What laboratory test is most useful in confirming a diagnosis of cholecystitis?

The HIDA scan, or Hepatobiliary Iminodiacetic Acid scan, is particularly effective in confirming a diagnosis of cholecystitis because it specifically evaluates the function of the gallbladder and its ability to take up a radiotracer. In the case of acute cholecystitis, the gallbladder is often inflamed and may not visualize on the scan due to its inability to concentrate the tracer, indicating a dysfunction consistent with the disease.

In addition, the HIDA scan is less invasive compared to surgical methods for diagnosis and provides dynamic information about gallbladder function and the status of the biliary tree, thus making it a superior choice for confirming cholecystitis over other tests.

While imaging techniques like CT scans can visualize the gallbladder and help identify complications such as gallbladder perforation or abscess, the HIDA scan offers specific insights into gallbladder functionality which is fundamental for diagnosing cholecystitis accurately. Other laboratory tests such as liver function tests and amylase may provide supportive information but do not confirm the diagnosis of cholecystitis directly.