Chapter 8. Hepatobiliary

The prevalence of hepatobiliary disease in the emergency and acute care settings is high. Ultrasound allows for accurate diagnosis in a large number of these cases. Emergency physicians who can effectively perform ultrasound benefit enormously from the ability to make rapid bedside diagnoses, especially in undifferentiated cases of vague abdominal pain.

The primary tools in the evaluation of acute hepatobiliary disease are ultrasound, hepatobiliary iminodiacetic acid scintigraphy (commonly referred to as HIDA scan or cholescintigraphy), computed tomography (CT), and endoscopic retrograde cholangiopancreatography (ERCP). Prior to the late 1980s and early 1990s, several imaging modalities were in use to diagnose hepatobiliary disease, such as oral and intravenous cholangiography. These methods took an extraordinary amount of time, required consumption or injection of potentially harmful contrast agents, and exposed the patient to radiation.1 Ultrasound largely replaced these imaging modalities in the 1980s. Ultrasound has the highest sensitivity for detecting the presence of gallstones while HIDA has a reported higher sensitivity for detecting the presence of acute cholecystitis.2 Data derived solely from a set of emergency department patients, however, suggest that emergency ultrasound of the gallbladder may prove as useful for the detection of acute cholecystitis as HIDA.3, 4 Although CT also has a role in the evaluation of patients with suspected hepatobiliary disease, its application is limited by its inability to detect 25% of gallstones. CT may play a greater role when other causes of abdominal pain are also being considered in the work-up of abdominal pain.5, 6 Ultrasound also has the added advantage of not exposing the patient to ionizing radiation. ERCP has its own unique risks, including pancreatitis and even death, and the test consumes a great deal of time and resources.

The clinical indications for performing emergency bedside hepatobiliary ultrasound by clinicians include

• gallstones and biliary colic,
• acute cholecystitis,
• jaundice and biliary duct dilatation,
• abdominal sepsis,
• ascites, and
• hepatic abnormalities.

Emergency physicians expect to see biliary pathology in up to a third of all abdominal pain cases they encounter.7 The classic presentation of biliary colic portrays an obese woman of child-bearing age with recurrent colicky pain in the right upper quadrant shortly after the consumption of a fatty meal. While gallstones are more prevalent in young, multiparous women than in young men, the ratio balances out with advancing age.8 In older patients, the pain does not wax and wane after meals but is constant and occurs mostly at night at predictable hours, lasting for an average of 1–5 hours.9 Physiologic studies conducted on patients while they were undergoing cholecystectomy concluded that a majority of patients with cholelithiasis will experience epigastric discomfort or dyspepsia with mechanical stimulation of the gallbladder. In fact, some feel that symptoms tend not to migrate to the right upper quadrant until the inflamed gallbladder irritates the peritoneum.10–12 Patients who experience right-sided pain may present complaining of right flank pain, shoulder pain, or chest pain.13 The resolution of symptoms in the setting of a clear history, absence of fever, and general improvement of the patient may cinch the diagnosis of biliary colic and preclude the necessity to image the gallbladder; however, most patients who present to the emergency department are symptomatic for some time. In these cases, emergency ultrasound can expedite the diagnosis and focus the clinician's effort and use of resources.7, 14 An algorithm that demonstrates how focused ultrasound can be utilized for decision making in patients with possible biliary colic is outlined (Figure 8-1).

Several studies demonstrate that emergency physicians with adequate experience acquire and interpret ultrasound images with skill similar to traditional imaging providers, especially when detecting gallstones.15, 16 In the hands of emergency physicians, the sensitivity and specificity for detecting gallstones (86–96% and 88–97%, respectively) resembled the pooled sensitivities and specificities in data gathered from imaging specialists (84% and 99%, respectively). One particular advantage to the emergency physician is increased efficiency.17 On average, emergency physicians take 10 minutes to conduct a focused examination of the gallbladder. This expedient and accurate information has been shown to effectively decrease emergency department length of stay and influence emergency physician's probabilistic judgments especially when diagnosing diseases that are not readily apparent by the clinical presentation.7, 17 Since the differential diagnosis for upper abdominal pain can include many different etiologies, emergency ultrasound of the gallbladder can streamline the number of diagnoses the emergency physician must consider when evaluating and treating the patient, especially when the presenting symptoms are consistent with biliary colic.

The clinician must take caution, however, when interpreting the findings of gallstones in a patient with atypical symptoms. Clolelithiasis is a prevalent disease and a majority of patients are asymptomatic. Although it may be convenient to attribute a patient's symptoms to biliary disease, the astute clinician will always remember that biliary colic remains a clinical diagnosis and not a sonographic diagnosis.

The diagnosis of acute cholecystitis cannot be made by any constellation of physical examination or laboratory findings. The patient may present with right upper quadrant pain, fever, and a leukocytosis. In the emergency department, however, these findings are not present in a majority of cases. The lack of clinical sensitivity makes the firm diagnosis of acute cholecystitis heavily dependent on imaging studies.18, 19 This becomes particularly problematic for the emergency physician when one considers that, in the United States, more patients require cholecystectomy (both elective and emergent) than appendectomy.20

In general, ultrasound is thought to have a 94% sensitivity and 84% specificity in identifying cases of acute cholecystitis.2 Focused emergency ultrasound performed by emergency physicians is reported to have a 91% sensitivity and a 66% specificity (of note, over two thirds of the emergency physicians in this study had no formal training). Ninety-five percent to 99% of patients with acute cholecystitis have gallstones.21 The sonographic Murphy's sign (pain elicited by pressing over the fundus of the gallbladder with an ultrasound probe) may be present in 98.8% of cases but is not by itself specific for cholecystitis. The sensitivity of the sonographic Murphy's sign for cholecystitis was 75% for emergency physicians performing the test at the bedside compared to 45% for the formal ultrasound examination.16–22 Nevertheless, the sonographic Murphy's sign helps localize the source of the abdominal pain and when clearly positive, along with an ultrasound that is positive for gallstones, suggests that the patient has at least a diagnosis of biliary colic (Figure 8-1). Although no single ultrasound finding predicts cholecystitis with sufficient accuracy for definitive diagnosis, studies have shown that a combination of positive findings increases the accuracy of ultrasound for this diagnosis. A combination of gallstones and a sonographic Murphy's sign had a positive predictive value of 92.2%, whereas a combination of gallstones and gallbladder wall thickening had a positive predictive value of 95.2% for cholecystitis.21

In general, the emergency physician can rely on the presence of gallstones and a thickened gallbladder wall in conjunction with the clinical presentation and laboratory findings to identify cases with a high probability of acute cholecystitis that will need further intervention.

In a patient with jaundice who presents to the emergency department, the emergency physician must decide whether the patient's hyperbilirubinemia is caused by a physical obstruction of the biliary tree or another disease process. Ultrasound is useful for detecting dilatation of intrahepatic ducts or the common hepatic and bile ducts.23 Ultrasound is less sensitive at defining the exact etiology of obstruction, which may include a pancreatic head tumor, ampullary carcinoma, common bile duct stone, or bile duct compression from another cancer.24 Once an obstructive process is detected, the next concern is whether the patient is presenting with clinical signs of cholangitis (fever, leukocytosis), which may precipitate the need for urgent ductal decompression (surgery, ERCP, transhepatic stenting). While ultrasound may detect dilated extra- or intrahepatic ducts and assist in the general management of these cases, other modalities such as CT and ERCP are usually utilized to direct diagnosis and treatment.

Early goal-directed therapy in patients with sepsis is known to decrease patient mortality.25 A majority of these patients tend to be elderly and often do not have a clear source of infection.26 In cases of abdominal sepsis in the elderly, approximately 25% are due to cholecystitis and cholangitis.27 Emergency ultrasound can serve as a prompt adjunct in potentially detecting the source of sepsis in critically ill patients when the etiology is not readily apparent.28

Detection of ascitic fluid is a useful diagnostic procedure when evaluating the patient with abdominal distention without signs of intestinal obstruction. On physical examination, the sensitivity of an abdominal fluid wave is low. In the emergency and acute care settings, determining whether a patient has ascites may influence initial management and disposition. For example, in a patient with abdominal pain or fever, the presence of ascites would require the clinician to consider the possibility of bacterial peritonitis.

Patients may present to the emergency department with a substantial number of hepatic abnormalities, such as liver mass or metastases, abscess, or hepatomegaly. Although it may be helpful for the clinician to have an understanding of the sonographic appearance of these conditions, the specific differentiation of these conditions lies outside the routine scope of practice for the clinician in the emergent setting.

A variety of solid and hollow organs are located in the right upper quadrant of the abdomen. The predominant organ is the liver, bordered superiorly by the diaphragm and coronary/triangular ligament confluence (Figure 8-2), inferomedially by the duodenum and head of pancreas, and inferiorly by the gallbladder, hepatic flexure of the ascending colon, and superior pole of right kidney. The gastric fundus is located posterolateral to the left hepatic lobe. The liver is divided (Figure 8-2) into right and left lobes by the major lobar fissure, which contains the middle hepatic vein and extends from the gallbladder fossa anteriorly to the inferior vena cava posteriorly. The right lobe is divided into anteromedial and posterolateral segments by the right hepatic vein, and the left lobe is divided into anterior and posterior segments by the left hepatic vein. After draining the liver of venous blood, all hepatic veins converge on the inferior vena cava posteriorly, just inferior to the atriocaval junction. The main portal vein courses from the intestinal venous drainage arcades, through the lesser omentum to the hepatic hilum, where it bifurcates into right and left branches and enters the liver (Figure 8-2A). The hepatic artery courses toward the hepatic hilum in the lesser omentum, occupying a position anterior to the main portal vein (Figure 8-2B). At the hilum, it divides into right and left branches and enters the liver parenchyma.

The biliary system begins with the intrahepatic right and left hepatic ducts, which course toward the hilum, uniting to form the extrahepatic common hepatic duct. After exiting the hilum, the common hepatic duct is joined by the cystic duct (from the gallbladder) to form the common bile duct, which courses anterior to the main portal vein, and usually to the right of the hepatic artery (Figure 8-2B) in the lesser omentum before entering the duodenum. It is important to remember the anatomical relationships of the hepatic artery, common bile duct, and main portal vein as they traverse the lesser omentum in the region of the hepatic hilum to form the main portal triad since this will aid in identification and differentiation during sonographic evaluation. Within the liver, branches of the main portal vein, proper hepatic artery, and biliary tree follow parallel pathways of distribution to the liver parenchyma in bundles known as lesser portal triads. Hepatic venous tributaries do not follow this system.

The gallbladder is divided into a fundus, body, and neck (Figure 8-2B). The fundus may project below the inferior hepatic margin, illustrating the anatomic basis for a “sonographic Murphy's sign” (a point of maximal tenderness elicited by compressing the gallbladder with the ultrasound probe). The body is contiguous with the inferior surface of the liver and narrows at the neck. The neck often contains spiral valves known as Spiral Valves of Heister that are occasionally misdiagnosed as impacted stones. The neck is continuous with the cystic duct, which empties into the common hepatic duct to create the common bile duct.

Patient positioning and respiratory maneuvers play an important role in the hepatobiliary ultrasound examination. The patient's body habitus will dictate which transducer is best; in difficult cases, adjustments to the probe frequency, gain, focus point, and harmonic settings can make the difference between an indeterminate and successful ultrasound examination.

When the patient's gallbladder lies inferior enough to the lowest rib, the patient can be scanned in the recumbent position. However, this tends to be the exception rather than the rule. The ribs overlie the gallbladder and interfere with direct visualization in most cases. To improve the chance of success, the patient should be positioned in the left lateral decubitus position (Figure 8-3A). The liver tends to shift due to gravity, which provides a better “acoustic window” and, in effect, pulls the gallbladder out from underneath the acoustic interference of the ribs. Occasionally, the patient must roll past the left lateral decubitus position to an almost prone position with the probe “underneath” the patient's abdomen, but this is quite rare. If the left lateral decubitus position is insufficient, then the patient should be asked to take and hold a deep breath. This maneuver fills the lungs, flattening the diaphragm and shifting the gallbladder down. When the common bile duct is measured, the same maneuvers can assist in bringing key structures into view.

For the abdominal ultrasound examination, there is no absolute “correct probe.” Most patients require a medium to low transducer frequency (2–5 MHz) to view the gallbladder. A phased array transducer can be helpful when there is no option but to image between ribs. However, a curvilinear transducer typically suffices in most cases. Initially, positioning the probe sagittally (probe indicator toward the patient's head) just inferior to the right costal margin may help locate the gallbladder. Probe positioning after localization should focus on obtaining standard images that are most familiar to consultants and fellow sonologists. Color Doppler can be used to confirm that the cystic structure is not a vessel. Since there is great variability in anatomy, probe position can vary between a cross-sectional and sagittal position.

Adjusting the depth, focus point(s), and gain optimizes most images in the emergency department. These knobs or buttons vary from machine to machine. The depth should be adjusted so that the gallbladder fills at least two thirds of the screen. The focus point(s) should be focused at the structures of interest.29 The gain, akin to brightness on a computer monitor, should not be set too high or low because image quality may be distorted. Some machines are currently equipped with tissue harmonic imaging (THI), which may help identify smaller stones typically not visualized without harmonics.30

A low- to medium-frequency ultrasound transducer will suffice for most typical examinations; however, if other options exist that may be of more benefit, the sonologist must be willing to adapt and use them. This may include the use of a linear transducer for a very anterior gallbladder in a thin patient. The goal is to answer a focused question that enhances the diagnostic workup or therapeutic disposition.

Evaluation of the Gallbladder and Common Bile Duct

Four components are necessary to complete the evaluation of the gallbladder in cases of suspected biliary colic and acute cholecystitis. First, the gallbladder should be viewed in at least two planes to minimize the chance of missing an inconspicuous finding. Second, the gallbladder should be traced from the fundus to the neck carefully examining for small stones impacted in the neck. Third, the anterior gallbladder wall should be measured at its clearest point, which is usually in the mid-portion of the ultrasound beam emanating from the transducer. If focal wall thickening is encountered, several measurements should be made, one of which includes the focally thickened area. Fourth, the common bile duct should be measured and traced as far medially as possible if dilated.

A sagittal approach will initially locate the gallbladder (Figure 8-3B). Placing the probe under the right costal margin at about the mid-clavicular line with the probe marker directed toward the patient's head, the sonologist can sweep the right upper quadrant until an image of the gallbladder is obtained (Figure 8-3C). This will usually be a transverse or oblique cut through the fundus. Having the patient take and hold a deep breath may be very helpful if the gallbladder is not readily identified. Color and power Doppler aid in delineating large vascular structures. The gallbladder should have no Doppler signal and is typically the most anterior cystic structure in the abdomen (Figure 8-3D). Conversely, identifying the main portal vein also helps identify the gallbladder. Typically, the main portal vein connects to the gallbladder via a thick fibrous band known as the main lobar fissure. Occasionally locating the main portal vein and following the main lobar fissure is the only way to locate an obscure gallbladder.

The next step is to obtain a longitudinal profile of the gallbladder by gently sweeping the ultrasound beam, keeping other three-dimensional aspects of the beam's orientation constant. Thus, a three-dimensional mental image of the gallbladder in long axis is built out of multiple two-dimensional images. The gallbladder neck should be interrogated whenever possible. Having the patient take a deep breath will help the sonologist identify the neck leading into the main portal triad. One of the most difficult skills for the novice sonologist to master is the technique of converting transverse or long-axis sections into longitudinal or short-axis cuts, respectively. To change planes, the transducer should be moved slowly, keeping some element of the gallbladder in view. This is the time to adjust the patient's position or perform respiratory maneuvers if the gallbladder is not initially visualized. Short-axis views should be obtained after the longitudinal images (Figure 8-4). These views assist with clarifying whether shadowing is from stones inside the gallbladder or from adjacent bowel gas outside the gallbladder. If imaging remains difficult after patient positioning and deep inspiratory efforts, consider intercostal views (Figure 8-5). These views are helpful when the gallbladder is positioned under the ribs and/or the patient is unable to take a deep breath.

The gallbladder should be scanned for the presence or absence of gallstones, determination of wall thickness, and for the presence or absence of pericholecystic fluid. An accurate measurement of wall thickness is made on the anterior wall that is perpendicular to the imaging plane (greater than 3 mm being abnormal). If gallstones are detected, the patient should be rolled or elevated into various positions in an attempt to document movement of the gallstones. If a stone or stones do not respond to gravity by rolling “downhill” with body position change, then they may be impacted in the gallbladder neck. Alternatively, the sonologist may be dealing with a calcified polyp or sessile mass. If clinically applicable, the probe should be used to compress the gallbladder in an attempt to elicit a “sonographic Murphy's sign.”

Identification of the portal vein in the longitudinal axis aids in finding the main portal triad (Figure 8-6A). The portal vein will have bright echogenic walls compared with the hepatic veins. It can usually be visualized coursing toward the porta hepatis. The main portal triad is made up of the main portal vein, hepatic artery, and the common bile duct. By rotating the probe 90 degrees (counterclockwise) from a longitudinal orientation, a transverse image of the portal vein with the associated common bile duct (anterior/lateral) and hepatic artery (anterior/medial) may be visualized (Figure 8-6B). This is the classic “Mickey Mouse sign.” It is advantageous to use color or power Doppler to identify vascular structures. The portal vein and hepatic artery will usually give off color Doppler signals while the remaining common bile duct will not (Figure 8-6C,D). Measurement of the common bile duct is made from inner wall to inner wall; normal is in general less than 7 mm thick.31–33 Tissue harmonics may also help delineate the common bile duct. However, tissue harmonics increases the measured thickness of walls and must be used with caution. The site of common bile duct obstruction from stones is often near its termination close to the pancreatic head. This area may be visualized in a thin patient with little interfering gas (Figure 8-7). It will be difficult to visualize this point in the majority of patients.

Evaluation of Acute Jaundice and Biliary Obstruction

No gallbladder examination is complete without evaluation of the bile ducts. The initial step of this examination technique is to locate the main portal triad, which can be accomplished in two ways. The first method uses the portal vein as a landmark and is described above. The second method involves tracing more peripheral branches of the portal venous system as they course centrally toward the hilum. Their echogenic walls and their normal enlargement can identify portal venous branches as they course centrally toward the hilum to join the main portal vein in the main portal triad. They are clearly distinguished from the hepatic venous system, with its thin, hypoechoic walls and enlargement as it converges on the inferior vena cava posteriorly (Figure 8-8). Without the presence of biliary tract disease, they are rarely visible within the hepatic parenchyma. Color Doppler helps differentiate between the portal and biliary trees by demonstrating flow within the former. (Figure 8-6). Once the main portal triad has been identified, examination and measurement of the common duct are performed. The duct is usually normal if the transverse diameter, in millimeters, is less than one tenth of the patient's age. However, after cholecystectomy, the common bile duct may normally range up to 1 cm in all age groups.

The most convenient method for intrahepatic duct evaluation involves transverse imaging of the left lobe of the liver. Intrahepatic ducts run in the transverse plane in this location, allowing longitudinal images of the ducts to be obtained by orienting the ultrasound beam axis transversely. Longitudinal imaging of the ducts allows easier detection and evaluation of abnormalities in the intrahepatic system. While it was once thought that any visualization of the intrahepatic ducts was abnormal, this may not be the case with modern equipment and the greatly improved resolution it delivers.

Gallbladder Disease

Emergency physicians will most commonly use ultrasound to detect gallstones and acute cholecystitis. Gallstones typically appear as echogenic foci with acoustic shadowing beneath the gallstone. They can range in size from that of a golf ball to the size of sand particles (Figures 8-9, 8-10, and 8-11), but over two thirds will be greater than 5 mm in diameter.34 The shadow is produced by ultrasound waves that are strongly reflected off of the gallstone. Shadowing may not be present if the gallstone diameter is less than 4 mm depending on the transducer being used and its frequency and resolution. Unless the gallstone is impacted in the neck of the gallbladder, gallstones will layer in the most dependent region of the gallbladder and will move with patient positional changes. This is important, as nonshadowing stones may, otherwise, be difficult to distinguish from echogenic nonshadowing cholesterol polyps (Figure 8-12).

In patients with cholelithiasis and the appropriate clinical presentation, additional sonographic findings consistent with cholecystitis may include one or more of the following: wall thickness greater than 4 mm (Figure 8-13), pericholecystic fluid, and the presence of a sonographic Murphy's sign. Ninety-two percent of patients with cholecystitis will have a thickened gallbladder wall > 3 mm. However, gallbladder wall thickening can occur in a variety of conditions such as pancreatitis, ascites, and alcoholic hepatitis; although sensitive for acute cholecystitis, gallbladder wall thickening cannot be considered pathognomonic.35, 36 The mean gallbladder measurement in patients with acute cholecystitis is typically 9 mm. For cases of chronic cholecystitis the mean measurement is 5 mm. Measurements between 3 and 5 mm are recognized as being abnormal but lack diagnostic certainty. The sonographic Murphy's sign is considered positive when the point of maximal tenderness elicited by pressure from the ultrasound probe occurs over the sonographically identified gallbladder. Further more, transducer pressure not directly over the gallbladder should elicit much less or no pain. Pericholecystic fluid is a less common finding, but when present it is quite specific for cholecystitis.37 The size of the gallbladder is not sensitive enough to rely on. Of note, no single sonographic sign is sensitive enough to make the diagnosis of acute cholecystitis and a small percentage of patients may present with no sonographic evidence of disease.21 Physicians must consider the clinical presentation of the patient and may need adjunctive testing or a high clinical suspicion to definitively diagnose these cases.

Complications include gangrenous and hemorrhagic cholecystitis. When organisms that produce gas are involved, emphysematous changes in the gallbladder wall may be seen. In cases of hemorrhagic cholecystitis, internal echoes caused by bleeding represent sloughing of the gallbladder mucosa. The wall of the gallbladder will be enlarged and have a striated appearance in these cases (Figure 8-14).38

Finally, the WES sign (wall echo shadow) is commonly seen in gallstone-filled gallbladders. This occurs when the gallbladder is contracted around many stones with most of the bile emptied. The WES sign consists of an anterior echogenic line arising from the near wall of the gallbladder, an intervening anechoic stripe generated from bile when present, and a posterior brightly echogenic line representing stone material followed by a prominent posterior acoustic shadow (Figure 8-15).

Jaundice and Biliary Obstruction

Biliary obstruction, regardless of underlying etiology, is often initially detected by demonstrating dilated biliary ducts on ultrasound. Dilated extrahepatic ducts will appear as an enlarged, anechoic tubular structure (with echogenic walls) in the main portal triad, anterior to and following the course of the main portal vein. This is referred to as the parallel channel sign (Figure 8-16). Dilatation of the extrahepatic ducts implies obstruction of the common bile duct. Common causes of extrahepatic obstruction include choledocholithiasis (Figure 8-17), pancreatic masses, and strictures. Left untreated, an extrahepatic obstruction will eventually also lead to dilatation of the intrahepatic ducts. Dilated intrahepatic ducts appear as anechoic tubules with echogenic walls coursing through the hepatic parenchyma. Morphologically, they are described as “antler signs” (Figure 8-18). Dilatation of the intrahepatic ducts alone suggests an obstructive process within the common hepatic duct or more proximal. Causes of primary intra-hepatic obstruction may include inflammatory conditions (Figure 8-19), intrahepatic masses, or biliary duct cancer. Although ultrasound is sensitive in detecting ductal dilation, it may be less accurate for detecting the underlying cause of the obstruction. For example, ultrasound has a sensitivity of 15–55% for detecting common duct stones.39 The precise etiology is often determined by other modalities such as CT or ERCP.

Common causes of nonobstructive jaundice are hepatitis and cirrhosis. Sonographically, hepatitis usually appears as a relatively decreased parenchymal echogenicity secondary to the increased fluid content of the tissue.40 The diaphragm and portal vessel walls are not involved in the edema, and remain brightly echogenic. Their relative “accentuated brightness” is the classic finding associated with acute hepatitis but this ultrasound finding is often not obvious. As inflammation becomes more chronic, and cirrhosis develops, the liver size decreases, parenchymal echogenicity and surface irregularity increase, and intrahepatic anatomy becomes distorted (Figure 8-20).41

Ascites

In patients presenting with abdominal distention, ultrasound can quickly differentiate between dilated gas filled loops of bowel and a patient with ascites (Figure 8-20). The ultrasound technique for detecting ascites is similar to that used in the FAST examination. The clinician should carefully note the echo characteristics of any intraperitoneal fluid detected. Large free floating echogenic particles may indicate clotted blood while multiple small free floating particles may indicate spilled abdominal contents and/or peritonitis (Figure 8-21). Most frequently the fluid is consistently anechoic. It is difficult to discern the etiology of ascites by ultrasound.42 Though the incidence of complications during paracentesis is 3%, ultrasound can assist in successfully sampling fluid collection for analysis.43, 44

Hepatomegaly and Splenomegaly

Ultrasound is an ideal bedside tool for detection of hepatomegaly. If the liver parenchyma of the right lobe extends to or beyond the inferior pole of the right kidney, hepatic enlargement is probable (Figure 8-22). Alternatively, a longitudinal scan can be obtained at the mid-hepatic line, and the liver is measured from the dome (diaphragm) to the inferior margin. Enlargement is considered to be a measurement greater than 12.8 cm.21 Since enlargement of the left lobe of the liver and splenomegaly can be confused on physical examination, the ultrasound evaluation for possible hepatomegaly should be completed with long-axis views of the spleen. Splenomegaly is confirmed when the length measured in long axis exceeds 12–14 cm (Figure 8-23).

A number of variants may be noted with respect to the gallbladder. Mucosal indentations may produce septations of the lumen (Figure 8-24), which can be mistaken for gallstones, although shadowing does not usually occur. Folds of the fundus may produce a Phrygian cap (Figure 8-25). Agenesis of the gallbladder has an incidence of less than 0.05%. Intrahepatic gallbladder, secondary to abnormal developmental migration of the gallbladder bud, should always be considered if not found in its typical location. Duplicated gallbladder occurs with an incidence of 0.02%. Biliary sludge may be detected as a dependent layer of variable nonshadowing echogenicity in the gallbladder (Figure 8-26). Although the sequelae of sludge are largely unknown, it is frequently detected in states associated with biliary stasis, such as limited oral intake.45 Tumefactive sludge is nonlayering, thickened, polypoid sludge that can be mistaken for a gallbladder wall tumor (Figure 8-27). A contracted gallbladder, commonly occuring in the postprandial patient, may be difficult to detect, and may demonstrate a nonpathologically thickened wall (Figure 8-28).

Riedel's lobe of the liver is a thin projection of otherwise normal hepatic tissue extending from the right lobe inferiorly toward the iliac crest (Figure 8-29). If not recognized, this could be mistaken for hepatomegaly. Simple hepatic cysts are often an incidental finding. Their features include sharp margins, no internal echoes, and increased “through transmission” (Figure 8-30).46 Hepatic abscesses, although an uncommon finding, are worthy of mention. Ultrasonographic features include thickened, poorly defined walls surrounding fluid of variable echogenicity, which is dependent on the nature of the internal pus (Figure 8-31).47

Intrinsic and metastatic tumors of the liver produce variable echo patterns, depending on histology and secondary tumor necrosis and hemorrhage.48 They can exhibit smooth, well-defined, or irregular borders, and can be of increased or decreased echogenicity relative to the general hepatic tissue. Necrosis produces areas of decreased echogenicity, whereas hemorrhage can create foci of increased or decreased echogenicity depending on the age and degeneration of blood. Common benign tumors include hemangiomas, with well-defined margins and a hyperechoic appearance (Figure 8-32), and hepatic adenomas, with well-defined margins and variable echogenicity (Figure 8-33). Common sources of metastatic lesions include colon, breast, and pancreas (Figure 8-34).49

1. Misidentifying the gallbladder. Oblique sections through the inferior vena cava and the duodenum can be mistaken for the gallbladder. This pitfall can be avoided by ensuring the main lobar fissure connects the assumed gallbladder to the main portal triad. Another method involves using Doppler color flow. The gallbladder is typically the most anterior cystic structure and will not demonstrate Doppler color flow. Bowel can easily take on the appearance of a gallbladder, especially if it contains both fluid and solids. Observing such a segment of bowel will typically result in visualization of peristaltic movement.

2. Inadequate visualization of the gallbladder and biliary system. Intestinal gas can interfere with complete imaging of the gallbladder and biliary system. The patient should be positioned in the left lateral decubitus to prone positions. If time permits, having the patient drink water may encourage gas to move and improve visualization.

3. Confusion with shadowing. A common error after detecting shadowing is making the diagnosis of a small gallstone impacted in the gallbladder neck without actually visualizing a gallstone. Causes of shadowing in the region of the gallbladder neck include the spiral valves of Heister (Figure 8-35), fat in the porta, duodenal gas, and edge artifacts from the gallbladder wall/fluid interface. A gallstone must be directly visualized before making this diagnosis. When a solitary gallstone is lodged in the neck of the gallbladder, however, it can be easily missed (Figure 8-36). A persistent clean shadow behind a rounded bright echo that is present from several viewing angles should be identified. Tissue harmonics may be exceedingly useful in detecting such small stones due to improve contrast resolution. A gallbladder packed with stones and containing little or no liquid bile may be confusing because of dense shadowing in the area that must be differentiated from shadowing caused by bowel gas (Figure 8-37).

4. Misdiagnosing cholelithiasis and cholecystitis. Cholesterol polyps and mucosal folds can be mistaken for gallstones. Bowel loops filled with echogenic material just under the gallbladder are a frequent finding and can appear to protrude into the gallbladder lumen. Making sure that any potential stone is actually within the gallbladder lumen will decrease the possibility of misinterpretation. Gallstones can be missed when they are small or when the entire gallbladder is not visualized because of intestinal gas or large mucosal folds. A thickened gallbladder wall is a nonspecific finding, and may be consistent with cholecystitis, hepatitis, ascites, hypoalbuminemia, and systemic volume overload states (Figure 8-38). The entire clinical picture should always be considered. In 2% of cases, cholecystitis may be diagnosed with the absence of gallstones (acalculous cholecystitis), which typically occur in patients who are chronically debilitated, diabetic, immunocompromised, on hyperalimentation, or recovering from a recent traumatic injury.

5. Misdiagnosing dilated intrahepatic ducts. Intrahepatic branches of the portal vein may be mistaken for dilated intrahepatic ducts as both have echogenic walls and become larger as they confluence toward the hepatic hilum. Color or power Doppler can help identify the vascular structures more precisely. Bile ducts do not demonstrate flow.

6. Misdiagnosing ascites. On ultrasound, ascites can be confused with hemoperitoneum, and vice versa. This can occur between simple transudative ascites and fresh blood (both typically echo free) and between complex exudative fluid and partially clotted blood (both with varying degrees of echogenicity). Clinical correlation, along with fluid sampling, should be used to make the correct diagnosis.

7. Cystic Duct stone. Stones in the cystic duct may be difficult to identify as the gallbladder may appear free of stones. A stone lodged in the cystic duct can appear in a different plane from the gallbladder and may be mistaken for bowel gas not associated with the gallbladder even by experienced sonographers. Any bright echo in vicinity of the gallbladder should be investigated, at least until peristalsis is seen.

8. Common bile duct stones. Common bile duct stones can be exceedingly difficult to identify, especially if they are not highly echogenic (Figure 8-17). Many common bile duct stones are not seen at all and the only indication is dilation of the duct. Complicating this further is the fact that the common bile duct may not be dilated with all stones, especially if only partial duct obstruction exists or the obstruction has occurred recently.

9. Misdiagnosis of Biliary Colic. In the United States, at least 20% of women and 8% of men over 40 years of age have been found to have gallstones at autopsy. It is estimated that 20 million persons in the United States have gallstones and at any given time, the vast majority are asymptomatic.50 When a patient presents with abdominal pain that is atypical and is found to have gallstones on ultrasound, the astute clinician would exercise caution when attributing the symptoms to gallbladder disease. Biliary colic remains a clinical diagnosis and not a sonographic diagnosis.

Case 1

Patient Presentation

A 64-year-old man was brought to the emergency department with complaints of epigastric pain, nausea, and vomiting. He had not tolerated food for the previous 48 hours because of dyspepsia. He noted a low-grade fever but no chills. The patient denied any chest pain, shortness of breath, or cough. He had no surgical history. He denied hematemesis or melena. He occasionally drank alcoholic beverages.

Vital signs revealed a temperature of 37.8°C; blood pressure, 118/58 mmHg; pulse, 119 beats per minute; respiratory rate, 18 breaths per minute. He appeared in moderate distress but nontoxic. There was no evidence of scleral icterus, the lungs were clear, and he did not exhibit costovertebral angle tenderness. The abdomen was tender in the epigastrium and right upper quadrant without guarding, and there were no pulsatile masses. Stool was guaiac negative.

Management Course

An ECG, chest radiograph, and urinalysis were normal. The white blood cell count was 13,400/μL. Lipase and chemistry profile were normal as were the liver transaminases. After administration of analgesics and intravenous fluids, he continued to complain of pain and dyspepsia. A focused emergency ultrasound examination of the right upper quadrant revealed a large gallstone, sludge, and a thickened anterior gallbladder wall. The patient was immediately given intravenous antibiotics; later in the day, he was taken to the operating room for laparoscopic cholecystectomy.

Commentary

Epidemiological and physiologic studies have not corroborated the stereotypical history and physical examination findings for cholecystitis. The ratio of biliary disease in men and women evens out later in life. Epigastric complaints occur as frequently as right upper quadrant complaints. The threshold for performing ultrasound on such patients in the emergency setting should be low to make an expeditious diagnosis.

Case 2

Patient Presentation

An 88-year-old woman was brought to the emergency department by ambulance. When the family arrived, they noted she had become increasingly confused and somnolent over the past 2 days because of “fatigue.” She was completely unresponsive and appeared short of breath. Vital signs revealed a temperature of 39.1°C; blood pressure, 78/52 mmHg; pulse, 128 beats per minute; and respirations, 28 breaths per minute; pulse oximetry, 90% on room air. She was minimally responsive and moaned occasionally with her eyes closed. Her lung examination revealed bibasilar crackles; heart rhythm was regular, but tachycardic; and her extremities were cool. Abdominal examination revealed diffuse tenderness. The patient was noted to be jaundiced.

Management Course

The patient was intubated for airway support. Intravenous fluids and pressors were initiated with good response. ECG and chest radiograph were normal. Urinalysis was normal. Further laboratory data revealed a white blood cell count of 14,000/μL, a normal lipase, a total bilirubin of 14 with a direct component of 9, and an ALT and AST that doubled. Lactate returned at 3.8. A focused ultrasound examination revealed multiple small gallstones in the gallbladder, a thickened anterior gallbladder wall, and a common bile duct that measured 1.2 cm. A diagnosis of cholangitis was made. The patient underwent ERCP and sphincterotomy with removal of two gallstones.

Commentary

Biliary pathology accounts for 25% of all suspected abdominal sepsis sources in the elderly. Focused emergency ultrasound can quickly identify a source of infection and expedite therapy. In addition, focused emergency ultrasound of the biliary tree can readily differentiate between obstructive and nonobstructive causes of jaundice and direct management between medical and surgical treatments.

Case 3

Patient Presentation

A 42-year-old man presented to the emergency department complaining of abdominal distention that began 20 hours before arrival. He admitted to chronic alcohol abuse and stated that he required “abdominal drainage” for a similar complaint in the past. He also complained of shortness of breath and vomited frequently. Prior records indicated a history of spontaneous bacterial peritonitis that required inpatient admission as well as a history of appendectomy when he was 14 years old.

Vital signs revealed a temperature of 37.3°C; blood pressure, 110/74 mmHg; pulse, 102 beats per minute; respirations, 18 breaths per minute. The patient appeared in mild discomfort, but nontoxic. There was no evidence of jaundice, heart sounds were normal, and lungs had rales at the bases bilaterally. His abdomen was distended and diffusely tender without rebound or guarding. There was also minimal edema in the lower extremities.

Management Course

ECG and chest radiograph were normal. White blood cell count was 9,800/μL. Basic chemistries and lipase were normal. The AST and ALT were 100 and 125 respectively, and bilirubin was normal. The presumptive diagnosis of a recurrence of spontaneous bacterial peritonitis was made and the admitting physician prepared for a paracentesis. Prior to the procedure, a focused ultrasound examination of the right upper quadrant was performed that revealed no evidence of ascites. The ultrasound probe was moved to the left lower quadrant where the paracentesis would have been performed and no pockets of free fluid were identified. An acute abdominal series revealed evidence of early small bowel obstruction later confirmed by CT. The patient was taken to the operating room for lysis of adhesions likely from prior appendectomy.

Commentary

Ascites may be difficult to detect on physical examination. In cases where the physician has a suspicion for ascites, focused bedside ultrasound provides a quick and efficient way to make the diagnosis. If ascites is present, ultrasound can identify a deep pocket easily drained for diagnostic or therapeutic purposes. If no ascites is visible, then the physician should look for other sources of abdominal distention such as a bowel obstruction.