01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Ultrasound is a dynamic, non-ionising examination suited to the superficial gallbladder and intrahepatic ducts. It can demonstrate echogenic mobile stones with posterior shadowing, sludge, gallbladder distension, focal tenderness under the probe, wall thickening and pericholecystic fluid. Each finding has limitations, so the impression should integrate symptoms, LFTs and inflammatory markers.
Biliary dilatation suggests impaired drainage but calibre varies with age, previous cholecystectomy and measurement site. The distal common bile duct can be obscured by bowel gas, and a small stone may not shadow. Thus an apparently stone-free duct is not the same as exclusion of choledocholithiasis when jaundice, pancreatitis, cholangitis, abnormal LFTs or duct dilatation persists.
MRCP maps the biliary and pancreatic ducts non-invasively and is useful after equivocal ultrasound. EUS detects small distal stones and allows close pancreatic assessment, but is invasive and operator-dependent. ERCP combines fluoroscopic duct imaging with sphincterotomy, extraction or stenting and should be directed toward a therapeutic purpose.
Key points
- For suspected gallstone disease, NICE recommends liver function tests and abdominal ultrasound as the initial diagnostic pair.
- Ultrasound is strong for gallbladder stones and biliary dilatation but may miss distal common bile duct stones or be limited by bowel gas and habitus.
- Diagnose acute cholecystitis from the combined clinical, laboratory and sonographic picture, not wall thickness alone.
- If ultrasound shows no duct stone but the bile duct is dilated or LFTs are abnormal, consider MRCP; consider EUS if MRCP is nondiagnostic.
- Use ERCP principally when duct therapy is required, because pancreatitis, bleeding, infection and perforation make it more than a diagnostic scan.
- In cholangitis or organ dysfunction, resuscitation, antibiotics and urgent drainage planning proceed without waiting for perfect non-invasive imaging.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
A mobile echogenic focus with clean posterior acoustic shadowing supports a stone; impacted neck stones may not move with position.
Stones plus focal sonographic tenderness, distension, wall thickening or pericholecystic fluid supports inflammation in the right clinical context.
Dilated ducts, jaundice and cholestatic LFTs raise concern for choledocholithiasis, stricture or tumour even when no stone is directly seen.
Biliary obstruction with infection can progress to hypotension, confusion and organ failure and requires urgent drainage planning.
A critically ill patient can develop gallbladder inflammation without stones; nonspecific findings require trend and specialist interpretation.
Obesity, bowel gas, pain, inability to cooperate and a deeply placed distal duct can prevent adequate visualisation without excluding disease.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Abdominal ultrasoundFirst step - Why
- Identify gallbladder stones, inflammation and biliary dilatation without ionising radiation.
- Interpretation and limitations
- A negative or limited scan does not exclude small distal duct stones, early inflammation or non-biliary pathology.
- 02
Liver function tests - Why
- Identify cholestasis and hepatic involvement alongside sonographic anatomy.
- Interpretation and limitations
- A dynamic cholestatic pattern supports obstruction but can arise from other hepatic or systemic illness.
- 03
MRCP - Why
- Map intrahepatic and extrahepatic ducts after unresolved non-invasive assessment.
- Interpretation and limitations
- Consider when ultrasound misses CBD stones but duct dilatation or abnormal LFTs persists; very small stones may remain occult.
- 04
Endoscopic ultrasound - Why
- Detect small distal duct stones and characterise pancreas when MRCP is nondiagnostic.
- Interpretation and limitations
- High-resolution assessment is invasive and should be used when its result will alter ERCP or surgery.
- 05
Contrast CT abdomen - Why
- Assess complications or alternative diagnoses such as pancreatitis, perforation, mass or abscess.
- Interpretation and limitations
- CT is not the most sensitive examination for uncomplicated gallbladder stones and a negative CT does not replace ultrasound.
- 06
Hepatobiliary scintigraphy - Why
- Assess cystic-duct patency in selected equivocal acute cholecystitis cases.
- Interpretation and limitations
- Delayed or absent gallbladder visualisation can support obstruction, but fasting, critical illness and hepatic dysfunction affect results.
04Clinical next stepsHow the result changes management or prompts escalation.
01Worked casePain with abnormal LFTsFirst stepA stable adult has episodic right upper quadrant pain, cholestatic LFTs and no fever.+
- 1Context: define pain timing, jaundice, fever, pancreatitis features, previous surgery and current physiology.
- 2Reasoning: obtain ultrasound and LFTs together; examine stones, gallbladder inflammation and duct calibre while noting visualisation limits.
- 3Outcome: if no duct stone is seen but dilatation or abnormal LFTs persists, arrange MRCP and consider EUS if uncertainty remains.
- 4Verification: ensure results are reviewed, symptoms are safety-netted and the surgical or endoscopic plan has named ownership.
02Gallstone routeStage the biliary questionGallstone disease is suspected without immediate organ dysfunction.+
- 1Order abdominal ultrasound and liver function tests as the initial pair recommended by NICE.
- 2AlternativeSeparate uncomplicated gallbladder stones, acute cholecystitis, duct obstruction, pancreatitis and an alternative diagnosis.
- 3Use MRCP for persistent duct suspicion; use EUS when MRCP is nondiagnostic and the answer changes intervention.
- 4DefinitiveRefer for definitive gallbladder or duct management according to symptoms, complications and operative fitness.
03Sepsis routeDo not delay drainageBiliary obstruction is accompanied by infection, hypotension, confusion or organ dysfunction.+
- 1Resuscitate, culture when feasible and give appropriate antibiotics without delaying source control.
- 2Use urgent ultrasound for gallbladder and duct assessment, but recognise that a negative study cannot exclude distal obstruction.
- 3Involve endoscopy, interventional radiology and surgery early to select ERCP, percutaneous drainage or operative management.
- 4Confirm that decompression occurred, physiology improves and retained stones or malignancy receive a follow-up plan.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Trend pain, fever, blood pressure, mental state, urine output, inflammatory markers and liver tests.
- Check whether the distal duct was visualised and whether the report states a limitation.
- After drainage or stone extraction, confirm clinical and biochemical improvement and document residual obstruction.
- Arrange definitive gallbladder management after acute stabilisation when clinically appropriate.
- Reassess urgently for recurrent fever, jaundice, vomiting, pancreatitis features or worsening pain.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Wall thickening is shared
Hypoalbuminaemia, ascites, hepatitis and right heart failure can thicken the gallbladder wall without primary cholecystitis.
Stones may be silent
Gallstones are common incidental findings; symptoms, inflammation and obstruction determine whether they explain the presentation.
CBD visibility varies
The proximal duct is often visible, while bowel gas may obscure the distal duct where small obstructing stones lodge.
MRCP is anatomical
MRCP maps fluid-filled ducts without instrumentation, while ERCP adds the ability to extract stones or place a stent.
Negative is not complete
A report should distinguish a confidently normal examination from non-visualisation caused by habitus, bowel gas or pain.
Pneumobilia has context
Central branching biliary gas may follow sphincterotomy or a bilioenteric anastomosis but can also accompany fistula or infection.
07Common pitfallsFrequent interpretation and management errors.
- 01
Calling acute cholecystitis from wall thickening alone.
- 02
Treating a non-visualised distal common bile duct as stone-free.
- 03
Ordering CT as a substitute for the recommended ultrasound and LFT pair in uncomplicated suspected gallstones.
- 04
Using ERCP solely as a low-risk diagnostic test.
- 05
Waiting for MRCP while a patient with cholangitis and organ dysfunction needs urgent drainage planning.