• Heavily T2-weighted coronal oblique fast spin-echo sequence to obtain source data (aligned along the plane of the common bile duct (CBD)) • Source data allows MIP reformats to be generated (highlighting fluid-filled structures) – usually a number of coronal MIP reformats over 180° • Secretin: this stimulates exocrine pancreatic secretion, distending the pancreatic duct and improving its visualization (acts immediately, returning to baseline at 10 min) • Functional MR cholangiography: using delayed imaging at 30–60 mins with the hepatobiliary excreted contrast agents Gd-EOB-DTPA (Primovist) or Gd-BOPTA (MultiHance) • Normal morphology: only central intrahepatic ducts are normally seen (≤ 3mm) • Right posterior hepatic duct (segments VI/VII): almost horizontal course • Right anterior hepatic duct (segments V/VIII): more vertical course • Left hepatic duct (segments II–IV): joins the right to form the common hepatic duct • Cystic duct insertion into common hepatic duct: right lateral (50%) • Common variants: an aberrant right posterior duct draining into the common hepatic duct or cystic duct • Technique: volume averaging artefacts in MIP reformats can obscure filling defects – source images must always be reviewed • Normal variants: a long cystic duct running parallel to the CBD, stimulating a distended CBD • Intraductal factors mimicking filling defects: aerobilia (non-dependent) • Extraductal factors: pulsatile vascular compression from adjacent vessels mimicking a stricture (but no proximal dilatation) • Hepatobiliary iminodiacetic acid (HIDA) scintigraphy: this is a bilirubin analogue labelled with 99mTc • There is normally accumulation of isotope within liver, bile ducts, gallbladder, duodenum and small bowel by 1 h • This allows direct bile and pancreatic duct opacification, as well as visual assessment of the duodenum and ampulla of Vater • The main complication is the precipitation of pancreatitis • The main pitfall is the presence of underfilled ducts above a stricture • Stones present within the gallbladder – this affects 15% of the Western population (F>M) • Gallstone composition: cholesterol (70%) • Reasons for non-visualization of the gallbladder: a previous cholecystectomy • Biliary sludge: this is composed of calcium bilirubinate granules, cholesterol crystals and glycoproteins
Biliary
METHODS OF INVESTIGATION
MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY (MRCP)
Technique
Stationary water appears as areas of high SI and adjacent soft tissue is low SI (therefore it is not reliant on contrast excretion and can be used in jaundiced patients)
Fasting reduces any unwanted signal from the adjacent intestine
Breath-hold or non-breath-hold (respiratory triggered) imaging
Normal anatomy
extrahepatic ducts ≤ 7mm (CBD up to 10mm post cholecystectomy) 
pancreatic duct ≤ 3mm 
accessory pancreatic duct in 45%
separate drainage of segment I
anterior (30%) 
posterior (20%)
drainage of the right anterior or posterior duct into the left hepatic duct 
a triple confluence at the hilum
Imaging pitfalls
MIP reformats can also over- and underestimate strictures
a contracted sphincter mimicking an impacted stone
flow phenomena (central signal void) 
debris 
haemorrhage
susceptibility artefact from surgical clips
HEPATOBILIARY SCINTIGRAPHY
It is injected intravenously with serial images obtained over 2–4 h (it requires near-normal bilirubin levels)
ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY (ERCP)
It also allows for: biopsy 
brushings 
sphincterotomy 
stone extraction 
biliary stenting 
biliary stricture dilatation
CHOLELITHIASIS AND CHOLEDOCHOLITHIASIS
CHOLELITHIASIS
DEFINITION
there is a small lifetime risk of developing a gallbladder carcinoma
pigment stones composed of calcium bilirubinate (up to 30%)
PEARLS
a non-fasting state 
an abnormal gallbladder position 
emphysematous cholecystitis 
a gallbladder full of stones
it is commonly see with fasting states, critically ill patients, pregnancy, and in those patients receiving total parenteral nutrition 
it resolves spontaneously in 50% of cases
CHOLECYSTITIS
ACUTE CALCULOUS CHOLECYSTITIS
Radiology Key
Fastest Radiology Insight Engine
the assessment of bile leaks and biliary communication with cysts 
the demonstration of segmental obstruction
a contracted gallbladder (e.g. following a recent meal)
it can also allow fine-needle aspiration cytology to be performed
larger stones tend to be laminated
gallstones appear as echogenic foci which cast acoustic shadows 
stone mobility is frequently demonstrated (unless it is impacted at the neck)
these are hypodense, hyperdense or of mixed density
small gallstones can be difficult to detect if they lie within any sludge
primary sclerosing cholangitis 
recurrent pyogenic cholangitis 
Caroli’s disease
obstructive jaundice 
pancreatitis
a duct diameter < 4mm carries a high negative predictive value for choledocholithiasis (regardless of the gallbladder status)
specificity > 95%)
it can diagnose stones that are <5mm in diameter 
its main weakness is its reliance on a near-normal serum bilirubin
this has a high sensitivity (up to 94%) and specificity (99%) 
its quality is independent of the serum bilirubin levels
haemobilia 
flow voids
hypoechoic line between two echogenic lines (arrow).*
the signs include:
gallbladder distension (>5cm) 
pericholecystic fluid and gallbladder wall striations (± wall hyperaemia on Doppler) 
gallstones (common bile duct stones are suggested by abnormal liver function tests)
subserosal oedema and gallbladder distension 
high-density bile 
pericholecystic fluid and inflammatory stranding within the pericholecystic fat 
variable enhancement of the gallbladder wall
emphysematous cholecystitis 
empyema formation
hepatitis 
pancreatitis 
gallbladder wall varices 
adenomyomatosis 
gallbladder carcinoma
internal membranous echoes resulting from sloughed mucosa 
pericholecystic fluid
discontinuous (±) irregular mucosal enhancement 
internal membranes (representing sloughed mucosa) 
a pericholecystic abscess
it accounts for 1% of cases of acute cholecystitis, and has a relatively high mortality rate
gallstones are only seen in <50% of patients
a curvilinear brightly echogenic band with acoustic shadowing seen within a non-dependent portion of the gallbladder (representing intraluminal gas)
this is usually found in critically ill patients
parenteral nutrition 
AIDS 
diabetes 
chemotherapy
gallbladder wall thickening 
echogenic contents (± sloughed membranes or mucosa) 
pericholecystic fluid
localized gallbladder tenderness is a good predictive sign but it is difficult to assess
intramural epithelial crypts (Rokitansky–Aschoff sinuses)
an ejection fraction < 35% indicates gallbladder dysfunction
it may simulate a malignancy radiologically and pathologically
the majority have gallstones (± perforation, abscess, or fistula formation)
