Morphological features of fluid collections on endoscopic ultrasound in acute necrotizing pancreatitis: do they change over time?

BACKGROUND: There have been attempts to develop universally applicable nomenclature for pancreatic fluid collections (PFCs) in acute pancreatitis. But PFCs following acute necrotizing pancreatitis (ANP) has not been studied by sensitive imaging techniques like endoscopic ultrasound (EUS). The aim of the study was to prospectively study morphological structure of pancreatic fluid collections occurring after ANP by serial EUS. METHODS: Patients with ANP having PFC at ≥4 weeks of onset of symptoms seen at our center from October 2011 to November 2012 were prospectively followed up with EUS at 6 weeks, 3 months and 6 months respectively and the amount of solid content in the collection was quantified as percentage amount of echogenic material. The symptomatic patients undergoing EUS/percutaneous drainage also underwent EUS prior to drainage for assessment of solid content. RESULTS: Of the 54 patients enrolled, 7 patients were lost to follow up or refused EUS. Forty seven patients (34 males; mean age 36.7±11.6 years) were studied. Etiology of acute pancreatitis was alcohol (n=22), gallstones (n=10), idiopathic (10), gallstones+alcohol (n=3) and drug induced (n=2). Contrast enhanced computed tomography done after 3 days of onset of ANP had shown less than 30%, 30-50% and more than 50% necrosis in 6 (13%), 14 (30%) and 27 (57%) patients respectively. On EUS at 6 weeks, 41/47 (87%) patients had fluid collection with solid debris. Follow up EUS at 3 and 6 months revealed progressively decreasing solid content in PFCs. CONCLUSIONS: All PFCs following ANP may not have solid necrotic content and over a period of time necrotic content tends to liquefy. This may have therapeutic implications.