| Objective To study MRI morphological changes of pancreatic ducts of piglets with chronic pancreatitis induced by the pancreatic duct ligation method, explore the overall form, division and MRI anatomical characteristics of pancreas and pancreatic ducts in both normal and chronic pancreatitis piglets, and analyze the relationship between pancreatic duct changes in piglets with chronic pancreatitis and the pathological severity of chronic pancreatitis. Method Thirty healthy guizhou piglets (21 male and 9 female; 6-15 months, body weight 26.2±3.6 kg [15-35 kg]) were included in this study. Five piglets were randomly selected as the normal control group, the remaining 25 piglets were served as the experimental group. The duct ligation operations were performed on pancreatic ducts between the right lobe of pancreas and the top part of the duodenum by using double 3.0 threads. 2-18 weeks after operations, MRI was respectively performed under anesthesia condition. MRI sequences were performed as follows: axial fat-suppression gradient echo T1-weighted, axis fat-suppression fast recovery fast spin-echo T2-weighted, coronal and axis single-shot fast spin-echo T2-weighted and magnetic resonance cholangiopancreatography. We used GE software on our computer to observe the pancreas of piglets and adjacent structures. Pancreatic ducts were observed on T2W (FRFSE or SSFSE) images and MRCP images including the followings: (1) the overall form and division of pancreatic ducts on MRCP, (2) the form of pancreatic ducts on T2W axial images including the linear, columnar, non-uniform stenosis coexisting with expansion or "beads-strings change", (3) the edge of pancreatic ducts (regular or irregular), (4) the diameter of pancreatic ducts (selecting the widest duct if ducts were divided into several parts; measuring the widest diameter on MRCP or T2W images), (5) branches of pancreatic ducts (observing the form [thin, cylindrical and cystic pancreatic ducts] and counting), (6) abnormal signals in pancreatic ducts. And then we removed the pancreas of piglets by laparotomy and observed the adjacent structures to the pancreas. After soaking in the solution of formalin, the pancreas of piglets was respectively cut in the right lobe of pancreas, median lobe of pancreas and left lobe of pancreas. After the dehydration, transparent, embedding, slice, washes and HE dyeing, slices of pancreas were observed under microscopy. The severity of chronic pancreatitis was graded into three degrees according to the histological characteristics of pancreatic fibrosis. The heaviest degree was defined for chronic pancreatitis if the severity of chronic pancreatitis was different among above three positions of pancreas. ResultThe integral form of the pancreas of piglet was reverse "Y" type for the control group and the experimental group before operations. Two parts of pancreas adjacent to the duodenum was respectively the right lobe of pancreas (adjacent the bottom of liver) and the median lobe of pancreas (beneath the right kidney). The left lobe of pancreas was pointing toward the bottom of spleen. The opening of the common bile duct was situated in the upper part of duodenum (below the gastric helicobacter 2-4cm). The opening of pancreatic ducts was situated in the duodenal inner cavity which was closely connected to the right lobe of pancreas (9-15cm from the gastric helicobacter to the opening of ducts). Chronic pancreatitis was respectively formed in 21 piglets(84%) among the experimental group including seven were mild (feed on 7.4±3.0 weeks), eight were moderate (feed on 8.8±2.4 weeks) and six were severe (feed on 14.0±2.8 weeks).On T2W and MRCP images, the common bile duct disappeared in the gastroduodenal transition zone in the control group and pancreatic ducts and branches did not show. Pancreatic ducts were shown on MRCP in seven piglets with mild chronic pancreatitis and the edge of pancreatic ducts was irregular in three of them. The dilated RPD, LPD and MPD constituted the "person" form in these piglets with moderate chronic pancreatitis. LPD demonstrated as "beads-strings change" in three piglets with moderate chronic pancreatitis and three piglets with severe chronic pancreatitis. The form of branches of pancreatic ducts was respectively thin in moderate chronic pancreatitis and thin, cylindrical and cystic in severe chronic pancreatitis. The remaining four piglets in the experimental group and the control group were pathological normal pancreas. The pancreatic acinar remained intact, however, the fibrosis desmoplasia appeared around them for seven piglets with mild chronic pancreatitis. Pancreatic fibrosis occurred in lobules and internal lobules accompanied by infiltrating inflammatory cells for eight piglets with moderate chronic pancreatitis. Pancreatic acinar disorder structures were accompanied by lots of infiltrating inflammatory cells and severe fusion fibrosis hyperplasia inside interlobular lobules for six piglets with severe chronic pancreatitis.The diameter of pancreatic ducts was respectively 0.9±0.3mm, 2.9±1.4mm and 4.8±1.2mm in mild chronic pancreatitis, moderate chronic pancreatitis and severe chronic pancreatitis. The expansion extent of pancreatic ducts (the diameter of pancreatic ducts) was correlated with the severity of chronic pancreatitis of piglets (r = .837, P < .05). The pancreatic branch displaying rate was respectively zero, 37.5%, 83.3% in mild chronic pancreatitis, moderate chronic pancreatitis and severe chronic pancreatitis. The pancreatic branch displaying rate increased following by the increasing of the severity of chronic pancreatitis of piglets.Conclusion1. The integral form of the pancreas of piglet was reverse "Y" type including the right lobe of pancreas, median lobe of pancreas and left lobe of pancreas. The panorama of dilated pancreatic ducts was "person" form including RPD, LPD and MPD.2. The import ways of the common bile duct and pancreatic ducts in piglets were different from those of human.3. The site of the pancreatic duct ligation was situated at the right lobe of pancreas which was close with the upper of duodenum. The success rate of chronic pancreatitis models by this surgical method was 84%. Separation of the pancreatic duct was not needed in this operation. Another advantage was that secondary changes of the panorama of dilated pancreatic ducts after operations were shown.4. The common bile duct disappeared in the gastroduodenal transition zone on MRCP in normal piglets and pancreatic ducts and branches did not show.5. These signs may refer to mild chronic pancreatitis of piglets: pancreatic ducts were initially shown and the edges of pancreatic ducts were fine irregular on MRCP images. The branches of pancreatic ducts were not shown in mild chronic pancreatitis of piglets.6. The non-uniform stenosis coexisting with expansion or "beads-strings change" of pancreatic ducts on axial T2W or MRCP images may refer to moderate or severe chronic pancreatitis of piglets.7. The expansion extent of pancreatic duct was correlated with the severity of chronic pancreatitis of piglets. The pancreatic branch displaying rate increased following by the increasing of the severity of chronic pancreatitis. The form of pancreatic branches was thin in moderate chronic pancreatitis, whereas that of branches were thin, cylindrical and cystic in severe chronic pancreatitis.
|
PDF Full Text Request