Synopsis
Select abdominal imaging by the anatomical and clinical question, understand contrast, radiation and MRI constraints, and reserve ERCP chiefly for biliary or pancreatic therapy with explicit prevention and recognition of complications.
- Ultrasound is first-line for gallstones, biliary dilatation, ascites and many liver questions; it is dynamic and radiation-free but limited by bowel gas, body habitus and operator dependence.
- Contrast-enhanced CT is fast and broad for acute abdomen, perforation, obstruction, ischaemia, bleeding, sepsis, trauma and cancer staging, but uses ionising radiation and often iodine.
- MRI offers high soft-tissue contrast without ionising radiation; liver protocols and enterography answer focused questions but take longer and require implant, claustrophobia and motion assessment.
- MRCP is a non-invasive, heavily fluid-sensitive MRI of bile and pancreatic ducts; it maps obstruction but cannot drain, extract a stone or obtain every required tissue sample.
- ERCP is primarily therapeutic: sphincterotomy, stone extraction, stenting and drainage. Diagnostic uncertainty is usually addressed first with ultrasound, MRCP, EUS or CT.
- In suspected common-bile-duct stones, NICE recommends liver blood tests and ultrasound, then MRCP when ducts are not cleared by ultrasound but are dilated or tests remain abnormal; consider EUS if MRCP is non-diagnostic.
- Acute cholangitis with obstruction needs resuscitation, antibiotics and urgent drainage; waiting for elective MRCP can be unsafe in a deteriorating patient.
- ERCP complications include pancreatitis, bleeding, infection, perforation and sedation injury; consent and a post-procedure escalation plan are mandatory.
Key red flags
Fever or sepsis, right upper-quadrant pain, jaundice and cholestatic tests with obstruction suggest infected biliary pressure. Hypotension, confusion or organ dysfunction requires emergency drainage planning.
Peritonism, shock, pain out of proportion, obstruction, major gastrointestinal bleeding or postoperative deterioration usually requires prompt contrast CT protocolled to the suspected emergency.
New persistent epigastric pain radiating to the back with enzyme elevation and clinical pancreatitis after ERCP requires fluid, analgesic, severity and complication assessment.
Severe pain, subcutaneous emphysema, peritonism, tachycardia, fever, haematemesis, melaena or falling haemoglobin warrants urgent CT and endoscopy, surgery and interventional-radiology coordination.
Investigation priorities
Assess gallstones, bile-duct calibre, liver texture and lesions, portal or hepatic flow, kidneys, pelvic organs and ascites; guide safe aspiration or drainage.
Management branches
Cholestatic tests, jaundice, biliary pain or ductal concern prompts imaging.
- Assess for sepsis and organ dysfunction, obtain liver tests and ultrasound, and start urgent cholangitis treatment when clinically indicated.
- If ultrasound does not show a duct stone but the duct is dilated or liver tests remain abnormal, use MRCP; consider EUS if MRCP remains non-diagnostic and suspicion persists.
- Use ERCP for therapeutic duct clearance or drainage before or at definitive surgical management, according to stability and local expertise.
- Document stent removal or exchange and cholecystectomy planning so temporary treatment does not become permanent by omission.