Acute interstitial edematous pancreatitis: Findings on non-enhanced MR imaging

Abstract

Aim: To study the appearances of acute interstitial edematous pancreatitis (IEP) on non-enhanced MR imaging.

Methods: A total of 53 patients with IEP diagnosed by clinical features and laboratory findings were underwent MR imaging. MR imaging sequences included fast spoiled gradient echo (FSPGR) fat saturation axial T1-weighted imaging, gradient echo T1-weighted (in phase), single shot fast spin echo (SSFSE) T2-weighted, respiratory triggered (R-T) T2-weighted with fat saturation, and MR cholangiopancreatography. Using the MR severity score index, pancreatitis was graded as mild (0-2 points), moderate (3-6 points) and severe (7-10 points).

Results: Among the 53 patients, IEP was graded as mild in 37 patients and as moderate in 16 patients. Forty-seven of 53 (89%) patients had at least one abnormality on MR images. Pancreas was hypointense relative to liver on FSPGR T1-weighted images in 18.9% of patients, and hyperintense in 25% and 30% on SSFSE T2-weighted and R-T T2-weighted images, respectively. The prevalences of the findings of IEP on R-T T2-weighted images were, respectively, 85% for pancreatic fascial plane, 77% for left renal fascial plane, 55% for peripancreatic fat stranding, 42% for right renal fascial plane, 45% for perivascular fluid, 40% for thickened pancreatic lobular septum and 25% for peripancreatic fluid, which were markedly higher than those on in-phase or SSFSE T2-weighted images (P<0.001).

Conclusion: IEP primarily manifests on non-enhanced MR images as thickened pancreatic fascial plane, left renal fascial plane, peripancreatic fat stranding, and peripancreatic fluid. R-T T2-weighted imaging is more sensitive than in-phase and SSFSE T2-weighted imaging for depicting IEP.

Figure 1

A 42-year-old woman with interstitial edematous pancreatitis. A: SPGR fat-suppressed T1-weighted (TR/TE = 170/1.6 ms) image shows pancreatic signal intensity comparable to that of liver; B: GRE in-phase (TR/TE = 150/4.4 ms) image shows pancreatic fascial plane (arrows) and peripancreatic fat stranding (arrow heads); C: SSFSE T2-weighted (TE = 90 ms) image shows increased pancreatic signal intensity (asterisk). Stranding in the pancreatic fascial plane (large arrow) and peripancreatic fat and thickened pancreatic lobular septum (small arrow) can also be seen; D: R-T T2-weighted (TR/TE = 11 800/93 ms) image shows above findings much better (Asterisk indicates pancreatic parenchyma, white arrows indicate thickened pancreatic lobular septum, white arrow head indicates pancreatic fascial plane, and black arrow and arrow head indicate fat stranding).

Figure 2

A 28-year-old man with IEP. A: SPGR fat-suppressed T1-weighted (TR/TE = 170/1.6 ms) image shows normal pancreatic signal intensity; B: pancreatic fascial (arrows) and peripancreatic fat (asterisk) stranding can be seen on GRE in-phase (TR/TE, 150/4.4 ms) image; C: SSFSE T2-weighted (TE = 90 ms) image; D: R-T T2-weighted (TR/TE = 12300/98 ms) image. Perivascular fluid (curve arrow) can be seen on latter two sequences. Thickened pancreatic lobular septum (arrow heads) can only be seen on R-T T2-weighted image (D); E: At the level of the head of the pancreas, R-T T2-weighted image (E) shows pancreatic fascial plane (white arrow), right renal fascia plane (white arrow head), fluid surrounding SMV (black arrow), and left anterior pararenal space and lateroconal plane fluid collections (asterisk).

Figure 3

A 45-year-old woman with IEP and cholelithiasis. (A) SPGR fat-suppressed T1-weighted (TR/TE = 170/1.6 ms) image shows normal pancreatic signal intensity. GRE in-phase (TR/TE = 150/4.4 ms) (B) and SSFSE T2 weighted (TE = 90 ms); (C) images show the pancreatic fascia plane (arrows) and the peripancreatic fat stranding (asterisk), which appear more extensive on R-T T2-weighted (TR/TE = 12 300/98 ms) image (D).

Figure 4

The same patient as in Figure 3. At the level of the head of the pancreas, left renal fascial plane (arrow) and anterior pararenal space fat stranding (asterisk) present on GRE in-phase (A), SSFSE T2-weighted (B) and R-T T2-weighted (C) images, but they are most prominent on R-T T2-weighted image.