<prompt> A patient complains of epigastric pain, radiating to back off and on. The investigation of choice is:MRICT ScanUSGRadio nucleotide scan  <response>: B i.e. CT Scan Stepwise diagnostic approch to a patients with suspected chronic pancreatitis. CT scan calcification, atrophy or dilated duct seen for diagnosis MRIMRCP with secretin-enhancement sMRCP Diagnostic criteriaCambridge class III, dilated duct, atrophy of gland, filling defect in duct suggestive of stone Endoscopic ultrasound EUS with quantification 5 of parenchymal ductal criteria Pancreatic function test with secretin- gastroduodenal SST or endoscopic ePFT collection method. Diagnostic criteria: peak 80meqL Endoscopic Retrograde Cholangio pancreaticography ERCP DC: Cambridge III, dilated main pancreatic duct 3 dilated side branch Acute Pancreatitis Any severe acute pain in abdomen or back should suggest the possibility of acute pancreatitis. Abdominal pain,is the major symptom of acute pancreatitis characteristically, the pain which is steady boring in character, is located in epigastrium periumbilical regionQ and often radiates to the backQ as well as to the chest, flank lower abdomen. The patient often obtains relief by sitting with the trunk flexed and knees drawn upQ. When a patient with possible predisposition to pancreatitis such as gall stone, alcoholism, ERCP, hyperigyceridemia, trauma, surgery and drugs like azathioprine, sulfonamides, estrogen, tetracycline, valproic acid, 6-merceptopurine anti HIV drugs presents with severe constant abdominal pain frequently aw nausea, fever, emesis, tachycardia, leukocytosis, hypocalcemia and hyperglycemia, the diagnosis of acute pancreatitis is usually enteained. Diagnosis of acute pancreatitis requires 2 of the following: typical abdominal pain, 3 fold or greater increase in serum amylase or lipase which usually establishesclinch the diagnosis if gut perforation, ischemia or infraction are excluded, however, levels does not indicate the severity and confirmatory findings on cross sectional abdominal imaging. A CTscan can confirm the diagnosis of acute pancreatitisQ even with less than a 3 fold increase in serum amylase and lipase levels. It also indicates severity of disease, risk of morbidity and moality and evaluates complication of acute pancreatitis. However, a CTscan within 3-5 days of symptom onset may underestimate the extent of tissue injury hence repeated again. Sonography is useful to evaluate gallbladder if gall stone disease is suspected as etiology. 