Approach Considerations
The workup for cholecystitis includes history and physical examination, laboratory tests (though these are not always reliable), plain x-ray of the abdomen, ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), hepatobiliary isotope scintigraphy (HBS), and endoscopy.
Imaging recommendations
The American College of Radiology (ACR) Appropriateness Criteria offer the following imaging recommendations [1] :
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Ultrasonography is the preferred initial imaging test for the diagnosis of acute cholecystitis; scintigraphy is the preferred alternative.
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CT scanning is a secondary imaging test that can identify complications of acute cholecystitis and extrabiliary disorders when ultrasonography has not yielded a clear diagnosis.
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CT scanning with intravenous (IV) contrast medium is useful in diagnosing acute cholecystitis in patients with nonspecific abdominal pain (NSAP).
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MRI, often with IV gadolinium-based contrast medium, is also a possible secondary choice for confirming a diagnosis of acute cholecystitis.
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MRI is a useful alternative to CT scanning for eliminating radiation exposure in pregnant women.
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Contrast agents should not be used in patients with renal dysfunction unless absolutely necessary.
Laboratory Tests
Although the laboratory criteria are not reliable in identifying all patients with cholecystitis, the following findings may be useful in arriving at the diagnosis:
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Leukocytosis with a left shift may be observed in acute cholecystitis.
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Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels are usually used to evaluate for the presence of hepatitis and may be elevated in acute cholecystitis or with common bile duct obstruction.
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Bilirubin and alkaline phosphatase (ALP) assays are used to evaluate for the presence of common bile duct obstruction caused by the inflammatory edema of acute cholecystitis.
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Amylase/lipase assays are usually used to evaluate for the presence of acute pancreatitis and may also be elevated mildly in acute cholecystitis.
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An elevated ALP level is observed in 25% of patients with acute cholecystitis.
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Urinalysis is used to rule out pyelonephritis and renal calculi.
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All females of childbearing age should undergo pregnancy testing.
A retrospective study by Singer et al, aimed at determining a set of clinical and laboratory parameters that could be used to predict the outcome of hepatobiliary isotope scintigraphy (HBS) in patients with suspected acute cholecystitis, found that of the 40 patients with pathologically confirmed acute cholecystitis, 36 (90%) did not have fever at the time of presentation and 16 (40%) did not have leukocytosis. [20] The study also found that no combination of laboratory or clinical values was useful in identifying patients at a high risk for a positive HBS finding.
Radiography
Gallstones may be visualized on noncontrast radiography (ie, plain X-rays) in 10%-15% of cases. This finding only indicates cholelithiasis, with or without active cholecystitis.
Subdiaphragmatic free air cannot originate in the biliary tract, and if present, it indicates another disease process. Gas limited to the gallbladder wall or lumen represents emphysematous cholecystitis, usually because of gas-forming bacteria, such as Escherichia coli and clostridial and anaerobic streptococci species. Emphysematous cholecystitis is associated with increased mortality and occurs most commonly in males with diabetes and with acalculous cholecystitis.
See Emphysematous Cholecystitis for more complete information on this topic.
A diffusely calcified gallbladder (ie, porcelainized) most commonly is associated with carcinoma, although two studies have found no association between partial calcification of the gallbladder and carcinoma. [21, 22]
Other findings seen on noncontrast radiography may include renal calculi, intestinal obstruction, or pneumonia.
See Acute Cholecystitis Imaging and Acalculous Cholecystitis Imaging for more complete information on these topics.
Ultrasonography
Ultrasonography is 90%-95% sensitive for cholelithiasis and acute cholecystitis, and it is 78%-80% specific. This imaging modality provides greater than 95% sensitivity and specificity for the diagnosis of gallstones more than 2 mm in diameter. Studies indicate that emergency clinicians require minimal training in order to use right upper quadrant ultrasonography in their practice. [23, 24, 25, 26, 27, 28]
Ultrasonographic findings that are suggestive of acute cholecystitis include the following: pericholecystic fluid, gallbladder wall thickening greater than 4 mm, and sonographic Murphy sign. [66, 67, 68, 69] Sonographic Murphy sign "is defined as maximal abdominal tenderness from pressure of the ultrasound probe over the visualized gallbladder." [70] Although sonographic Murphy sign is sensitive for cholecystitis, the presence of pericholecystic fluid and thickening of the gallbladder wall is nonspecific. [69] However the presence of gallstones helps to confirm the diagnosis: The combination of the Murphy sign and cholelithiasis has a high positive predictive value (PPV). [68, 70]
Ultrasonography is performed best following a fast of at least 8 hours because gallstones are visualized best in a distended bile-filled gallbladder.
Contrast-enhanced ultrasonography (CEUS) with the agent perflubutane (Sonazoid) shows promise for its use in the diagnosis of gangrenous cholecystitis. [29] In a study comprising 27 patients with acute cholecystitis who underwent preoperative CEUS, 15 patients had a final diagnosis of gangrenous cholecystitis and 12 patients had uncomplicated cholecystitis, all confirmed via histologic examination. Of the 15 patients diagnosed with gangrenous cholecystitis, CEUS detected perfusion defects in 10 patients (66.7% sensitivity, 100% specificity; 100% PPV and 70.6% negative predictive value [NPV]). Review of the movie clips of the CEUS raised the sensitivity to 73.3% and the NPV to 75%. [29] Interobserver agreement was good (κ coefficient = 0.64).
Disadvantages of ultrasonography include the fact that this imaging modality is operator and patient dependent, it is unable to image the cystic duct, and it has a decreased sensitivity for common bile duct stones. In addition, in the setting of concomitant acute pancreatitis, ultrasonographic findings alone are not adequate to accurately identify acute cholecystitis. [30]
See Acute Cholecystitis Imaging and Acalculous Cholecystitis Imaging for more complete information on these topics.
Computed Tomography Scanning and Magnetic Resonance Imaging
The sensitivity and specificity of computed tomography (CT) scanning and magnetic resonance imaging (MRI) in predicting acute cholecystitis have been reported to be greater than 95%. [31] Spiral CT scanning and MRI (unlike endoscopic retrograde cholangiopancreatography [ERCP]) have the advantage of being noninvasive, but they have no therapeutic potential and are most appropriate in cases where bile duct stones are unlikely.
Findings suggestive of acute cholecystitis include wall thickening (>4 mm), pericholecystic fluid, subserosal edema (in the absence of ascites), intramural gas, and sloughed mucosa.
Diffusion-weighted (DW) MRI shows potential for differentiating between acute and chronic cholecystitis. [32] In a study comprising 83 patients with abdominal pain, Wang et al noted that increased signal on high b-value images were highly sensitive and moderately specific for acute cholecystitis. [32]
CT scanning and MRI are also useful for viewing the surrounding structures if the diagnosis is uncertain.
See Acute Cholecystitis Imaging and Acalculous Cholecystitis Imaging for more complete information on these topics.
Hepatobiliary Isotope Scintigraphy
Hepatobiliary isotope scintigraphy (HBS) has been found to be up to 95% accurate in diagnosing acute cholecystitis. The reported sensitivities and specificities of biliary scintigraphy are in the range of 90%-100% and 85%-95%. (See the following two images.)
In a typical study, the gallbladder, common bile duct, and small bowel fill within 30-45 minutes. If the gallbladder is not visualized, intravenous morphine administration can improve the accuracy of HBS by increasing the resistance to flow through the sphincter of Oddi, resulting in filling of the gallbladder if the cystic duct is patent. The addition of morphine also reduces the number of false-positive scan results observed in patients who are critically ill and immobilized with viscous bile.
See Acute Cholecystitis Imaging and Acalculous Cholecystitis Imaging for more complete information on these topics.
Endoscopic Retrograde Cholangiopancreatography
Endoscopic retrograde cholangiopancreatography (ERCP) may be useful for visualizing the anatomy in patients at high risk for gallstones if signs of common bile duct obstruction are present. A study performed by Sahai et al found that ERCP was preferred over endoscopic ultrasonography and intraoperative cholangiography for patients at high risk for common bile duct stones undergoing laparoscopic cholecystectomy. [33]
Disadvantages of ERCP include the need for a skilled operator, high cost, and complications such as cholangitis and pancreatitis, which occur in 3%-5% of cases.
See Acute Cholecystitis Imaging and Acalculous Cholecystitis Imaging for more complete information on these topics.
Histologic Findings
Edema and venous congestion are early acute changes. Acute cholecystitis is usually superimposed on a histologic picture of chronic cholecystitis. Specific findings include fibrosis, flattening of the mucosa, and chronic inflammatory cells. Mucosal herniations known as Rokitansky-Aschoff sinuses are related to increased hydrostatic pressure and are present in 56% of cases. Focal necrosis and an influx of neutrophils may also be present. Advanced cases may show gangrene or perforation.
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Acute Cholecystitis. Normal finding on hepatoiminodiacetic acid (HIDA) scan.
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Acute Cholecystitis. Abnormal finding on hepatoiminodiacetic acid (HIDA) scan.
