Comparison of abdominal ultrasound, endoscopic ultrasound and magnetic resonance imaging in detection of necrotic debris in walled-off pancreatic necrosis

Background: Walled-off pancreatic necrosis (WOPN) is an important complication of acute pancreatitis that is diagnosed by imaging modalities such as endoscopic ultrasound (EUS) or magnetic resonance imaging (MRI), which can clearly visualize necrotic debris. The effectiveness of abdominal ultrasound (USG) in detecting solid debris in WOPN is not clear. Methods: A total of 52 patients (37 males, mean age 38.9 ± 12.6 years) with symptomatic WOPN were prospectively studied using EUS, MRI and USG. These investigations were done at a mean of 11.7 ± 5.5 weeks of onset of acute pancreatitis and within two days. Results: WOPN was detected by EUS & MRI in all patients, whereas USG could not detect it in 4 (7.6%) patients (3 had predominantly solid WOPN, whereas one had air foci in WOPN). USG, MRI and EUS could detect solid debris in all patients with detectable WOPN. EUS and USG detected <10% debris in 10 (20%) patients, whereas MRI detected <10% debris in 14 (27%) patients. EUS and USG detected 10–40% debris in 33 patients whereas MRI detected 10–40% debris in 30 (58%) patients. More than 40% debris was better characterized on EUS and MRI with both detecting >40% debris in 8 patients (15%) compared to 5 (11%) patients having >40% debris on USG. EUS detected collaterals around WOPN that were not detected on USG or MRI. Conclusion: USG can characterize the majority of WOPN, with accuracy comparable to that of EUS/MRI. However its limitations are the inability to detect collaterals around WOPN and characterize collections with high solid content or air.