Cholangitis is a clinical diagnosis (fever, jaundice, raised inflammatory markers); imaging proves biliary dilatation, finds the level and cause of obstruction, and looks for the complication that changes management — a liver abscess or portal vein thrombosis.
Orient first
- The Tokyo Guidelines diagnose acute cholangitis on systemic inflammation + cholestasis + imaging of biliary dilatation or its cause — imaging is one leg, not the whole diagnosis (verify the current edition).
- Stones in the common bile duct are the commonest cause; a blocked stent, malignant stricture and post-procedural strictures follow.
- Pus in the ducts is not reliably seen; the job is level, cause and complications, so the endoscopist can drain it.
Acquire the study
- Curvilinear probe 3–5 MHz; left lateral decubitus and deep inspiration for the distal duct; measure the CBD inner wall to inner wall at the widest point in the longitudinal plane.
The manoeuvre
- Measure the CBD calibre in mm at the porta and distally; compare against the age- and cholecystectomy-adjusted upper limit (verify local limit).
- Intrahepatic ducts: parallel channel sign on colour Doppler (no flow in the duct beside the portal vein).
- Follow the CBD to the ampulla: an echogenic focus with posterior acoustic shadowing = stone; absence of shadow does not exclude a soft stone.
- Gallbladder: stones, wall and sludge; a hepatic abscess (complex hypoechoic lesion) in the liver.
What confirms it
- Biliary dilatation with an obstructing cause (stone, stricture, blocked stent) in a patient meeting the clinical criteria.
What licenses you to exclude it
- Non-dilated ducts do not exclude cholangitis — early or intermittent obstruction, or a stented duct, may not dilate; the diagnosis stays clinical.
The classic misread
- Calling the distal CBD normal when bowel gas hides it — say it was not seen, and recommend MRCP.