Acute pancreatitis other imaging findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Monish Thuvooru Muthu Kalyanaraman, M.B.B.S[2]
Other Imaging Findings
This microchapter addresses imaging modalities used in acute pancreatitis beyond CT, MRI/MRCP, transabdominal ultrasound, and chest radiography. These include plain abdominal radiography, endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasound (EUS), angiography for hemorrhagic complications, and image-guided percutaneous drainage. While plain radiography has a limited role in modern practice, ERCP, EUS, angiography, and percutaneous drainage remain essential components of the diagnostic and interventional armamentarium for acute pancreatitis and its complications.[1]
Plain Abdominal Radiography
Plain abdominal radiographs have a limited and largely historical role in the diagnosis of acute pancreatitis. The ACR Appropriateness Criteria note that conventional radiographs have limited utility but may be obtained during initial evaluation of nonspecific abdominal pain to assess for bowel obstruction, free air, or calcified gallstones.[1] Classic but nonspecific plain-film findings include:
- Sentinel loop — a focally dilated segment of proximal small bowel (usually jejunum) adjacent to the inflamed pancreas, resulting from localized ileus.
- Colon cutoff sign — gaseous distension of the proximal colon with abrupt termination at the splenic flexure, caused by spasm from contiguous peripancreatic inflammation along the phrenicocolic ligament.
- Gaseous distension of the duodenal loop — present in approximately 50% of patients in one classic series.[2]
- Gasless abdomen — rare but associated with severe pancreatitis.[2]
- Pancreatic calcifications — suggest underlying chronic pancreatitis (acute-on-chronic presentation).
These findings are nonspecific and insensitive; they should not be relied upon for diagnosis. Plain radiography is most useful when obtained incidentally during evaluation of undifferentiated abdominal pain and may provide clues that redirect the workup toward pancreatitis.[1]
Endoscopic Retrograde Cholangiopancreatography (ERCP)
ERCP is primarily a therapeutic procedure in the context of acute pancreatitis. Its role has been refined considerably, with multiple RCTs demonstrating that routine urgent ERCP does not benefit most patients with biliary pancreatitis.
Current Guideline Recommendations
- Concurrent cholangitis: Urgent ERCP within 24 hours of admission is indicated (ACG 2024: strong recommendation, moderate quality evidence).[3]
- Persistent biliary obstruction without cholangitis: ERCP may be considered when there is progressive cholestasis (rising bilirubin >3–5 mg/dL) in the setting of severe or moderately severe acute pancreatitis.[3]
- Biliary pancreatitis without cholangitis or ongoing obstruction: ERCP is not recommended, regardless of predicted severity. The APEC trial demonstrated that urgent ERCP with sphincterotomy did not reduce the composite endpoint of major complications or mortality compared with conservative management (38% vs 44%) in predicted severe biliary acute pancreatitis without cholangitis.[4][5]
- Screening for choledocholithiasis: When biliary stones are suspected but cholangitis is absent, MRCP or EUS should be used rather than diagnostic ERCP (ACG 2024: conditional recommendation).[3]
Key Trial: APEC
This multicenter RCT randomized 232 patients with predicted severe biliary acute pancreatitis (without cholangitis) to urgent ERCP with sphincterotomy (<24 hours) versus conservative treatment. No significant difference was found in the primary composite endpoint (mortality + major complications). Cholangitis was significantly less common in the ERCP group (2% vs 10%), supporting the role of ERCP when cholangitis is present or develops.[4]
Complications of ERCP
A 2025 systematic review and meta-analysis of 380 studies and >2 million patients reported the following adverse event rates:[6]
- Post-ERCP pancreatitis: 4.6% overall (6.5% in first-time patients)
- Bleeding: 1.5%
- Cholangitis: 2.5%
- Perforation: 0.5%
- ERCP-attributable mortality: 0.2%
Prevention of post-ERCP pancreatitis: Rectal NSAIDs (indomethacin 100 mg), prophylactic pancreatic duct stenting, and aggressive periprocedural hydration reduce the incidence of post-ERCP pancreatitis in high-risk patients (ACG 2024: conditional recommendation, moderate evidence).[3][6]
Endoscopic Ultrasound (EUS)
EUS serves two major roles in acute pancreatitis: (1) diagnostic evaluation of idiopathic or recurrent acute pancreatitis and (2) therapeutic drainage of pancreatic/peripancreatic collections.
Diagnostic Role
- EUS is the preferred initial diagnostic test for unexplained acute and recurrent pancreatitis (AGA Clinical Practice Update 2022).[7]
- EUS uncovers a potential etiology in 29–88% of patients with idiopathic acute pancreatitis, most commonly occult biliary lithiasis (microlithiasis, sludge).[7]
- EUS has a significantly higher overall diagnostic yield than MRCP (pooled RR 2.01; 95% CI 1.42–2.85), driven primarily by its superiority for biliary etiologies (RR 3.67). MRCP may be superior for detecting pancreas divisum.[8]
- Occult ampullary or pancreatobiliary malignancy is identified in up to 5% of patients after a single episode of unexplained acute pancreatitis and up to 12% with recurrent acute pancreatitis.[7]
- Optimal timing is 2–6 weeks after resolution of the acute episode to allow inflammatory changes to subside.[7]
Therapeutic Role (EUS-Guided Drainage)
- EUS-guided transmural drainage is the first-line intervention for symptomatic walled-off necrosis (WON) and pancreatic pseudocysts that are endoscopically accessible.[9][10]
- Lumen-apposing metal stents (LAMS) have become the preferred device, providing a large-bore transluminal port for drainage and, when needed, direct endoscopic necrosectomy (DEN).
- The endoscopic step-up approach (EUS-guided drainage → DEN if needed → surgical debridement if needed) is the current standard of care, with the TENSION and MISER trials demonstrating non-inferiority to surgical step-up and lower rates of pancreatico-cutaneous fistulae.[5]
Angiography for Hemorrhagic Complications
Visceral artery pseudoaneurysm is a rare but life-threatening complication of necrotizing pancreatitis, occurring in approximately 6.4% of patients with necrotizing pancreatitis.[10] The most commonly involved vessels are the splenic artery (35–50%) and gastroduodenal/pancreaticoduodenal arteries (20–25%).
- CT angiography is the initial diagnostic modality for suspected pseudoaneurysm or hemorrhage.[11]
- Transcatheter angiographic embolization is the first-line treatment for pseudoaneurysm, using coils, cyanoacrylate glue, or other embolic agents to isolate inflow and prevent back-filling via collaterals.[12]
- Mortality from ruptured pseudoaneurysm remains high (10–20% in recent series) despite improvements in angiographic techniques.[12]
- Any significant bleeding from a percutaneous drain in the setting of WON, or upper GI bleed during endoscopic necrosectomy, should be considered a potential visceral artery bleed until proven otherwise.[12]
Image-Guided Percutaneous Drainage
Percutaneous catheter drainage (PCD) under CT or ultrasound guidance remains an important component of the step-up approach for management of infected necrotizing pancreatitis:
- PCD provides rapid source control in critically ill patients who are too unstable for endoscopic intervention.[9]
- PCD monotherapy is definitive in approximately 35–51% of patients with symptomatic WON.[9]
- The preferred route is a retroperitoneal flank approach to avoid enteric contamination and to provide a tract for subsequent sinus tract endoscopy or VARD if needed.
- PCD is particularly valuable for collections extending into the paracolic gutters or pelvis, which are not effectively drained by endoscopic transmural stents.[9]
- Dual-modality drainage (combined percutaneous + endoscopic) is increasingly utilized for extensive or complex collections.
Clinically Actionable Recommendations
- Do not order plain abdominal radiographs specifically to diagnose acute pancreatitis — they are nonspecific and insensitive.
- Perform urgent ERCP within 24 hours only when concurrent cholangitis is present; do not perform routine early ERCP for biliary pancreatitis without cholangitis.
- Use MRCP or EUS rather than diagnostic ERCP to screen for choledocholithiasis when cholangitis is absent.
- Perform EUS 2–6 weeks after resolution of unexplained or recurrent acute pancreatitis to identify occult etiologies, including biliary microlithiasis and malignancy.
- For suspected pseudoaneurysm or hemorrhagic complications, obtain CT angiography and proceed to angiographic embolization as first-line treatment.
- Use percutaneous drainage as a bridge to definitive intervention or as monotherapy in infected necrosis when endoscopic access is not feasible.
References
- ↑ 1.0 1.1 1.2 Expert Panel on Gastrointestinal Imaging, Porter KK, Zaheer A; et al. (2019). "ACR Appropriateness Criteria® Acute Pancreatitis". J Am Coll Radiol. 16 (11S): S316–S330. doi:10.1016/j.jacr.2019.05.017.
- ↑ 2.0 2.1 Davis S, Parbhoo SP, Gibson MJ (1980). "The Plain Abdominal Radiograph in Acute Pancreatitis". Clin Radiol. 31 (1): 87–93. doi:10.1016/s0009-9260(80)80088-2.
- ↑ 3.0 3.1 3.2 3.3 Tenner S, Vege SS, Sheth SG; et al. (2024). "American College of Gastroenterology Guidelines: Management of Acute Pancreatitis". Am J Gastroenterol. 119 (3): 419–437. doi:10.14309/ajg.0000000000002645.
- ↑ 4.0 4.1 Schepers NJ, Hallensleben NDL, Besselink MG; et al. (2020). "Urgent Endoscopic Retrograde Cholangiopancreatography With Sphincterotomy Versus Conservative Treatment in Predicted Severe Acute Gallstone Pancreatitis (APEC): A Multicentre Randomised Controlled Trial". Lancet. 396 (10245): 167–176. doi:10.1016/S0140-6736(20)30539-0.
- ↑ 5.0 5.1 Boxhoorn L, Voermans RP, Bouwense SA; et al. (2020). "Acute Pancreatitis". Lancet. 396 (10252): 726–734. doi:10.1016/S0140-6736(20)31310-6.
- ↑ 6.0 6.1 Bishay K, Meng ZW, Khan R; et al. (2025). "Adverse Events Associated With Endoscopic Retrograde Cholangiopancreatography: Systematic Review and Meta-Analysis". Gastroenterology. 168 (3): 568–586. doi:10.1053/j.gastro.2024.10.033.
- ↑ 7.0 7.1 7.2 7.3 Strand DS, Law RJ, Yang D, Elmunzer BJ (2022). "AGA Clinical Practice Update on the Endoscopic Approach to Recurrent Acute and Chronic Pancreatitis: Expert Review". Gastroenterology. 163 (4): 1107–1114. doi:10.1053/j.gastro.2022.07.079.
- ↑ Udaikumar J, Nimmagadda R, Potluri V; et al. (2026). "Comparing Endoscopic Ultrasound (EUS) vs. Magnetic Resonance Cholangiopancreatography (MRCP) in the Etiological Evaluation of Idiopathic Acute Pancreatitis (IAP): A Systematic Review and Meta-Analysis". Dig Dis Sci. 71 (3): 1108–1118. doi:10.1007/s10620-025-09408-x.
- ↑ 9.0 9.1 9.2 9.3 Baron TH, DiMaio CJ, Wang AY, Morgan KA (2020). "American Gastroenterological Association Clinical Practice Update: Management of Pancreatic Necrosis". Gastroenterology. 158 (1): 67–75.e1. doi:10.1053/j.gastro.2019.07.064.
- ↑ 10.0 10.1 Trikudanathan G, Yazici C, Evans Phillips A, Forsmark CE (2024). "Diagnosis and Management of Acute Pancreatitis". Gastroenterology. 167 (4): 673–688. doi:10.1053/j.gastro.2024.02.052.
- ↑ Wu BU, Banks PA (2013). "Clinical Management of Patients With Acute Pancreatitis". Gastroenterology. 144 (6): 1272–1281. doi:10.1053/j.gastro.2013.01.075.
- ↑ 12.0 12.1 12.2 Maurer LR, Fagenholz PJ (2023). "Contemporary Surgical Management of Pancreatic Necrosis". JAMA Surg. 158 (1): 81–88. doi:10.1001/jamasurg.2022.5695.