Diagnostic and Severity Assessment of Acute Pancreatitis Using Acoustic Radiation Force Impulse Shear Wave Elastography (ARFI-SWE): A Case-Control Study.

Background Acute pancreatitis has a variable clinical course, making early severity assessment important. Conventional ultrasonography may have limitations, while CT involves radiation exposure. Acoustic radiation force impulse shear wave elastography (ARFI-SWE) provides quantitative assessment of tissue stiffness and may help evaluate pancreatic involvement and disease severity. This study assessed pancreatic ARFI-SWE parameters in acute pancreatitis and their relationship with the modified CT severity index (MCTSI), Revised Atlanta Classification (RAC), and symptom duration. Methods This hospital-based case-control study included 46 patients with acute pancreatitis and 46 healthy controls. ARFI-SWE was performed using a Siemens ACUSON Sequoia ultrasound system with a 6C1 HD convex transducer (Siemens Healthineers, Erlangen, Germany). Three measurements were obtained from the pancreatic head and body, with the median value used for analysis. Shear wave velocity was recorded in m/s and stiffness in kPa. Contrast-enhanced CT was performed using a 160-slice UCT780 scanner (United Imaging, Shanghai, China). MCTSI scores were categorized as mild, moderate, or severe. RAC severity was also recorded. Time since symptom onset was categorized as 48 hours. Results Age and sex distributions were comparable between patients and controls (age: 44.13 ± 15.71 vs. 38.61 ± 13.21 years, P=0.071; sex, P=0.834). Pancreatic head and body thickness and main pancreatic duct diameter were significantly greater in patients than controls (30.28 ± 3.81 vs. 25.78 ± 2.85 mm; 24.35 ± 3.14 vs. 15.24 ± 2.14 mm; and 3.226 ± 0.520 vs. 1.243 ± 0.513 mm; all P<0.001). Acoustic radiation force impulse (ARFI) head and body velocities were also higher in patients (2.845 ± 0.476 vs. 1.219 ± 0.143 m/s and 2.949 ± 0.642 vs. 1.161 ± 0.139 m/s), as were head and body stiffness values (22.861 ± 5.947 vs. 4.596 ± 0.731 kPa and 22.730 ± 6.040 vs. 4.139 ± 0.639 kPa; all P<0.001). By MCTSI, 15 (32.6%) patients had mild, 21 (45.7%) moderate, and 10 (21.7%) severe disease; by RAC, 13 (28.3%) were mild, 22 (47.8%) moderately severe, and 11 (23.9%) severe. MCTSI and RAC showed a strong association (Fisher-Freeman-Halton exact test=64.516, P<0.001). ARFI parameters increased significantly across MCTSI severity categories (all P<0.001). MCTSI score showed strong correlations with head velocity (ρ=0.839), body velocity (ρ=0.898), head stiffness (ρ=0.805), and body stiffness (ρ=0.811). In regression analysis, body velocity had the highest explanatory value (R²=0.786). For severe MCTSI-defined disease, area under the curve (AUCs) were 0.935 for head velocity, 1.000 for body velocity, 0.854 for head stiffness, and 0.858 for body stiffness. ARFI parameters also increased significantly with increasing time since symptom onset. Conclusion ARFI-SWE showed significantly higher pancreatic shear wave velocity and stiffness in patients with acute pancreatitis than in healthy controls. ARFI parameters were strongly associated with MCTSI severity and showed good to excellent discrimination of severe disease, with body velocity demonstrating the strongest association. Increasing values with symptom duration further support ARFI-SWE as a noninvasive adjunct for quantitative assessment of acute pancreatitis severity.