Imaging of Obstructive jaundice

Xray, USG and CT findings of Obstructive Jaundice

1. Imaging of obstructive Jaundice (X-ray, USG & CT) OSR Dr. Yash Kumar Achantani

2. Jaundice Jaundice is a yellowish discoloration of the skin, mucous membranes and of the white of the eyes caused by elevated levels of the chemical bilirubin in the blood (hyperbilirubinemia). The term jaundice is derived from the French word jaune , which means yellow. Jaundice is not a disease per se, but rather a visible sign of an underlying disease process. Jaundice is typically seen when the level of bilirubin in the blood exceeds 2.5-3 mg/ dL (milligrams per deciliter ).

3. Types It can be largely divided into two types: Non-obstructive, i.e. pre-hepatic and hepatic causes. Obstructive, i.e. post-hepatic causes. Imaging has a major role in detecting the obstructive causes.

4. Causes Prehepatic Haemolytic anaemia Mechanical heart valve Hypersplenism Hepatic Acute hepatitis / acute liver failure Cirrhosis Gilbert syndrome

5. Post-hepatic (a.k.a. Obstructive jaundice) Benign causes Choledocholithiasis Strictures, e.g. post-inflammatory/infectious, primary sclerosing cholangitis External biliary tree compression, e.g. pancreatic pseudocyst, Mirizzi syndrome. Malignant causes Portal lymphadenopathy Cholangiocarcinoma Carcinoma of head of pancreas Hepatocellular carcinoma Gallbladder carcinoma

6. BILIARY ANATOMY The intrahepatic pattern of bile branching is best described according to the system of Healey and Schroy , to which can be applied the Couinaud system for numbering segments.

7. Variations of biliary branching patterns. The more common are A, B and C.  

8. The cystic duct typically joins the common hepatic duct in the middle third of the extrahepatic bile duct (often referred to as the ‘common duct’ on US for convenience), which then continues as the common bile duct. The cystic duct usually joins the right side of the common duct but can pass behind or in front of the common duct to join it from the left. The cystic duct can join the common duct at a very low level in which case it may be mistaken for the common duct on imaging. Uncommonly it may join a right-sided duct, which is usually a low, aberrant right sectoral or segmental duct . Some of these variations predispose patients to duct injury at cholecystectomy.

9. Other variations include Ducts of Luschka or subvesical ducts (an intrahepatic duct running adjacent to the gallbladder fossa, unaccompanied by a portal vein branch, and emptying into either the right hepatic or common hepatic duct) Cystohepatic ducts (small ducts that drain directly into the gallbladder or cystic duct) It is important to remember that the anterior position of the left intrahepatic ducts affects the pattern of filling at direct cholangiography. During PTC or T-tube cholangiography it may be necessary to roll the patient to the left to ensure good left-duct filling. Conversely the left ducts fill first at endoscopic retrograde cholangiopancreatography (ERCP) with the patient in the prone position. Furthermore, as the patient is usually oblique during ERCP, the left-sided ducts are often projected to the right and may be misinterpreted as being right-sided ducts if there is incomplete filling of intrahepatic ducts.

10. Methods of Investigation ORAL CHOLECYSTOGRAPHY COMPUTED TOMOGRAPHIC (CT) CHOLANGIOGRAPHY MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY PERCUTANEOUS TRANSHEPATIC CHOLANGIOGRAPHY INTRAOPERATIVE CHOLANGIOGRAPHY T-TUBE CHOLANGIOGRAPHY HEPATOBILIARY SCINTIGRAPHY ENDOSCOPIC ULTRASOUND

11. ORAL CHOLECYSTOGRAPHY Oral cholecystography (OCG) relies on the overnight absorption of an oral contrast agent, such as sodium ipodate , which is absorbed from the bowel, excreted into the bile and then concentrated in the gallbladder. Gallstones appear as filling defects in the gallbladder and may layer on a horizontal beam film. Nonopacification of the gallbladder signifies either absence or pathology of the gallbladder provided that the common bile duct is opacified . Ultrasound (US) has replaced OCG for the diagnosis of gallstones. More recently oral contrast agents have been used for CT cholangiography, although most centres use intravenous cholangiography IV biliary contrast agents.

12. Normal GB Cholelithiasis

13. CT CHOLANGIOGRAPHY CT cholangiography has been used to describe two techniques using negative and positive contrast methods, respectively. The negative contrast makes use of bile as a negative contrast agent to display the biliary tree using various reformatting techniques. The reformats improve the CT evaluation of bile duct obstruction, though they do not improve the detection of duct stone. Positive contrast agents are either IV or oral contrast agents that are excreted preferentially by the liver to opacify the bile ducts. The oral agents, such as iopanoic acid and sodium ipodate , were commonly used for OCG in the past, and the IV agents, such as sodium iotroxate , were used for conventional IV cholangiography using planar tomography. IV agents achieve diagnostic duct opacification more reliably than oral agents but are not universally available. Adequate contrast excretion relies on near-normal hepatocyte function, so the technique is of no value in the investigation of jaundice, and usually fails if bilirubin levels are more than two to three times normal.

14. Most centres now use IV contrast agents for CT cholangiography, so-called CT-intravenous cholangiography (CT-IVC). This technique involves the IV infusion of an agent such as sodium ipodate with helical CT performed about 30 min later. Multislice helical CT allows high resolution scanning and multiplanar reformatting. Since CT-IVC relies on the excretion and subsequent passage of a contrast agent, it provides a functional dimension not obtained with conventional magnetic resonance cholangiography (MRC), allowing the direct demonstration of bile leaks, biliary communication with cysts and segmental obstruction. CT-IVC can be made difficult by the presence of intraductal gas. This is more easily recognized than with MRCP and repeating the examination with the patient prone can overcome the problem.

15. Normal CT cholangiogram

16. PERCUTANEOUS TRANSHEPATIC CHOLANGIOGRAPHY PTC has been substantially replaced by ERCP and MRCP. Its role now is mostly as part of transhepatic biliary intervention, although occasionally it is used diagnostically. A 22 g Chiba needle is used to puncture the right or left intrahepatic ducts from the right flank or, for left ducts, from an epigastric approach. The epigastric approach is used if the left ducts cannot be opacified from the right or as part of a left-lobe approach to biliary drainage. Any coagulation disorder should be reversed with vitamin K prior to the procedure, which is performed with broad-spectrum IV antibiotic cover and conscious sedation.

17. If the ducts are dilated the needle is withdrawn gradually with suction applied and when bile is aspirated(reduces the risk of bile leak and endotoxaemia by reducing intraductal pressure) contrast medium is injected to opacify the biliary tree. Samples should be taken for microbiology and, if malignant obstruction is suspected, cytological examination. Care should be taken to opacify the entire biliary tree, especially in cases of lobar or segmental biliary obstruction. One common pitfall is the failure to fill the left hepatic ducts from a right-sided approach and this should be suspected if there are no ducts opacified in the midline.

18. The white arrow points to filling defect consistent with the stone in the lower CBD

19. INTRAOPERATIVE CHOLANGIOGRAPHY Intraoperative cholangiography (IOC) is performed either routinely or selectively during cholecystectomy to detect choledocholithiasis , confirm duct stone clearance and provide a roadmap in an attempt to reduce the risk of bile duct injury.

20. T-TUBE CHOLANGIOGRAPHY If the common bile duct has been explored at cholecystectomy a T-tube is usually left in place and cholangiography performed via this tube after about 7 d, prior to its removal. Cholangiography should confirm stone clearance and the free passage of contrast medium into the duodenum. Care must be taken to avoid the injection of air bubbles.

21. Normal post cholecystectomy

22. Choledocolithiasis

23. ENDOSCOPIC ULTRASOUND Biliary endoscopic ultrasound (EUS) provides high-frequency grey-scale imaging (and in some systems colour Doppler imaging) for evaluation of the extrahepatic biliary tree and pancreas. It allows direct visualization of the duodenum and fine-needle aspiration cytology. More sophisticated and expensive systems of ‘mother-daughter’ probes allow intraductal examination of the common bile duct, but are not in routine use.

24. A polypoidal lesion within the ampulla consistent with a biopsy-proven adenoma

25. A small distal common bile duct stone

26. Role of Imaging in investigation of Obstructive jaundice

27. The principal role of imaging in the jaundiced patient is the identification and detailed assessment of major bile duct obstruction. US is the preferred initial imaging investigation, but will usually be supplemented with a combination of CT, MRCP, direct cholangiography and, in some centres, endoscopic and/or intraoperative US. The questions that need to be addressed are: 1     Is bile duct obstruction present? 2     What is the anatomical level of obstruction ? 3     What is the cause of the obstruction ? 4     If the obstruction appears to be malignant T

28. The first task is to determine if there is intrahepatic and/or extrahepatic duct dilatation as a marker of duct obstruction. The intrahepatic ducts should measure no more than 2–3 mm centrally; more peripherally they are usually only just visible on US and should be clearly smaller than the adjacent portal vein branches. Mild dilatation of the intrahepatic ducts may occur without duct obstruction in the elderly. The maximum diameter of the normal common duct (includes the common hepatic and common bile duct) is influenced by age and where the duct is measured. A diameter of >7 mm is commonly used as a predictor of bile duct obstruction in the jaundiced patient but this is only a guide In the normal older population values of 8 mm or more are not unusual. If there has been a cholecystectomy the upper limit of ‘normal’ is less well defined and the duct tends to be larger, commonly up to 10 mm.

29. If only the very upper end of the common duct is seen and is not dilated this does exclude pathological dilatation of the more inferior portion. Conversely, if there is mild dilatation of the suprapancreatic portion but the duct tapers to a normal size in its pancreatic portion, further imaging is not mandatory and should be guided by the clinical likelihood of duct obstruction. Hilar biliary obstruction will produce only intrahepatic duct dilatation, whilst more distal obstruction will result in extrahepatic dilatation followed by intrahepatic dilatation. Approximately 95 per cent of patients with bile duct obstruction have biliary dilatation, the degree of which is related to the duration and completeness of the obstruction. In the remaining 5 per cent there are usually sufficient clinical/biochemical indicators of duct obstruction to suggest that cholangiography of some form (MRCP or ERCP) is warranted. Most cases of biliary obstruction without duct dilatation are due to choledocholithiasis, primary sclerosing cholangitis or postoperative stricturing.

30. The next question is to determine the anatomical level, namely whether it is hilar (at or close to the confluence of the right and left hepatic ducts), or low/mid common duct . This helps with the differential diagnosis as well as in the selection of further imaging tests. The main differential diagnoses are summarized in. Anatomical Location Malignant Benign Hilar Gall bladder HCC Low/ Mid duct Pancreatic CA Ampullary CA Pancreatitis (acute or chronic) Either Cholangiocarcinoma Metastases Lymphoma Benign biliary tumors Stones, Mirizzi Syndrome, Post op stricture, PSC, Hemobilia , Parasites.

31. The next questions relate to the detailed evaluation of malignant obstruction in regard to tumour resectability and biliary decompression options. In malignant hilar obstruction any evaluation should assess the proximal extent of stricturing into the right and left hepatic ducts, the presence of lobar atrophy, the patency of the portal veins (main, right and left branches) and the presence of any intrahepatic or local extrahepatic metastases. The proximal extent of stricturing is classified according to the modified Bismuth classification . In malignant low obstruction, usually due to pancreatic carcinoma, the main factors to assess are tumour size, vascular involvement (portal vein, superior mesenteric vein and superior mesenteric artery), lymph node metastases and hepatic metastases

32. Modified Bismuth classification of malignant hilar biliary obstruction based on proximal extent of tumour

33. CHOLEDOCHOLITHIASIS At least 90 per cent of bile duct stones are stones that have passed from the gallbladder, so-called secondary stones. Primary stones are those that arise in the bile duct and these are pigment stones. For patients younger than 60 years undergoing cholecystectomy 8–15 per cent have duct stones, the figure increasing substantially in older patien .

34. Ultrasound This is the most commonly used initial imaging modality. Sensitivity varies greatly with the upper range being 50–80 per cent. The sensitivity in jaundiced patients tends to be better. Positive stone diagnosis depends on the demonstration of an intraductal echogenic focus in both the longitudinal and transverse planes. US measurement of bile duct diameter has value as a predictor of the presence of bile duct stones, apart from the direct detection of stones. If the bile duct diameter is <4 mm in patients undergoing cholecystectomy the likelihood of duct stones is very low. As the diameter increases, the likelihood of duct stones also increases Duct dilatation and acoustic shadowing are each absent in about 30 per cent of cases.

35. Choledocholithiasis . Small shadowing stone (arrow) in dilated bile duct.

36. Choledocholithiasis : A. Dilated CBD with calculus seen in longitudinal US scan

37. Diameter of <4 mm carries a high negative predictive value for choledocholithiasis regardless of the presence of the gallbladder. It is useful, therefore, to report bile duct diameter in suspected gallstone disease. Endoscopic US is more accurate than transcutaneous US, with a sensitivity of >90 per cent and an even higher specificity . It is relatively expensive and invasive and its use depends on local expertise. Conditions that may mimic stones on US are: 1. Intraductal gas - usually recognizable by its linear nature and its movement. 2. Haemobilia and sludge - they produce more diffuse echoes than stones. 3. Surgical clips, hepatic artery calcification and duodenal diverticula - these do not lie within the lumen of the duct 4. Parasites .

38. CT Similar to gallstones, bile duct calculi depending on their composition, may appear calcified, of soft tissue density, isodense or hypodense with respect to bile. Unenhanced CT is better for their detection as most calculi are slightly hyperdense. High attenuation calculi can easily be seen on CT; contrasted against the lower attenuation of bile or that of ampullary soft tissue. Bile duct calculi may reveal a faint hyperdense rim with a central low density area (rim sign). Even impacted stone with no surrounding bile can be detected by noting that the visualized calcific nodule (stone) lies in the course of the CBD.

39. Approximately 50% of the bile duct calculi are of faint attenuation only slightly greater than the surrounding bile or are isoattenuating of adjacent pancreas. Detection of these stones is facilitated by looking for a rim or crescent of bile that outlines these subtle intraluminal densities. Abrupt termination of dilated CBD in absence of any direct evidence of calculus is an indirect sign of choledocholithiasis. This finding is however nonspecific and is more often due to a malignant etiology . When a strong suspicion of CBD stone exists, water should be used to opacify bowel. Positive oral contrast should be withheld as it may obscure stones impacted at the ampulla of Vater. CT visualisation of bile duct calculi is optimized with the thin collimation isotropic MDCT scanners.

40. MDCT has revived interest in CT cholangiography. CT cholangiography has shown to provide excellent visualization of the biliary anatomy with 95% sensitivity for choledocholithiasis. On cholangiography, calculi within the bile ducts are seen as round or faceted filling defects within the contrast column. These defects are usually mobile. When impacted, a typical convex border of the contrast column in the distal CBD is seen outlining the proximal stone margin and obstruction to flow of contrast is noted. Air-bubbles are a common problem at cholangiography, but can usually be differentiated by their smooth, round appearance and their tendency to group together and rise to the non-dependent surface as compared to stones which are usually faceted or elliptical and tend to fall at the dependent portion of the biliary tree.

41. Choledocholithiasis . A distal common bile duct stone (arrow) is slightly dense compared with the surrounding low-density bile.

42. Choledocholithiasis . CT-IVC shows a small stone within the opacified distal common bile duct.

43. Choledocholithiasis . CT scan shows a rounded hyperdense calculus in the distal CBD surrounded by a crescent of bile

44. Axial CT abdomen (a) and coronal reconstruction (b) in a 75-year-old man with a history of abdominal pain and jaundice. (a) Black arrow points to dilated intrahepatic ducts. (b) Coronal CT shows large 1.2 cm obstructing calcified gallstone in the suprapancreatic portion of the common bile duct. Previous endovascular repair of abdominal aortic aneurysm noted.

45. BENIGN BILIARY STRICTURES Benign strictures of the biliary tree can be due to surgical and other trauma, chronic pancreatitis, gallstones and duodenal ulcer. POSTOPERATIVE BILIARY STRICTURES Benign strictures are most often a sequel of direct injury or ischemic injury to bile ducts during biliary tract surgery. In patients suspected of postoperative CBD strictures, US should be carried out as a screening procedure. In the presence of proximal dilatation of CBD with smooth tapering stenosis or sudden cut off of CBD, no further investigation is required. If US findings are equivocal or normal despite strong clinical suspicion of CBD stricture, MRCP and if required ERCP/PTC should be performed.

46. Postoperative CBD stricture—US showing dilated proximal part of the CBD with sudden cut off

47. POST-INFLAMMATORY STRICTURES Post-inflammatory strictures can be caused by cholangitis, chronic pancreatitis, gallstones and penetrating or perforating duodenal ulcer. In chronic pancreatitis, strictures occur in less than half of the patients. The most frequent configuration on cholangiography is about 3 to 5 cm, smooth, concentric, often tapered narrowing of the intrapancreatic portion of the CBD. An hour-glass configuration or deviation by a pseudocyst may also be seen. Strictures associated with gallstones are often short and sometimes web like. These may be single or multiple and may involve any portion of the biliary tree.

48. Common duct stricture may result from fibrosis secondary to an adjacent inflamed gallbladder. US, CT and MRI primarily demonstrate biliary dilatation but may also reflect the primary pathology leading to strictures e. g. pancreatitis, gallstones or CBD stones.

49. Cholangiographic appearance of bile duct strictures (as identified by Caroli & Nora) . Type I: Long retropancreatic stenosis. Type II: Dilatation of the main bile duct, stricture of the sphincter of oddi. Type III: Hourglass stricture. Type IV: Symptomatic of either a cyst (a), or a cancer (b and c). Type V: Cancer of the pancreas.

50. CT scan showing pancreatic calcification and common bile duct dilatation (arrow).

51. PRIMARY SCLEROSING CHOLANGITIS Primary sclerosing cholangitis (PSC) is a chronic progressive cholestatic disease of unknown etiology that occurs more commonly (70%) in males and has a median age of onset of 40 years. Radiology plays a crucial role in the diagnosis of PSC as clinical features are nonspecific, there is no specific serological marker and histology alone is not diagnostic. Cholangiography is the most definitive imaging modality for the diagnosis of PSC. In most cases ERCP is sufficient and PTC is performed only if certain segments of the biliary tract are not opacified at ERCP.

52. Diffuse, multifocal, short (1-2 cm in length) strictures in both intrahepatic and extrahepatic bile ducts are the hallmark of PSC. Strictures alternate with normal or mildly dilated intervening duct resulting in a beaded duct appearance. Other manifestations of PSC are shorter (1-2 mm) band-like strictures and small diverticulum- like outpouchings (1mm to 1 cm), seen most frequently in the extrahepatic bile ducts and also intraluminal webs. Fibrous obliteration of peripheral bile ducts can result in "pruned-tree" appearance. In approximately 50% patients with PSC bile duct irregularity is seen as subtle brush-border like appearance to coarse, shaggy or frankly nodular appearance.

53. Cross sectional imaging in PSC reveals thickening and dilatation of bile ducts. Duct wall thickening often with marked contrast enhancement, skip dilatations and stenosis and mural webs have also been demonstrated on CT as well. Upper abdominal lymphadenopathy is frequently seen in patients with PSC and does not necessarily indicate development of cholangiocarcinoma. PSC induced cirrhosis induces unique morphological changes in the liver. There occurs atrophy of the lateral segments of the left lobe of liver in addition to atrophy of posterior segments of the right hepatic lobe and marked hypertrophy of the caudate lobe. The liver appears rounded with a lobulated contour.

54. Cholangiocarcinoma occurs in about 10 per cent of affected patients and is notoriously difficult to diagnose early. It should be suspected if there is progressive duct dilatation proximal to a stricture, or if a nodule >1 cm in diameter is identified. Dual-phase, contrast-enhanced CT, especially when correlated with cholangiography, can improve cholangiocarcinoma detection.

55. Primary sclerosing cholangitis. CT-IVC (maximum intensity, oblique coronal reformat) shows multiple intrahepatic and extrahepatic segments of stricturing .

56. Primary sclerosing cholangitis. An intraoperative cholangiogram shows strictures and characteristic diverticula-like outpouchings affecting the common duct.

57. Primary sclerosing cholangitis. Typical bile duct wall thickening on US (arrows).

58. MIRIZZI SYNDROME Mirizzi syndrome is an uncommon complication of long standing cholelithiasis characterized by common hepatic duct or CBD obstruction due to extrinsic compression from an impacted gallstone in the cystic duct or gallbladder neck or from associated inflammatory changes. It may be complicated by fistula formation between the gallbladder and common hepatic duct/common bile duct secondary to an eroding stone. The hallmark imaging features include cholelithiasis with intrahepatic biliary dilatation and dilated common duct till the porta hepatis beyond which the CBD is normal in calibre. Multiplanar reformatted images are particularly useful in depicting the extrinsic nature of the obstruction. Definite diagnosis of internal biliary fistula can be established by ERCP/PTC.

59. Mirizzi syndrome. MRCP (A) shows a stricture of the lower common duct caused by a stone (arrow) lying in an expanded cystic duct on ERCP (B). Multiple gallbladder stones are also seen.

60. CHOLEDOCHAL CYSTS Choledochal cyst is an uncommon congenital cystic dilatation of the bile duct. Most patients present in childhood although no age is exempt. The triad of jaundice, right upper quadrant pain and a palpable subcostal mass is diagnostic but is not seen in all cases. Reported complications of choledochal cysts include secondary calculus formation, pancreatitis, biliary cirrhosis, cyst rupture with bile peritonitis, cholangitis, intrahepatic abscess, portal vein thrombosis and malignant transformation into cholangiocarcinoma.

61. Todani et al 24 have classified choledochal cysts into five types: Type I: Fusiform cystic dilatation of extrahepatic CBD. Type II: Eccentric fluid-filled cyst (diverticulum) Type III: Localised cystic dilatation of distal intramural segment of CBD Type IVA: Multiple intrahepatic and extrahepatic bile duct cysts. Type IVB: Multiple extrahepatic bile duct cysts. Type V: Multifocal saccular dilatation of IHBR ( Caroli's disease). Ultrasonography is preferred for initial evaluation. It reveals an anechoic cystic structure separate from the gall bladder that communicates with the hepatic ducts. CT, MRI and cholangiography can accurately diagnose and classify choledochal cyst. MRCP is equivalent to ERCP in detecting and defining the morphology of choledochal cysts and in detecting the presence of anomalous union of the pancreatic and bile ducts.

62. Biliary cystic disease classification (after Todani ).

63. Type I choledochal cyst Type IV choledochal cyst

64. Type IV choledochal cyst on PTC with extrahepatic as well as intrahepatic cystic dilatation of bile ducts and a characteristic long common channel shared by the common bile duct and pancreatic duct (arrow).

65. Choledochal cyst type V: Caroli’s Disease. Ultrasound (A) and axial T2W MR image (B) shows saccular dilatation of the intra-hepatic biliary ducts

66. PARASITIC DISEASES Although many parasites of the gastrointestinal tract may traverse the biliary tract, clinically significant infestation is seen most commonly with Ascaris lumbricoides, Clonorchis sinensis and Echinococcus granulosus. Ascaris lumbricoides: Ultrasound is the most valuable diagnostic tool that reveals the worms as tubular, nonshadowing, echogenic structures in the dilated biliary ducts. When alive the worms can be seen to move. On unenhanced CT, they appear as hyperattenuating tubular structures surrounded by less attenuated bile. In transverse sections on both US and CT, a "bull's eye" image may be seen caused by the worm inside a dilated bile duct. On cholangiography, the worms may be seen as smooth cylindrical filling defects.

67. Biliary Ascariasis. US scan (A) showing linear echogenic lesion in the dilated CBD. (B) ERCP confirms the same finding

68. Clonorchis sinensis: Clonorchis sinensis is the most important among liver flukes. Adult worm resides in the intrahepatic bile ducts where it causes biliary obstruction, incites an inflammatory response with recurrent pyogenic cholangitis and in later stages causes periductal fibrosis. These worms appear as small short and curvilinear leaf like filling defects (2 to 10 mm in length) on cholangiograms. The flukes tend to concentrate in the peripheral bile ducts. Cross sectional imaging is therefore characterized by the presence of dilatation of small (peripheral) intrahepatic bile ducts with concomitant thickening of the duct wall and periductal tissues. CT reveals branching low attenuation structures in the liver due to bile duct dilatation and associated periductal fibrosis. Complications of clonorchiasis include: development of cholangiocarcinoma which also tend to be peripheral in this setting, intraductal calculi formation, cholangiohepatitis and liver abscess formation.

69. Hydatid cyst: The cyst may rupture into the biliary system. In patients with rupture into the biliary system, daughter cysts and membranes pass into the common bile duct producing surgical obstructive jaundice. Accurate preoperative diagnosis of biliary communication of hydatid disease is possible on US, CT, MRI and cholangiography.

70. AMPULLARY STENOSIS Biliary obstruction may be caused by morphologic stenosis of the ampulla of Vater or sphincter of Oddi. Although unclear, probable causes include passage of gallstones and pancreatitis. Imaging studies are frequently abnormal but not always conclusive. On US, CT and cholangiography (ERCP/MRCP) bile duct and sometimes pancreatic duct dilatation may be seen. Ultrasound may show partial obstruction by demonstrating an increase in CBD diameter following a fatty meal.

71. ERCP is the most valuable study for assessing the diagnosis of papillary stenosis, where direct endoscopic inspection of the papilla is possible. Tumors of the papilla or surrounding duodenum may be identified, if present. Cholangiographic findings of common bile duct dilatation, an elongated or rigid ampullary segment and failure of the common duct to empty contrast material in 45 minutes are suggestive of ampullary stenosis.

72. HEMOBILIA Hemobilia or bleeding into the biliary tree has many causes, most frequent being trauma. Other causes include cholangitis, gallstones, tumors, hepatic artery aneurysms, coagulopathy and interventional procedures. Definite diagnosis rests with either direct endoscopic observation of blood entering the duodenum from the ampulla of Vater or angiographic demonstration of the bleeding site in the liver, gallbladder or biliary tract. Cholangiography may show clotted blood as a cast-like filling defect in the bile ducts and may reveal a bile duct leak or a biliary vascular communication. Blood may be seen as echogenic material in gallbladder or CBD on US. On CT, blood is seen as high attenuating area (> 50 HU) in the gallbladder or bile ducts.

73. BENIGN TUMORS OF THE BILE DUCT Benign bile duct tumours are very rare. Adenomas are the most common type. Other benign tumors include fibroma, granular cell tumor, myeloblastoma, neurofibroma, hamartoma, lipoma and leiomyoma. Benign tumors are most frequently found in the periampullary region or in the common bile duct and are quite uncommon in the common hepatic or intrahepatic ducts. Most adenomas are asymptomatic and detected incidentally, Sonographically they are moderately echogenic nonshadowing filling defects. The lack of shadowing and relatively low echogenicity suggests a tumor rather than a stone. On CT, these are seen as soft tissue masses indistinguishable from noncalcified stones. Cholangiographically the tumors usually present as round or oval filling defect with smooth borders which do not change their position. Papillary adenomas can be multiple.

74. Cholangiocarcinoma Cholangiocarcinoma is an uncommon tumour that arises from the bile duct epithelium and that tends to spread by local infiltration. Incidence peaks in sixth or seventh decade and is slightly more common in males. Anatomically cholangiocarcinoma are classified as: • Intrahepatic peripheral cholangiocarcinoma (10%): Arises peripheral to secondary biliary confluence. • Hilar cholangiocarcinoma (25%): Arises from right or left hepatic ducts or from primary biliary confluence. • Extrahepatic cholangiocarcinoma (65%)

75. Morphologically these tumors are classified as: • Mass forming cholangiocarcinoma. • Periductal infiltrating cholangiocarcinoma. • Intraductal cholangiocarcinoma. Patients with hilar or extrahepatic cholangiocarcinoma usually present early with painless jaundice while intrahepatic cholangiocarcinoma remains asymptomatic till late. Cholangiocarcinoma is slow growing and metastasizes late so that survival is long if jaundice can be relieved. Local and distant metastases are uncommon even at autopsy. Ultrasonography is used for initial evaluation and can quickly establish the presence and level of biliary obstruction. CT, MRI and MRCP are required for staging and treatment planning. Cholangiography (ERCP/PTC) is often used to assess the extent of biliary involvement and for palliation.

76. Intrahepatic (Peripheral) Cholangiocarcinoma Ultrasonography reveals a hypoechoic, isoechoic or hyperechoic mass, which may be homogenous or heterogeneous. Unenhanced CT reveals a hypodense solitary mass that may have satellite lesions. On enhanced CT/MRI , the tumor shows thin rim or thick band of peripheral and patchy enhancement. The central area of the tumor, which contains fibrous tissue, does not enhance during early phase but becomes hyperdense during the delayed phase, 4-20 minutes after injection, a feature which may help to differentiate it from HCC. Focal intrahepatic biliary ductal dilatation and atrophy of the segment of the liver drained by these ducts with retraction of overlying liver capsule may also be seen. Peripheral cholangiocarcinoma can also be of periductal infiltrating type or intraductal polypoidal type and these may cause segmental bile duct dilatation and lobar atrophy.

77. Hilar Cholangiocarcinoma ( Klatskin Tumor) Hilar cholangiocarcinoma are usually periductal infiltrating type and most often arise at the primary confluence or in the proximal common hepatic duct. Sonographic findings include intrahepatic bile ductal dilatation with or without isolation of right and left sided ducts and lobar atrophy. Definite mass is rarely seen on US and demonstration of dilated intrahepatic ducts without any evidence of extrahepatic dilatation alone should raise the suspicion of hilar cholangiocarcinoma. Uncommonly the tumor may be seen on US as bile duct wall thickening and less commonly as a polypoidal lesion. The tumors are moderately echogenic, reflecting the fibrous nature of the tumor.

78. CT (particularly MDCT) are superior to US in identification of these small tumors. Although the tumor appears hypodense to liver in both unenhanced and enhanced CT scans, the focally thickened bile duct wall due to infiltrating tumor may appear hyperdense to the liver in the arterial and portal venous phase. In keeping with their fibrous rich stroma, delayed enhancement can be seen 8-15 minutes after contrast injection. Lobar hepatic atrophy is seen in one fourth of patients with cholangiocarcinoma and this finding coupled with biliary dilatation is strongly suggestive of cholangiocarcinoma. Atrophy results from long standing biliary obstruction or portal venous involvement and results in crowding of dilated bile ducts and volume loss most often affecting the left lobe of liver. Lymph nodal metastases can be seen in periportal and peripancreatic regions. Retroperitoneal adenopathy, proximal intestinal obstruction and peritoneal dissemination occur in advanced stages.

79. Klatskin tumor

80. Hilar Cholangiocarcinoma are Graded according to Bismuth Classification. Type I: Involves common hepatic duct only, confluence Patent. Type II: Involves primary confluence. Type III: Involves primary and either right/left side secondary confluence. Type IV: Involves bilateral secondary confluence

81. Small hilar cholangiocarcinoma (arrowhead) producing obstruction of the right posterior sectoral duct (short arrow), right anterior sectoral duct (long arrow) and left hepatic duct. (A) Thick section oblique coronal MRCP. (B) Axial portal phase CT. (C) Longitudinal US. (D) Transverse colour Doppler US (open arrow: normal left portal vein).

82. Extrahepatic Cholangiocarcinoma Extrahepatic cholangiocarcinoma are usually small and have better prognosis than Klatskin tumors. Ultrasound demonstrates biliary dilatation proximal to an abrupt obstruction. Demonstration of mass is rare, so that differentiation from benign strictures may be difficult. In the absence of history of previous surgery, cholangiocarcinoma should be suspected when abrupt obstruction of distal duct is seen without visualisation of a mass or calculus and the pancreas is normal. The bile duct at the level of obstruction in cholangiocarcinoma is narrowed if the process is primarily desmoplastic and widened if there is an obstructing intraluminal mass.

83. CT manifestations of cholangiocarcinoma include biliary demonstration of a mass. The diagnosis is suggested by abrupt cut-off without a mass or calculus. Diffuse, enhancing wall thickening may be seen. If a mass is seen, it is hypodense in nonenhanced scans and shows delayed enhancement. Rarely, a peripheral ring enhancement pattern is seen. Cholangiography reveals a short stricture which appears as U or V shaped occlusion having nipple, rat tail, smooth or irregular termination with prestenotic dilatation. Periampullary carcinoma is the term used to describe tumours that arise from or within 1 cm of the papilla of Vater. These include pancreatic, bile duct, ampullary and duodenal cancers. On imaging, the biliary obstruction is seen till the level of ampulla, with or without dilatation of pancreatic duct is seen.

84. Periampullary Carcinoma. Contrast enhanced axial CT (A) and coronal reformatted image (B) shows an enhancing polypoidal mass at the lower end of CBD causing biliary obstruction

85. Metastatic adenocarcinoma. PTC shows a long stricture of the common duct involving the hilar confluence. The stricture has a characteristic scalloped appearance.

86. Carcinoma Head of the Pancreas The commonest tumor of the pancreas is an adenocarcinoma of ductal origin. It is usually seen in the middle aged and elderly and is twice as common in males as in females. Jaundice is the main complaint of the tumor of pancreatic head. Body and tail tumors may initially present with pain and weight loss. The typical pancreatic cancer is a solid scirrhous tumor which has a decreased vascular perfusion as compared to the normal pancreatic tissue. The mass has definable margins although they are not encapsulated. Most carcinomas have grown large enough to alter the contours of the gland by the time they are detected.

87. There is a strong tendency to constrict or obstruct the ducts that lie within their paths of growth and the main pancreatic duct thus causing the dilataion and rupture of ducts upstream which hence leads to the escape of fluid into the substance of pancreas leading to acute pancreatitis, extra pancreatic effusion or pancreatic pseudocyst formation. Most pancreatic adenocarcinomas arise in the head and hence, obstruction of the CBD and concurrent neighboring pancreatic duct is frequently affected in this disease. Metastatic lymphadenopathy adjacent to suprapancreatic part of the bile duct can also cause ductal obstruction. The portal, splenic and superior mesenteric vein (SMV) lying adjacent to the pancreas are particularly susceptible to involvement. Deodedum is most commonly invaded in the CA head of pancreas.

88. Metastatic dissemination of pancreatic carcinoma occurs to regional lymph nodes, i.e. coeliac, common hepatic, superior mesenteric and para-aortic; hepatic via portal venous drainage, omental and peritoneal via intraperitoneal shedding of tumor cells. The hallmark of pancreatic metastasis is the small size of individual lesions, so the regional lymph nodes with deposits may not be significantly enlarged and peritoneal seedlings are rarely more than a few millimetres in size. Imaging of pancreatic cancer involves both diagnosis and staging of the tumor.

89. Ultrasonography (US) Pancreatic carcinomas are usually hypoechoic as compared to normal parenchyma. Necrotic tumors may show heterogenous echo pattern, ductal obstruction and dilatation may also be visualized. Vascular involvement is seen on US as thickening of periarterial tissues in which, normally echogenic fat immediately adjacent to the artery is replaced by tissue of lower echogenicity. Color Doppler is now being extensively used for detection of vascular invasion of pancreatic tumors and relationship between tumor and neighbouring vessels, namely the superior mesenteric, common hepatic, coeliac, splenic and gastroduodenal vessels.

90. EUS uses a 7-12 MHz 360o radial scanner, the tip of which is placed in the second part of duodenum for the pancreatic head, portal vein and papilla, in the duodenal bulb for the head, neck and distal CBD and through the stomach for imaging of body, tail and the pancreatic duct. EUS is especially sensitive for small (< 2 cm) solid tumors. Computed Tomography (CT) CT is now considered to be the imaging modality of choice for the detection and presurgical staging of pancreatic cancer. The normal pancreas enhances to a greater extent than pancreatic adenocarcinoma, hence, tumors will be easier to detect when the normal pancreas is optimally enhanced ,this is achieved by bolus infusion of 150 ml of 60 % iodinated contrast material at rates of 2-3 ml/sec.

91. Spiral scans are obtained during the pancreatic arterial and portal venous phases. The arterial phase images are acquired 25 seconds after the start of injection of IV contrast material at 3 ml/sec. Venous phase images are obtained 70 seconds after the start of contrast infusion. This allows for optimal visualization of both the mesenteric arteries and veins and is essential for detecting vascular invasion. When performing CT evaluation of pancreatic tumors, high density oral contrast should be avoided and water should be used as oral contrast. With multidetector CT multiple discrete phases of vascular and parenchymal enhancement can easily be achieved. The triple phase acquisition includes a nonenhanced phase, a late arterial phase, i.e. 10 second delay from the time of peak aortic enhancement and a portal venous phase with a 35 second delay. The portal venous phase is best for detection of liver metastasis and for visualization of venous structures.

92. Longitudinal US shows a very dilated bile duct (13 mm) and a large pancreatic head carcinoma

93. Multislice CT with curved coronal reformat displaying a pancreatic head tumour (arrows) obstructing the common bile duct and pancreatic duct.

94. Carcinoma of the pancreas. PTC shows a distal common duct stricture that is tight and is shouldered proximally.

95. Ultrasound (a) and axial CT image (b) in a patient with painless jaundice. (a) The typical focal hypoechoic solid mass in the head of the pancreas with abrupt cut off the common bile duct (CBD) and pancreatic duct (PDUCT) referred to as the double-duct sign. (b) Axial CT (white arrows) showing the margins of this locally advanced pancreatic cancer invading the duodenum.

96. Coronal CT image through the upper abdomen in a 45-year-old male patient with painless jaundice showing a “mushroom”-shaped lesion consistent with an ampullary tumour (white arrows). Note double-duct sign (black arrows) point to abrupt cut off and dilatation of the common bile duct and pancreatic duct.

97. METASTASES AND LYMPHOMA Metastases and lymphoma may result in hilar or mid/low biliary obstruction. Cholangiographically they mimic other malignant causes of obstruction. The strictures can be long and may have a characteristic scalloped appearance on cholangiography , and on sectional imaging abnormal soft tissue is usually evident. Intraductal metastases are rare but may be seen with a variety of tumours, most notably melanoma.