Suspected acute cholecystitis

ACR AC Right Upper Quadrant Pain (2022 update); Tokyo Guidelines 2018

The clearest ultrasound-first indication in the abdomen, and the request most often submitted as a CT. Ultrasound answers the question with no radiation, and it is the only modality that combines the imaging findings with a sonographic Murphy sign obtained at the point of tenderness.

Right upper quadrant pain, often post-prandial, with fever or leucocytosis and local tenderness.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Fever or sepsis

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

Ultrasound abdomen — full survey

Ultrasound abdomen

What we'd amend, and why

Stones are strongly reflective with clean posterior shadowing and move with gravity, which is a set of properties no other modality resolves as well — small stones are frequently invisible on CT because their attenuation matches bile. Ultrasound also delivers the one finding that cannot be obtained from any cross-sectional dataset: focal tenderness elicited under the transducer directly over the gallbladder, combined in real time with wall thickening, distension and pericholecystic fluid. It is equally appropriate in pregnancy, where it remains the first test.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayadult — Adults, including pregnancy
rulerule-fasting-prep — Patient preparation: fasting, enteric contrast and lactation advice; checked by Scheduling team

Decision support only. Local protocol takes precedence.

Handled at the scanner(1)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

Patient preparation: fasting, enteric contrast and lactation advice
Confirm the correct preparation was issued and followed. Three separate things are commonly conflated and should not be: (1) routine intravenous iodinated or gadolinium contrast requires NO fast — the ACR Manual states fasting is not required before routine intravascular contrast administration; (2) oral or rectal contrast protocols have their own timing which is a protocol requirement, not a fast; (3) planned sedation or anaesthesia does require fasting, on anaesthetic rather than contrast grounds.
Scheduling teamBefore the scan
Flags back if: The patient has not taken the oral or rectal preparation on which the protocol depends, or is incorrectly fasted or unfasted for a planned sedation or anaesthetic.
Fasting is diagnostic preparation here, not safety preparation: a contracted gallbladder after a recent meal has a physiologically thick wall and mimics the disease. Four to six hours nil by mouth is typical, but an unwell patient should not be starved repeatedly to chase an ideal scan.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Febrile or septic — complicated cholecystitis and biliary sepsis

Role	Study & protocol	Why this answers the question
First line	Ultrasound abdomen Ultrasound abdomen — full survey usually appropriate	Ultrasound still leads, and fever is a reason to do it sooner rather than a reason to do something else. It supplies the stone, the wall thickening, the pericholecystic fluid and the sonographic Murphy sign that together make the diagnosis, and it does so at the bedside in a patient who may be too unwell to move. The one thing that must not follow is reassurance: in a septic patient a normal-looking gallbladder does not close the question, because acalculous cholecystitis in the critically ill has no stone to find, and because the sepsis may be arising from the duct rather than the gallbladder — which is a drainage problem, not an imaging one.
Second line	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase usually appropriate	This is the rung that moves. In the septic patient the escalation question is what the gallbladder has done to the rest of the abdomen — a wall that has stopped enhancing or is discontinuous, gas in the wall or lumen, a pericholecystic or hepatic collection, and portal venous or hepatic arterial involvement — and it is equally the question of whether the gallbladder is the source at all, because a perforated ulcer, a hepatic abscess and a right-sided colitis all present as right upper quadrant pain with fever. Portal-venous CT answers both in one acquisition and it answers them in minutes. Cholangiography does neither: it is the correct second study when the escalation is biochemical rather than septic, which is the ordinary pathway, and it is displaced here rather than removed.
Problem solving	MRCP (MR Cholangiopancreatography) MRCP — standard unenhanced	Cholangiography keeps its place for the febrile patient whose liver function tests point at the duct as well, and it is the right way to resolve an inconclusive ultrasound in pregnancy without radiation or gadolinium. It is behind CT here only because it does not answer the complication question, and it should never be the study a septic patient waits for when decompression is what they need.

Fever with jaundice and rigors is cholangitis rather than cholecystitis, and that is a drainage emergency handled by the obstructive jaundice card — the gallbladder is not the organ to keep scanning.
A patient too unwell for surgery is still a patient in whom a drainable gallbladder matters: percutaneous cholecystostomy is a real endpoint of this pathway, and the report should say whether it is feasible.

Adults, including pregnancy

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Ultrasound abdomen Ultrasound abdomen — full survey usually appropriate	Stones are strongly reflective with clean posterior shadowing and move with gravity, which is a set of properties no other modality resolves as well — small stones are frequently invisible on CT because their attenuation matches bile. Ultrasound also delivers the one finding that cannot be obtained from any cross-sectional dataset: focal tenderness elicited under the transducer directly over the gallbladder, combined in real time with wall thickening, distension and pericholecystic fluid. It is equally appropriate in pregnancy, where it remains the first test.
Second line	MRCP (MR Cholangiopancreatography) MRCP — standard unenhanced	When ultrasound is equivocal, or when the liver function tests suggest a duct stone as well, heavily T2-weighted cholangiography shows the stone as a signal void within bright bile and simultaneously demonstrates gallbladder wall oedema. In pregnancy this is the preferred way to resolve an inconclusive ultrasound, because it adds no radiation and needs no gadolinium.
Problem solving	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase	CT earns its place when the differential is broad or when a complication is suspected: perforation, emphysematous change, or gallstone ileus. It is also the study that shows the alternative diagnoses in an unwell patient whose ultrasound was normal. Used as the opening study it both misses stones and adds dose. Where the ultrasound is equivocal and the specific question is whether the cystic duct is obstructed rather than what else is going on, cholescintigraphy is the more accurate test than either CT or MRI, and is the right escalation in that narrower situation.

A negative ultrasound in a patient who remains septic does not close the question; acalculous cholecystitis and biliary sepsis both need escalation rather than reassurance.
Acalculous cholecystitis is the trap in the critically ill, the ventilated and the parenterally fed: there is no stone to find, the wall changes are non-specific in a patient with fluid overload and hypoalbuminaemia, and the diagnosis is usually made by putting the imaging together with the clinical trajectory rather than by a single convincing scan.

Pitfalls

Accepting a CT request for uncomplicated right upper quadrant pain. Stones isodense to bile are routinely invisible on CT, so a negative CT is weak evidence.
Equating gallstones with cholecystitis. Stones are common and often incidental; the diagnosis needs the inflammatory findings and the clinical picture together.
Treating a thick gallbladder wall as specific — it is seen in hepatitis, heart failure, hypoalbuminaemia and simply after eating.
Sending a pregnant patient to CT because the ultrasound was inconclusive, when MRI is the intended next step.
Missing that deranged liver function has already moved the question to the common bile duct, which needs cholangiography rather than a repeat gallbladder scan.
Reading fever with jaundice and rigors as severe cholecystitis. That triad is cholangitis, the treatment is duct drainage rather than cholecystectomy, and repeating gallbladder imaging is how the decompression gets delayed.
Reporting a negative ultrasound as excluding cholecystitis in a critically ill patient. Acalculous disease has no stone to find, and the diagnosis has to be assembled from the wall, the clinical picture and the trajectory.

Priors — what to pull first

Check for a previous cholecystectomy before accepting the request — it ends the question and redirects it to the bile duct.
A previous ultrasound documenting stones changes the question from "are there stones" to "is this gallbladder acutely inflamed".

What makes a good request

Fasting for several hours before the scan distends the gallbladder; a contracted post-prandial gallbladder can make wall thickness uninterpretable.
Deranged liver function or a dilated duct shifts the question from the gallbladder to the bile duct, and the pathway changes with it.
The Tokyo Guidelines diagnosis is a composite: local signs (a positive Murphy sign or right upper quadrant tenderness), systemic signs (fever, raised white cell count or C-reactive protein) and imaging findings together. Imaging is one of three arms, so a request that supplies the other two gets a far more useful report — and imaging alone neither makes nor excludes the diagnosis.
Where ultrasound is equivocal and the diagnosis still matters, cholescintigraphy is the most accurate single test — non-visualisation of the gallbladder at sixty minutes indicates cystic duct obstruction — and it is worth naming as an option even though this library carries no hepatobiliary scintigraphy study node.
Grade the severity, because it decides the operation. Grade I disease goes to early laparoscopic cholecystectomy; Grade III — organ dysfunction — is the patient in whom percutaneous cholecystostomy is the realistic answer, and the report should say whether the gallbladder is accessible for it.

Scoring this once it is done

The classification and risk tools this question ends in.

Acute Cholecystitis Risk (Ultrasound + Clinical)SRU Gallbladder Polyp Follow-up (2022 Consensus)

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

Ultrasound abdomen — full survey CT Abdomen and Pelvis — Portal Venous Phase MRCP — standard unenhanced

Confirm locally

Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.