Relationship Between The Morphology Of Pancreaticobiliary Junction And Acute Pancreatitis: An MRI Study

Purpose: To investigate the correlation between the morphology (angle andtype) of the pancreaticobiliary junction and the incidence of acute pancreatitisusing magnetic resonance imaging (MRI).Materials and Methods:1. Between February2012and May2012at our institution, MRIexaminations were performed in122patients who underwenttwo-dimensional MRCP. All patientsˊage, gender, height and weight weremeasured and recorded. Sixty-four patients were enrolled into our studyaccording to inclusion and exclusion criteria, and divided into Group A and B,respectively. Group A contain thirty-two subjects with normal pancreas, andGroup B includes32patients with acute pancreatitis.2. The examination of the patients was performed on a3.0Tsuperconducting scanner (MR750, GE Medical Systems, Waukesha, WI)using a32channel phased-array abdominal coil for signal reception withrespiratory gating and the patients laying in the supine position. All patientswere deprived of eat and drink about6～8hours before examination. Theaxial fast spoiled gradient echo (FSPGR) T1-weighted imaging, axial single shot fast spin-echo (SSFSE) T2-weighted MR imaging, respiratory-triggered(R-T) axial fast recovery fast spin-echo (FRFSE) T2-weighted MR imagingwith fat suppression, and coronal SSFSE T2-weighted MR imaging wereperformed as routine work. The MRCP adopted a two-dimensional single shotfast spin-echo (SSFSE) by breath-hold. After choosing the positioning imagein axial T2-weighted with fat suppression, the thick-slab sequences wereacquired with a radial loop being centred at the level of the distal commonbile duct within the period of duodenal wall. Twelve images at intervals of15。were radial loop, one of which was standard coronary plane. The images wereacquired during breath-hold at end expiration depending on patients,breathing. The imaging parameters for the SSFSE sequences were as follows:repetition time (TR)=6000ms, echo time (TE)=900ms, number ofexcitation (NEX)=1, FOV=38cm, matrix=384×256, slice thickness (ST)=40mm with no gap, and scan time=3seconds for one slice. The total scantime was about31s～86s.3. All MRCP images were acquired and subsequently loaded in medicine(DICOM) format. All MR imaging data were measured three times by the tworadiologists independently using the same computer-aided design (CAD)software. They should reach an agreement on larger differences. Interobserveragreement was evaluated using intra-class correlation coefficient (ICC) statistics. The average angles were acquired from two observers. The anglesbetween Group A and B were compared by two independent sample t-tests.The study analyzed and evaluated the diagnostic efficiency of the angle of thepancreaticobiliary junction on acute pancreatitis, which adopted the ROCcurves.4. According to the type of biliary duct and main pancreatic duct joiningthe duodenal wall, the joining was classified into three categories: normaltype (V type), B-P type and P-B type. The comparison for the three types inGroup A and B was performed by the chi-square test and Fisher’s exact testfor nominal data. The study analyzed the relationship between three types andangles of the pancreaticobiliary junction by analysis of variance.5. Factors associated with the acute pancreatitis (sex, age, height andweight, V type, B-P type, P-B type and the angle of the pancreaticobiliaryjunction) were analyzed by logistic regression in order to establish the riskmodel of acute pancreatitis.Results:1. The angle of the pancreaticobiliary junction in Group A was smallerthan in Group B (51.45°±13.51°vs.65.50°±16.72°, P<0.05). Based on thereceiver operating curve analysis for the angle of the pancreaticobiliaryjunction to detect the presence of pancreatitis, the area under the curve was 0.75with a sensitivity of75%and specificity of75%when the cutoff angle ofthe pancreaticobiliary junction was57.74°.2. According to the type of biliary duct and main pancreatic ductjoining the duodenal wall, the incidence of acute pancreatitis in the V type orin the B-P type was higher than in the P-B type (10/15vs.9/28, or13/21vs.9/28, respectively, all P<0.05), whereas there were no significant difference inthe incidence of acute pancreatitis between the V type and B-P type (P>0.05).The angles with V type, B-P type and P-B type were no significant difference(P>0.05), and the average values of the angle of the pancreaticobiliaryjunction were59.42°±20.41°、59.04°±11.93°、57.54°±17.40°,respectively.3. According to the binary logistic regression analysis, the relativefactors of acute pancreatitis were the angle of the pancreaticobiliary junction,weight and P-B type. The general regression equation for the acutepancreatitis was Y=－1.376+0.1X4－2.159X7+0.052X8. Among these, theangle of the pancreaticobiliary junction(X8) and weight(X4) were risk factorfor acute pancreatitis (OR=1.11,95％CI:1.01～1.21and OR=1.05,95％CI:1.01～1.10respectively), while the P-B type(X7) was the protective factorof acute pancreatitis (OR=0.16,95％CI:0.02～0.74). For64models, thenegative predictive rate was81.3%(26/32) and positive predictive rate was84.4%(27/32), comprehensive predictive rate with82.8%. Conclusions:1. The morphology (angle and type) of the pancreaticobiliary junctionis closely related to the incidence of acute pancreatitis，whereas there were norelationship between angle and type of the pancreaticobiliary junction.2. The angle of the pancreaticobiliary junction is one of risk factors foracute pancreatitis. As the angle increasing, the incidence of acute pancreatitisis relatively higher.3. The incidence of acute pancreatitis in P-B type is relative less than Vtype and B-P type.