A 50-year-old woman comes to the emergency department with severe upper abdominal pain. The pain started suddenly and is sharp and colicky. She has also vomited several times throughout the day, including once while in the emergency department. The patient describes several prior episodes of similar abdominal pain that resolved spontaneously without treatment. Her other medical problems include complicated appendicitis when she was 22 years old. Her temperature is 37.8 C (100 F) and pulse is 112/min. Abdominal examination shows cessation of inspiration with deep palpation of the right upper quadrant. Laboratory assessment shows a serum bilirubin of 0.8 mg/dL and a serum alkaline phosphatase of 100 U/L. Initial imaging studies are equivocal. Which of the following diagnostic test results would be most specific for acute cholecystitis?
Acute cholecystitis is caused by gallstone obstruction of the cystic duct in more than 90% of cases. Ingestion of fatty foods then stimulates contraction of the gallbladder against the impacted stone, resulting in severe colicky pain. Mechanical disruption of the gallbladder mucosa and release of inflammatory mediators (eg, lysolecithin, prostaglandins) cause the obstructed gallbladder to become inflamed and edematous. As blood supply to the distended organ becomes compromised, secondary bacterial infection frequently develops. Potential complications include gangrene and perforation, with subsequent formation of a pericholecystic abscess or generalized peritonitis.
Ultrasonography is the preferred initial imaging test for the diagnosis of acute cholecystitis; however, nuclear medicine hepatobiliary scanning (ie, cholescintigraphy) can be an alternate means when ultrasonography is inconclusive. During a hepatobiliary scan, a radiotracer is administered intravenously and is preferentially taken up by hepatocytes and excreted into bile. Images of the tracer as it moves through the hepatobiliary system and intestine are then obtained for up to several hours after injection.
Show Explanatory Sources
In patients with a patent cystic duct, the gallbladder will be seen as the radiotracer accumulates and concentrates within (image C). In acute or chronic cholecystitis, the radiotracer will be taken up by the liver with progressive excretion into the common bile duct and proximal small bowel, but the gallbladder will not be visualized due to the obstruction (image A and B).
(Choice A) Distended duodenum on an upper gastrointestinal series would be suggestive of small-bowel obstruction (as seen with gallstone ileus).
(Choice B) The presence of echogenic structures within the gallbladder on ultrasound can be suggestive of acute cholecystitis in the setting of fever and abdominal pain, but it is not diagnostic. Cholelithiasis can also cause more benign biliary colic, or be an incidental asymptomatic finding in the setting of other abdominal pathology. Ultrasound findings more specific for acute cholecystitis include gallbladder wall thickening, pericholecystic fluid, and a positive sonographic Murphy sign.
(Choice D) Mild increases in serum aspartate and alanine aminotransferase levels can occur in acute cholecystitis, but they are nonspecific and do not aid the diagnosis.
(Choice E) Most patients have insufficient calcium in their gallstones to be visualized on an abdominal x-ray.
Educational objective:
Acute cholecystitis is most often caused by gallstones obstructing the cystic duct. The diagnosis can be made by identifying signs of gallbladder inflammation (eg, wall thickening, pericholecystic fluid) on ultrasonography. When ultrasound is inconclusive, nuclear medicine hepatobiliary scanning (ie, cholescintigraphy) can be used to assess cystic duct patency and make the diagnosis.