Anomalous Pancreatobiliary Ductal Union
Anomalous pancreatobiliary ductal union (APBDU) is a congenital pancreatic anomaly resulting from an abnormally long (>1.5 cm) common channel between the terminal ends of the bile duct and pancreatic duct. The putative mechanism is bile reflux into the pancreatic duct, which may result in pancreatitis. APBDU can be diagnosed on MRCP or ERCP. The causal association of APBDU with pancreatitis has not been proven.
Choledochocele
This is the cystic dilatation of the intraduodenal part of the bile duct and may cause obstruction to pancreatic outflow. Treatment involves deroofing of the choledochocele by endoscopic sphincterotomy.
Annular Pancreas
This is a rare congenital anomaly due to failure of rotation of the ventral bud. This results in a band of pancreatic tissue encircling the second part of the duodenum. It may cause AP but the association is weak. Annular pancreas generally remains asymptomatic in adults. In a retrospective series of 198 patients (mean age 55.1 ± 18.3 years) with radiologically and/or surgically confirmed annular pancreas, 60% of patients were asymptomatic. Among symptomatic patients, only 16% had AP (i.e. about 7% of adult patients with annular pancreas presented with AP) [68].
Idiopathic Acute Pancreatitis
A patient is labelled as having idiopathic AP if no etiology is identified after clinical evaluation, biochemical investigations (including serum calcium and triglyceride level), and abdominal imaging by ultrasound and CT [21].
Investigative Work‐up
All patients with AP must undergo a diagnostic work‐up to find the cause of the pancreatitis. Figure 2.1 shows an algorithmic approach for investigating a patient with AP. Careful history of alcoholism, smoking, medications, family history of pancreatitis, and basic investigations including abdominal USG, and serum calcium and triglyceride levels are essential for initial work‐up. In patients without an identifiable cause, EUS and MRCP should be performed to establish the etiological diagnosis. A repeat evaluation after three to six months of negative work‐up may reveal a cause (e.g. gallstones and occult tumor). A patient with truly idiopathic AP should be advised follow‐up because he or she is at risk of recurrence and may even develop chronic pancreatitis in the long term and thus requires periodic careful assessment.
Figure 2.1 Investigative work‐up and treatment for patients with acute pancreatitis to prevent recurrence. CBD, common bile duct; EUS, endoscopic ultrasound; LFT, liver function test; MRCP, magnetic resonance cholangiopancreatography; RAP, recurrent acute pancreatitis.
Source: adapted from Jagannath and Garg [69]. Reproduced with permission of Springer Nature.
Concluding Remarks
Establishing an etiological diagnosis is extremely important in patients with AP to identify the cause and prevent recurrence. Alcohol and gallstones are the most common causes of AP. Biliary pancreatitis is diagnosed if there is elevation of hepatic transaminases on the first day of AP which normalizes in a few days in a patient with gallstones and/or a dilated bile duct. In patients with suspicion of biliary etiology but without demonstrable gallstones, subsequent transabdominal/endoscopic ultrasound after recovery may demonstrate gallstones. Heavy alcohol consumption (>60 g/day) for at least five years may cause alcoholic pancreatitis. Hypercalcemia and HTG are important metabolic causes of AP. Smoking is a risk factor for AP. Patients with idiopathic pancreatitis aged over 50 years should be evaluated for occult pancreatobiliary malignancy if there is no other obvious cause of AP. Patients with AP should undergo an algorithmic investigative work‐up.
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