Study On Imaging Anatomy Of Draining Pathways Of Pancreatic Fluid To Pleural Cavity In Acute Pancreatitis

Background:Accompanied by the constitution of draining pathways from the peripancreatic spaceto the mediastinum, fluid collections in the mediastinum has the potentiality to transformto the pancreaticopleural fistula and the mediastinal pseudocyst. As sever complicationsof pancreatitis, the clinicians often made misdiagnosis to the above two entities due tonot fully recognization of their pathological anatomy. The overall ability of CT toprovide accurate delineation of the fistula of above two entities is disputable. Theradiological anatomic study of draining pathways from the peripancreatic space to themediastinum will be beneficial for the promotion of the positive diagnosis of themediastinal pseudocyst and pancreaticopleural fistula, and it may help clinicians to applythe optimal treatment for the above two entities.Objective:Firstly, the left extraperitoneal space (LES) is the frequently involved space ondraining pathways to the mediastinum. So the detailed spatial relationships to its relatedspaces were studied. Secondly, the detailed pathways from the peripancreatic space to themediastinum in acute pancreatitis were formulated. Finally, there is a high frequency thatthe retrocrural space is involved on pathways to the mediastinum, and fluid collections inthe mediastinum may further develop to the pleural effusion. As we know the pleuraleffusion is the risk factor for severity in the acute pancreatitis. The scoring system basedon the CT manifestations of retrocrural space involvement (RCSI) in acute pancreatitiswould be eatablished. This scoring system was used to predict the occurrence of thepleural effusion and the prognosis of patients.This study is composed by three parts. The first part is the study of the anatomicfeatures of the LES and its spatial associations with related spaces by visualizationtechnology, in random sections and in three-dimensions (3D). The second part is thestudy of the anatomic pathways of peripancreatic fluid extension through diaphragmatichiatuses to mediastinum that may potentially transform to fistulas under different diseaseseverity or different necrotic area of pancreas in acute pancreatitis combined CT imageswith Second Chinese Visible Human (CVH2) images, so that the diagnostic accuracy of the pancreaticopleural fistula and mediastinal pseudocyst will be increased. The thirdpart is the study of a scoring system based on the RCSI, compared it with the CT severityindex (CTSI), in evaluating the occurrence of pleural effusion and the severity of acutepancreatitis.Material and Methods:In the first part of this study, we integrated with Mimics and Amira software. Weused thin-slice cross-sectional images of the upper abdomen, retrieved from the Chineseand American Visible Human dataset and the Chinese Virtual Human dataset, to displayanatomic features of the LES and spatial relationships of the LES to its related spaces,especially the gastric bare area. The anatomic location of the LES was presented on3Dsections reconstructed from CVH2images and CT images.In the second part of this study, successive cross-sectional images includingdraining pathways were retrieved from CVH2dataset. CT images of51patients withacute pancreatitis treated during the year of2011were reviewed. Draining pathways onCT images were explored by using the multiply reconstructed technology compared withthose pathways on CVH2images. The distribution of the draining pathways of patientswith pacreatitis was observed according to the disease severity.In the third part of this study, we reviewed contrast-enhanced CT images of241patients with acute pancreatitis taken within3–5days of admission in2010. The RCSIscoring system, which includes assessment of infectious conditions involving theretrocrural space and spreading of peripancreatic fluid into or out of the retrocrural space,was established by use of the Delphi method. Two radiologists independently assessedthe RCSI and CTSI scores. The predictive points of the of RCSI and CTSI scoringsystems in evaluating the occurrence of pleural effusion and severity of acute pancreatitiswere estimated using receiver operating characteristic (ROC) curves.Principal Findings:The studies of the anatomic features of the LES and spatial relationships to itsrelated spaces have ascertained that the LES consisted of the left sub-diaphragmatic fatspace and gastric bare area. The appearance of the fat pad at the cardiac notchcontributed to converting the shape of the anteroexternal surface of the LES fromtriangular to trapezoidal. Moreover, the LES was adjacent to the lesser omentum and thehepatic bare area in the anterointernal and right rear direction, respectively. The research about the anatomic pathways of peripancreatic fluid draining tomediastinum in acute pancreatitis have confirmed that the most important two routes intomediastinum were from the peripancreatic space to the LES via or via not theretromesenteric plane, and further to the retrocrural space across esophageal hiatus.Secondly, the opened draining pathways across esopheageal hiatus into the retrocruralspace in pancreatic head necrosis were less than that in pancreatic body cases, but theseverity had increased. Besides, we firstly formulated the presence of pathways via thenarrow space between the costal and crural diaphragm into the retrocrural space.We investigated the RCSI scoring system in acute pancreatitis by using CT. And wedemonstrated that the RCSI score could accurately predict the occurrence of pleuraleffusion. The area under the ROC curve for the RCSI versus CTSI score was0.852±0.026versus0.810±0.027for predicting the occurrence of pleural effusion, and0.816±0.031versus0.977±0.010for the severity of acute pancreatitis. Applying ROCanalysis to our data showed that a CTSI score of3was the best cutoff value, above whichsevere acute pancreatitis could identified.Conclusion:The visualization technique has been used in studying the adjacent relationship ofabdominal spaces for the first time. This technique is a promising new method forexploring detailed communication relationships among other abdominal spaces, and willpromote research on the dynamic extension of abdominal diseases, such as inflammatorydiseases and intra-abdominal carcinomatosis.After the entire anatomy of draining pathways to mediastinum is defined in detail,the sensitivity of detecting the mediastinal pseudocyst and pancreaticopleural fistula willbe increased. With the pathological progress, the appearance or disappearance ofdraining routes may serve as complements to the CT severity index, thus it may helpclinicians to apply the optimal treatment for the above two entities.The RCSI scoring system can predict the occurrence of pleural effusion (better thanthe CTSI score), and the severity of acute pancreatitis.