eMedicine Specialties > Emergency Medicine > Gastrointestinal

Cholecystitis and Biliary Colic: Differential Diagnoses & Workup

Author: Rahul Sharma, MD, MBA, FACEP, Assistant Professor, Weill Medical College of Cornell University; Attending Physician, Department of Emergency Medicine, New York Presbyterian Hospital-Weill Cornell Medical Center
Coauthor(s): Peter A D Steel, MA, MBBS, Staff Physician, Department of Emergency Medicine, Joan and Sanford I Weill Medical College of Cornell and Columbia University College of Physicians and Surgeons, New York Presbyterian Hospitals
Contributor Information and Disclosures

Updated: Jul 28, 2009

Differential Diagnoses

Workup

Laboratory Studies

• Labs with cholelithiasis and gallbladder colic should be completely normal. WBC, aspirate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin, and alkaline phosphate may be helpful in the diagnosis of cholecystitis. However, presence of normal lab values does not exclude cholecystitis.
• Because biliary obstruction is limited to the gallbladder in uncomplicated cholecystitis, elevation in the serum total bilirubin and alkaline phosphatase concentrations may not be present. A study by Singer et al examined the utility of laboratory values in acute cholecystitis diagnosed by hepatic 2,6-dimethyliminodiacetic acid (HIDA) scan.³ No difference was found in mean WBC, AST, ALT, bilirubin, and alkaline phosphate between patients diagnosed with cholecystitis and those without.
• An elevated WBC is expected but not reliable. In a retrospective study, only 61% of patients with cholecystitis had a WBC greater than 11,000. A WBC greater than 15,000 may indicate perforation or gangrene.
• Comprehensive metabolic panel with bicarbonate may exhibit the following:
  • AST, ALT, and alkaline phosphate levels may be elevated; however, as with other laboratory tests, these levels are not sensitive for excluding cholecystitis. When the AST and ALT are elevated significantly, a common bile duct stone is more likely.
  • An elevation of AST, ALT, or alkaline phosphate should raise the possibility of other biliary system pathology such as cholangitis, choledocholithiasis, or the Mirizzi syndrome (obstruction of the common bile duct by an impacted stone in the distal cystic duct).
  • Note calcium level (Ranson criteria) if evidence of biliary pancreatitis exists.
  • Other abnormalities (eg, renal insufficiency) are not related to cholecystitis but may indicate a comorbid condition.
• Mild elevation of amylase up to 3 times normal may be found in cholecystitis, especially when gangrene is present.
• Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are not expected to be elevated unless sepsis or underlying cirrhosis is present. Coagulation profiles are helpful if the patient needs operative intervention.
• For febrile patients, send 2 sets of blood cultures to attempt to isolate the organism in the presence of bacteremia from bacterial superinfection.
• Although expected to be normal, urinalysis is essential in the workup of patients with abdominal pain to exclude pyelonephritis and renal calculi.
• Conduct a pregnancy test for women of childbearing age.

Imaging Studies

• Ultrasonography and nuclear medicine studies are the best imaging studies for the diagnosis of both cholecystitis and cholelithiasis. Ultrasonography is usually favored as the first test, whereas hepatobiliary scintigraphy is usually reserved for the 20% of patients in whom the diagnosis is unclear after ultrasonography has been performed. 
•  Plain radiography, CT scans, and endoscopic retrograde cholangiopancreatography (ERCP) are diagnostic adjuncts.
• Abdominal radiographs
  • The advantages of abdominal radiographs include their readily availability and low cost. However, abdominal radiographs have low sensitivity and specificity in evaluating biliary system pathology, but they can be helpful in excluding other abdominal pathology such as renal colic, bowel obstruction, perforation. Between 10 and 30% of stones have a ring of calcium and, therefore, are radiopaque. A porcelain gallbladder also may be observed on plain films.
  • Emphysematous cholecystitis, cholangitis, cholecystic-enteric fistula, or postendoscopic manipulation may show air in the biliary tree. Air in the gallbladder wall indicates emphysematous cholecystitis due to gas-forming organisms such as clostridial species and Escherichia coli.
• Computed tomography scan
  • CT scan is not the test of choice and is recommended only for the evaluation of abdominal pain if the diagnosis is uncertain. CT scan can demonstrate gallbladder wall edema, pericholecystic stranding and fluid, and high-attenuation bile.
  • A helical CT scan with fine cuts through the biliary tract has not been well studied and may be useful.
  • Advantages: For complications of cholecystitis and cholangitis, gallbladder perforation, pericholecystic fluid, and intrahepatic ductal dilation, CT scan may be adequate. CT scan provides better information of the surrounding structures than sonogram and HIDA. CT scan is also noninvasive.
  • Disadvantages: CT scan misses 20% of gallstones because the stones may be of the same radiographic density as bile. CT scan is also more expensive and takes longer since the patient usually has to drink oral contrast. Also, given the radiation dose, it may not be ideal in the pregnant patient.
• Ultrasonography

• Ultrasonography is the most common test used in the ED for the diagnosis of biliary colic and acute cholecystitis. It is 90-95% sensitive for cholecystitis and 78-80% specific. For simple cholelithiasis, it is 98% sensitive and specific.
• Ultrasonography may be diagnostic for biliary disease, help exclude biliary disease, or may reveal alternative causes of the patient's symptoms.
• Findings include gallstones or sludge and one or more of the following conditions:
  • Gallbladder wall thickening (>2-4 mm) - False-positive wall thickening found in hypoalbuminemia, ascites, congestive heart failure, and carcinoma
  • Gallbladder distention (diameter > 4 cm, length >10 cm)
  • Pericholecystic fluid from perforation or exudate may be seen as a hypoechoic or anechoic region seen along the anterior surface of the gallbladder within the hepatic parenchyma.
  • Air in the gallbladder wall (indicating gangrenous cholecystitis)
  • Sonographic Murphy sign (86-92% sensitive, 35% specific), pain when the probe is pushed directly on the gallbladder (not related to breathing)
• Some ED sonographers recommend the diagnosis of cholecystitis if both a sonographic Murphy sign and gallstones (without evidence of other pathology) are present.
• In a study by Ralls et al, involving 497 patients with suspected acute cholecystitis, the positive predictive value of the presence of stones and a positive ultrasonographic Murphy's sign was 92%, and that of stones and thickening of the gallbladder wall was 95%. The negative predictive value of the absence of stones combined with either a normal gallbladder wall or a negative Murphy's sign was 95%.⁴
• Additional findings in the presence or absence of gallstones: Dilated common bile duct or dilated intrahepatic ducts of the biliary tree indicate common bile duct stones. In the absence of stones, a solitary stone may be lodged in the common bile duct, a location difficult to visualize sonographically.
• Advantages of sonography include the following:
  • Images other structures (eg, aorta, pancreas, liver)
  • Identifies complications (eg, perforation, empyema, abscess)
  • Rapidly performed at the bedside and by the ED physician (see Bedside Ultrasonography, Gallbladder Disease)
  • No radiation (important in pregnancy)
• Disadvantages of sonography include the following:
  • Operator dependent and patient dependent
  • Inability to image the cystic duct
  • Decreased sensitivity for common bile duct stones
• Biliary scintigraphy (HIDA, diisopropyl iminodiacetic acid [DISIDA]), nuclear medicine studies
  • Depending on the ED, either sonography or nuclear medicine testing is the test of choice for cholecystitis. HIDA scans have sensitivity (94%) and specificity (65-85%) for acute cholecystitis. They are sensitive (65%) and specific (6%) for chronic cholecystitis. Oral cholecystography is not practical for the ED.
  • HIDA and DISIDA scans are functional studies of the gallbladder. Technetium-labeled analogues of iminodiacetic acid (IDA) or diisopropyl IDA-DISIDA are administered intravenously (IV) and secreted by hepatocytes into bile, enabling visualization of the liver and biliary tree.
  • Normal scans are characterized by normal visualization of gallbladder in 30 minutes.
  • With cystic duct obstruction (cholecystitis), the HIDA scan shows nonvisualization (ie, considered positive) of the gallbladder at 60 minutes and uptake in the intestine as the bile is excreted directly into the duodenum. This finding has a sensitivity of 80-90% for acute cholecystitis.
  • Obstruction of the common bile duct causes nonvisualization of the small intestine.
  • The rim sign is a blush of increased pericholecystic radioactivity, tracer adjacent to the gallbladder, present in approximately 30% of patients with acute cholecystitis and in 60% with acute gangrenous cholecystitis.
  • False-negative results (filling in 30 min) are found in 0.5% of studies, and filling between 30-60 minutes is associated with false-negative rates of 15-20%.
  • False-positive results (10-20%) occur when the gallbladder does not visualize despite a nonobstructed cystic duct. Causes include fasting patients receiving total parenteral nutrition; severe liver disease, which leads to abnormal uptake of the tracer; cystic-duct obstruction induced by chronic inflammation, and biliary sphincterotomy, which decreases resistance to bile flow leading to excretion of the tracer into the duodenum. The specificity of the test can be improved by intravenous administration of morphine, known as morphine cholescintigraphy, which induces spasm of this sphincter, increasing back pressure to fill the gallbladder.⁵
  • Advantages of HIDA/DISIDA scans include the following:
    • Assessment of function
    • Normal-appearing gallbladder (by ultrasound); obstructed cystic duct abnormal on DISIDA scan but not ultrasound.
    • Simultaneous assessment of bile ducts
  • Disadvantages of HIDA/DISIDA scans include the following:
    • High bilirubin (>4.4 mg/dL) possibly decreases sensitivity
    • Recent eating or fasting for 24 hours also possibly affects study
    • No imaging of other structures in the area

Other Tests

• Endoscopic retrograde cholangiopancreatography
  • ERCP provides both endoscopic and radiographic visualization of the biliary tract. It can be diagnostic and therapeutic by direct removal of common bile duct stones.
  • Ultrasound is 50-75% sensitive for choledocholithiasis. CT and HIDA scans are not better. Therefore, when a dilated common bile duct is found or elevated LFTs are present, suspicion should remain high for common bile duct stones, and an ERCP should be considered.
  • Debate exists as to when an ERCP should be performed. In general, since cholecystitis is caused by obstruction of the ducts, the risk of common bile duct stones is approximately 10%. Given its potential for complications, ERCP should be used when there is a high potential for intervention and it should not be used solely as a diagnostic modality.
  • Some studies have classified people as low risk for common bile duct stones based on (1) lack of jaundice, (2) elevated transaminases, and (3) a common bile duct diameter of less than 8 mm. In this population, the risk of common bile duct stones may be as low as 1%. In patients with any of the risk factors, the rate of stones was 39%. Therefore, in general, people with any of the risk factors for common bile duct stones should undergo operative or ERCP evaluation of the common bile duct.
  • Major complications of ERCP include pancreatitis and cholangitis.

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