Discordance between radiological and clinical findings among patients presenting with elevated lipase and abdominal pain.

Background and aims: False positive lipase elevation is a diagnostic challenge in acute pancreatitis (AP) but has not been systematically studied. We evaluated patients presenting with serum lipase elevation and correlated this with abdominal imaging findings, considered the gold standard for AP diagnosis.

Methods: Patients with abdominal pain, serum lipase ≥ 3-fold the upper limit of normal (ULN), and abdominal imaging within 48 hours of their lipase check were identified. An independent expert pancreas radiologist blinded to clinical data reviewed the images for features of AP. For patients without imaging changes of AP, repeat imaging obtained within 30 days was reviewed. Among patients with elevated lipase but no imaging changes of AP, other etiologies of lipase elevation were identified. Patients were stratified by the degree of lipase elevation, and imaging findings were compared between groups.

Results: 234 patients had lipase ≥ 3-fold the ULN, abdominal pain, and underwent CT or MRI with intravenous contrast. 60.2% had AP findings on their initial imaging, and another 13% had AP or sequelae on imaging within 30 days. In patients without imaging findings of AP, the use of opioid analgesics was the most commonly suspected cause of lipase elevation (24.7 %), followed by abdominal trauma/surgery (12.9%). Among lipase elevations, a cutoff of ≥ 6-fold the ULN had the highest accuracy (70.1%) for diagnosing AP.

Conclusion: Lipase elevation without imaging findings of AP is found in nearly 1/4 of patients and may suggest non-AP causes of lipase elevation. This has clinical implications, but increasing lipase cutoff to ≥ 6-fold ULN has only a modest increase in diagnostic accuracy, suggesting the need for a better biomarker for AP diagnosis.