Efficacy of Secretin MRCP in the Diagnosis and Follow up of Auto Immune Pancreatitis

Overview

BACKGROUND: Auto immune pancreatitis (AIP), a benign pancreatic disease has certain morphological forms which mimics pancreatic malignancy in radiological appearance. There is no singe diagnostic test which can accurately differentiate these two conditions. In the past, AIP accounted for up to 27% of Whipple resections performed for suspected adenocarcinoma. AIMS: To evaluate the efficacy of Secretin assisted Magnetic resonance cholangio pancreatography (MRCP) in differentiating AIP and pancreatic malignancy. METHODS: 100 patients suspected with AIP will be consented to participate in the study to undergo secretin MRCP in addition to their other standard investigations. Patients will be categorized as those with AIP and with pancreatic malignancy based on these results and will be followed. Follow up will eventually give the true diagnosis when patients with pancreatic malignancy undergo pancreatic surgery and their pancreatic tissue is examined by histopathologist. AIP patients will undergo steroid trial which will give the true diagnosis. The preliminary diagnosis results based on standard investigations with and without inclusion of secretin MRCP will be compared to the true diagnosis.

A total of 100 patients with suspicion of Auto Immune Pancreatitis will be identified from the multidisciplinary pancreatic cancer clinic at Johns Hopkins and from the Pancreatitis clinic of the Division of Gastroenterology, Johns Hopkins Hospital. After written, informed consent is obtained; preliminary screening will be done which includes medical history and physical examination including weight and vital signs. Serum immunoglobulin G4 (IgG4) levels will also be evaluated. If the patient meets exclusion/inclusion criteria, screening eligibility and signs informed consent, they will be included in the study. Study investigators and/or their delegate will complete the patient demographic form, medical history form, baseline physical examination, baseline laboratory evaluation and concomitant medication evaluation as per the protocol. Any other investigational procedure such as endoscopic ultrasonography - fine-needle aspiration (EUS - FNA) or esophagogastroduodenoscopy (EGD) with papillary biopsy for IgG4 which assists in the differentiation between AIP and Pancreatic malignancy may be performed based on the treating physician's discretion. Involvement of other organs by AIP and Pancreatic malignancy will be obtained based on the medical history, examination and imaging findings. The patients will be subjected to MRI and MRCP with the MRCP performed in two stages namely before injection of secretin and after intravenous injection of 0.4mcg/Kg of synthetic human secretin (CHIROSTIM, Human Secretin, CHIRHOCLIN Inc., Burtonsville, MD). All the subjects will be given 3 cups (approximately 500-600cc) of pineapple juice 5-10 minutes before the imaging procedure. Pineapple juice will act as a negative oral contrast which nulls the signal in stomach and duodenum, thereby suppressing gastrointestinal overlap over pancreas. MR Examination will be performed using 3.0 T magnet and it will include non contrast enhanced scanning followed by gadolinium enhanced scanning, performed during the arterial dominant, venous dominant and late phases. The secretin MRCP is performed through serial breath-hold T2-weighted sequences run during the first 8-12 min after the intravenous administration of secretin. Based on the result from the above investigations, the patients will be categorized as those suspected with AIP and those suspected with Pancreatic malignancy. Patients with suspected malignancy will eventually undergo surgical resection of pancreas under their treating physician and the pancreatic tissue examination will provide the true diagnosis. Patients with suspected AIP will undergo a steroid trial for at least 3 months, at the end of which a repeat MRI, secretin MRCP will be performed and the diagnosis will be confirmed based on the response to steroid therapy.