CT Characterization of Bile Duct Dilatation: Differential Diagnosis of Obstructive Jaundice

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1 대한방사선의학회지 1992 ; 28 (4) : 601 ""608 Journal of Korean Radiological Society, July, 1992 CT Characterization of Bile Duct Dilatation: Differential Diagnosis of Obstructive Jaundice Jae Hoon Lim, M.D., Yup Yoon, M.D., Young Tae Ko, M.D., Dong Ho Lee, M.D., Ik Yang, M.D. - Abstract- Department o[ Diagnostic Radiology Kyung Hee University Hospital Each Disease affecting the bile ducts tends to produce characteristic pattern of biliary dilatation: recurrent pyogenic cholangitis causes dilatation and straightening of the larger(central) intrahepatic ducts ; clonorchiasis causes dilatation of the smaller (peripheral) intrahepatic ducts; and carcinoma along the extrahepatic ducts causes (proportional) dilatation and tortuosity of both larger and smaller intrahepatic ducts. To evaluate the speci 디 city of the pattern and morphology of the dilated biliary tree on CT scans (CT characterization) three independent radiologists who were unfamiliar with the cases were asked to classify 62 CT scans in patients with obstructive jaundice. The case population consisted of 14 cases with recurrent pyogenic cholangitis, 18 cases with clonorchiasis and 30 cases with carcinoma along the extrahepatic ducts. which were intermixed randomly. Classification was made only on the basis ofct characterization: those scans showing primary lesions, i.t., stone, aggregate of flukes. or tumor mass were excluded or masked. All the scans of every case showing the extrahepatic bile duct were masked. Radiologists correctly classified 54 of the 62 cases (87%): ten of the 14 patients with recurrent pyogenic cholangitis(71 %). 17 of the 18 patients with clonorchiasis(94%) and 27 of the 30 patients with carcinoma along the extrahepatic bile ducts(90%). We believe that CT characterization ofbile duct dilatation is useful in the differential diagnosis of obstructive jaundice. especially when a primary pathologic lesion is not depicted in CT scans. Index Words: Bile ducts, CT Bile ducts, calculi Bile ducts. neoplasms Bile ducts. clonorchiasis Cholangitis INTRODUCTION Sonography and CT are the two most noninvasive diagnostic armamentarium in the differential diagnosis of obstructive jaundice. Differentiation of obstructive jaundice from non-obstructive jaundice is possible over 98% of the time by recognizing the dilated bile ducts. However, accuracy of identification of the causes of bile duct obstruction is 71-88% by sonography(l, 2) and 63-70% by CT(2. 3). The primary lesion is often elusive. and ultrasonogram. CT scan, or cholangiogram just reveals biliary dilatation: in these cases, however, diagnosis could be suggested on the basis of pattern of dilatation, that is distribution and shape ofthe dilated biliary tree. and further appropriate procedure could be tailored. 이논문은 년 2 월 10 일접수하여 1992 년 4 월 28 일에채택되었음. Received r ebruary 10. Accepted April Authors attempted to assess the diagnostic value of CT characterization of the biliary tree in the differential diagnosis of the three most common biliary tract diseases, namely recurrent

2 Journal of Korean Radiological Society 1992 ; 28(4):601""608 pyogenic cholangitis(rpcj, clonorchiasis, and car- CT scans were obtained with a CT/T 9800 cinoma along the bile ducts. MATERIALS AND METHODS The study population consisted of 14 patients with RPC, 18 patients with clonorchiasis, and 30 patients with carcinoma along the bile ducts (ten patients with cholangiocarcinoma of the extrahepatic ducts, 13 patients with pancreatic head carcinoma, and seven patients with carcinoma of the ampulla of Vater). These were consecutive cases during the period from April1988 to March 1991 except following cases; (1) those cases showing direct evidence of a disease on CT, namely stones in RPC, aggregate of f1ukes in clonorchiasis or mass in carcinoma(when the direct evidence was only in the extrahepatic ducts, those cases were included, because every CT slice of all the cases showing extrahepatic ducts was masked): (2) those cases having two kinds of diseases, such as clonorchiasis and cholangiocarcinoma, or clonorchiasis and RPC; (3) those cases that underwent interventional procedure before CT scanning since a catheter in the bile ducts implies malignant biliary obstruction in our hospital: (4) those cases in which the diagnosis was not confirmed. There was no case of sclerosing cholangitis or Caroli disease during the same period. There were four cases of choledochal cyst but these were excluded since the extrahepatic dilatation was evident and quite characteristic for the disease. Among the 14 patients with RPC, the diagnosis was based on the surgical findings and cultures in ten patients, and clinical as well as endoscopic retrograde cholangiographic findings in the other four patients. Clonorchiasis was diagnosed on the basis of demonstration of ova of Clonorchis sinensis in stool in 14 patients, and skin test (veronalbuffered saline extract of adult worms of Clonorchis sinensis, 1; 10,000 dilution) in four patients. In cancer, 19 cases were diagnosed surgically and/or pathologically, and the remaining 11 cases were diagnosed on the basis of clinical and cholangiographic findings Quick scanner (GE Medical Systems,Milwaukee) in 48 patients and other commercially available third generation scanners in the remaining 14 patients. Some CT scans were obtained both before and after contrast enhancement but we reviewed only the postcontrast scans. Postcontrast scanning was performed after bolus injection of 150 ml of 60% iothalamate meglumine (iodine content, 28%), (Conray; Mallinckrodt Institute Canada, Quebec, Canada). Contiguous scans with l-cm collimation (n=51), or 5-mm collimation with 2-mm interslice gap (n = 11) were obtained covering the entire liver and pancreas. The CT scans were mixed randomly. Every CT slice of all the cases showing extrahepatic bile ducts were omitted or masked so that the radiologists should think there might be a lesion in the extrahepatic bile duct or pancreas in all the cases included in this study. Three radiologists (two gastrointestinal radiologists [YTK. DHL) and one chest radiologist [YY) who were unfami1iar with the cases and blinded to the clinical information were asked to review the CT scans at the same session but answer independently. Before the test cases were reviewed, there was a brief introduction session explaining the proposed criteria using typical cases of each disease. Radiologists were not informed about the number of cases included for each disease. Each radiologist was asked to diagnose one ou t of three diseases. The radiologist were asked to diagnose RPC when the larger intrahepatic bile ducts (central one-halffrom the p 아 ta hepatis) are predominantly dilated with no dilatation of the smaller bile ducts ( central" dilatation, Fig. 1, 2) in association with abrupt tapering and straightening; clonorchiasis when the small or medium sized intrahepatic bile ducts (peripheral one-halffrom the porta hepatis, namely tertiary, quaternary and more peripheral division) are predominantly dilated ( peripheral'. dilatation, Fig. 3); carcinoma when the entire biliary tree is dilated proportionally (more dilatation in central and less in peripheral) with some

3 Jae Hoon Li m, et al : CT Characterization of 8ile Duct D i l~tation Fig. 1. Central dilatation in a 66-year-old man with recurrent pyogenic cholangitis. CT scan shows dilatation of the large intr 와 1epatic ducts including the right and left hepatic ducts and segmental ducts. Bile ducts are straight and taper abruptly toward the periphery. The dilated bile ducts are within central one-half of the liever for the porta hepatis. tortuosity of ducts ( proportional" dilatation. Fig. 4. 5). When there was disagreement in the diagnosis. they were asked to discuss and agree to diagnose one disease. RESULTS Fig. 2. Central dilatation in a 45-year-old woman with recurrent pyogenic cholangitis. Cholangiogram shows dilatation of the extrahepatic bile ducts and larger intrahepatic bile ducts but peripher 려 bile ducts are not dilated at all. Dilated intrahepatic bile ducts are rigid. straight and taper abrupt1y toward the periphery Note numerous lling defects of stones in the extrahepatic ducts. Only using the CT pattern of bile duct dilatation, the three observers correctly classified 42 of the 62 cases (68%). In 15 cases in which observers initially disagreed but agreed after discussion, their classification was correct in 12 cases and incorrect in three cases. In the remaining five cases, all observers agreed but classification was incor- a b Fig. 3. Peripheral dilatation in a 52-year-old man with clonorchiasis. (a) CT scan shows diffuse uniform dilatation of the intrahepatic ducts. predominantly in the periphery of the liver. The central ducts are also dilated but minimally dilated. (b) Endoscopic retrograde cholangiogram shows diffuse dilatation ofthe small and medium sized intrahepatic bile ducts in the left hepatic lobe. Note more severe dilatation at the periphery of the liver. The left h epatic duct and extrahepatic ducts are minimally dilated

4 Journal of Korean Radi 이 ogical Society 1992 ; 28(4):601"'608 a Fig. 4. Proportional dilatation in a 72-year-old woman with carcinoma of the head of,the pancreas. (a) CT scan shows dilatation of the large and small intrahepatic bile ducts. The larger bile ducts are dilated more severely than the smaller bile ducts. Note slight tortuosity and gradual tapering ofthe dilated bile ducts. (b) Percutaneous transhepatic cholangiogram (through a catheter) shows severe dilatation ofthe extrahepatic ducts (EHD) and larger intrahepatic ducts and gradual tapering toward the periphery. Note tortuosity of the intrahepatic bile ducts b rect. Thus three radiologists together made correct diagnosis in 54 of the 62 cases (87%) and incorrect diagnosis in eight cases (13%). Regarding individua1 disease. observers correctly classified ten ofthe 14 patients with RPC(71 %). 17 ofthe 18 patients with clonorchiasis (94%). 와ld 27 ofthe 30 patients with carcinoma along the extrahepatic ducts(90%). Observers misclassified four cases of RPC: three cases were misinterpreted as carcinomas (Fig. 6) and one case as clonorchiasis. Three carcinomas were misclassified as RPC in two cases (Fig. 7) 없ld clonorchiasis in one case. One case of clonorchiasis was misclassified as carcinoma(fig. 8). DISCUSSION Pattern of biliary dilatation in each bile duct disease is different from the others; for example. in Caroli disease. intrahepatic cystic biliary dilatation is quite characteristic; in sclerosing cholangitis. biliary tree is tortuous. focally dilated. naπow and discontinuous; in choledocha1 cyst. extrahepatic ducts are cystically dilated. More com- Fig.5. Proportional dilatation in a 67-year-old man with carcinoma of the ampulla ofvater. The right and left hepatic ducts. segmental and subsegmental bile ducts are dilated a:ld taper gradually toward the periphery. Far peripheral ducts are not dilated. Note slight tortuosity of the dilated ducts. mon diseases. especially in orienta1 countries such as RPC. clonorchiasis and cancer along the bile ducts genera1ly cause the characteristic pattern of biliary dilatation. In RPC. the extrahepatic bile ducts and the larger ( central") intrahepatic ducts. such as the

5 Jae Hoon Li m, et al : CT Characterization of Bile uuct Dilatation Fig. 6. Proportional dilatation caused by recurrent pyogenic cholangitis in a 72-year-old man. Three observers classified as proportional dilatation and diagnosed as carcinoma. Fig. 8. Proportional dilatation caused by clonorchiasis in a 56-year-old man. Three observers classified as proportional dilatation and diagnosed as carcinoma. Fig.7. Central dilatation caused by carcinoma ofthe ampulla of Vater in a 54-year-old man. Three observers classified as central dilatation and diagnosed as recurrent pyogenic cholangitis. right and left hepatic ducts and its first tributaries are dilated while small tributaries are not dilated (4-7) (Fig. 1. 2). The dilated 1arger intrahepatic ducts taper abruptly and straight as one goes to the periphery of the liver, resulting in an arrowhead' configuration toward the periphery of the liver (7). This pattem ofbiliary dilatation is due probab1y to 10ss of e1asticity of the 1arger bile ducts by recurrent infection. and inf1ammationlfibrosis of the small intrahepatic bile ducts. In clonorchiasis, the small ( peripheral") or meduim-sized intrahepatic bile ducts are dilated diffuse1y, while the 1arge intrahepatic ducts and extrahepatic bile ducts are norma1 or slightly dilated(8-12) (Fig. 3). Dilatation of the smaller bile ducts is cased by the f1uke itself as the f1ukes reside in the smaller intrahepatic ducts and causes mechanical obstruction, adenomatous hyperp1asia ofthe bile ducts, mucus hyperproduction and periducta1 fibrosis (8-10). Extrahepatic duct involvement is generally uncommon. In cancer of the bile duct such as cho1angiocarcinoma, carcinoma of the pancreas and ampulla ofvater, the entire bile ducts proximal to the mass are dilated proportional1y" regard1ess of the level of obstruction (Fig. 4, 5). though the severity of dilatation depends upon the degree and duration of obstruction. In moderate to severe dilatation, biliary tree becomes tortuous. Fig. 8 illustrates the characteristic pattem of bile duct dilatation in patients with RPC, clonorchiasis and carcinoma. CT is very sensitive in the delineation of the dilated biliary tree(ct characterization) and determination of the level of obstruction. However, delineation of the causes of biliary obstruction is sometimes difficult or impossible. Some stones in the bile ducts are not visualized as attenuation of stones is similar to bile or adjacent liver paren

6 Journal of Korean Radi 이 ogical Society 1992 ; 28(4):601"'608 chyma(7). Flukes in the small intrahepatic bile ducts are too small to be seen (12). Carcinoma of the bile duct or pancreas could be well delineated b c Fig. 9. Schematic drawing of characteristic bile duct dilatation. a. Central dilatation in patients with recurrent pyogenic cholangitis. Note straightening, abrupt peripheral tapering decreased arborization and obtuse angle of branching. b. Peripheral dilatation in patients with clonorchiasis. Note normal extrahepatic ducts. and too many dilated peripheral intrahepatic bile ducts. c. Proportional dilatation in patients with carcinoma. Note tortuosity of the dilated intrahepatic bile ducts. in general. but sometimes when a mass is sm외 1, its delineation is difficult(2.3). In our 62 cases. primary pathology was depicted on CT in 30 cases (48%) and equivoc외 in five cases (8%): in 27 cases (44%). the cause of obstruction was not depicted. The low rate of depiction of primary cause of obstruction is because of relatively large proportion of clonorchiasis. CT is particularly insensitive in depicting f1ukes: aggregates of f1ukes were demonstrated in only two of the 18 cases (11 %) of clonorchiasis. In RPC, stone was demonstrated in nine ofthe 14 cases (64%) and equivocal in one case. In the 30 carcinomas. mass was demonstrated in 19 cases (63%) and equivocal in four cases. Clinical significance of CT characterization of bile duct dilatation is its usefulness in patients whose CT discloses only biliary dilatation with no evident primary pathology. For example. the primary pathology was demonstrated in only 11 % in clonorchiasis but correct diagnosis could be made in 94% on the basis ofct characterization. In four ofthe 14 cases ofrpc (29%). the stone was not demonstrated. In seven of the 30 carcinomas(23%) along the bile ducts. the cancer mass was not demonstrated in CT: the masses were too small or incorporated with the adjacent organ or the pancreas and only abrupt obstruction of the bile duct was demonstrated. In these CT scans, the cause of bile duct obstruction could be suggested only on the basis of CT cholangiogram and further appropriate procedure could be tailored. When RPC is suggested on the basis of CT characterization. endoscopic retrograde cholangiography is indicated as a next step for diagnosis as well as a road map" for a surgeon. When clonorchiasis is suggested, stool test for ova of Clonorchis sinensis is indicated: endoscopic retrograde cholangiography or percutaneous transhepatic cholangiography is too invasive for these patients. When carcinoma is suggested. endoscopic retrograde cholangiography or per

7 cutaneous transhepatic cholangiography and/or percutaneous transhepatic biliary drainage is considered as a next procedure. The study is somewhat artificial and not in a real clinical setting in that only three common diseases were included and interpreters were to consider only three diseases and to pick the most likely ofthe three. In clinical setting. by contract a radiologist is faced with considering many other diagnostic possibilities including sclerosing cholangitis. Caroli disease and choledochal cyst. In our country. however. other biliary tract diseases other than the three common diseases. such as sclerosing cholangitis are rare. Caroli disease and choledochal cyst are very easy to diagnose as the biliary dilatation is quite characteristic. Another problem. which are tried to avoid. is that these three diseases are interrelated. that is two or three diseases may be present simultaneously. or one disease may cause another diseases as clonorchiasis may be the cases ofrecurrent pyogenic cholangitis or carcinoma of the bile ducts (11-13). The other point is in patients with RPC with localised dilatation of the intrahepatic bile ducts. such as the lateral segment of the left hepatic lobe or posterior segment of the right hepatic lobe. caused by stricture: in these patients. the intrahepatic bile ducts are dilated sometimes up to the periphery. Authors thank Hye Young Lee for her help in the illustrations of this manuscript. REFERENCES Jae Hoon Li m, et al : CT Characterization of Bile Duct Dilatation 160: Baron RL, Stanley RJ, LeeJKY, etal. Aprospective comparison ofbiliary obstruction using computed tomography and ultrasonography. Radiology 1982: 145: Wastie ML. Cunningham IGE. Roentgenologic findings in recurrent pyogenic cholangitis. AJR 1973;119: Lam SK. Wong KP, Chan PKW. Ngan H, Ong GB. Recurrent pyogenic cholangitis: a study by endoscopic retrograde cholangiography. Gastroenterology 1978:74: Chau EMT. Leong LLY, Chan FL. Recurrent pyogenic cholangitis: u1trasound evaluation compared with endoscopic retrograde cholangiopancreatography. Clin Radiol 1987: 38: Chan F-L, Man S-W, Leong LLY. Fan S-T. Evaluation of recurrent pyogenic cholangitis withct analysis of 50 patients. Radiology 1989; 170: Okuda K, Emura T. Morokuma K, Kojima S, Yokagawa M. Clonorchiasis studied by percutaneous cholangiography and a therapeutic trial of toluene-2, 4-diiso-thiocyanate. Gastroenterology 1973:65: Choi TK. Wong KP. Wong J. Cholangiographic appearance in clonorchiasis. Br J Radiol 1984; 57: Lim JH, Ko YT. Lee DH. Kim SY. Clonorchiasis: sonographic findings in 59 proved cases. AJR 1989;152; Choi BI. Park JH. Kim YI. et al. Peripheral cholangiocarcinoma and clonorchiasis: CT findings. Radiology 1984;169: Laing FC. Jeffrey RB Jr. Wing VW. Nyberg DA. 12. Choi BI. Kim HJ. Han MC. Do YS, Han MH. Lee Biliary dilatation: defining the level and cause by SH. CT findings of clonorchiasis. AJR 1989; real-time US. Radiology : : Gibson RN. Yeung E. Thompson JN. et al. Bile 13. Lim JH. Oriental cholangiohepatitis: pathologic. duct obstruction: radiologic evaluation of level. clinical and radiological features. AJR 1991: cause. and tumorresectability. Radiology 1986: 157:

8 Journal of Korean Radiological Society 1992 ; 28(4): 국문 요약 CT 에나타난담관확장의특징 : 폐쇄성황달의감별진단 경희대학교의과대학진단방사선과학교실 임재훈 윤엽 고영태 이동호 양익 우리나라에흔한 3 가지담도질환, 즉재발성화농담관염, 간홈충증과담관암은각각특정적인담관확장을초래하는 데, 재발성화농담관염은중심담관의확장, 간홉충증은말초담관의확장, 그리고담관암은전반적인담관확장을초래 한다. 저자들은전산화단충촬영상에서담관결석이나종괴등의질병자체가보이지않는경우전산화단충상에나타난 담관확장의유형만으로판단하여얼마나이들병을진단할수있는가를검토하였다. 화농담관염 14 예, 간홉충증 18 예와담관암 30 예의전산화단충촬영상을섞어 3 명의방사선과전문의에게주고 CT 에나타난담관폐쇄의유형만으로 3 가지병을진단하게하였다. 전체 62명중 54명 ( 87% ) 에서담관확장의유형만으로진단이가능하여재발성화농담관염, 간홉충증및담관암에서 전산화단충촬영에나타난담관확장의특정은폐쇄성황달의진단에매우유용하고, 특히질병자체가잘나타나지않 는예에서유용하게이용할수있다고믿는다