Detection of painless pancreatitis by computed tomography in patients with post-endoscopic retrograde cholangiopancreatography hyperamylasemia

Objectives Post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis is diagnosed on the basis of pancreatic pain and hyperamylasemia. However, because the diagnosis of abdominal pain is not objective, there may be some cases of painless pancreatitis among patients with post-ERCP hyperamylasemia (PEH). We reviewed the computed tomography (CT) findings of PEH cases to determine the incidence of painless pancreatitis. Methods Between July, 2005 and December, 2011, CT was performed in 91 patients with hyperamylasemia 18 h after ERCP. We reviewed the CT findings and graded the severity of pancreatitis according to the Balthazar grading system. Grades C, D, and E were defined as pancreatitis. Results Thirty-four patients (37%) had pancreatitis according to the CT findings. There was a significant difference in the serum amylase levels between the positive- and negative-CT finding groups (1306 ± 833 vs. 786 ± 315 IU/L, respectively; p = 0.0012). Receiver operating characteristic curve analysis showed that the amylase cut-off value for discriminating between the 2 groups was 795 IU/L (6.36 times the upper normal limit). Conclusions Thirty-seven percent of PEH patients had painless pancreatitis. CT is useful to determine pancreatitis in patients taking analgesics, steroids, or anti-immunological drugs and those with diabetes mellitus and 18-h serum amylase levels of >6 times the normal upper limit.