Journal of Medical Sciences and Health

Intoduction

MRCP (magnetic resonance cholangio- pancreatography) with other MRI (magnetic resonance imaging) sequences like T1WI (T1 weighted images), T2WI (T2 weighted images) and DWI (diffusion weighted imaging) is a widespread, exciting and still emerging tool for the non-invasive assessment of the pancreatic and biliary ductal tree. ¹ Obstructive jaundice is one of the most frequent forms of hepatobiliary disease and it faces several difficulties in diagnosis and management. Patients with jaundice are initially referred for the USG followed by other appropriate imaging modalities like CECT (contrast enhanced computed tomography), MRCP & ERCP (endoscopic retrograde cholangio-pancreatography). ²  Bowel gas, debris, fluid in duodenum and obesity make the assessment of CBD calculus or stricture difficult in the USG (ultrasonography).

MRCP is a non-invasive diagnostic technique for the direct visualization of the biliary ducts images similar to that produced in PTC (percutaneous transhepatic cholangiography) and ERCP. ³ MRCP is becoming the initial imaging tool for hepato-biliary pathology in some institutions and ERCP has been reserved for the therapeutic interventions like CBD calculus removal, CBD stent placement or ampullary dilatation. Common indications for the MRCP usually include unsuccessful ERCP, contraindication of ERCP and presence of biliary-enteric anastomosis. Advantages of MRCP are - non-invasive, no radiation, no requirement of anaesthesia, less operator dependent, better visualization of ducts proximal to obstruction, in combination of other MRI sequences (T1WI and T2WI) allows detection of extraductal disease, and it doesn’t have ERCP related complications like pancreatitis, infection, bleeding, bile duct injury/leak and even death sometimes. Disadvantages of MRCP are - decreased spatial resolution, imaging of non-distended biliary tree is usually difficult and intervention can’t be done at the same sitting.  

USG has been still considered as the initial screening imaging modality in the study of biliary obstructive disease and other pathology, due to its accessibility, speed, ease of performance and low cost. ⁴ It is operator dependent and plays a key role in initial evaluation of the pathology. Traditional Computed Tomography (CT) scan is usually considered more accurate than USG to determine the specific cause and level of biliary obstruction. ⁵  But CT has some limitations and 10% CBD calculus which is radiolucent can be missed in CT scan.

Biliary strictures are also not visualized directly. It’s the diagnosis of exclusion, seen most often as abrupt termination of CBD without any mass lesion. Length and extent of the stricture is also difficult to determine by CT scan. Hence intravenous cholangiography (IVC), percutaneous transhepatic cholangiography (PTC) and endoscopic retrograde cholangio-pancreatography (ERCP) are used for the assessment of extent of stricture segment. ⁶

Due to limited role of the USG and CT scanning and invasive imaging technique of the IVC, PTC and ERCP; MRCP plays an excellent role in the assessment of the hepato-biliary tree and pancreatic duct for the diagnosis of the cause and level of obstruction.  7

Materials and Methods

The study was a retrospective, single institutional study done during the last two years (January 2018 – December 2019) at IGIMS, Patna, Bihar (A tertiary care hospital). The study protocol was approved by the Institutional Ethical Committee (IEC) for human research approval. 

Data was collected from the departmental record for USG findings, medical record for history and PACS (Picture archiving and communicating system) for MRCP findings. Hundred patients were included in our study and their identity were kept anonymous.

Results

Discussion

In our study, 55% of the study population was female and 45% was male. Male to female (M/F) ratio was 0.82:1 which was comparable to those reported by  Goyani et al ² and Huis et al ⁸ being 0.76:1 and 0.69:1 respectively. However, in the study by Sharma et al M/F ratio was found to be 1.29:1. ⁹

More numbers of patients were present in 46-60 years (32%) followed by 31-45 years (28%). Least number of patients were present at extremes of age i.e. <15 years and >75 years (3% each). This result  was comparable to the study conducted by Siva Prasad A et al ⁶ being biliary disease in 62% in the age group >40 year and 6% in the age group of less than 18 years and by Awadhesh Pratap Singh Kushwah in year 2015 who found the peak incidence in 51-60 year of age. ¹⁰ Nehal Diwanji et al in 2016 found that the peak incidence of pancreato-biliary disease was seen in 61-70 years of age. 11 

Benign and malignant pathologies were found in 64%  and 36% of patients respectively. Goyani et  al ⁸ found that the benign and malignant lesions were present in 53.33% and 46.66% of the patients. Huis et al ⁸ observed that the benign and malignant lesions were present in 74.17% and 25.83% of patients. However, other studies by Siddique et al ¹² , Sharma et al ⁹ , Moghimi et al ¹³ and Cheema et al ¹⁴ found that the malignant lesions were more common than the benign lesions. 

Benign lesions were most common in the age range of 46-60 years (23%) and most of the malignant lesions were detected in the age range of 31-45 years of age group (13%). Goyani et  al ² and various other authors found that the most common age range in the benign and malignant lesions were 1-40 years and 41-70 years. This change in age pattern could be due to the changing trends of the disease with time.

USG and MRCP detected lesions were benign in 63% and 62% respectively and were malignant in 34% and 35% of cases respectively. 

Neither USG nor MRCP was able to differentiate the lesion in 6 patients. These indeterminate cases were confirmed to be benign or malignant by ERCP and biopsies. Biopsy proven cases of benign and malignant lesions were 3 in number in each category. Biopsy proven cases of benign lesions were 3 in number that remained indeterminate in USG. One was benign (distal CBD organised sludge) and 2 were malignant (one was periampullary mass and another was pancreatic head mass) lesions among USG detected lesions in indeterminate category. Two were benign (one was benign biliary stricture and another was choledocholithiasis) and one was malignant (distal cholangiocarcinoma) among MRI/MRCP detected lesions in indeterminate category.

There was additional detection of hepatic cholangiolar abscess, postoperative biliary duct injury, small hepatic metastasis, distal CBD calculus or mass, accurate assessment of primary biliary confluence patency and various anatomic variants like pancreatic divisum, bifid configuration of the MPD and long cystic duct insertion by MRCP/MRI which USG failed to do. While choledochal cysts were detected both by USG and MRCP with 100% accuracy. USG showed its advantages in detection of the Mirizzi syndrome, gallbladder adenomyomatosis and chronic liver disease. MRCP combined with T1WI, T2WI and DWI sequences showed differentiation of distal cholangiocarcinoma and sludge which USG failed to do so. 

Diagnostic accuracy and sensitivity of detecting malignant lesions and diagnostic accuracy of detecting benign lesions by MRI with MRCP was greater than that of USG ¹⁵ . Sensitivity of detecting benign lesions by USG was similar to that of MRI with MRCP. This could be explained by the use of graded compression technique and also use of THI (tissue harmonic imaging) which allows better visualization of the distal CBD; hence improved sensitivity and diagnostic accuracy by USG in our study. Ortega et al described that harmonic imaging, by improving contrast resolution, stressed the difference between the anechoic duct lumen and the surrounding soft tissues ¹⁶ . 

Overall sensitivity, specificity and diagnostic accuracy of MRI with MRCP (97%, 85% and 92.75%) sequence were greater than that of USG (92%, 80% and 85.5%) in our study. Verma et al demonstrated the overall sensitivity, specificity and diagnostic accuracy were 80.77%, 95.83% and 88% for cases with benign condition on USG and the same for the malignant condition of biliary obstruction were 92.3%, 86% and 100% on MRCP ¹⁷ . Francesco SF et al found that the sensitivity, specificity and diagnostic accuracy of the USG were 16.67%, 97.29% and 78.62% and of MRCP were 90%, 94% and 93.13% respectively ^18.    

Conclusion

MRCP combined with other MRI sequences was superior to the USG in identifying benign and malignant pathology. MRCP is the modality of choice of imaging investigation for the characterization of the lesion specially in obese patients or to choose the patients who are ideal candidate for the MRCP. It also helps in the decision making regarding the management. It also allowed for the evaluation of the various anatomic variants of the pancreato-biliary system. However, ultrasound remains the primary investigating modality of choice. However, with use of recent advances of USG like harmonic imaging and 3-D/volume imaging there is significant improvement in the lesion characterization.