After routine investigations, including a thorough history, routine laboratory study, and noninvasive imaging with transcutaneous ultrasonogram, 10% to 25% of cases of acute pancreatitis have no readily identifiable cause and are termed idiopathic. But modern medicine has made notable advances in uncovering various causes of acute pancreatitis, and several new diagnostic tools that allow clinicians to less invasively approach the patient without sacrificing the diagnostic yield have been introduced. By being knowledgeable of these new changes and by their proper use in a proper circumstances, clinicians will be able to find the cause more accurately and earlier. This better management will not only improve the well-being of the patients but also reduce the number of “true” idiopathic acute pancreatitis to a minimum.
Acute pancreatitis is a common disorder, and it begins as an inflammatory process involving the exocrine pancreas, which is associated with a number of other disease states that are collectively known as the “causes” or “etiologies” of acute pancreatitis. 1,2 In clinical practice, a causal explanation is found in 75% to 90% of patients with acute pancreatitis after a thorough history, routine laboratory study, and noninvasive imaging with transcutaneous ultrasonogram (US). 3–6 After these routine investigations, 10% to 25% of cases of acute pancreatitis have no readily identifiable cause and are termed idiopathic. 3–6
The clinical impact of idiopathic acute pancreatitis (IAP) is evident that about 40% (the largest subgroup) of fatal acute pancreatitis cases have an unknown cause. 7,8 Evaluation and therapy are important because >50% of untreated patients with IAP experience recurrent episodes. 6,9,10 Although gallstone pancreatitis remains controversial, many disorders characterized as causing acute recurrent pancreatitis may progress to chronic pancreatitis with irreversible morphologic and functional change. 6,11,12 If the inciting factors are eliminated early enough, pathologic change of the pancreas may regress and prevent the progression to the chronic pancreatitis. 4,12,13 Once the diagnosis of acute pancreatitis is established with certainty, therefore, the most likely cause should be identified and treated, if possible, to prevent recurrence.
The extent and direction of the evaluation may impact the frequency with which an etiology can be found and, in turn, how often the label “idiopathic” can be applied. With expanding knowledge on all the conditions with which acute pancreatitis is associated and of technology advances in pancreaticobiliary imaging and its functional status, few patients would be found to have “true” IAP. This review is intended to outline a number of factors known to be related to the development of IAP and to describe systemic approach to identify the cause.