1st investigations to order
CT or MRI of the abdomen
If sepsis is suspected, request contrast-enhanced CT or MRI for diagnosing gangrenous cholecystitis or gallbladder perforation.
Use CT for diagnosing emphysematous cholecystitis.
Evidence: Comparison of imaging studies
Evidence shows that several imaging methods accurately rule out cholecystitis, although the diagnostic accuracy and costs of investigations vary.
Despite evidence that cholescintigraphy is more accurate than ultrasound and MR imaging at diagnosing acute cholecystitis, other factors such as availability, cost, and the ability to view an area outside of the biliary tract mean that ultrasound is generally the preferred initial test.
A systematic review, including 57 studies, sought to estimate the diagnostic accuracy of:
It found that the sensitivity of cholescintigraphy (96%, 95% CI 94% to 97%) was significantly higher than the sensitivity of ultrasonography (81%, 95% CI 75% to 87%) and magnetic resonance imaging (85%, 95% CI 66% to 95%) for diagnosing acute cholecystitis. There were no significant differences in specificity between cholescintigraphy (90%, 95% CI 86% to 93%), ultrasonography (83%, 95% CI 74% to 89%), and MR imaging (81%, 95% CI 69% to 90%).
The 2018 Tokyo guidelines and the UK 2014 National Institute for Health and Care Excellence (NICE) guidelines both recommend ultrasound as a reasonable initial choice, based on issues such as low invasiveness, low risk, widespread availability, ease of use, and cost‐effectiveness.
The NICE guideline recommends magnetic resonance cholangiopancreatography (MRCP) if abnormalities are present in the bile duct or liver function tests but ultrasound has not detected common bile duct stones.
Two health economic studies found that MRCP appeared cost-effective compared with endoscopic retrograde cholangiopancreatography for diagnosing common bile duct stones.
Note that in a patient with sepsis, use CT (or MRI) to identify the cause.
The specific findings indicating cholecystitis include:
Irregular thickening of the gallbladder wall
Poor contrast enhancement of the gallbladder wall (interrupted rim sign)
Increased density of fatty tissue around the gallbladder
Gas in the gallbladder lumen or wall
Membranous structures within the lumen (intraluminal flap or intraluminal membrane)
If sepsis is not suspected, use abdominal ultrasound to confirm diagnosis of cholecystitis and to exclude differential diagnoses.
Use ultrasound as the first investigation to identify the presence of gallstones.
The following signs on ultrasound are indicative of acute cholecystitis:
Thickened gallbladder wall (>3 mm)
Positive sonographic Murphy's sign (may be absent in gangrenous cholecystitis)
Check white cell count for an indication of infection or inflammation.
White cell count may be elevated in severe disease
Request liver function tests to indicate whether further imaging is required, such as magnetic resonance cholangiopancreatography.
May show elevated bilirubin, alkaline phosphatase, alanine aminotransferase, and gamma glutamyl transferase due to acute focal liver inflammation or cholestasis in adjacent liver tissue or due to common bile duct stones
Alanine aminotransferase can also be elevated if a stone has passed down the common bile duct, or if there is focal inflammation of the liver parenchyma in severe cholecystitis
serum lipase or amylase
Identify or exclude the presence of acute pancreatitis. Use serum lipase testing (if available) in preference to serum amylase.
blood cultures and/or bile cultures
Request in patients with grade II (moderate) and III (severe) disease in order to identify an infection that may be the cause of sepsis.
See Assessing severity in Diagnosis recommendations for guidance on how to define grade of cholecystitis.
There are no blood tests that will specifically confirm the diagnosis of cholecystitis, but they help to build the clinical picture of how unwell the patient is and can help to exclude other diagnoses.
Will confirm infective organism, if present
Investigations to consider
magnetic resonance cholangiopancreatography (MRCP)
Request MRCP if ultrasound has not detected common bile duct stones but the bile duct is dilated and/or liver function test results are abnormal.
Consider endoscopic ultrasound if MRCP does not allow a diagnosis to be made.
The findings of acute cholecystitis on MRI are:
Thickening of the gallbladder wall (≥4 mm)
Enlargement of the gallbladder (long axis ≥8 cm, short axis ≥4 cm)
Gallstones or retained debris
Fluid accumulation around the gallbladder
Linear shadows in the fatty tissue around the gallbladder
endoscopic ultrasound (EUS)
Consider EUS if MRCP does not allow a diagnosis to be made.
EUS is good at detecting distal common bile duct stones. If MRCP does not show a stone but the patient has deranged LFTs, EUS is an excellent test but invasive; therefore, have a high index of suspicion before requesting this test.
May detect stones not identified by MRCP or abdominal ultrasound
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