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Biliary tract disease exists as a spectrum that ranges from asymptomatic gallstones to biliary colic, cholecystitis, choledocholithiasis, and cholangitis. The incidence of gallstones is approximately 10%–20% and is dependent on several factors such as age, gender, fertility, race, ethnicity, and associated comorbidities. Only 1%–3% of individuals with gallstones report being symptomatic. Biliary colic occurs when a gallstone temporarily obstructs either the common bile duct (CBD) or cystic duct. Usually, biliary colic is self-limited and treated with analgesia and elective cholecystectomy. Cholecystitis results from prolonged obstruction of the cystic duct and causes inflammation of the gallbladder (GB), necessitating more urgent surgical removal. Complications of cholecystitis can lead to infection, empyema, gangrene, necrosis, perforation, and sepsis. Cholecystitis is usually caused by an obstructing gallstone, but acalculous blockage does occasionally occur.
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Choledocholithiasis is a result of prolonged obstruction of the CBD. This disease can also occur post cholecystectomy when there are retained gallstones after surgery. Cholangitis is an ascending infection of the biliary tract. It can be due to prolonged obstruction from a gallstone and a resultant bacterial infection of the bile. It is a rare complication of cholecystitis, usually occurring in the elderly or in patients with associated comorbidities. Cholangitis has a high morbidity and mortality that increases with a delay in diagnosis.
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Ultrasound is a rapid, noninvasive, well-tolerated, and sensitive modality in diagnosing both biliary colic and cholecystitis. Therefore, it is the first imaging modality of choice for suspected biliary disease in both the critical care and outpatient setting. The use of bedside ultrasound is important in order to rapidly identify this disease and prevent complications that result from diagnostic delays. The sensitivity of ultrasound has been reported to be as high as 95%. The four sonographic signs of cholecystitis (stones, sonographic Murphy's sign, wall thickening, and pericholecystic fluid) are highly specific when all four are present, although this is uncommon and any of the four signs may be nonspecific, particularly in isolation. The combination of a positive sonographic Murphy's sign and gallstones has been shown to have a positive predictive value for cholecystitis as high as 96%. Hepatobiliary iminodiacetic acid (HIDA) scans (nuclear medicine scans) are used when ultrasound results are equivocal and the diagnosis is still suspected. HIDA scans have a reported sensitivity and specificity of roughly 95%.
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Ultrasound is not highly sensitive for diagnosing choledocholithiasis. Although it may not be the best modality for diagnosing choledocholithiasis, the combination of a dilated common bile duct on ultrasound with lab abnormalities helps narrow the diagnosis. Endoscopic retrograde cholangiopancreatography (ERCP) and magnetic resonance cholangiopancreatography (MRCP) remain the gold standards for diagnosing this entity. Cholangitis is a clinical diagnosis (Charcot's triad: fever, right upper quadrant [RUQ] pain, and jaundice) associated with findings of cholecystitis or choledocholithias identified on ultrasound.
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In addition to GB pathology, bedside ultrasound can be useful in evaluating for liver abnormalities, such as cysts, masses, abscesses, and hepatomegaly. A pancreatic pseudocyst or mass may ...