in our study, amylase levels were higher in GB compared to CC in the fusiform group. Iwai et al. also detected significantly higher biliary amylase levels in GB (91,284 ± 24,238 U/L) compared to CC (42,160 ± 9,091 U/L) in fusiform dilatation. [19] In our study, both CC and GB showed inflammatory changes with no dysplasia in either groups perhaps due to the age of presentation. However, we feel that these differences may predispose to dysplasia/metaplasia in GB epithelium especially in the fusiform group if treatment is delayed.

Obstructive cholangiopathy can lead to liver fibrosis in 35-66.7% patients although progression to cirrhosis is known to occur only in 2.1-11.8%. [20] Gong et al. noted a higher fibrosis score in the infantile group (2.5 ± 0.9) compared to pediatric group (1.5 ± 1.2) (P < 0.05) with most of the patients with obstructive jaundice having spherical dilatation. [21] In our study also, 60% patients with spherical dilatation had features of fibrosis or cirrhosis on HPE compared to 25% with fusiform dilatation. Overall, cirrhosis was seen in 57% infants and 6.7% older children (P < 0.05). Fibrosis was more common in older children and was milder in fusiform dilatation.

Spherical cysts tend to be narrow distally and also have shorter common channel. They are thus more likely to present with obstructive cholangitis especially in infancy with consequent changes in the liver. Fusiform cysts are wide distally and have a higher association with a long common channel and raised biliary amylase levels especially in the GB as seen in our study. The etiology of CC is still speculated upon. Our study suggests that the factors contributing to these two common shapes of CC are different. Further studies are required to assess the dynamics of the  Sphincter of Oddi More Details in children without AUPBJ.

Although no dysplastic changes were observed in any patient, early complete cyst excision and reconstruction prevents pancreatic reflux into biliary tract and injury to the liver. 3D MRCP improves preoperative anatomical delineation of the CC and common channel.

   References Top

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  [Figure 1]

  [Table 1], [Table 2]

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