Ultrasound of theGallbladder and B iliar y Tre e : Back to Basics Brian Boyd, MD*, Ellie R. Lee, MD KEYWORDS Bile duct Portal vein Cholecystitis Intrahepatic duct Common bile duct KEY POINTS Ultrasound is the modality of choice and is well suited for the initial evaluation of the gallbladder and biliary tree. Ultrasound imaging benefits include lower cost, faster acquisition time, portability, and the advantage of being a dynamic examination. Although ultrasound may be the initial modality that identifies biliary tract malignancy, crosssectional imaging with computed tomography and MR imaging will be required to evaluate the extent of disease. Sonographic findings in the biliary system are often nonspecific, but when combined with clinical history, these can often help to determine the diagnosis. Videos of Adenomyomatosis, Intrahepatic Biliary Dilation, Gallbladder mass imaging accompany this article at http://www.ultrasound.theclinics.com/ Ultrasound is the initial imaging modality of choice to evaluate the biliary tract. Because acute gallbladder disease is a common cause of right upper quadrant pain and cholecystectomy remains one of the most common abdominal surgeries performed, ultrasound imaging of the gallbladder and biliary tree accounts for a significant portion of the volume in many radiology practices. Although MR imaging, more specifically magnetic resonance cholangiopancreatography (MRCP), and computed tomography (CT) scans are being increasingly ordered as part of the diagnostic workup, ultrasound remains the workhorse modality for initial imaging. Ultrasound imaging benefits include lower cost, faster acquisition time, portability, and the advantage of being a dynamic examination. The structure and location of the gallbladder and bile ducts lends itself to ultrasound evaluation. The fluid-filled nature of the gallbladder and bile ducts provides a natural contrast resolution from the surrounding organs in the upper abdomen.1 In addition, the liver typically functions as a solid tissue acoustic window through which the biliary system can be visualized. The primary goal of this article is to review the fundamentals of gallbladder and biliary imaging as it pertains to the diagnostic radiologist. The basic anatomy, normal measurements, common diseases, and pertinent ultrasound findings of the biliary tract are also reviewed. The authors have nothing to disclose. Department of Radiology, University of North Carolina, 2107 Old Clinic Bldg, Chapel Hill, NC 27599-7510, USA * Corresponding author. E-mail address:
[email protected] Ultrasound Clin 9 (2014) 567–586 http://dx.doi.org/10.1016/j.cult.2014.07.009 1556-858X/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved. ultrasound.theclinics.com INTRODUCTION 568 Boyd & Lee GALLBLADDER ANATOMY Ovoid, anechoic viscus Lies along posterior liver surface and interlobar fissure Three parts: neck, body, fundus Wall thickness less than 3 mm Less than 10 cm in length and 5 cm in diameter The gallbladder is an ovoid, hollow viscus normally filled with simple fluid (bile) and therefore predominantly anechoic on ultrasound when distended (Fig. 1). The gallbladder wall is thin, smooth, and relatively hyperechoic, measuring less than 3 mm in thickness in a normal, fasting patient.2 The gallbladder typically lies along the inferior surface of the liver between the left and right lobes, but can vary in orientation from patient to patient. The gallbladder is divided into 3 main parts: fundus, body, and neck (see Fig. 1A). Unlike the stomach, the fundus is the distal most aspect of the gallbladder. The body lies between the neck and the fundus with the neck being the most proximal aspect of the gallbladder, leading into the cystic duct. The neck is a potential site for stones to become impacted, which can lead to cystic duct obstruction and acute cholecystitis (Fig. 2). The gallbladder varies in shape, size, and contour from one normal patient to another. The normal size of the gallbladder should be less than 10 cm in length from neck to fundus and less than 5 cm in diameter at the widest point of the body (see Fig. 1). Prominent folds can be noted in the normal gallbladder. A common variation in shape caused by such a fold is the phrygian cap (Fig. 3); this is caused by a prominent fold at the junction of the body and fundus. Stones can Fig. 2. Gallstone. Echogenic gallstone with posterior shadowing located in the gallbladder neck (solid arrow). settle in this folded portion with no clinical significance. BILIARY TREE ANATOMY Component of the portal triad Divided into intra- and extrahepatic ducts Right/left hepatic ducts less than 2 mm in diameter Normal common bile duct less than 7 mm in diameter, varies with age and cholecystectomy The bile ducts can be separated into 2 major categories: intrahepatic and extrahepatic. The intrahepatic biliary ducts are one of the components that form the portal triad. The portal triad is a complex of a bile duct, portal vein, and hepatic artery that branches together throughout the liver (Fig. 4). Because there is no consistent orientation Fig. 1. Normal gallbladder. (A) Longitudinal view of the gallbladder. The gallbladder is divided into 3 parts: fundus (F), body (B), and neck (N). Normal gallbladder length less than 10 cm. (B) Transverse view of the gallbladder. Normal gallbladder diameter less than 5 cm (cursors). Phrygian cap. the beginning of the extrahepatic biliary tree. The location of the common hepatic duct and cystic duct confluence can vary. In the postcholecystectomy patient. The intrahepatic ducts tend to follow the same branching pattern as the other structures of the portal triad. referred to as the “Mickey Mouse” appearance with the portal vein as the head and the common bile duct and the hepatic artery as the ears. of the bile ducts relative to the other 2 vascular structures. separating into the right and left hepatic lobes along the Couinaud segmental anatomy of the liver. This duct is later joined by the cystic duct to form the common bile duct.6–8 There is considerable controversy over the impact of age and cholecystectomy on the normal common bile duct diameter. expected finding versus a new. drain liver segments V/VIII and VI/VII. and the cystic duct is often not well visualized on ultrasound. but even in normal patients older than 70 years of age with an intact gallbladder. Transverse view of the portal triad in the porta hepatis consists of the portal vein (asterisk). The site where the right hepatic artery crosses the common bile duct. 3. that concluded that increasing age and cholecystectomy does result in common bile duct dilatation. There are several recognized variations in the pattern described earlier.8 Therefore. The age at which this dilatation becomes significant is approximately 70 years. Note a shadowing stone within this folded portion (solid arrow). common bile duct diameter is equally.8 The dilatation can extend into the common hepatic duct. A review of the literature shows a variety of “normal” values with a general consensus that a common bile duct diameter equal or greater than 7 mm is abnormal and warrants further investigation (Fig. but this is the most common. and hepatic artery (arrowhead). variable than with increasing age alone and can be seen up to 1 cm. common bile duct (solid arrow). in addition to providing novel research. respectively. The left-lobe intrahepatic ducts typically divide between the medial segments IVa and IVb and lateral segments II and III. 5). 569 . most often to the posterior. The more peripheral intrahepatic ducts are considered abnormal if they can be visualized or if they are greater than or equal to one-half the diameter of the adjacent portal vein (Fig. the diameter did not exceed 7. Additional folds are seen in the body and neck (arrowheads). 6). One of the more recent studies included a thorough review of the literature. The definition of common bile duct dilatation is not a simple issue.Ultrasound of the Gallbladder and Biliary Tree Fig. The right-lobe intrahepatic ducts typically divide into anterior and posterior branches that Fig. color and/or spectral Doppler can be used to distinguish the bile ducts from the adjacent vessels.4 The right and left hepatic ducts are centrally located in the porta hepatis and normally measure less than 2 mm in diameter. can be used as an approximation of this demarcation when the cystic duct is not visualized. In a patient who has undergone prior cholecystectomy. if not more.3. but generally not into the intrahepatic ducts. Also. Portal triad. comparison with prior examinations is essential in differentiating a stable. the common bile duct should be considered dilated if it is equal to or greater than 8 mm in an individual older than the age of 70 years.6 mm. Prominent fold at the junction of the gallbladder body and fundus (dashed arrow).5 The right and left hepatic ducts join to form the common hepatic duct. The segmental and lobar branches coalesce centrally to form the right and left hepatic ducts. 4. possibly pathologic biliary dilatation. ULTRASOUND TECHNIQUE Fasted patient. 7). His description involved elicitation of pronounced pain by hooking a finger beneath the right costal margin. and then striking that finger forcibly down with the other hand eliciting severe pain. The transducer is held firmly in place as the patient is asked to take a deep breath. Examination of the gallbladder is initially performed in the supine position. If the gallbladder is contracted due to a postprandial state. prone. Cholelithiasis is a common finding in the symptomatic as well as the asymptomatic patient. The normal common bile duct measures less than 7 mm in diameter (cursors). (A) Transverse view of the left hepatic lobe demonstrates mild intrahepatic biliary dilatation (arrows). 4 to 6 hours Transverse and longitudinal planes Patient positioning to assess for mobility and/ or layering Sonographic Murphy sign An important factor in gallbladder and biliary ultrasound is the fasting status of the patient. Patients may evidence this pain by abruptly ceasing inspiration. Absence of a sonographic Murphy sign may be seen in the setting of recent analgesic administration or altered mental status.570 Boyd & Lee Fig. The sign is considered positive if the patient admits to intense focal pain at the site of the transducer. gallstones. and gallbladder sludge cannot be reliably assessed (Fig. and upright standing positions. GALLSTONES Common finding Major risk factor for acute cholecystitis Highly echogenic with dense posterior shadow Wall-echo-shadow (WES) sign Fig. The gallbladder is typically scanned after 4 to 6 hours of fasting to avoid gallbladder contraction. The gallbladder should be imaged in both transverse and longitudinal planes with different patient positions as necessary to assess for mobile gallstones or layering sludge. Other maneuvers are routinely used including right and left decubitus. Risk factors for developing gallstones include . Dilated intrahepatic bile ducts. asking the patient to take a deep breath. Notice the consistent size along the entire length of the duct. Murphy as a physical examination maneuver to differentiate gallbladder pathology from other causes of abdominal pain many years before the advent of ultrasound.9 The sonographic Murphy sign is a simple adaptation of this original description that takes advantage of the real-time ability to confirm placement of the transducer directly over the gallbladder. If a patient has not fasted for at least 4 hours before the examination. 5. Normal common bile duct. 6. the examination should be delayed or rescheduled for a time when the patient can be adequately fasted. A technique that deserves specific attention is the sonographic Murphy sign. (B) Color Doppler imaging of the liver is useful in differentiating portal vein (V) from bile duct (cursors). the gallbladder can be anywhere along the spectrum of distended to contracted and findings such as gallbladder wall thickening. The original Murphy sign was described by Dr John B. This patient was rescheduled and instructed on the appropriate fasting time before the examination (4–6 hours). Gallstones greater than 4 mm in size will likely cause posterior acoustic shadowing. hence WES (Fig. When a gallbladder is filled with multiple gallstones or a single large gallstone. critical illness. tumefactive sludge or tumor. gallstones have high acoustic impedance and appear highly echogenic (Fig. the calcium or air within the gallbladder wall disrupts the normal. and diabetes. which is then followed by posterior shadowing (S) from the stones. the mobility of the gallstones is important to demonstrate to distinguish them from other entities. pregnancy. female gender. Differentiation of cholelithiasis from emphysematous cholecystitis and porcelain gallbladder is important given the implications of the latter 2 processes. (B) Transverse view of the right upper quadrant demonstrates apparent wall thickening due to underdistention (arrows).11 Risk factors for the formation of sludge include rapid weight loss. the question can arise as to whether there is air or calcium in the gallbladder wall itself. Regardless of their composition. thin appearance of the wall and therefore only one echogenic line and posterior shadowing will be visualized. (A) Longitudinal view of the right upper quadrant demonstrates a contracted gallbladder (arrows) with an echogenic inner mucosal layer and hypoechoic outer muscular layer. This question can be answered by looking for the WES sign. (A) Single. such as polyp.10 Also. 7. Gallstones. Contracted gallbladder. 8. increased age. BILIARY SLUDGE Biliary sludge is a mixture of particulate matter that precipitates in bile. it is generally accepted as the major risk factor for developing biliary colic or acute cholecystitis. 9). Fig.1 Although asymptomatic cholelithiasis is not a disease that requires immediate intervention. Gallstones are most often primarily composed of cholesterol. the echogenic gallbladder wall (W) is still visible as a distinct structure due to a thin layer of hypoechoic bile overlying the brightly echogenic surface of the gallstones (E). Note the bright echogenic signal of the stones with homogeneous posterior shadowing in both images (asterisk). obesity. In the instance of porcelain gallbladder or emphysematous cholecystitis. pigmented stones can be seen. but in patients with a history of a chronic hemolytic process. pregnancy. 8). (B) Multiple small stones in the gallbladder body and neck (solid arrow). When a gallbladder is filled with stones. 1 demonstrates a normally distended gallbladder on the repeat examination.Ultrasound of the Gallbladder and Biliary Tree Fig. 571 . large gallstone in the gallbladder fundus (solid arrow). and prolonged total parenteral Fig. dependently layering echogenicity within the gallbladder that moves with changes in patient positioning and does not demonstrate posterior shadowing (Fig. Amorphous. 12). and pericholecystic fluid (Fig. the overall sensitivity Fig. regardless of size. applying color or spectral Doppler. a positive sonographic Murphy sign. gallbladder distention. which differentiates them from gallstones greater than Cholecystitis is defined as inflammation of the gallbladder. These sludge balls will not shadow. nonshadowing echogenic material within the gallbladder lumen that moves freely and usually assumes a dependent position (solid arrows) as seen on the supine (A) and prone (B) images. 11). called tumefactive sludge.15 Although subsequent studies have challenged the validity of the sonographic Murphy sign. This obstruction can lead to gallbladder distention and inflammatory changes in the gallbladder wall. calculous cholecystitis accounts for 90% to 95% of cases. Imaging the patient in more than one additional position. Of these 2. that can adhere to the gallbladder wall.11–13 Although the composition would suggest a precursor to gallstone formation. 9. nutrition. Wall-echo-shadow (WES) sign. a positive sonographic Murphy sign. The presence of stones. It is divided into calculous and acalculous cholecystitis depending on whether gallstones are present. Gallbladder sludge. raising the question of a polyp or tumor. . which may eventually lead to ischemia. thin layer of hypoechoic bile (asterisk) and echogenic stone surface (E) with homogeneous posterior shadowing (S). or repeating the examination at a later date will often help to differentiate a sludge ball from a polyp or tumor. and wall thickening were originally found to have the highest positive and negative predictive values. the incidence of cholelithiasis in patients with known biliary sludge is approximately 5% to 15%. gallbladder wall hyperemia. 10. 10). emphysematous. biliary sludge will form into globular “sludge balls”. CHOLECYSTITIS Most often caused by gallstones Acalculous cholecystitis typically seen in critically ill patients Complicated cholecystitis: gangrenous.14 Calculous cholecystitis can be further subdivided into acute and chronic cholecystitis. Acute cholecystitis is typically caused by gallstones lodged in the gallbladder neck or cystic duct. Longitudinal image of the gallbladder demonstrates an echogenic curvilinear line representing the gallbladder wall (W). Occasionally.572 Boyd & Lee 4 mm in size that typically shadow or polyps that demonstrate blood flow (Fig.11 Sludge typically appears as an amorphous. perforation Fig. The findings classically associated with the diagnosis of acute cholecystitis include gallbladder wall thickening (>3 mm). and necrosis of the gallbladder wall. superinfection. which may suggest decompression. and complex fluid collections adjacent to the gallbladder suggesting abscess (Fig.19. A shadowing echogenic gallstone is also seen (dashed arrow) and provides an excellent comparison in the different appearances of the 2 entities. no internal vascularity was seen.19. Tumefactive sludge or “sludge ball”. male gender. Globular. On color Doppler. Acute cholecystitis. (B) Transverse view of the gallbladder demonstrates marked edematous wall thickening (asterisk) and trace pericholecystic fluid (FF). It can result from severe or prolonged inflammation or infections.16. Large shadowing stone in the gallbladder neck (arrow) with markedly edematous gallbladder wall thickening (cursors). Hispanic descent.20 Risk factors generally associated with elevated complication rates include diabetes. Gangrenous cholecystitis is defined as necrosis within the gallbladder wall. but the morbidity and mortality are high. in the range of 7 mm for gangrenous versus 4 mm for uncomplicated acute cholecystitis. Emphysematous cholecystitis is rare and caused by rapidly progressing infection of the gallbladder with a gas-forming organism. as opposed to the homogeneous posterior shadowing caused by stones Fig. 14). loss of the normal ovoid gallbladder shape. which appears as irregular or small round echogenic foci that demonstrate a heterogeneous posterior shadowing. and specificity of these 3 “primary” signs along with the other “secondary” signs fall into the 80% to 90% range. The patient presented with right upper quadrant pain and exhibited a positive sonographic Murphy sign. can be seen in gangrenous cholecystitis (Fig.20 Some of these complications can be identified by specific sonographic features. accounting for less than 1% to 2% of cases. Perforation of the gallbladder can be associated with prolonged cholecystitis. 11. 13). (A) Longitudinal view. but can also be seen in the setting of trauma. gas is seen within the gallbladder wall and lumen.19.22 Although difficult to delineate from stones and sludge.16 However. In addition. There is an association with diabetes. and cardiovascular disease. Findings that may suggest perforation include a focal defect in the gallbladder wall.Ultrasound of the Gallbladder and Biliary Tree Fig. 12.21 Some of these studies also suggested that absence of the sonographic Murphy sign should raise the suspicion of necrosis related to denervation of the nervous supply to the gallbladder. and a white blood cell count greater than 15K (10^9/L) should raise the concern for this complication. seen as irregular bands of echogenic material. 573 . In addition to the typical findings of acute cholecystitis. recent studies have shown that a markedly thickened gallbladder wall. Older studies suggested that echogenic striations within the gallbladder wall were an indicator of necrosis. the sludge ball demonstrated mobility. echogenic lesion within the gallbladder lumen (solid arrow) that does not demonstrate posterior shadowing. sloughing of the gallbladder wall as well as the presence of thrombus in the lumen of the gallbladder.16–18 Complications associated with acute cholecystitis are rare. (A) Transverse image of the gallbladder demonstrating a defect in the wall (solid arrow) as well as pericholecystic fluid (arrowhead). although it can be seen in normal patients and is accentuated by a contracted gallbladder. 15).574 Boyd & Lee Fig. Gallbladder wall hyperemia has been specifically suggested as a way to differentiate acute from chronic cholecystitis. (Fig. The patient population in which it is seen is fairly specific. . sonographic Murphy sign. Sloughing of the gallbladder wall is identified. (B) T1-weighted axial MR image confirms the findings from the ultrasound (solid arrow: perforation. 16). Gangrenous cholecystitis. supported the diagnosis of acute cholecystitis with rupture.23–25 Acalculous cholecystitis is a difficult diagnosis to establish and is more a diagnosis of exclusion. arrowhead: pericholecystic fluid). A focal defect is identified in the gallbladder wall (arrow). indicating necrosis. air within the wall can mimic a stone-filled gallbladder. Note that the gallbladder wall is thickened. such as gallbladder distention. It is most often associated with patients Fig. The primary contribution of ultrasound in the workup is identifying the presence of gallstones in the absence of any other additional findings to suggest acute cholecystitis. However. and hyperemia. Additional findings. A cirrhotic liver is partially visualized and ascites is present (not directly related to the cholecystitis). CT can be considered to confirm the presence of air in the gallbladder wall. not seen on these images. 13. as evidenced by the linear echogenicities (solid arrows) within the gallbladder lumen. Perforated gallbladder. (C) Another ultrasound image of gallbladder perforation. 14. Pneumobilia can also be seen with emphysematous cholecystitis. Chronic calculous cholecystitis is associated with gallstones and chronic inflammation and leads to gallbladder wall thickening and fibrosis (Fig. A thickened gallbladder wall can be the result of many other nonbiliary tract disease processes including congestive heart failure. 19). however. Biloma can be differentiated with the use of cholescintigraphy or cholangiography. hemorrhage. Gallbladder wall thickening is one of the major findings associated with most forms of cholecystitis.26. Assessment of a sonographic Murphy sign in this patient population is often difficult. or receive prolonged parenteral nutrition. Xanthogranulomatous cholecystitis is a rare form of chronic inflammation. By itself. hypoalbuminemia. but can be present. including a negative sonographic Murphy sign. GALLBLADDER WALL THICKENING AND PORCELAIN GALLBLADDER Fig. No stones were present and the bile ducts were not dilated. Each of these procedures can result in injury to the gallbladder and/or the biliary tree. and acute hepatitis (Fig. These complications appear as diffuse or focal fluid collections with varying degrees of echogenicity and heterogeneity depending on the exact cause and chronicity (Fig. which include gallbladder distention. The 3 major complications include bile leak/ biloma. 17).Ultrasound of the Gallbladder and Biliary Tree Fig. Air within the gallbladder wall (solid arrow) appears as a single curvilinear echogenicity with heterogeneous. Acalculous cholecystitis. bands within the gallbladder wall. positive sonographic Murphy sign. Sonographic findings for this diagnosis include hypoechoic nodules and Fig.29 In addition. sphincterotomy.28. and abscess. and often biliary sludge. have sustained significant burns or trauma. Contrast this with the dense posterior shadowing (asterisk) from the gallstone (arrowhead). cholangiostomy.27 INTERVENTIONAL COMPLICATIONS Common interventions associated with the biliary tract include cholecystectomy.12 Sonographic findings are similar to that of acute cholecystitis. 15. many intrinsic biliary diseases cause 575 . gallbladder wall thickening. Sludge was not seen in this case. it is very nonspecific. Patient had no additional findings to suggest acute cholecystitis. The patient had been in the intensive care unit for 30 days for an unrelated illness and was noted to have an increasing bilirubin level without clinical evidence to suggest another cause. Chronic cholecystitis. “dirty” posterior shadowing. but in the absence of stones (Fig. The gallbladder wall is markedly thickened (arrows). 16. Cholescintigraphy confirmed the diagnosis. and biliary stent placement. Mildly thickened gallbladder wall (cursors) and gallstones (solid arrow). pericholecystic fluid. Emphysematous cholecystitis. These are felt to represent the collections of lipid laden macrophages that define this disease pathologically. 18). cholecystostomy. 17. who are critically ill. renal failure. Overall. The most recent studies have found that polyps less than 7 mm in size are unlikely to be neoplastic in nature and do not warrant imaging follow-up. and localized. 18. Note the wall thickening of the adjacent bowel loop (solid arrow) and ascites. segmental (annular). Gallbladder fossa hematoma. called cholesterolosis. Porcelain gallbladder is calcification in the wall of the gallbladder. or segmental wall thickening with multiple intramural echogenic foci that can cause posterior ring-down or comet tail . and typically characterized by size alone (Fig. Gallbladder wall thickening. typical of hematoma. 19. nonmobile. Porcelain gallbladder is associated with a high rate of gallbladder malignancy. and although recent studies have disputed the rate of association. Markedly edematous. involves only accumulation of cholesterol crystals in macrophages within the gallbladder wall. This is an important fact to keep in mind if the solitary abnormality on ultrasound is gallbladder wall thickening. Polyps greater than 1 cm are considered higher risk for malignancy and resection is recommended. There are 3 morphologic types: generalized. A drain was placed for concern of developing abscess. thickened gallbladder wall (arrowheads) secondary to hypoproteinemia. These lesions are nonshadowing. However. 20). A complex collection in the gallbladder fossa is heterogeneous with a retractile appearance of the central echogenic focus (arrow). cholesterol polyps are the most common cause (Video 1). prophylactic resection is still recommended. but confirmed aseptic hematoma.35 This process is caused by hyperplasia of the epithelial and muscular layers of the gallbladder wall and causes invaginations along the inner gallbladder wall to form. adenomyomas. adenomas.31 Fig. a follow-up ultrasound demonstrated near complete resolution of the fluid collection (arrow). The sonographic appearance of adenomyomatosis is that of diffuse. and cholesterol crystals. a recent study showed a low risk of malignancy in polyps less than 2 cm in size and suggested that surgery may not be immediately required in younger (<50 years). thrombus.576 Boyd & Lee Fig.32–34 Ultrasound imaging follow-up is recommended for polyps above this cut off. An often associated pathologic condition. gallbladder wall thickening as noted throughout this article. or tumors. These are known as Rokitansky-Aschoff sinuses and can accumulate bile. Sonographic appearance may vary from an interrupted thin to thick echogenic line within the gallbladder wall with posterior shadowing (Fig. focal. sludge. asymptomatic patients. (B) After the drain was removed. 21). but additional considerations include adherent stones or sludge balls.33 Adenomyomatosis is a benign process that occurs in the gallbladder wall. inflammatory polyps. GALLBLADDER POLYPS AND ADENOMYOMATOSIS Polypoid lesions of the gallbladder can represent several different entities.30. (A) Patient was several days status post-cholecystectomy with persistent right upper quadrant pain. Porcelain gallbladder can be difficult to differentiate with a stone-filled gallbladder and CT can be considered for further evaluation. associated with gallstone disease and chronic cholecystitis. 23. 24).37. such as cholangitis and pancreatitis. Biliary obstruction due to stones is the most common of the 3 categories. CHOLEDOCHOLITHIASIS Low overall incidence. Given these numbers and variability. it is termed primary and if the stones originated from the gallbladder. If the stones form within the ducts. Cholesterolosis can have a similar appearance.36 There is increased morbidity and mortality associated with the sequelae of common duct obstruction. Although the biliary system is well evaluated overall through the use of ultrasound. Porcelain gallbladder. is higher and slightly less variable with reported values between 60% and 100%. (A) Longitudinal and (B) transverse views of the gallbladder demonstrate curvilinear echogenicity in the gallbladder wall (arrow) with posterior acoustic shadowing (asterisk).and extrahepatic bile ducts (Fig. Intramural cystic spaces or diverticula may also be seen with adenomyomatosis. inflammatory/infectious. but significant morbidity/mortality Low sensitivity. Video 2). 20. but without wall thickening. which results in a greater level of diagnostic confidence. with approximately 5% of patients being asymptomatic. and neoplastic. highly echogenic foci with posterior shadowing (Fig. reverberation artifact (Fig. high operator dependence for identification on ultrasound Decreased conspicuity compared to gallstones Mirizzi syndrome and other rare complications of chronic impaction Pneumobilia Choledocholithiasis is defined as stones within the bile ducts. BILIARY OBSTRUCTION Obstruction of the biliary system can be identified sonographically by identifying dilated intra.36. (C) CT confirmation of calcification in the gallbladder wall (arrowhead).37. Stones within the common bile duct are similar in sonographic appearance to stones within the gallbladder. The incidence of stones in the common bile duct varies somewhere between 5% and 15% in patients undergoing cholecystectomy. MRCP demonstrates a more consistent. however. The 577 . This disease process can be divided into 3 major categories: stone-related. MRCP is increasingly used in patients with suspected common bile duct stones. its sensitivity for identifying common duct stones is low and operator dependent with a wide range of reported values between 20% and 80%.Ultrasound of the Gallbladder and Biliary Tree Fig. higher sensitivity and specificity. They appear as round. 22).38 The specificity. it is termed secondary.39 It can help identify the specific patients who would benefit from therapeutic endoscopic retrograde cholangiopancreatography. and upright (C) views from the same patient demonstrating an echogenic. Fig. Gallbladder polyp. (A) Focal area of subtle gallbladder wall thickening with tiny internal echogenic focus causing ring-down artifact. (B) More prominent focal wall thickening at the gallbladder fundus (arrow) that does not demonstrate vascularity on color Doppler (C).578 Boyd & Lee Fig. The lesion does not demonstrate mobility with changes in patient position. . Multiple ultrasound images of the gallbladder in the supine (A). typical of adenomyomatosis (arrow). 21. (D) Power Doppler images of the gallbladder polyp demonstrate a vascular stalk within the lesion (arrow). nonshadowing polypoid lesion on the posterior gallbladder wall (arrow). left lateral decubitus (B). Adenomyomatosis. 22. (D) CT image of this same patient demonstrates the soft tissue density of the focal adenomyomatosis in the gallbladder fundus (arrow). Biliary duct dilatation. B) Shadowing common bile duct stone (arrowhead) with ductal dilatation (arrows). This syndrome is rare in developed Western countries with an annual incidence of less than 1%. These factors likely contribute to the low overall sensitivity and high operator dependence in identifying common duct stones.40 Mirizzi syndrome can lead to formation of an erosive fistula between the gallbladder or cystic duct and adjacent structures like the common bile duct. Pneumobilia characteristically appears as bright. Many common bile duct stones are located in the distal common bile duct near the ampulla of Vater. in contradistinction to that from gallstones. is described as heterogeneous due to the incomplete and irregular reflection of sound waves. liver. INFLAMMATORY AND INFECTIOUS BILIARY OBSTRUCTION Acute bacterial cholangitis is the most common infectious cause in the United States. this can be seen rarely with the erosive complications leading to fistula formation from the gallbladder and bile ducts to the adjacent bowel. 23. 579 . bowel gas in this region further limits evaluation. biliary enteric anastomosis. Sonographic findings include the appearance of acute or chronic cholecystitis with biliary duct dilatation. but is more commonly associated with biliary or surgical procedures such as sphincterotomy. 25). The air can be coalescent and appear linear in appearance. The portal vein (V) and common bile duct are nearly equal in diameter. (A) Severe intrahepatic biliary dilatation (arrows). or biliary stent placement. (A. Pneumobilia is air within the biliary tree. only difference is the decreased conspicuity of common duct stones secondary to a relative lack of surrounding bile as compared with stones within the gallbladder. or duodenum. Choledocholithiasis. However. Posterior shadowing from pneumobilia. highly echogenic foci within the bile ducts (Fig. Mirizzi syndrome occurs when there is compression or obstruction of the common hepatic or common bile duct from an impacted stone in the gallbladder neck or cystic duct. Pneumobilia can also arise from air in the gallbladder caused by emphysematous cholecystitis. Fig.Ultrasound of the Gallbladder and Biliary Tree Fig. (B) Marked dilatation of the common bile duct (cursors). 24. The most unique finding in pneumobilia is visualizing the echogenic air bubbles moving through the bile ducts on real-time imaging. Recurrent pyogenic cholangitis is more common in East Asia. and choledocholithiasis (Fig. Longstanding stasis and inflammation often leads to severe atrophy and cirrhosis of the affected segment. which tends to be more peripheral in location. 26).42. right upper quadrant pain. Stones can form directly in the biliary ducts and result in chronic biliary obstruction. Sonographic findings include findings of biliary ductal .41 The most common organisms are gramnegative enteric bacteria. or oriental cholangiohepatitis. CT and MR imaging are helpful adjuncts in evaluating for this sequela.43 Sonographic findings include biliary ductal dilatation containing sludge and stones within one or more segments of the liver. Pneumobilia. stasis. This disease entity. The ultrasound findings of inflammatory obstruction are often nonspecific because they can be seen with many of the various distinct clinical entities. Imaging findings include biliary ductal dilatation. and jaundice—is a medical emergency. there is an increased risk of cholangiocarcinoma. Bowel gas within the duodenum is also seen (arrowhead). Human immunodeficiency virus (HIV) cholangiopathy and primary sclerosing cholangitis (PSC) have a similar appearance on US. circumferential bile duct wall thickening. although these may not be present. this disease process is common in East Asia with reported incidence rates of up to 20%. and recurrent inflammation. this can be associated with opportunistic infections. Known as primary hepatolithiasis. classically associated with Charcot triad—fever. such as cryptosporidium or cytomegalovirus in patients with advanced disease. Bright linear echogenic focus in the common bile duct (arrow) causing heterogeneous posterior shadowing as well as ring-down artifact (dashed arrow). This cause is most commonly associated with common bile duct stones in more than 80% of cases. but in North America the incidence remains low. (B) Color Doppler image confirms air is within the common bile duct (arrow). 25. Hemobilia Inflammatory causes of biliary obstruction include infectious and noninfectious causes. Note that the echogenic foci are more central in the liver as opposed to portal venous gas. (A) Air within the common bile duct. indicating air within the intrahepatic ducts. adjacent to the main portal vein (V). These findings are not specific and are common among the other inflammatory causes of biliary obstruction. HIV cholangiopathy could be considered a subset of both acute bacterial and sclerosing cholangitis. The most commonly encountered infectious cause in the United States is acute bacterial cholangitis. A finding more specific to acute bacterial cholangitis are hepatic abscesses.580 Boyd & Lee Fig. In addition. recurrent pyogenic cholangitis. (C) Branching echogenic structures with faint acoustic shadowing identified in the liver (arrows). Ultrasound can visualize these as vague hypoechoic lesions within the liver once they develop central liquefactive necrosis. Of the 1. Acute cholangitis. Biliary sclerosis has also been related to immunoglobulin G4–related systemic disease. The appearance is similar to that of a biliary stent: a tubular structure composed of parallel echogenic lines within the bile ducts. dilatation and wall thickening.46 The worm migrates from the small bowel into the biliary tree through the ampulla of Vater causing biliary obstruction. the process is considered to be idiopathic and is known as PSC. which is also dilated. 27). 26. Depending on the severity of cirrhosis. 581 . This entity. It has a strong association with inflammatory bowel disease and occurs more frequently in men. additional findings of portal hypertension can also be present. choledocholithiasis.46 The overriding pathophysiology in noninfectious inflammatory biliary obstruction is chronic inflammation that leads to fibrosis and scarring. The characteristic sonographic features of PSC are irregular.4 billion cases globally.45 The final infectious cause that will be discussed is ascariasis. If the cause of the inflammation cannot be identified. circumferential bile duct wall thickening and an overall beaded appearance of the biliary tree as a result of alternating areas of focal stricture and dilatation (Fig. PSC affects the entire biliary tree. and jaundice (Charcot triad). Portal vein (V). (A) Longitudinal and (B) transverse views of the portal triads demonstrate increased echogenicity about the portal triads and the “double barrel” appearance of the portal vein and enlarged adjacent bile duct (arrow). The imaging finding most specific to this cause is that of the worm itself. The papilla of Vater is typically inflamed and can be seen as an echogenic nodule in the distal common bile duct.44 The ductal dilatation is irregular demonstrating areas of focal dilatation and stricture as in PSC. only approximately 4 million are diagnosed in the United States and many of these individuals are immigrants from endemic regions.Ultrasound of the Gallbladder and Biliary Tree Fig. prior surgery or trauma. The lack of a history of stent placement as well as other clinical risk factors such as immigration from an endemic region and young age should raise the suspicion for ascariasis. (C) Color Doppler image at the level of the porta hepatis showing the markedly thickened common bile duct wall (arrowhead). PSC is a common risk factor for developing cholangiocarcinoma. a parasitic roundworm. This patient presented with fever. Associated findings can include choledocholithiasis and hepatic cirrhosis. This process can be secondary to a variety of causes such as AIDS. like recurrent pyogenic cholangitis. is exceedingly rare in the United States compared to other parts of the world. and ischemia. The wall of the bile duct demonstrates circumferential thickening. right upper quadrant pain. (C) An endoscopic retrograde cholangiopancreatography (ERCP) image demonstrates dilatation. which are reported together with primary hepatic cancer. This disorder is commonly due to iatrogenic biliary trauma related to biliary procedures and liver biopsies and can also occur spontaneously in patients on anticoagulation. PSC. biliary cancers are highly fatal due to the typically advanced stage at the time of presentation. duodenal (particularly ampullary). Hemobilia is often associated with many of the disease entities described earlier. and regional metastatic disease and can involve the bile duct. (A. stricturing. such as CT or MR imaging. including cirrhosis and ascites. is required to complete the workup.47 Although this incidence is lower in comparison with the other major cancers such as colon. Blood within the biliary system is similar in appearance to hemorrhage and thrombus elsewhere in the body. the blood could be primarily hypoechoic with low-level echoes (acute hemorrhage) or heterogeneously echogenic with areas of retraction (chronic thrombus). Extrinsic neoplasms include pancreatic. The characteristic appearance of a malignant stricture is an abrupt caliber change from a proximally dilated bile duct to a stenotic or often nonvisualized distal bile duct. . 27. and beading of the intrahepatic bile ducts.582 Boyd & Lee Fig. or vascular malformations. additional imaging is required Neoplasms that cause biliary obstruction can either be extrinsic or intrinsic. not accounting for intrahepatic ductal malignancies. Depending on the acuity of the bleeding. so an additional modality. underlying coagulopathy. B) Ultrasound images demonstrate dilated intrahepatic bile ducts (arrows) that have thickened walls and an irregular beaded appearance. with an estimated 9810 new cases in 2012. and prostate. breast. Ultrasound is generally not the optimum modality to identify and fully evaluate the primary tumor and extent of disease. Findings related to the chronic sequela of PSC are seen. BILIARY TRACT MALIGNANCIES Primary gallbladder carcinoma makes up 98% of gallbladder malignancy Cholangiocarcinoma classified by location within the biliary tree Ultrasound alone is usually inadequate to diagnose cholangiocarcinoma. The incidence of intrinsic biliary tract malignancies has increased in recent years. The most common location is in the perihilar region (Klatskin tumor). 583 .49 It is more common in women by 3:1 and occurs more frequently in older patients with an average age at presentation of 72 years. within the tumor.Ultrasound of the Gallbladder and Biliary Tree Cholangiocarcinoma is the primary malignancy of the biliary tree. adjacent to the main portal vein (V). It is associated with recurrent biliary tract infections and chronic inflammatory conditions.1 Cholangiocarcinoma is classified by its location along the biliary tree. CT or MR imaging will generally be required to evaluate the extent of disease. 28). Gallbladder carcinoma. most notably PSC. primarily adenocarcinoma. which can be diffuse or focal. isoechoic mass at the hilum (arrowhead). 28. The patient was inoperable and nodularity along the gallbladder raised the suspicion of gallbladder carcinoma. often blending into the background liver. (A–C) Massive. T2-weighted axial MR image (D) and fluoroscopic spot image from a percutaneous cholangiogram (E) further demonstrate the characteristic malignant stricture (arrows) and massive proximal intrahepatic biliary dilatation. The central intrahepatic bile ducts come to an abrupt end (arrow) at the site of a vague. Although ultrasound may be the initial modality that raises the suspicion of biliary tract malignancy. diffuse intrahepatic biliary dilatation.51 The Todani classification system breaks the cysts down by appearance (Table 1). CHOLEDOCHAL CYSTS Congenital cystic dilatation of the biliary tree is most commonly seen in individuals of East Asian descent. or coexistent gallstones may be present.50. Video 3). Calcification can be present within the gallbladder wall. Sonographic findings are nonspecific and include biliary dilatation. Hilar cholangiocarcinoma (Klatskin tumor). but brushings from the ERCP confirmed cholangiocarcinoma.52 The Type I cysts are the most common and defined as typically diffuse or focal segmental Fig. It is more common in older patients with a peak incidence in the 8th decade of life. It can also present as diffuse irregular gallbladder wall thickening or as a focal polypoid mass that demonstrates internal vascularity (Fig. followed by distal bile ducts and finally intrahepatic48 [see “Liver and Spleen” by Drs Srivastava and Beland in this issue for more on intrahepatic cholangiocarcinoma]. and intrahepatic masses that follow the normal branching of the biliary tree (Fig. 29. accounts for 98% of all gallbladder malignancies.49 Gallbladder carcinoma presents most frequently as an irregular mass that replaces the gallbladder. thickening of the bile duct walls. ) . Watanabe Y. (A) Invasive mass (M) replacing the gallbladder. (Courtesy of D. Narusue M. operative procedures. Central hypoechoic region represents necrosis (arrowhead).584 Boyd & Lee Fig.and Diffuse or focal dilatation of the common bile duct (CBD) Diverticulum of the CBD Choledochocele—localized fusiform dilatation of the distal CBD Multiple dilatations of the intraand extrahepatic ducts Multiple dilatations of the extrahepatic duct Caroli disease—multiple dilatations of the intrahepatic ducts Data from Todani T. Gallbladder carcinoma. difficult to delineate from the adjacent liver. 29. 30). MD. PV. are dilatation limited to the intraduodenal segment of the common bile duct. (C) Different patient. NC. choledochoceles. and review of thirty-seven cases including cancer arising from choledochal cyst. Warshauer. Congenital bile duct cysts: classification. Fig. Type IVa cysts appear as multiple saccular or fusiform dilatations of the intra. Type III cysts. et al. Fusiform dilatation of the common bile duct (cursors). Pathology confirmed gallbladder carcinoma. Chapel Hill.134(2): 263–9. Type II cysts are true diverticula of the common bile duct. with permission. Table 1 Choledochal cysts Type I (most common) Type II Type III Type IVa Type IVb Type V dilatation of the common bile duct (Fig. 30. Heterogeneous mass (M) filling the gallbladder lumen. (B) Color Doppler image of the same patient demonstrates the internal vascularity of the mass. Choledochal cyst (Type I). Internal calcifications (arrows). Am J Surg 1977. portal vein. What is the upper limit of normal for the common bile duct on ultrasound: how much do you want it to be? Am J Gastroenterol 2000.186(5):481–5. 3rd edition. Good LI. Stefanidis D. There is an associated risk of cholangiocarcinoma. Russell E. Naftali T. 11. Radiological anatomy of the biliary tract: variations and congenital abnormalities. 24. Soloway RD. Best Pract Res Clin Gastroenterol 2003.07. Radiology 1985. Diagnostic ultrasound. Teefey SA. Charboneau JW. 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