Biliary MRI / MRCP – Generic Standard Protocol

1. Executive Summary

Magnetic resonance cholangiopancreatography (MRCP) is the non-invasive gold standard for imaging the biliary and pancreatic ductal systems. It has effectively replaced diagnostic ERCP for most morphological ductal assessments, reserving ERCP for therapeutic procedures. The combination of MRCP with a comprehensive liver MRI protocol — T2 sequences, T1 pre/post-contrast, and DWI — constitutes the biliary MRI examination, which provides complete morphological, functional, and tissue characterisation information that no single modality can match.

The fundamental diagnostic capability of MRCP is the depiction of fluid-containing ductal structures — bile ducts, pancreatic duct, cystic lesions communicating with ducts — using heavily T2-weighted sequences in which static or slow-moving fluid produces very high signal against a suppressed tissue background. This is achievable without contrast, without radiation, and without the procedural risk of ERCP, making biliary MRI the appropriate first-line investigation for all non-emergency ductal pathology questions.

The ACR appropriateness criteria [1] designate MRCP as the primary modality for biliary obstruction workup when ultrasound findings are inconclusive, and as the preferred method for pancreatic and biliary duct anatomical assessment prior to surgical planning. The European guidelines for pancreatobiliary diseases endorse MRCP as equivalent or superior to CT for ductal characterisation in choledocholithiasis, cholangiocarcinoma, and primary sclerosing cholangitis [2, 3].

1.1 Core Strengths

Non-invasive ductal morphology: MRCP provides three-dimensional ductal anatomy — intrahepatic and extrahepatic bile ducts, common bile duct (CBD), cystic duct, gallbladder, Wirsung duct, Santorini duct, and accessory pancreatic ducts — without contrast injection or endoscopy. The resolution of 3D navigator MRCP (1.5–2 mm isotropic) is sufficient to characterise ductal strictures, filling defects, calibre variations, and anatomical variants.

Simultaneous liver, biliary, and pancreatic assessment: biliary MRI integrates MRCP with full T2, T1, and DWI coverage of the liver, pancreas, and peripancreatic tissue in a single 40–50 minute examination. This integrated approach provides: duct morphology (MRCP) + parenchymal characterisation (T2/T1) + lesion detection (DWI) + enhancement characterisation (post-contrast T1). CT cannot provide this combined assessment in a single protocol.

Choledocholithiasis detection: MRCP has sensitivity approximately 85–95% and specificity 95–99% for CBD stones [4, 5], superior to ultrasound (sensitivity ~70%) and comparable to ERCP for stones ≥ 5 mm. Small stones (< 3 mm) at the ampullary level remain the detection limit.

PSC and cholangiopathy: MRCP is the imaging standard for primary sclerosing cholangitis (PSC), providing the "beaded" pattern of multifocal stricturing and dilation that is characteristic of this disease [2].

No radiation, no procedural risk: for serial surveillance (PSC follow-up, post-transplant biliary anastomosis monitoring, IPMN surveillance), MRCP avoids the cumulative radiation dose of CT and the procedural risk of ERCP.

Functional secretin-enhanced MRCP (conditional): intravenous secretin stimulates ductal secretion, temporarily dilating the MPD and improving visualisation of the pancreatic ductal system and exocrine functional reserve. This provides unique information unavailable from any other modality.

1.2 Intrinsic Limitations of the Generic Protocol

Spatial resolution vs. diagnostic ERCP: MRCP at clinical field strengths (1.5T–3T) cannot match the spatial resolution of direct cholangiography. Subtle early strictures in PSC, small ampullary lesions, and details of the ampullary sphincter mechanism may be below MRCP resolution. For these indications, ERCP with direct visualisation and tissue sampling remains superior.

Stones < 3 mm: very small stones — particularly those near or at the ampulla — may be invisible on MRCP due to partial volume averaging and signal intensity competition from surrounding fluid.

Post-surgical anatomy: after hepaticojejunostomy, Roux-en-Y gastric bypass, or Whipple procedure, the normal biliary anatomy is completely altered. The segment of the anastomosis, the blind loop, and the altered ductal connections require specific planning that the generic MRCP protocol may not fully address. Dedicated post-surgical child protocols are required.

Motion sensitivity: MRCP acquisitions — particularly the navigator-triggered 3D acquisition — are sensitive to respiratory irregularity. In patients with poor navigator efficiency (< 50% acceptance), the 3D MRCP acquisition time doubles or triples, potentially degrading image quality.

Biliary metallic stents: metallic biliary stents (particularly stainless steel) produce extensive T2* signal loss on both MRCP and standard T2 sequences. The biliary anatomy adjacent to and within the stent is non-assessable. Plastic stents produce substantially less artefact. For patients with metallic biliary stents, 1.5T may be preferred and the diagnosis should acknowledge the stent limitation.

When dedicated child protocols are required: post-surgical biliary anatomy (hepaticojejunostomy, Whipple); primary sclerosing cholangitis staging and surveillance; choledochal cyst classification; secretin-enhanced MRCP for exocrine function; biliary-enteric fistula; living donor liver transplant biliary mapping; intraductal papillary mucinous neoplasm (IPMN) surveillance.

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2. Main Clinical Indications

2.1 Standard Indications

Obstructive jaundice workup is the most common biliary MRI indication. When ultrasound demonstrates biliary dilatation but does not establish the cause — or when the ultrasound is technically limited — biliary MRI with MRCP provides: the level of obstruction (intrahepatic, hilar, CBD, periampullary); the morphology of the obstructing lesion (stone vs. stricture vs. mass); and the relationship of the obstruction to the liver parenchyma and vessels. The generic protocol is adequate for this indication when the clinical question is obstruction level and aetiology. Dedicated protocols are required when the question is surgical staging of a specific malignancy.

Choledocholithiasis is the second most common indication. After ultrasound identifies biliary dilatation or when clinical suspicion of CBD stones is high (elevated liver enzymes, biliary colic, post-cholecystectomy pain), MRCP is the appropriate non-invasive alternative to diagnostic ERCP. The generic protocol — including 3D MRCP + 2D thick-slab projections at multiple angulations — provides sufficient coverage for CBD stone detection [4, 5]. Post-cholecystectomy retained stones, dropped stones, and Mirizzi syndrome are all addressed by the generic protocol.

Primary sclerosing cholangitis (PSC) diagnosis and follow-up: MRCP is the imaging modality of choice for PSC diagnosis, staging (Amsterdam classification), and interval follow-up surveillance. The generic protocol provides the ductal morphology needed for PSC assessment. Dedicated PSC protocols may additionally include: post-contrast T1 for periductal enhancement; DWI for hepatic parenchymal changes; specific interval surveillance decisions per ESGE/BSG guidelines [2].

Post-liver transplant biliary assessment: anastomotic and non-anastomotic strictures, biliary leak, choledocholithiasis, and biliary cast syndrome are all assessed by MRCP post-transplant. The generic protocol is appropriate for initial assessment; the post-surgical anatomy must be documented and the protocol adapted accordingly.

Pancreatobiliary junction variants and anomalies: pancreatic divisum, anomalous pancreatobiliary junction (APBJ), choledochal cysts (Todani classification), and other ductal variants are non-invasively characterised by MRCP. These are frequently identified incidentally or in the workup of recurrent pancreatitis. Secretin-enhanced MRCP improves pancreatic divisum and APBJ characterisation.

Pre-operative biliary mapping: before cholecystectomy, hepatic resection, or pancreatic surgery, MRCP provides ductal anatomy that reduces the risk of inadvertent biliary injury. Cystic duct variants, low-insertion variants, and accessory ducts are identified pre-operatively.

IPMN surveillance: pancreatic intraductal papillary mucinous neoplasms require serial MRI/MRCP monitoring for worrisome features and high-risk stigmata (see MRI Pancreas master page). The generic biliary protocol provides the MRCP component; the full pancreatic protocol is integrated.

2.2 Urgent Red Flags Requiring Expedited or Emergency Imaging

Biliary MRI is primarily an elective modality. Emergency biliary imaging is usually CT (for pancreatitis severity) or ERCP (for urgent drainage). However, the following scenarios warrant expedited biliary MRI:

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3. Preparation Reference

Universal MRI safety screening is covered in the general MRI preparation page and is not repeated here.

3.1 Anatomy-Specific Preparation Items

Fasting — the most important preparation for biliary MRI: a 4–6 hour fast is mandatory before biliary MRI/MRCP. The reasons are specific to biliary imaging:

1. Gallbladder distension: fasting allows the gallbladder to fill with concentrated bile, maximising T2 signal within the gallbladder and enabling detection of small calculi, polyps, and wall thickening. A contracted post-prandial gallbladder is difficult to assess and may falsely appear as a pathologically thickened wall.

1. Duodenal fluid reduction: food and gastric secretions produce T2-bright fluid in the duodenum and proximal jejunum that overlaps anatomically with the CBD and ampullary region on MRCP projections. Fasting substantially reduces this signal competition.

1. Bowel peristalsis: food intake stimulates bowel peristalsis, which produces motion artefacts — particularly relevant for the hepatic hilum and periampullary regions where fine ductal structure is critical.

Minimum fasting time: 4 hours for most adults. 6 hours if secretin-enhanced MRCP is planned. Children: 4 hours for formula or solid food; 2 hours for clear liquids.

Negative oral contrast (optional but recommended for ampullary assessment): ingestion of 200–500 mL of water or pineapple juice 15–30 minutes before MRCP reduces T2-bright duodenal signal competition with the common bile duct and ampulla. Pineapple juice contains manganese from bromelain, which acts as a natural T2 contrast agent suppressing duodenal signal on MRCP while leaving the CBD unaffected. This is low-cost, well-tolerated, and directly improves periampullary resolution on MRCP. Not universally used but strongly recommended for periampullary indications.

Antiperistaltic agents: IV hyoscine butylbromide (Buscopan, 20–40 mg) or glucagon (0.1 mg) significantly reduces duodenal and jejunal peristalsis, improving the quality of MRCP at the periampullary level and improving the quality of hepatic parenchymal sequences. Contraindications: narrow-angle glaucoma, BPH for Buscopan; pheochromocytoma for glucagon. Use is centre-dependent and biliary indication is strongest.

Prior biliary interventions and surgical history: the patient history must document: prior cholecystectomy, ERCP or sphincterotomy, biliary stent (type — plastic vs. metal), prior biliary surgery (hepaticojejunostomy, choledochoduodenostomy), and transplant status. This information fundamentally changes the expected ductal anatomy and the diagnostic interpretation.

Biliary stent documentation: type of stent (plastic or metallic), position, and date of placement must be known before scanning. Metallic biliary stents produce extensive susceptibility artefact on T2 and MRCP that renders the biliary anatomy non-assessable at and adjacent to the stent. This limitation must be documented in the report.

Renal function: required before gadolinium injection per standard protocol (see Liver master page, Section 3.1).

3.2 Patient Positioning on the MRI System

Standard position: supine, head-first or feet-first depending on scanner and patient comfort. Arms elevated above the head reduces aliasing in the FOV; for biliary imaging, arm position follows the same approach as the liver protocol (see Liver master page, Section 3.2).

Coil selection: multi-channel phased-array body matrix coil (minimum 16 channels) combined with the integrated spine coil. For biliary MRI, the coil configuration is identical to the liver protocol. The biliary tree is centred in the upper abdomen; no specialised biliary coil exists.

Centring: isocentre at the level of the hepatic hilum — approximately at the level of the xiphisternum. The hepatic hilum (portal bifurcation, CBD origin, hepatic duct confluence) is the most critical anatomical target and should be at or near isocentre. Verify on the three-plane localiser that: the liver dome, the hepatic hilum, and the pancreatic head are all within the MRCP coronal coverage; the gallbladder fundus is included in the inferior margin.

MRCP-specific coil positioning: for optimal MRCP, the anterior surface coil should be positioned centred on the right upper quadrant, not the midline. The CBD courses just to the right of the portal vein in the hepatoduodenal ligament; centering on the right upper quadrant maximises SNR at the biliary hilus and CBD.

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4. Standard Protocol Design

The biliary MRI protocol integrates MRCP sequences with the standard liver MRI sequences (T2, T1, DWI, post-contrast). The MRCP sequences (both 3D navigator and 2D thick-slab) are always pre-contrast — post-contrast MRCP is degraded by gadolinium in bile ducts when hepatobiliary agents are used, or by gadolinium in blood vessels obscuring the CBD.

4.1 Mandatory Core Sequences

4.2 Conditional Sequences

4.3 Rationale Summary Per Sequence

T2 single-shot (HASTE/SSFSE) provides the motion-robust initial survey of the liver and biliary tree. For biliary indications, HASTE provides: gallbladder morphology (size, wall, contents); intrahepatic biliary dilatation (IHBD) presence and distribution; hepatic parenchymal signal; any obvious biliary masses. The motion immunity of single-shot acquisitions is particularly valuable for jaundiced or uncomfortable patients who cannot maintain consistent breath-holds.

T2 TSE respiratory-triggered provides higher-quality T2 for detailed biliary anatomy. On triggered T2, the CBD in the hepatoduodenal ligament is visible as a thin T2-bright tubular structure; intrahepatic ducts are individually traceable; the gallbladder wall is characterised; any periductal tissue changes (periductal fibrosis in PSC, periductal oedema in acute cholangitis) are depicted. A coronal T2 TSE is essential for the biliary protocol because it provides the longitudinal view of the CBD, intrahepatic ducts, and their hilar convergence — the assessment plane that cannot be adequately covered by axial sequences alone.

3D MRCP (navigator-triggered) is the core sequence of the biliary protocol. Technical details are provided in Section 10. From the clinical perspective, the 3D MRCP provides:

• Continuous 3D representation of the biliary and pancreatic ductal systems
• Full MPR capability in any oblique plane — allowing the radiologist to follow any duct segment through its full course
• Visualisation of side-branch IPMN communication with the MPD
• Anatomical variants (aberrant right posterior hepatic duct, low-inserting cystic duct, pancreatic divisum)
• Detection of filling defects within ducts (stones appear as low-signal foci within the T2-bright duct lumen)
• Stricture characterisation (abrupt vs. gradual narrowing; length; associated mass)

2D thick-slab MRCP (multiple angulations) provides the "overview" equivalent to an ERCP cholangiogram. Each 2D slab projection is acquired in a single 3–4 second breath-hold. Multiple projections at different angulations (typically 5–7 projections: straight coronal + 15–30° LAO and RAO + posterior oblique variants) cover all ductal segments from multiple perspectives. The thick slab provides excellent signal-to-noise for the overview but cannot be reformatted — it is complementary to 3D MRCP. A well-planned 2D MRCP slab at 30° RAO typically provides the best single-projection overview of the CBD, CHD, and intrahepatic ducts simultaneously, comparable to the frontal projection of ERCP.

T1 IP/OP serves the same functions as in the liver protocol (see Liver master page) with one biliary-specific addition: T1 signal within the biliary tree. Normal bile is T1-dark (similar to fluid). T1-bright bile indicates: haemobilia (blood in bile ducts), highly concentrated inspissated bile (Mirizzi-associated), proteinaceous material, or gadolinium from prior hepatobiliary contrast injection. This pre-contrast T1 baseline is essential for post-contrast interpretation.

DWI for biliary indications: DWI is primarily used for hepatic parenchymal assessment (as in the liver protocol) but has specific biliary applications: (a) cholangiocarcinoma characterisation — most CCA shows restricted diffusion; (b) lymph node assessment at the hepatic hilum and porta hepatis; (c) periductal fibrosis assessment in PSC (restricted diffusion in areas of active inflammation). DWI is not the primary sequence for ductal morphology but provides complementary tissue characterisation.

Post-contrast T1 — see Section 6.2 for indications. When contrast is administered, the post-contrast T1 adds: mural enhancement of biliary lesions; enhancement pattern of hilar masses; portal vein and hepatic artery assessment (critical for cholangiocarcinoma staging); liver parenchymal phases for synchronous liver pathology.

4.4 Sequence Matching and Cross-Sequence Consistency

The 3D MRCP must be planned before contrast administration. All post-contrast sequences must use the same geometric prescription as the pre-contrast T1 3D for accurate liver comparison.

For serial examinations (PSC follow-up, IPMN surveillance, post-transplant monitoring), the MRCP angulation must be reproduced. Document in the report: the 3D MRCP coronal angulation (degrees of obliquity from the standard coronal plane); the inferior and superior coverage limits; the field strength. These must be matched at every follow-up to allow accurate comparison of ductal diameter measurements and stricture extent.

When a hepatobiliary contrast agent (gadoxetate) is used, the 3D MRCP and all liver pre-contrast sequences must be completed before injection. Post-injection hepatobiliary phase (at 10–20 minutes) may provide additional biliary anatomy through the T1-bright bile signal, but the primary MRCP must always be pre-contrast.

4.5 Fat Suppression — Biliary-Specific Considerations

Fat suppression is applied to T1 sequences in the biliary protocol as in the standard liver protocol (Dixon preferred at 3T). There are two biliary-specific considerations:

Fat suppression on T2 TSE for biliary indications: coronal T2 TSE for biliary overview is typically acquired without fat suppression. This preserves periportal fat signal as a landmark for the CBD course and hepatoduodenal ligament anatomy. Fat-saturated T2 may be used when periductal inflammation or fibrosis assessment is the primary question (PSC active inflammation; cholangiocarcinoma periductal extension).

MRCP: no fat suppression needed on the sequence itself because the heavy T2 weighting (TE 600–800 ms) suppresses all tissue signal including fat — only free fluid remains. However, some implementations apply a fat saturation pre-pulse before the 3D MRCP readout to further suppress residual fat signal from motion-contaminated fat adjacent to the liver dome and right lobe. This is vendor- and centre-dependent.

Gadolinium in hepatobiliary phase and MRCP interaction: when gadoxetate is used for the liver protocol and the biliary phase is added, the hepatobiliary phase T1 3D coronal provides indirect biliary mapping (gadolinium excreted in bile → bile ducts appear T1-bright). This "T1 MRCP" or "hepatobiliary phase cholangiography" provides complementary biliary anatomy but is NOT a substitute for the pre-contrast MRCP. Specifically, the T1 biliary phase: (a) shows actively draining ducts (secretory function); (b) identifies bile leaks (gadolinium extravasation into pericholecystic or periductal spaces); (c) demonstrates biliary-enteric anastomosis patency. The 3D MRCP pre-contrast remains mandatory even when hepatobiliary phase is acquired.

5. Optimisation Strategy

5.1 Artifact Reduction by Source

Respiratory motion — primary MRCP quality failure: the 3D navigator-triggered MRCP is the most motion-sensitive sequence in the biliary protocol. A navigator efficiency below 50% doubles the acquisition time and may produce ghosting artefacts that blur ductal structures. Mitigation: (a) ensure the navigator is positioned correctly at the liver-diaphragm interface before starting; (b) instruct the patient on normal quiet breathing (not deep breathing — diaphragm excursion increases with deep breathing, reducing navigator acceptance); (c) use a 5–8 mm acceptance window rather than the narrowest possible — smaller windows reduce efficiency without proportional quality improvement; (d) if navigator efficiency remains < 40% after repositioning, switch to breath-hold MRCP (2D thick-slab only) as the salvage strategy.

Duodenal fluid overlapping the CBD: bright T2 duodenal fluid competes with CBD signal on MRCP projections, particularly in the right anterior oblique projections. This can obscure a small CBD stone or a subtle periampullary stricture. Mitigation: (a) fasting 4–6 hours (reduces gastric and duodenal fluid); (b) negative oral contrast (pineapple juice or water — reduces duodenal T2 signal); (c) antiperistaltic agents (reduces peristalsis-driven fluid motion that degrades the CBD-adjacent region); (d) use the posterior oblique projections and MPR on 3D MRCP which separate the CBD from overlying duodenal fluid.

Metallic biliary stent susceptibility: stainless steel biliary stents produce T2* signal loss that extends 1–3 cm beyond the stent margins, obscuring the adjacent biliary anatomy on both MRCP and T2 sequences. This is not correctable — it must be documented. Mitigation: 1.5T over 3T (4× less susceptibility blooming); wider bandwidth sequences reduce chemical shift component; STIR-based sequences partially reduce metal artefact on T2 sequences but cannot restore MRCP signal.

Chemical shift in the CBD region: the CBD runs in close proximity to the peripancreatic and hepatoduodenal fat. At narrow bandwidth on T2 and MRCP sequences, chemical shift displacement at the fat-duct interface can produce apparent thickening of the CBD wall or apparent filling defects simulating stones. Mitigation: adequate bandwidth (≥ 200 Hz/px at 3T); verify with post-contrast T1 and coronal T2.

Susceptibility from surgical clips: cholecystectomy clips in the gallbladder fossa produce T2* signal loss on MRCP in the cystic duct stump region, which can simulate a retained stone or stricture. Always review the localiser and T1 for clip position before interpreting MRCP findings at the gallbladder fossa.

Underfilled gallbladder in non-fasted patients: a contracted gallbladder may be falsely interpreted as wall thickening, cholecystitis, or mass. Always confirm fasting status before gallbladder assessment.

Dielectric effect at 3T in the upper abdomen: see Liver master page (Section 5.1). Relevant for T1 pre- and post-contrast sequences; less relevant for heavily T2-weighted MRCP sequences.

5.2 Protocol Efficiency and Throughput

A complete biliary MRI with MRCP — including 3D navigator MRCP, 2D thick-slab MRCP, T2 sequences, T1 IP/OP, DWI, and post-contrast T1 — can be completed in 40–50 minutes at 3T.

For pure MRCP-only requests (ductal morphology without liver evaluation): 3D navigator MRCP + 2D thick-slab MRCP + axial HASTE T2 + DWI can be completed in 20–25 minutes. This abbreviated approach is appropriate for: (a) IPMN surveillance in a patient with known and stable disease; (b) post-ERCP follow-up of a specific ductal intervention; (c) patients who cannot tolerate the full protocol duration.

Adding secretin extends the protocol by 10–15 minutes and requires IV access and pharmaceutical availability.

5.3 Field Strength Considerations

3T is preferred for biliary MRI and MRCP: higher SNR enables finer spatial resolution on the 3D MRCP (1–1.5 mm isotropic vs. 1.5–2 mm at 1.5T), improving detection of small CBD stones, subtle hilar strictures, and side-branch IPMN. The 3T SNR advantage is particularly relevant for the 3D MRCP, where the fine ductal structures are at the spatial resolution limit.

Key 3T challenge: B0 inhomogeneity from the adjacent duodenum and stomach degrades fat suppression on T1 sequences (Dixon preferred — see Liver master page). For the MRCP sequence itself, B0 inhomogeneity is less critical because the heavy T2 weighting is B0-independent.

1.5T preferred when metallic biliary stents are present (4× less susceptibility artefact), and for patients with suboptimal B0 homogeneity who cannot benefit from 3T optimisation.

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6. Contrast Use Principles Specific to Biliary MRI

6.1 Non-Contrast Standard Protocol — Sufficient For

Non-contrast biliary MRI (T2 sequences + MRCP + DWI without gadolinium) is diagnostically adequate for:

• Choledocholithiasis detection and CBD stone characterisation
• PSC diagnosis and morphological staging
• Pancreatic divisum and ductal variant identification
• IPMN surveillance for morphological worrisome features (ductal communication, cyst size)
• Choledochal cyst characterisation and classification
• Post-cholecystectomy assessment for retained stone or biliary anatomy
• Biliary dilatation level and aetiology assessment in most cases
• Pregnancy (gadolinium deferred; non-contrast MRCP is diagnostic)

For the majority of biliary indications, the diagnostic question is answered by ductal morphology — which is a MRCP capability that requires no contrast. Contrast substantially adds value only when tissue characterisation beyond ductal morphology is required.

6.2 Gadolinium Indicated — Region-Specific Contexts

Gadolinium-enhanced sequences are required or strongly useful for:

• Cholangiocarcinoma staging: enhancement pattern (periductal infiltrating vs. mass-forming vs. intraductal); vascular invasion; portal vein and hepatic artery encasement; lymph node characterisation; satellite nodules. All require post-contrast T1 dynamic phases.
• Gallbladder carcinoma: enhancement of wall thickening vs. mass; liver invasion depth; cystic duct and CBD involvement.
• Benign biliary stricture vs. malignant stricture: periductal enhancement in PSC active inflammation; mural nodule enhancement in biliary adenoma or IgG4-related cholangiopathy.
• Post-transplant biliary assessment with tissue characterisation: hepatic artery patency (requires arterial phase); parenchymal enhancement for rejection assessment; cholangiographic phase (hepatobiliary agent).
• Hepatobiliary phase for biliary leak mapping (gadoxetate): gadolinium excreted in bile identifies the site of bile leak as extravasation of T1-bright bile into the periductal space.
• Any solid or enhancing biliary lesion requiring characterisation.

Hepatobiliary vs. extracellular agents for biliary imaging: when hepatobiliary ductal mapping is required (bile leak, anastomosis patency, accessory duct identification), gadoxetate (Primovist/Eovist) is the agent of choice because it is excreted in bile. Extracellular agents do not opacify bile ducts and cannot provide the hepatobiliary phase cholangiographic effect. For standard biliary indications (stone, stricture, mass enhancement characterisation), extracellular agents are adequate.

6.3 Post-Contrast Acquisition Timing

For cholangiocarcinoma staging: arterial phase (20–25 s from bolus, or bolus-triggered), portal venous phase (60–70 s), and delayed phase (3–5 min). The delayed phase is particularly important for cholangiocarcinoma because the fibrous desmoplastic stroma enhances progressively — delayed phase imaging shows the maximum enhancement extent that defines the ductal invasion length.

For hepatobiliary phase with gadoxetate: standard liver protocol timing applies (see Liver master page, Section 6.3). For biliary-specific indication, acquire an additional coronal T1 3D at 10–20 minutes to provide the cholangiographic view with gadolinium in bile.

For biliary leak mapping with gadoxetate: the hepatobiliary phase coronal T1 at 10–20 minutes will show contrast extravasation at the leak site as focal T1 bright signal outside the normal biliary tree.

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7. Reporting Essentials

7.1 Interpretation Framework

Biliary MRI reporting follows a systematic ductal anatomy analysis combined with parenchymal and vascular assessment:

Ductal analysis (primary): is the biliary tree dilated? If yes, at what level — intrahepatic only, hilar, extrahepatic, or periampullary? Is the obstruction focal or multifocal? Is there a filling defect (stone), stricture (luminal narrowing), or mass (extrinsic compression or intrinsic lesion)? Is there a wall abnormality (thickening, nodularity, enhancement)?

Parenchymal analysis: liver parenchyma for atrophy (indicating chronic obstruction or PSC), lobar hypertrophy patterns, fibrosis features; gallbladder for stones, polyps, mass; pancreas for parenchymal changes related to ductal pathology.

Vascular analysis: portal vein patency; hepatic artery status; any vascular encasement (critical for staging cholangiocarcinoma).

Broad diagnostic axes: obstructive vs. non-obstructive; benign vs. malignant cause; focal vs. diffuse (PSC is diffuse; stone is focal); inflammatory vs. neoplastic vs. congenital.

7.2 Mandatory Reporting Checklist

Technical quality:

• [ ] State field strength, contrast agent if used
• [ ] Note MRCP quality (adequate / limited: motion, stent artefact)
• [ ] Note fasting status if relevant to gallbladder assessment
• [ ] Note antiperistaltic agent use

Biliary tree:

• [ ] Intrahepatic biliary dilatation: present/absent; distribution (central vs peripheral; right vs left; segmental)
• [ ] Common hepatic duct diameter (mm)
• [ ] CBD diameter (mm) — normal ≤ 6 mm (≤ 8 mm post-cholecystectomy)
• [ ] CBD morphology: normal / dilated / stricture (level, length, morphology) / filling defect
• [ ] Level of obstruction if present
• [ ] Cystic duct: visible / not visible; anatomical variant if noted
• [ ] Hepatic duct confluence: normal / involved / Bismuth-Corlette classification if mass

Gallbladder:

• [ ] Present / absent (post-cholecystectomy)
• [ ] Size (distended / normal / contracted)
• [ ] Wall: normal / thickened (diffuse/focal; smooth/irregular)
• [ ] Contents: normal bile / stones / sludge / polyps / mass
• [ ] Pericholecystic fluid: absent / present

Pancreatic duct:

• [ ] Diameter at body (mm) — normal ≤ 3 mm
• [ ] Smooth / irregular / stricture / dilation
• [ ] Communication with cystic lesions
• [ ] Pancreatic divisum: present / absent (dominant dorsal duct)

Pancreatic parenchyma (when applicable):

• [ ] See Pancreas master page for full checklist

Vasculature:

• [ ] Portal vein: patent / thrombosis / encasement
• [ ] Hepatic artery: patent / encasement (for cholangiocarcinoma)

Lymph nodes:

• [ ] Hepatic hilum
• [ ] Portocaval region
• [ ] Para-aortic

7.3 Structured Reporting

Reports must include: Indication (specific biliary question: obstruction, stone, PSC, mass); Technique (field strength, MRCP type: 3D navigator + 2D slab, contrast if used, fasting, antiperistaltic agent); Comparison (prior MRCP or ERCP, with key ductal measurements); Findings (systematically organised as above); Impression (direct answer to clinical question; ductal measurement if relevant; differential if indicated; BISECT or Amsterdam grade if PSC); Recommendations (ERCP for therapeutic intervention; repeat MRCP interval; endoscopic biopsy if mass); Limitations (motion, stent artefact, suboptimal preparation).

7.4 Incidental Findings — Clinical Decision Framework

Usually benign, document only: small cholecystolithiasis (< 1 cm) without biliary dilatation or wall abnormality; gallbladder polyp < 5 mm in a patient without risk factors; minimal intrahepatic ductal dilatation (< 2 mm above normal) without a cause identified; normal-variant ductal anatomy (e.g., low cystic duct insertion, right posterior sectoral duct arising from CHD).

Follow-up required: gallbladder polyp ≥ 5 mm (repeat ultrasound in 6–12 months per ESGE guidelines); CBD ≥ 8 mm in a patient post-cholecystectomy without an obvious cause; isolated pancreatic duct dilation > 3 mm without a mass — follow with repeat imaging; small hepatic lesion indeterminate on this protocol.

Requires urgent clinical communication: unsuspected cholangiocarcinoma features (hilar mass with ductal dilatation and lobar atrophy); unexpected severe biliary dilatation not previously documented; gallbladder mass features; portal vein tumour thrombus; bile duct perforation or leak; hepatic abscess formation adjacent to biliary obstruction.

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8. MRI Technologist Pearls

8.1 Sequence Order Logic

The sequence order for biliary MRI is critical because:

1. MRCP must always be pre-contrast
2. Navigator-triggered 3D MRCP can be overlapped with other sequence planning time

Recommended order:

1. Three-plane localiser
2. HASTE T2 axial ← survey; check gallbladder, ducts; planning reference
3. T2 TSE triggered axial ← liver and duct quality
4. 3D MRCP navigator ← start this running; free-breathing; use acquisition time for planning
5. T2 TSE coronal ← biliary overview
6. T1 IP/OP ← pre-contrast T1 baseline
7. 2D thick-slab MRCP (multiple angulations) ← brief breath-holds
8. DWI ← pre-contrast
9. T1 3D pre-contrast ← final pre-contrast reference
10. Contrast injection → dynamic phases if indicated
11. Hepatobiliary phase coronal if gadoxetate (10–20 min post-injection)

The 3D MRCP navigator (step 4) can run simultaneously during the planning of steps 5–7, saving approximately 5–8 minutes of total examination time.

8.2 Positioning Tricks

For patients with hepatomegaly: the liver may push the right hemidiaphragm superiorly; check the navigator position is still on the liver-lung interface and not within the lung; re-scout if needed.

For post-cholecystectomy patients: adjust the inferior coverage to fully include the cystic duct stump and periampullary region — dropped stones and cystic duct remnant pathology are in this region.

For patients with bilateral intrahepatic duct dilatation: plan a second coronal T2 TSE specifically angled to follow the right posterior sectoral duct (which inserts lower and more posteriorly than the right anterior duct) — it is the most commonly missed ductal segment on standard coronal MRCP.

8.3 Fast Salvage Protocol

This 12–14 minute protocol answers most ductal morphology questions without dynamic contrast. Acceptable for choledocholithiasis and PSC assessment; insufficient for cholangiocarcinoma staging.

8.4 Common Avoidable Errors

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9. Quality Control Checklist

• [ ] MRCP acquired before any contrast injection — mandatory
• [ ] 3D MRCP navigator efficiency documented (acceptable: > 50%)
• [ ] Full biliary tree coverage: liver dome to ampulla
• [ ] Gallbladder included in coronal MRCP coverage
• [ ] 2D thick-slab: minimum 5 angulations performed
• [ ] CBD clearly visible from hilum to ampulla on at least one MRCP projection
• [ ] Pancreatic duct (Wirsung) visible from head to tail
• [ ] Motion artefacts assessed — ductal structures not blurred beyond diagnostic threshold
• [ ] Antiperistaltic agent use documented if administered
• [ ] Fasting status documented
• [ ] Metallic stent presence noted; affected segments documented
• [ ] T2 TSE coronal acquired for lobar atrophy and hepatic parenchyma overview
• [ ] T1 3D pre-contrast acquired for T1 baseline
• [ ] Post-contrast sequences acquired at appropriate timing if indicated
• [ ] Hepatobiliary phase coronal acquired at 10–20 min if gadoxetate used

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11. Evidence Gaps and Ongoing Debate

Optimal fasting duration for MRCP: the 4–6 hour standard fasting recommendation is evidence-based for gallbladder distension, but the optimal duration for minimising duodenal fluid overlap with the CBD has not been formally studied. Some centres use 6-hour fasting as standard; others accept 4 hours. The incremental benefit of 6 vs 4 hours for CBD stone detection has not been prospectively compared.

Negative oral contrast: pineapple juice, blueberry juice, and ferumoxsil have all been evaluated as duodenal signal suppressors for MRCP. No comparative study has demonstrated clinically significant diagnostic differences between these agents or compared them with water for CBD stone detection. Use remains centre-dependent.

3D MRCP vs. 2D thick-slab diagnostic equivalence: 3D navigator MRCP is widely accepted as superior for subtle stricture characterisation and IPMN assessment, but no prospective randomised study has demonstrated clinically superior outcomes for specific biliary diagnoses when 3D MRCP is added to an optimised 2D thick-slab protocol. For choledocholithiasis detection specifically, 2D thick-slab MRCP may be diagnostically equivalent for stones ≥ 5 mm.

Role of DWI in biliary malignancy: DWI has been proposed as a tool for distinguishing benign from malignant biliary strictures (cholangiocarcinoma restricts diffusion; benign strictures typically do not). Published data show variable sensitivity (60–80%) and specificity (70–85%), insufficient for clinical decision-making without histopathological confirmation. DWI is not currently accepted as a replacement for tissue sampling in biliary stricture characterisation.

Secretin-MRCP standardisation: the secretin injection timing, the number and timing of dynamic acquisitions, and the exocrine function scoring thresholds vary significantly across published series. No universally accepted standardised protocol has been adopted.

AI-assisted MRCP analysis: preliminary studies report automated stone detection on MRCP with sensitivity 80–90% and specificity 85–95% for CBD stones ≥ 5 mm. Automated stricture detection and ductal measurement algorithms are in development. No FDA/EMA-cleared clinical tool exists at the time of writing.

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12. Evidence-Based References

A. Guidelines / Consensus / Society Recommendations

B. Systematic Reviews / Meta-analyses

C. Important Prospective / Original Studies

D. Technical MRI Papers

E. Landmark Historical References

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End of document — Biliary MRI / MRCP Generic Standard Protocol — MRIninja v1.0 — May 2026

This master page is the reference for all future biliary MRI child pages including: Primary sclerosing cholangitis (PSC) protocol; cholangiocarcinoma staging protocol; choledochal cyst classification; secretin-enhanced MRCP for exocrine function; post-liver transplant biliary assessment; IPMN with biliary communication; hepatobiliary phase biliary leak mapping.