Magnetic Resonance Cholangiopancreatography

Number: 0384

Table Of Contents

Policy

Scope of Policy

This Clinical Policy Bulletin addresses magnetic resonance cholangiopancreatography.

1. Medical Necessity

   Aetna considers magnetic resonance cholangiopancreatography (MRCP) medically necessary when any of the following is met:

   1. Preoperative evaluation of the common bile duct prior to laparoscopic cholecystectomy in persons with elevations of their transaminases or common bile duct dilatation on abdominal imaging (ultrasound or CT scan); or
   2. Other members not meeting criterion 1 who, based on the initial work-up, only require diagnosis of suspected pancreaticobiliary pathology without the need for therapeutic intervention; or
   3. Member has a documented allergy to iodine-based contrast materials, or has a general history of atopy; or
   4. Member has altered biliary tract anatomy that precludes endoscopic retrograde cholangiopancreatography (ERCP) (e.g., post-surgical biliary tract alterations, prior gastrectomy, choledochojejunostomy, etc.); or
   5. Member has undergone unsuccessful ERCP and requires further evaluation; or
   6. Member is an infant or young child, or is an adult who is debilitated or uncooperative in such a manner that ERCP is unsafe or cannot be performed; or
   7. Member requires definition of pancreaticobiliary anatomy proximal to a biliary tract system obstruction that cannot be opened by ERCP; or
   8. Member requires evaluation for a suspected congenital anomaly of the pancreaticobiliary tract (e.g., aberrant ducts, choledochal cysts, pancreas divisum, etc.); or
   9. Diagnosing biliary obstruction in orthoptic liver transplant recipients; or
   10. Diagnosing a disrupted or disconnected pancreatic duct in acute pancreatitis; or
   11. Postsurgical surveillance of intraductal papillary mucinous neoplasm of the pancreas (IPMN).

2. Experimental, Investigational, or Unproven

   The following interventions are considered experimental, investigational, or unproven because the effectiveness of these approaches has not been established:

   1. MRCP for all other indications including the following (not an all-inclusive list) (e.g., diagnosing autoimmune pancreatitis, and monitoring and predicting disease outcomes of persons with primary sclerosing cholangitis) for indications other than the ones listed above;
   2. MRCP without IV contrast in the staging of pancreatic cancer, except in cases of renal failure or other contraindications to administration of gadolinium intravenous contrast;
   3. Quantitative magnetic resonance cholangiopancreatography for evaluation of bile duct, gallbladder, liver, pancreas and pancreatic duct diseases.

Background

Ultrasonography (US) and computed tomography (CT) scanning have been the standard non-invasive techniques for showing biliary calculi and pancreatic diseases, although magnetic resonance imaging (MRI) and more recently endoscopic ultrasound have shown excellent results.  Magnetic resonance cholangiopancreatography (MRCP) is a new non-invasive modality that shows fluid in the biliary and pancreatic ducts in an axial or three-dimensional image format, somewhat comparable in appearance and diagnostic accuracy to radiographic techniques seen with direct contrast endoscopic retrograde cholangiopancreatography (ERCP).  The major advantages of MRCP include:

1. does not require administration of exogenous contrast materials; and
2. the potential avoidance of a purely diagnostic ERCP with its attendant complications of cholangitis and post-ERCP pancreatitis.

The major disadvantages of MRCP include:

1. the lack of therapeutic capability;
2. MRCP images are not satisfactorily comparable to those provided by ERCP;
3. inability to provide information with regard to resectability of pancreatic cancer; and
4. MRCP equipment is not available at every institution.

Endoscopic retrograde cholangiopancreatography remains the gold standard in the diagnostic work-up of the pancreaticobiliary system.  The real benefits of ERCP, as well as transhepatic cholangiography, include:

1. ability to offer therapeutic intervention at the time of the diagnostic procedure;
2. manometry can be performed;
3. the ampulla of Vater can be directly visualized; and
4. the radiographic images obtained with ERCP have a higher spatial resolution.

In current clinical practice, the majority of patients evaluated for biliary tract disease have a high pre-test likelihood of having a problem requiring therapy (sphincterotomy, stone removal, stenting, etc.), and should be directed toward ERCP for this reason.

Magnetic resonance cholangiopancreatography may have a role in those situations where initial evaluation suggests a benign cause of biliary pathology requiring further cholangiographic confirmation but not necessarily intervention.  It may also be useful in cases of failed ERCP before transhepatic cholangiography, especially in cases where minimal intrahepatic dilatation is suggested by ultrasound or CT, making percutaneous transhepatic cholangiography more difficult.  With complex problems of the biliary tree, MRCP may allow a definitive diagnosis, which may help plan a directed intervention (endoscopic or transhepatic) that would have an increased likelihood of success, with decreased risk.  The utility of MRCP to assess bile duct injuries, primary sclerosing cholangitis, sphincter of Oddi dysfunction, and acute pancreatitis is unknown.

Fernandez-Esparrach and colleagues (2007) compared the diagnostic value of endoscopic ultrasonography (EUS) and MRCP in:

1. patients with a dilated biliary tree unexplained by US (group 1), and
2. the diagnosis of choledocholithiasis in patients with non-dilated biliary tree (group 2).

Patients were prospectively evaluated with EUS and MRCP.  The gold standard used was surgery or EUS-FNA and ERCP, intra-operative cholangiography, or follow-up when EUS and/or MRCP disclosed or precluded malignancy, respectively.  Likelihood ratios (LR) and pre-test and post-test probabilities for the diagnosis of malignancy and choledocholithiasis were calculated.  A total of 159 patients met one of the inclusion criteria but 24 of them were excluded for different reasons.  Therefore, 135 patients constituted the study population.  The most frequent diagnosis was choledocholithiasis (49 % in group 1 and 42 % in group 2, p = 0.380) and malignancy was more frequent in group 1 (35 % versus 7 %, respectively, p < 0.001).  When EUS and MRCP diagnosed malignancy, its prevalence in this series (35 %) increased up to 98 % and 96 %, respectively, whereas it decreased to 0 % and 2.6 % when EUS and MRCP precluded this diagnosis.  In patients in group 2, when EUS and MRCP made a positive diagnosis of choledocholithiasis, its prevalence (42 %) increased up to 78 % and 92 %, respectively, whereas it decreased to 6 % and 9 % when any pathological finding was ruled out.  The authors concluded that EUS and MRCP are extremely useful in diagnosing or excluding malignancy and choledocholithiasis in patients with dilated and non-dilated biliary tree.  Thus, they are critical in the approach to the management of these patients.

McMahon (2008) evaluated the relative roles of MRCP and EUS in the investigation of common bile duct (CD) calculi using "evidence-based practice" methods.  A focused clinical question was constructed.  A structured search of primary and secondary evidence was performed.  Retrieved studies were appraised for validity, strength and level of evidence (Oxford/CEBM scale: 1 to 5).  Retrieved literature was divided into group A: MRCP slice thickness greater than or equal to 5 mm, group B: MRCP slice thickness = 3 mm or 3D-MRCP sequences.  Six studies were eligible for inclusion (3 = level 1b, 3 = level 3b).  Group A: sensitivity and specificity of MRCP and EUS were (40 %, 96 %) and (80 %, 95 %), respectively.  Group B: sensitivity and specificity of MRCP and EUS were (87 %, 95 %) and (90 %, 99 %), respectively.  The authors concluded that MRCP should be the first-line investigation for CD calculi and EUS should be performed when MRCP is negative in patients with moderate or high pre-test probability.

Autoimmune pancreatitis (AIP) represents a special type of chronic pancreatitis.  It occurs most commonly in elderly males with painless jaundice or mild abdominal pain.  It is a relatively newly recognized type of pancreatitis that is characterized by diffuse or focal swelling of the pancreas due to lympho-plasmacytic infiltration and fibrosis of the pancreatic parenchyma.  It is also known as ducto-centric AIP, lobulo-centric AIP, idiopathic duct-destructive pancreatitis, and lympho-plasmacytic sclerosing pancreatitis.  The differential diagnosis of AIP versus pancreatic cancer is important because AIP has been found to respond to steroid treatment.

Fukumori and colleagues (20050 stated that MRCP visualizes only the main pancreatic duct (MPD) in the pancreas head region.  Furthermore, while MRCP imaging of the MPD may be helpful in the diagnosis of AIP, a negative result does not preclude such diagnosis.

Carbognin et al (2009) retrospectively determined MRI, MRCP, and secretin-MRCP findings in patients with AIP.  A total of 28 patients with histopathologically proven AIP were reviewed.  In 14 cases, secretin-enhanced MRCP was performed.  The observers evaluated pancreatic parenchymal enlargement, signal intensity abnormalities, enhancement, vascular involvement, bile-duct diameter and MPD narrowing (diffuse/focal/segmental).  After secretin administration, the presence of the "duct-penetrating" sign was evaluated.  Magnetic resonance imaging showed diffuse pancreatic enlargement in 8/28 (29 %) cases, focal pancreatic enlargement in 16/28 (57 %) cases and no enlargement in 4/28 (14 %) cases.  The alteration of pancreatic signal intensity was diffuse in 8/28 (29 %) cases (8 diffuse AIP) and focal in 20/28 (71 %) cases (20 focal AIP).  Delayed pancreatic enhancement was present in all AIP, with peripheral rim of enhancement in 8/28 (29 %) AIP (1/8 diffuse, 7/20 focal); vascular encasement was present in 7/28 (25 %) AIP (1/8 diffuse, 6/20 focal); distal common bile duct narrowing was present in 12/28(43 %) AIP (5/8 diffuse, 7/20 focal).  Magnetic resonance cholangiopancreatography showed MPD narrowing in 17/28 (61 %) AIP (4/8 diffuse, 15/20 focal), MPD dilation in 8/28 (29 %) AIP (3/8 diffuse, 5/20 focal) and normal MPD in 1/8 diffuse AIP.  Secretin-MRCP showed the duct-penetrating sign in 6/14 (43 %) AIP (1 diffuse AIP with MPD segmental narrowing, 5 focal AIP with MPD focal narrowing), demonstrating integrity of the MPD.  The authors concluded that delayed enhancement and MPD stenosis are suggestive for AIP on MR and MRCP imaging.

Kamisawa et al (2009) stated that it is important to differentiate AIP from pancreatic cancer.  Irregular narrowing of the MPD is a characteristic finding in AIP; it is useful for differentiating AIP from pancreatic cancer stenosis.  These investigators evaluated the usefulness of MRCP for the diagnosis of AIP and assessed if MRCP could replace ERCP for diagnosing AIP.  The MRCP and ERCP findings of 20 AIP patients were compared.  On MRCP, the narrowed portion of the MPD was not visible, while the non-involved segments of the pancreatic duct were visible.  The degree of upstream dilatation of the proximal MPD was milder in AIP than in pancreatic cancer patients.  In the skipped type, only skipped narrowed lesions were not visible.  After steroid therapy for AIP, the non-visualized MPD became visible.  The authors concluded that MRCP can not replace ERCP for the diagnosis of AIP, since narrowing of the MPD in AIP was not visible on MRCP.  Moreover, MRCP findings of segmental or skipped non-visible MPD accompanied by a less dilated upstream MPD may suggest the presence of AIP.

In a review on AIP, Detlefsen and Drewes (2009) stated that pathologically, AIP shows narrowing of the pancreatic ducts and the intra-pancreatic portion of the common bile duct.  Obstructive jaundice is a common symptom at presentation, and pancreatic cancer represents an important clinical differential diagnosis.  In late stages of the disease, the normal pancreatic parenchyma is often replaced by large amounts of fibrosis.  Histologically, there seem to be 2 subtypes of the disease:

1. one showing infiltration with IgG4-positive plasma cells but lacking granulocytic epithelial lesions (GELs), and
2. the other showing GELs but lacking strong IgG4 positivity.

On the basis of conventional pancreatic imaging (e.g., contrast-enhanced CT, EUS, dynamic T2-weighted MRI, and trans-abdominal US), together with serological measurement of IgG4 and evaluation of other organ involvement, many AIP patients can be identified.  The remaining patients require further diagnostic work-up.  In these patients, pancreatic core needle biopsy and a trial with steroids (since AIP responds to steroid treatment) can help to differentiate AIP from pancreatic cancer.

Greenberger (2009) noted that the diagnostic criteria of AIP proposed by the Mayo Clinic (the "HISORT" criteria) are most commonly used in the United States and include the presence of one or more of the following:

• Diagnostic histology (based on resection specimen or pancreatic core needle biopsy)
• Response to steroid therapy of pancreatic (only in those patients in whom a trial with steroid is indicated)/extra-pancreatic manifestations
• Typical imaging (CT and pancreatography) plus any of the following:
  
  
  • Compatible histology (i.e., at least supportive of AIP); or
  • Elevated serum IgG4 levels; or
  • Other organ involvement.

Moreover, Greenberger (2009) stated that ERCP or MRCP may reveal a narrowed MPD and dorsal pancreatic duct; diffuse, irregular narrowing of the pancreatic duct (beaded appearance), or a focal stricture of the pancreatic duct, proximal or distal common bile duct; or irregular narrowing of the intra-hepatic ducts.  A stricture in the common bile duct or the finding of a lesion in the head of the pancreas often prompts consideration of malignancy.  Thus, it may not be possible to distinguish AIP from pancreatic cancer based upon the results of these imaging tests alone.

Primary sclerosing cholangitis (PSC) is an immune-mediated, chronic cholestatic liver disease characterized by progressive inflammation and fibrosis of the bile ducts, resulting in biliary cirrhosis and is associated with a high-risk of cholangiocarcinoma (CCA), which develops in 10 to 30 % of PSC patients.  Early detection of CCA in PSC is achieved by using serum tumor markers (carbohydrate antigen 19-9 [CA 19-9] and carcinoembryonic antigen [CEA]), endoscopic ultrasonography [EUS], as well as fluorescent in situ hybridization [FISH] techniques to enhance the accuracy of biliary cytology (Abbas and Lindor, 2009).  Weismüller and colleagues (2008) stated that the diagnosis of PSC is primarily based on endoscopic cholangiography although MRI is increasingly used; biochemistry and immuno-serology as well as histology play only a minor role.  Due to the high-risk of developing CCA and also other tumours of the GI tract, surveillance strategies are essential, however they have yet to be established and evaluated.  Karnam and associates (2009) stated that ERCP remains preferred in patients with PSC.  Moreover, the role of MRCP in the diagnosis and management of bile duct malignancy is not yet defined.

Weber and associates (2008) stated that MRCP is a less-invasive alternative to ERCP for the diagnosis of PSC.  These investigators evaluated the diagnostic accuracy of MRCP in PSC compared with ERCP, and assessed the diagnostic accuracy of different T2w sequences.  A total of 95 patients (69 PSC, 26 controls) were evaluated using both ERCP and MRCP.  Exclusion criteria included secondary sclerosing cholangitis and contraindications to MRCP.  The diagnosis of PSC was confirmed in 69 patients based on ERCP as the reference gold standard.  Magnetic resonance cholangiopancreatography was performed using a 1.5 Tesla MR unit, using breath hold, coronal and transverse half-Fourier acquisition single-shot turbo spin-echo (HASTE), coronal-oblique, fat-suppressed half-Fourier rapid acquisition with relaxation enhancement (RARE), and coronal-oblique, fat-suppressed, multi-section, thin-section HASTE (TS-HASTE) sequences.  The MRCP morphological criteria of PSC were evaluated and compared with ERCP.  The sensitivity, specificity, and diagnostic accuracy were 86 %, 77 %, and 83 %, respectively, using the MRCP-RARE sequence, and increased further to 93 %, 77 %, and 88 %, respectively, by the inclusion of follow-up MRCP in 52 patients, performed at 6- and 12-month intervals.  HASTE and TS-HASTE sequences showed significantly lower diagnostic accuracy but provided additional morphologic information.  The authors concluded that MRCP can diagnose PSC but has difficulties in early PSC and in cirrhosis, and in the differentiation of cholangiocarcinoma, Caroli's disease, and secondary sclerosing cholangitis.  A positive MRCP would negate some diagnostic ERCP studies; but a negative MRCP would not obviate the need for ERCP.

In a prospective study, Nebiker and colleagues (2009) analyzed the rate of clinically inapparent common bile duct (CBD) stones, the predictive value of elevated liver enzymes for CBD stones, and the influence of the radiological results on the peri-operative management.  A total of 465 patients were cholecystectomized within 18 months, mainly laparoscopically.  Pre-operative MRCP was performed in 454 patients.  With MRCP screening, clinically silent CBD stones were found in 4 %.  Elevated liver enzymes have only a poor predictive value for the presence of CBD stones (positive predictive value, 21 %; negative predictive value, 96 %).  Compared to the recent literature, the post-operative morbidity in this study was low (0 % bile duct injury, 0.4 % residual gallstones).  The authors concluded that although MRCP is diagnostically useful in the peri-operative management in some cases, its routine use in the diagnosis related group (DRG)-era may not be justified due to the costs.

Jorgensen et al (2011) stated that biliary complications are the second leading cause of morbidity and mortality in orthotopic liver transplant (OLT) recipients.  Endoscopic retrograde cholangiography is considered the diagnostic criterion standard for post-orthotopic liver transplantation biliary obstruction, but incurs significant risks.  These researchers ascertained the diagnostic accuracy of MRCP for biliary obstruction in OLT patients.  A systematic literature search identified studies primarily examining the utility of MRCP in detecting post-orthotopic liver transplantation biliary obstruction.  A meta-analysis was then performed according to the Quality of Reporting Meta-Analyses statement.  A meta-analysis of 9 studies originally performed at major transplantation centers was carried out.  A total of 382 OLT patients with clinical suspicion of biliary obstruction were included in this analysis.  major outcome measures were sensitivity and specificity of MRCP for diagnosis of biliary obstruction.  The composite sensitivity and specificity were 0.96 (95 % confidence interval [CI]: 0.92 to 0.98) and 0.94 (95 % CI: 0.90 to 0.97), respectively.  The positive and negative likelihood ratios were 17 (95 % CI: 9.4 to 29.6) and 0.04 (95 % CI: 0.02 to 0.08), respectively.  All but 1 included study had significant design flaws that may have falsely increased the reported diagnostic accuracy.  The authors concluded that high sensitivity and specificity demonstrated in this meta-analysis suggested that MRCP is a promising test for diagnosing biliary obstruction in patients who have undergone liver transplantation.  However, given the significant design flaws in most of the component studies, additional high-quality data are necessary before unequivocally recommending MRCP in this setting.

Giljaca et al (2015) stated that EUS and MRCP are tests used in the diagnosis of common bile duct stones in patients suspected of having common bile duct stones prior to undergoing invasive treatment.  There has been no systematic review of the accuracy of EUS and MRCP in the diagnosis of common bile duct stones using appropriate reference standards.  These researchers determined and compared the accuracy of EUS and MRCP for the diagnosis of common bile duct stones.  They searched MEDLINE, EMBASE, Science Citation Index Expanded, BIOSIS, and Clinicaltrials.gov until September 2012.  In addition, they searched the references of included studies to identify further studies and of systematic reviews identified from various databases (Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment (HTA), Medion, and ARIF (Aggressive Research Intelligence Facility)).  They did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively.  These investigators included studies that provided the number of true positives, false positives, false negatives, and true negatives for EUS or MRCP.  They only accepted studies that confirmed the presence of common bile duct stones by extraction of the stones (irrespective of whether this was done by surgical or endoscopic methods) for a positive test, and absence of common bile duct stones by surgical or endoscopic negative exploration of the common bile duct or symptom free follow-up for at least 6 months for a negative test, as the reference standard in people suspected of having common bile duct stones.  They included participants with or without prior diagnosis of cholelithiasis; with or without symptoms and complications of common bile duct stones, with or without prior treatment for common bile duct stones; and before or after cholecystectomy.  At least 2 authors independently screened abstracts and selected studies for inclusion.  Two authors independently collected the data from each study.  They used the bi-variate model to obtain pooled estimates of sensitivity and specificity.  The authors included a total of 18 studies involving 2,366 participants (976 participants with common bile duct stones and 1,390 participants without common bile duct stones); 11 studies evaluated EUS alone, and 5 studies evaluated MRCP alone; 2 studies evaluated both tests.  Most studies included patients who were suspected of having common bile duct stones based on abnormal liver function tests; abnormal trans-abdominal ultrasound; symptoms such as obstructive jaundice, cholangitis, or pancreatitis; or a combination of the above.  The proportion of participants who had undergone cholecystectomy varied across studies.  Not one of the studies was of high methodological quality.  For EUS, the sensitivities ranged between 0.75 and 1.00 and the specificities ranged between 0.85 and 1.00.  The summary sensitivity (95 % CI) and specificity (95 % CI) of the 13 studies that evaluated EUS (1,537 participants; 686 cases and 851 participants without common bile duct stones) were 0.95 (95 % CI: 0.91 to 0.97) and 0.97 (95 % CI: 0.94 to 0.99).  For MRCP, the sensitivities ranged between 0.77 and 1.00 and the specificities ranged between 0.73 and 0.99.  The summary sensitivity and specificity of the 7 studies that evaluated MRCP (996 participants; 361 cases and 635 participants without common bile duct stones) were 0.93 (95 % CI: 0.87 to 0.96) and 0.96 (95 % CI: 0.90 to 0.98).  There was no evidence of a difference in sensitivity or specificity between EUS and MRCP (p value = 0.5).  From the included studies, at the median pre-test probability of common bile duct stones of 41 % the post-test probabilities (with 95 % CI) associated with positive and negative EUS test results were 0.96 (95 % CI: 0.92 to 0.98) and 0.03 (95 % CI: 0.02 to 0.06).  At the same pre-test probability, the post-test probabilities associated with positive and negative MRCP test results were 0.94 (95 % CI: 0.87 to 0.97) and 0.05 (95 % CI: 0.03 to 0.09).  The authors concluded that both EUS and MRCP have high diagnostic accuracy for detection of common bile duct stones.  People with positive EUS or MRCP should undergo endoscopic or surgical extraction of common bile duct stones and those with negative EUS or MRCP do not need further invasive tests.  However, if the symptoms persist, further investigations will be indicated.  The 2 tests are similar in terms of diagnostic accuracy and the choice of which test to use will be informed by availability and contra-indications to each test.

An UpToDate review on “Magnetic resonance cholangiopancreatography” (Karnam et al, 2015) states that “Common bile duct stones -- The choice of procedure varies with the clinical setting and local availability.  In patients with cholangitis, for example, ERCP is preferred because it permits therapeutic drainage of the obstruction.  However, MRCP may be performed if cholangitis is not severe and the risks of ERCP are high.  MRCP may also be useful after unsuccessful or incomplete ERCP and in imaging the CBD in patients undergoing laparoscopic cholecystectomy.  Endoscopic ultrasound may also be an option in individuals considered at increased risk for ERCP”.

National Comprehensive Cancer Network’s clinical practice guideline on “Pancreatic adenocarcinoma” (Version 1.2017) states that “MR cholangiopancreatography (MRCP) without IV contrast should not be utilized in the staging of pancreatic cancer, except in cases of renal failure or other contraindications to administration of gadolinium intravenous contrast”.

Magnetic Resonance Cholangiopancreatography for Diagnosis of Choledocholithiasis

Markum and colleagues (2017) stated that biliary stone disease is one of the most common conditions leading to hospitalization.  In addition to ERCP, EUS and MRCP are required in diagnosing choledocholithiasis.  In a retrospective study, these investigators compared the sensitivity and specificity of EUS and MRCP against ERCP in diagnosing choledocholithiasis.  This trial was conducted after prospective collection of data involving 62 suspected choledocholithiasis patients who underwent ERCP from June 2013 to August 2014.  Patients were divided into 2 groups.  The first group (31 patients) underwent EUS and the 2nd group (31 patients) underwent MRCP.  Then, ERCP was performed in both groups.  Sensitivity, specificity, and diagnostic accuracy of EUS and MRCP were determined by comparing them to ERCP, which is the gold standard.  The male-to-female ratio was 3:2.  The mean ages were 47.25 years in the 1st group and 52.9 years in the 2nd group.  Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for EUS were 96 %, 57 %, 87 %, 88 %, and 80 % respectively, and for MRCP were 81 %, 40 %, 68 %, 74%, and 50 %, respectively.  The authors concluded that EUS is a better diagnostic tool than MRCP for diagnosing choledocholithiasis.

Magnetic Resonance With Breath-Hold 3-Dimensional Magnetic Resonance Cholangiopancreatography for Surveillance of Pancreatic Intraductal Papillary Mucinous Neoplasm

In a retrospective study, Kang and colleagues (2020) examined the clinical feasibility of abbreviated MRI using breath-hold 3-dimensional MRCP (3D-MRCP) (aMRI-BH) for pancreatic intraductal papillary mucinous neoplasm (IPMN) surveillance.  A total of 123 patients with 158 pancreatic IPMNs (pathologically proven [n = 73] and typical image feature with greater than or equal to 2-year stability [n = 85]) who underwent conventional MRI (cMRI) consisting of contrast-enhanced pancreato-biliary MRI with conventional and BH-3D-MRCP were included.  Two readers independently evaluated aMRI-BH protocols consisting of heavily T2-weighted, pre-contrast T1-weighted, and BH-3D-MRCP sequences.  The diagnostic performance of aMRI-BH for detecting malignant IPMNs was assessed using the following criteria: category 3, presence of mural nodule 5 mm or bigger and/or main pancreatic duct (MPD) 10 mm or bigger; category 2, more than one of the following: cyst size 30 mm or greater, mural nodule smaller than 5 mm, thickened cyst walls, MPD of 5 to 9 mm, lymphadenopathy, and an abrupt MPD caliber change with distal atrophy; and category 1, none of the above.  Categories 2 or 3 were considered positive results of surveillance.  Inter-reader agreement of image features by intra-class correlation and κ statistics were analyzed.  The total acquisition times of cMRI and aMRI-BH were 32.7 ± 8 and 5.5 ± 2.1 mins, respectively (p < 0.01).  Among 158 IPMNs, 33 lesions were malignant.  The aMRI-BH presented a sensitivity of 100 % and a NPV of 100 % for evaluating malignant IPMNs in both readers, with substantial inter-reader agreements (intra-class correlation or к values, range of 0.73 to 0.93 for cMRI and 0.57 to 0.94 for aMRI-BH) in significant imaging features based on revised Fukuoka guidelines, except for thickened cyst walls and lymphadenopathy (к values: 0.10 and 1.00 for cMRI and 0.13 and 0.49 for aMRI-BH, respectively).  The authors concluded that aMRI-BH provided high sensitivity and NPV to evaluate malignant IPMNs by using pre-determined criteria, and aMRI-BH might be a potential tool for pancreatic IPMN surveillance with significantly lower acquisition time.  These preliminary findings need to be validated by well-designed studies.

Magnetic Resonance Cholangiopancreatography for Prediction of Disease Outcomes in Sclerosing Cholangitis

Patil and colleagues (2019) noted that MRCP has not been assessed as a surrogate biomarker in pediatrics.  In a retrospective, single-center, cohort study, these researchers determined the inter-rater reliability, prognostic utility, and constructed validity of the modified Majoie endoscopic retrograde cholangiopancreatography classification applied to MRCP in a pediatric PSC cohort.  This trial included children with PSC undergoing diagnostic MRCP between 2008 and 2016.  Six variations of the Majoie classification were examined: intra-hepatic duct (IHD) score, extra-hepatic duct (EHD) score (representing the worst intra-hepatic and extra-hepatic regions, respectively), sum IHD-EHD score, average IHD score, average EHD score, and sum average IHD-EHD score.  Inter-rater reliability was assessed using weighted Kappas and intra-class correlation coefficients (ICCs).  Ability to predict time to PSC-related complications (ascites, esophageal varices, variceal bleed, liver transplant [LT], or cholangiocarcinoma) (primary outcome) and LT (secondary outcome) was assessed with Harrell's concordance statistic (c-statistic) and uni-variate/multi-variable survival analysis.  Construct validity was further assessed with Spearman correlations.  A total of 45 children were included (67 % boys; median of 13.6 years).  The inter-rater reliability of MRCP scores was substantial to excellent (Kappas/ICCs, 0.78 to 0.82).  The sum IHD-EHD score had the best predictive ability for time to PSC complication and LT (c-statistic, 0.80 and SE, 0.06; and c-statistic, 0.97 and SE, 0.01, respectively).  Higher MRCP scores were independently associated with a higher rate of PSC-related complications, even after adjusting for the PSC Mayo risk score (hazard ratio [HR], 1.74; 95 % CI: 1.14 to 2).  MRCP sum scores correlated significantly with METAVIR fibrosis stage, total bilirubin, and platelets (r = 0.42, r = 0.33, r = -0.31, respectively; p < 0.05).  The authors concluded that an MRCP score incorporating the worst affected intra-hepatic and extra-hepatic regions was reliable and predicted meaningful outcomes in pediatric PSC.  The drawbacks of this study included its small sample size (n = 45), retrospective nature (including retrospective review of liver biopsy reports), and relatively short follow-up (minimum of 3 months).  These researchers stated that next steps include prospective validation and responsiveness assessment with a larger external cohort with longer follow-up. 

Pre-Operative Magnetic Resonance Cholangiopancreatography Before Planned Laparoscopic Cholecystectomy

Rhaiem and colleagues (2019) noted that the most feared complication of laparoscopic cholecystectomy (LC) is biliary tract injuries (BTI).  These researchers carried out a prospective study to examine the role of pre-operative MRCP in describing the biliary tract anatomy and to examine its potential benefit to prevent BTI.  From January 2012 to December 2016, a total of 402 patients who underwent LC with pre-operative MRCP were prospectively included.  Routine intra-operative cholangiography was not performed.  Patients' characteristics, pre-operative diagnosis, biliary anatomy, conversion to laparotomy, and the incidence of BTI were analyzed.  Pre-operative MRCP was performed prospectively in 402 patients; LC was indicated for cholecystitis and pancreatitis in 119 (29.6 %) and 53 (13.2 %) patients, respectively.  A total of 105 (26 %) patients had anatomical variations of biliary tract; 3 BTI (0.75 %) occurred with a major BTI (Strasberg E) and 2 bile leakage from the cystic stump (Strasberg A).  For these 3 patients, biliary anatomy was modal on MRCP.  No BTI occurred in patients presenting "dangerous" biliary anatomical variations.  The authors concluded that MRCP could be a valuable tool to study pre-operatively the biliary anatomy and to recognize "dangerous" anatomical variations; and subsequent BTI might be avoided.  Moreover, these researchers stated that further randomized trials are needed to examine its real value as a routine investigation before LC.  The authors stated that this study had several drawbacks.  It was a purely descriptive study without a group control.  This was because these investigators thought of reviewing results of MRCP in their patients before conducting a controlled study.  It was also a mono-centric study.

Magnetic Resonance Cholangiopancreatography for Diagnosis of a Disrupted or Disconnected Pancreatic Duct in Acute Pancreatitis

Timmerhuis and colleagues (2021) noted that severe pancreatitis may result in a disrupted pancreatic duct, which is associated with a complicated clinical course.  Diagnosis of a disrupted pancreatic duct is not standardized in clinical practice or international guidelines.  In a systematic review, these investigators examined the literature on imaging modalities for diagnosing a disrupted pancreatic duct in patients with acute pancreatitis.  They carried out a systematic search in PubMed, Embase and Cochrane library databases to identify all studies evaluating diagnostic modalities for the diagnosis of a disrupted pancreatic duct in acute pancreatitis.  All data regarding diagnostic accuracy were extracted.  These researchers included 8 studies, examining 5 different diagnostic modalities in 142 patients with severe acute pancreatitis.  Study quality was evaluated, with proportionally divided high- and low-risk of bias and low applicability concerns in 75 % of the studies.  A sensitivity of 100 % was reported for EUS and ERCP.  The sensitivity of MRCP with or without secretin was 83 %.  A sensitivity of 92 % was reported for a combined cohort of secretin-MRCP and MRCP.  A sensitivity of 100 % and specificity of 50 % was found for amylase measurements in drain fluid compared with ERCP.  The authors concluded that the findings of this review suggested that various diagnostic modalities were accurate in diagnosing a disrupted pancreatic duct in patients with acute pancreatitis.  Amylase measurement in drain fluid should be standardized.  Moreover, these researchers stated that given the invasive nature of other modalities, secretin-MRCP or MRCP would be recommended as first diagnostic modality; however, further prospective studies are needed.

Pancreatic duct disruption or disconnection is a potentially severe complication of necrotizing pancreatitis.  With no existing treatment guidelines on pancreatic duct disruption or disconnection, a potentially severe complication of necrotizing pancreatitis, the Dutch Pancreatitis Study Group (Boxhoorn et al, 2021) evaluated current expert opinion regarding the diagnosis and treatment of pancreatic duct disruption and disconnection.  An online case vignette survey was sent to 110 international expert pancreatologists.  The response rate was 51 % (n = 56).  Consensus was defined as agreement by at least 75 % of the experts.  Consensus statements were evaluated based on the Grades of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.  Once the decision was made to evaluate pancreatic duct integrity, 44 of 56 experts (79 %) preferred magnetic resonance imaging (MRI) and/or magnetic resonance cholangio-pancreatography (MRCP) (consensus statement GRADE C).

Quantitative Magnetic Resonance Cholangiopancreatography

Goldfinger et al (2020) stated that magnetic resonance cholangiopancreatography (MRCP) is an important tool for non-invasive imaging of biliary disease; however, its assessment is currently subjective, resulting in the need for objective biomarkers.  In a prospective study, these investigators examined the accuracy, scan/rescan repeatability, and cross-scanner reproducibility of a novel quantitative MRCP (qMRCP) tool on phantoms and in-vivo; they also reported normative ranges derived from the healthy cohort for duct measurements and tree-level summary metrics.  Phantoms: 2 bespoke designs, 1 with varying tube-width, curvature, and orientation, and 1 exhibiting a complex structure based on a real biliary tree.  A total of 20 healthy volunteers, 10 patients with biliary disease, and 10 with non-biliary liver disease were included in this study.  MRCP data were acquired using heavily T2 -weighted 3D multi-shot fast/turbo spin echo acquisitions at 1.5T and 3T.  Digital instances of the phantoms were synthesized with varying resolution and signal-to-noise ratio.  Physical 3D-printed phantoms were scanned across 6 scanners (2 field strengths for each of 3 manufacturers).  Human subjects were imaged on 4 scanners (2 field strengths for each of 2 manufacturers).  Bland-Altman analysis and repeatability coefficient (RC) were employed for statistical analyses.  Accuracy of the diameter measurement approximated the scanning resolution, with 95 % limits of agreement (LoA) from -1.1 to 1.0 mm.  Excellent phantom repeatability was observed, with LoA from -0.4 to 0.4 mm.  Good reproducibility was observed across the 6 scanners for both phantoms, with a range of LoA from -1.1 to 0.5 mm. Inter- and intra-observer agreement was high.  qMRCP detected strictures and dilatations in the phantom with 76.6 % and 85.9 % sensitivity and 100 % specificity in both.  Patients and healthy volunteers exhibited significant differences in metrics including common bile duct (CBD) maximum diameter (7.6 mm versus 5.2 mm, p = 0.002), and overall biliary tree volume 12.36 ml versus 4.61 ml, p = 0.0026).  The authors concluded that the findings indicated that qMRCP provided accurate, repeatable, and reproducible measurements capable of objectively assessing cholangiopathic change.  These researchers stated that this novel method has the potential to improve both clinical management and the execution of interventional trials.

Gilligan et al (2020) noted that autoimmune liver diseases (AILD), including primary sclerosing cholangitis (PSC), autoimmune sclerosing cholangitis (ASC), and autoimmune hepatitis (AIH), have overlapping clinical features but distinct management strategies and outcomes.  In a cross-sectional study, these researchers examined the diagnostic performance of qMRCP parameters for distinguishing PSC/ASC from AIH in children and young adults.  This institutional review board (IRB)-approved trial included subjects from an institutional AILD registry that underwent baseline serum liver biochemistry testing and 3D fast spin-echo MRCP.  The biliary tree was extracted and modeled from MRCP images using novel proprietary software (MRCP+ ™; Perspectum Diagnostics; Oxford, U.K.), and quantitative parameters were generated (e.g., biliary tree volume; number and length of bile ducts, strictures, and dilations; bile duct median/maximum diameters).  Mann-Whitney U tests were carried out to compare laboratory values and MRCP metrics between patient cohorts (clinical diagnosis of PSC/ASC versus AIH).  ROC curves and multivariable logistic regression were used to evaluate diagnostic performance of serum biochemistry values and MRCP parameters for discriminating PSC/ASC from AIH.  A total of 30 % (14/47) of MRCP examinations failed post-processing due to motion artifact.  The remaining 33 patients included 20 males and 13 females, with a mean age of 15.1 ± 3.9 years; 18 patients were assigned the clinical diagnosis of PSC or ASC and 15 of AIH.  All but 1 qMRCP parameter were significantly different between cohorts (p < 0.05) and predictive of diagnosis (ROC p < 0.05), including numbers of BD strictures (area under curve [AUC] = 0.86, p < 0.0001) and dilations (AUC = 0.87, p < 0.0001) and total length of dilated ducts (AUC = 0.89, p < 0.0001).  Laboratory values were not significantly different between cohorts (p > 0.05).  The best multi-variable model for distinguishing PSC/ASC from AIH included total length of dilated ducts (odds ratio [OR], 1.08; 95 % CI: 1.02 to 1.14) and maximum left hepatic duct diameter (OR, 1.21; 95 % CI: 0.57 to 2.56) [AUC = 0.92].  The authors concluded that qMRCP parameters provided good discrimination of PSC/ASC from AIH.  These researchers stated that these findings suggested that qMRCP has the potential to provide numerous imaging biomarkers of AILD, although there is need for further studies to determine if this technique is sensitive to change over time and if it is associated with, or predictive of, important clinical outcomes.

The authors stated that this study had several drawbacks.  First, these investigators had a relatively small-analyzed sample size of 33 patients.  Second, the post-processing algorithm used in this trial required further research to better characterize its accuracy and repeatability within and across scanner platforms.  Furthermore, this algorithm is not yet widely available and requires expert input, potentially limiting its clinical application.  Third, these researchers did not directly compare qualitative versus quantitative interpretation of the registry baseline MRCP examinations; but instead relied upon clinical diagnosis as the reference standard, which incorporated clinical MRCP as well as other clinical data, such as laboratory values and histopathology.  Fourth, these investigators included patients with small duct PSC/ASC, even though, by definition, these patients do not have qualitative findings on MRCP and could represent false negative cases in the MRCP analyses; thus, slightly lowering the AUROCs of the various qMRI parameters.  However, it was conversely possible that subtle cholangiopathy in small duct PSC/ASC may be detected by quantitative, and not qualitative, MRCP; therefore, further investigations are needed.

Janowski et al (2021) noted that AIH and ASC are 2 very closely related autoimmune liver diseases with overlapping clinical features and similar management strategies.  In a cross-sectional study, these investigators examined the use of quantitative imaging markers to distinguish ASC from AIH in pediatrics.  A total of 66 subjects (n = 52 AIH, n = 14 ASC) aged 14.4 ± 3.3 years scheduled to undergo routine biopsy and baseline serum liver biochemistry testing were invited to undergo MRI (non-contrast abdominal MRI and 3D fast spin-echo MRCP).  Multi-parametric MRI was used to measure fibro-inflammation with corrected T1 (cT1), while the biliary tree was modelled using qMRCP (MRCP +).  Mann-Whitney U tests were performed to compare liver function tests with imaging markers between patient groups (ASC versus AIH).  ROC curves and stepwise logistic regressions were used to identify the best combination of markers to discriminate between ASC and AIH.  Correlations between liver function tests and imaging markers were performed using Spearman's rank correlation.  cT1 was significantly correlated with liver function tests (range of 0.33 ≤ R ≤ 56, p < 0.05), as well as with fibrosis, lobular and portal inflammation (range of 0.31 ≤ R ≤ 42, p < 0.05).  A total of 19 MRCP + metrics correlated significantly with liver function tests (range of 0.29 ≤ R ≤ 0.43, p < 0.05).  Gamma-glutamyl transferase (GGT) and MRCP + metrics were significantly higher in ASC compared to those with AIH.  The best multi-variable model for distinguishing ASC from AIH included total number of ducts and the sum of relative severity of both strictures and dilatations AUC: 0.91 (95 % CI: 0.78 to 1.0).  The authors noted that qMRCP metrics are a good discriminator of ASC from AIH.  Moreover, these researchers stated that future studies looking at longitudinal assessment would yield a better understanding of the changes associated with these metrics, and thus will reveal the impact these metrics have on monitoring of disease progression over time, the sensitivity of the metrics to change and their associations with important clinical outcomes.

The authors stated that while the findings of this study were promising, there were several drawbacks to this trial.  First, this study had a relatively small cohort of ASC patients.  Nevertheless, as multiple studies have shown the prevalence of ASC in AIH to range from 1.7 % to 33.0 %, the size of this cohort may be considered representative of current clinical frequencies.  Second, no comparisons between qualitative and quantitative MRCP were carried out; therefore, the differences between the 2 forms of interpretation were not evaluated.  Third, patients with PSC were also not included in the cohort recruited into this study as it was not part of standard of care at IPCZD to routinely biopsy this patient group.  This exclusion was a limitation to this trial as investigation into the similarities/differences between the sclerosing cholangitis types was not conducted.  Thus, studies looking at the use of these metrics to differentiate between sclerosing cholangitis types are needed to better understand the sensitivity of this new technique.  Fourth, this was a cross-sectional study, and evaluation of the use of these markers to both monitor disease progression/regression or their ability to predict clinical outcomes was not carried out.  

Selvaraj et al (2022) stated that MRI with MRCP (MRI-MRCP) in PSC is currently based on qualitative assessment and has high inter-observer variability.  These investigators examined the performance of quantitative metrics derived from a three-dimensional (3D) biliary analysis tool in adult patients with PSC.  MRI-MRCP, blood-based biomarkers, and FibroScan were prospectively performed in 80 subjects with large-duct PSC and 20 healthy subjects.  Quantitative analysis was carried out using MRCP+ and qualitative reads were carried out by radiologists; inter-reader agreements were compared.  Patients were classified into high-risk or low-risk for disease progression, using Mayo risk score (MRS), Amsterdam-Oxford model (AOM), upper limit of normal (ULN) alkaline phosphatase (ALP), disease distribution, and presence of dominant stricture.  Performance of non-invasive tools was assessed using binomial logistic regressions and ROC curve analyses.  Quantitative biliary metrics performed well to distinguish abnormal from normal bile ducts (p < 0.0001).  Inter-observer agreements for MRCP+ dilatation metrics (intra-class correlation coefficient, 0.90 to 0.96) were superior to modified Amsterdam intrahepatic stricture severity score (κ = 0.74) and Anali score (κ = 0.38).  MRCP+ intra-hepatic dilatation severity showed excellent performance to classify patients into high-risk and low-risk groups, using predictors of disease severity as the reference (MRS, p < 0.0001; AOM, p = 0.0017; 2.2 × ULN ALP, p = 0.0007; 1.5 × ULN ALP, p = 0.0225; extra-hepatic disease, p = 0.0331; dominant stricture, p = 0.0019).  MRCP+ intra-hepatic dilatation severity was an independent predictor of MRS > 0 (OR, 31.3; p = 0.035) in the multi-variate analysis.  The authors concluded that intra-hepatic biliary dilatation severity calculated using MRCP+ was elevated in patients with high-risk PSC and may be used as an adjunct for risk stratification in PSC.  These investigators stated that this exploratory study has provided the groundwork for examining the use of novel quantitative biliary metrics in multi-center studies.  They stated that longitudinal studies with repeat measurements in the same patient will be required and validated first before it can be considered for use in clinical trials.

The authors stated that this study had several drawbacks.  First, clinical outcomes are slow to develop in PSC; thus, risk stratification against other biomarkers that have been validated against clinical endpoints were used in this study.  However, these surrogate biomarkers themselves are imperfect, and none has achieved level III validation.  Second, the directionality of the occurrence of stricture(s) and dilatation(s) is not currently defined in the MRCP+ algorithm; therefore, it is assumed that dilatations are up-stream to strictures.  Third, this trial was a small, single, tertiary‐center study to identify candidate metrics.  Given the heterogeneity of the disease, multi-center studies with larger cohorts of patients with PSC are needed to validate the metrics presented here.  Although these researchers have assessed the inter-observer and intra-observer variability in PSC, they have not carried out a scan-rescan reproducibility study specifically in PSC; the data supporting reproducibility came from 6 patients with PSC, and further validation would be needed.  Fourth, these researchers used FibroScan, which samples a lower volume of the liver compared to MRE, as a reference to stage liver fibrosis.  This could be relevant in evaluating a disease with heterogeneous distribution of fibrosis, such as in PSC.  Fifth, examining cost effectiveness of off‐site data processing and capital expenditure of MRCP+ versus the conventional qualitative approach to image analysis was beyond the scope of this study.  The benefit of having an expert radiologist to make a judgement call on a poor-quality MRI‐MRCP acquisition in the right clinical context could not be under-estimated, as shown by the fact that all 80 scans could be read by the radiologists while only 76 scans could be processed by MRCP+.

Ismail et al (2022) examined the association of MRCP+ parameters with biochemical scoring systems and MRE in patients with PSC.  These investigators evaluated the incremental value of combining MRCP+ with morphological scores in associating with biochemical scores.  MRI images, liver stiffness measurements by MRE, and biochemical testing of 65 patients with PSC that were retrospectively enrolled between January 2014 and December 2015 were obtained.  MRCP+ was used to post-process MRCP images to obtain quantitative measurements of the BDs and biliary tree.  Linear regression analysis was used to test the associations.  Bootstrapping was used as a validation method.  The total number of segmental strictures had the strongest association with Mayo Risk Score (R2 = 0.14), minimum stricture diameter had the highest association with Amsterdam Oxford Prognostic Index (R2 = 0.12), and the percentage of duct nodes with width 0 to 3 mm had the strongest association with PSC Risk Estimate Tool (R2 = 0.09).  The presence of ducts with medians of greater than 9 mm had the highest association with MRE (R2 = 0.21).  The strength of association of MRCP+ to Mayo Risk Score was similar to ANALI2 and weaker than MRE (R2 = 0.23, 0.24, 0.38 respectively).  MRCP+ enhanced the association of ANALI 2 and MRE with the Mayo Risk Score.  The authors concluded that MRCP+ demonstrated a significant association with biochemical scores and MRE.  The association of MRCP+ with the biochemical scores was generally comparable to ANALI scores; MRCP+ enhanced the association of ANALI2 and MRE with the Mayo Risk Score.  Moreover, these researchers stated that MRCP+ has the potential to act as a risk stratifier in PSC; and MRE outperformed MRCP+ for risk stratification.

Eaton et al (2022) noted that several quantitative and qualitative MRI metrics have been reported to predict outcomes among those with PSC.  These researchers compared the reproducibility and prognostic performances of MRI biomarkers and examined if combining these measurements would add value.  They carried out a retrospective review of 388 patients with PSC who underwent a MRE and MRCP.  Liver stiffness (LS) was determined by validated automated software, whereas spleen volume was calculated by semi-automated software, and radiologists manually determined the ANALI scores.  The primary endpoint was hepatic decompensation.  LS and spleen volume values had perfect and near-perfect agreement (intra-class correlation coefficient of 1.00 and 0.9996, respectively), whereas ANALI with and without gadolinium had a moderate inter-rater agreement between 3 radiologists (kappa = 0.42 to 0.54 and 0.46 to 0.57, respectively).  As a continuous variable, LS alone was the best predictor of hepatic decompensation (concordance score = 0.90; 95 % CI: 0.87 to 0.93).  A quantitative-only MRI model [LS (greater than 4.70 kPa = 2 or less than or equal to 4.70 kPa = 0) + spleen volume (greater than 600 mm3 = 1 or less than or equal to 600 mm3 = 0)] had the optimal reproducibility and performance (concordance score = 0.85; 95 % CI: 0.80 to 0.89) and enabled patient risk stratification by estimating the 5-year incidence of hepatic decompensation: 7.49 %, 44.50 %, 70.00 %, and 91.30 % (score 0 to 3).  The authors concluded that quantitative MRI markers of fibrosis and portal hypertension generated by automated and semi-automated software were highly reproducible.  LS was the single best imaging predictor of hepatic decompensation.  However, a quantitative MRI score using LS and spleen volume was well-suited to risk stratify individuals with PSC.

The authors stated that this study had several drawbacks.  First, it was a retrospective study carried out at a single center.  Yet, this cohort represented the largest assembly of patients with PSC who underwent any form of MRI that was systematically analyzed to identify prognostic features to-date.  Furthermore, the individual prognostic importance of LS measured by MRE and spleen volume has been demonstrated in other centers.  However, it will be important to validate these findings.  Second, these investigators did not examine the relationship between changes in imaging over time and the development of adverse outcomes.  Although changes in LS measured by MRE are associated with hepatic decompensation in PSC, it remains unclear if a change in the composite MRI model would similarly predict adverse events (AEs).  Third, although MRE has been available for more than 10 years and has other advantages for those with PSC, it is not as prevalent as transient elastography particularly outside of North America.  Consequently, it would be prudent to validate if combining spleen volume and LS measured by transient elastography has value.

Cazzagon et al (2022) noted that individuals with PSC have a variable and often progressive disease course that is associated with biliary and parenchymal changes.  These changes are typically examined by MRI, including qualitative assessment of MRCP.  In a retrospective study, these researchers examined the association of novel objective quantitative MRCP metrics with prognostic scores and patient outcomes.  This trial included a total of 77 individuals with large-duct PSC with baseline MRCP images, which were post-processed to obtain quantitative measures of bile ducts using MRCP+.  The subjects' ANALI scores, liver stiffness by vibration-controlled transient elastography, and biochemical indices were collected at baseline.  Adverse outcome-free survival was measured as the absence of decompensated cirrhosis, liver transplantation (LT), or liver-related death over a 12-year period.  The prognostic value of MRCP+-derived metrics was assessed by Cox regression modelling.  During a total of 386 patients-years, 16 cases of decompensation, 2 LTs, and 5 liver-related deaths were recorded.  At baseline, around 50 % of the patients were classified as being at risk of developing disease complications.  MRCP+ metrics, especially those describing the severity of bile duct dilatations, were correlated with all prognostic factors.  Univariate analysis showed that MRCP+ metrics representing duct diameter, dilatations, and the percentage of ducts with strictures and/or dilatations were associated with survival.  In a multivariable-adjusted analysis, the median duct diameter was significantly associated with survival (HR 10.9, 95 % CI: 1.3 to 90.3).  The authors concluded that MRCP+ metrics in individuals with PSC correlated with biochemical, elastographic, and radiological prognostic scores and were predictive of adverse outcome-free survival.  These researchers proposed further supporting arguments in favor of the use of MRI for prognostic purposes in PSC.

The authors stated that this study had several drawbacks including the small sample size (n = 77), the limited number of major clinical events observed in this cohort, and the retrospective design.  All these drawbacks may have reduced the significance of the association between MRCP+ metrics and prognosis and did not allow these investigators to compare the prognostic value of MRCP+ metrics with other prognostic scores.

The European Association for the Study of the Liver’s clinical practice guidelines on “Sclerosing cholangitis” (EASL, 2022) stated that artificial intelligence has enabled quantitative MRCP (MRCP+), which is a novel technique to automatically segment biliary anatomy and provide quantitative biliary tree metrics; and some preliminary retrospective studies suggested the use of MRCP+ as a prognostic tool for prediction of clinical outcomes in PSC.

Cristoferi et al (2023) noted that MRCP is the gold standard for diagnosis of patients with PSC.  The semi-quantitative MRCP-derived Anali scores proposed for risk stratification, have poor-to-moderate inter-reader agreement.  In a retrospective study, these investigators examined the prognostic performance of quantitative MRCP metrics in PSC.  This trial included PSC patients undergoing MRCP.  Images were processed using MRCP+ software that provided quantitative biliary features, semi-automatically extracted by artificial intelligence (AI)-driven analysis of MRCP-3D images.  The prognostic value of biliary features has been assessed for all hepato-biliary complications.  A total of 87 PSC patients have been included in the analysis.  Median follow-up from MRCP to event/censoring of 30.9 months (Q1-Q3 = 13.6 to 46.6).  An adverse outcome occurred in 27 (31.0 %) patients.  The number of biliary strictures (HR = 1.05 per unit, 95 % CI: 1.02 to 1.08, p < 0.0001), spleen length (HR = 1.16 per cm, 95 % CI: 1.01 to 1.34, p = 0.039), adjusted for height, age at MRCP, and time from diagnosis to MRCP predicted higher risk of hepatobiliary complications.  These were incorporated into a the quantitative MRCP-derived PSC (qMRCP-PSC) score (C-statistic = 0.80).  After 3-fold cross-validation, qMRCP-PSC out-performed the Anali score in this cohort (C-statistic of 0.78 versus 0.64) and enabled the discrimination of survival of PSC patients (log-rank p < 0.0001).  The authors concluded that qMRCP-PSC score identified patients at higher risk of hepatobiliary complications and out-performed the available radiological scores.  It represents a novel quantitative biomarker for disease monitoring and a potential surrogate endpoint for clinical trials.  Moreover, these researchers stated that further studies, with prospective, standardized data collection and larger patient’s cohorts, are needed for confirmation.

The authors stated that this study had several drawbacks.  First, the median follow-up from the MRCP to event/censoring was relatively short with 30.9 months; however, considering that biliary complications occur earlier in PSC natural history and tend to re-occur becoming a LT indication, a score estimating medium-term outcomes might be useful both in clinical practice and clinical trials to predict intermediate event.  Second, this trial was retrospective and conducted in 2 hospitals using 2 different MRI scanners and, despite the same acquisition protocols, this might have introduced a bias.  However, the MRCP-derived metrics of the 2 groups when compared did not reveal significant differences.  Indeed, it might be seen as MRCP+ software strength that could analyze images performed from different MRI scans and, therefore, more adaptable to clinical practice.  Third, these researchers did not include biochemical parameters to adjust their model since, given the retrospective nature of the study, many of the laboratory examinations were not exactly correspondent to the time of the scanning.  However, considering the weakness of liver function tests in prediction in PSC; and their fluctuation over time, these investigators anticipated that they would not have a major impact on the discriminative power of the MRCP-based model.  Fourth, this trial did not have an external validation cohort; however, by using a cross-validation approach , they were able to confirm that the qMRCP-PSC demonstrated promising out-of-sample generalizability

Magnetic Resonance Cholangiopancreatography Versus Endoscopy Retrograde Cholangiopancreatography for Detection of Anatomic Variants of the Pancreatic Duct in Children

Lin et al (2022) compared the effectiveness of MRCP with ERCP in children for the identification of pancreatic duct variants.  These investigators identified children with a pancreatic duct variant by ERCP and separately queried their MRCP database for similar variants.  Patients with a paired ERCP-MRCP were reviewed.  A total of 3 radiologists blinded to the ERCP and MRCP findings were asked to independently review the MRCP studies and define the pancreatic duct anatomy.  These blinded reviewers also graded the MRI examination quality.  A total of 74 pairs of ERCP-MRCP examinations were identified.  Pancreas divisum was the most frequent ductal variant encountered (73 %).  There was fair agreement between the radiology reviewers as to the quality of the MRI studies (Fleiss Kappa agreement).  Concordance of the reviewers with that of the ERCP was moderate for the exact diagnosis, moderate for the presence of pancreas divisum, and fair for agreement on the presence of any duct variant.  Concordance among reviewers was moderate for the exact diagnosis, moderate for normal versus abnormal, and substantial for the presence of pancreas divisum.  The authors concluded that diagnostic limitations exist when comparing MRCP with the gold reference standard of ERCP, specifically when assessing for pancreatic duct variants in children.

References