Imaging of inflammatory disease of the pancreas

Abstract

Increasingly acute and chronic pancreatitis (AP and CP) are considered a continuum of a single entity. Nonetheless, if, after flare-up, the pancreas shows no residual inflammation, it is classified as AP. CP is characterised by a long cycle of worsening and waning glandular inflammation without the pancreas ever returning to its baseline structure or function. According to the International Consensus Guidelines on Early Chronic Pancreatitis, pancreatic inflammation must last at least 6 months before it can be labelled CP. The distinction is important because, unlike AP, CP can destroy endocrine and exocrine pancreatic function, emphasising the importance of early diagnosis. As typical AP can be diagnosed by clinical symptoms plus laboratory tests, imaging is usually reserved for those with recurrent, complicated or CP. Imaging typically starts with ultrasound and more frequently with contrast-enhanced computed tomography (CECT). MRI and/or MR cholangiopancreatography can be used as a problem-solving tool to confirm indirect signs of pancreatic mass, differentiate between solid and cystic lesions, and to exclude pancreatic duct anomalies, as may occur with recurrent AP, or to visualise early signs of CP. MR cholangiopancreatography has replaced diagnostic endoscopic retrograde cholangiopancreatography (ERCP). However, ERCP, and/or endoscopic ultrasound (EUS) remain necessary for transpapillary biliary or pancreatic duct stenting and transgastric cystic fluid drainage or pancreatic tissue sampling, respectively. Finally, positron emission tomography-MRI or positron emission tomography-CT are usually reserved for complicated cases and/or to search for extra pancreatic systemic manifestations. In this article, we discuss a broad spectrum of inflammatory pancreatic disorders and the utility of various modalities in diagnosing acute and chronic pancreatitis.

Figure 1.

Acute interstitial oedematous pancreatitis in a 37-year-old female a, Axial CE-CT; b, axial turbo spin-echo T2 weighted (HASTE) image with fat-suppression; c, axial DWI, b-value = 50; d, pre-; and e, f, post-contrast arterial and portal venous 3D-GRE T1 weighted images with fat-suppression. The pancreatic tail and a part of the body are swollen and the lobules diminished compared to the rest of the pancreas. Mild peripancreatic stranding (arrow) is present. On the HASTE image, the pancreatic duct is minimally dilated. Increased signal (arrowheads) is seen in the pancreatic tail and the affected part of the body on T2 and DWI. Low signal intensity on T1 and inhomogeneous but preserved enhancement in the pancreatic tail and body represent oedema and no necrosis (arrowheads). DWI, diffusion-weighted image.

Figure 2.

Acute necrotising pancreatitis in a 57-year-old male a and b, Axial CECT, arterial and portal-venous phases. c and d, Pre-contrast; and e and f, post-contrast arterial and portal venous axial 3D-GRE T1 weighted images with fat-suppression. On CECT, negligible pancreatic body and tail enhancement (arrows) compared to that of the head and neck (asterisk) indicates partial glandular necrosis (arrows). The tubular hyperintense structures along the periphery of the gland on pre-contrast MR images represent haemorrhagic areas (arrowheads). MR images post-contrast show little or no enhancement of the pancreatic body and tail which had decreased signal intensity pre-contrast (arrows).

Figure 3.

Acute interstitial oedematous pancreatitis with peripancreatic fluid in a 54-year-old male a, Axial; and b, coronal CE-CT scan images, portal venous phase. The sausage-shaped pancreas has nearly homogeneous attenuation though much-diminished contrast enhancement (arrows). Free fluid surrounds the gland (asterisk). The absence of a capsule excludes a pseudocyst. c, Axial T1 weighted fast low-angle shot (FLASH) image with fat-suppression shows mild diffuse swelling and decreased signal intensity of the pancreas which makes the peripancreatic fluid barely visible. d, Axial turbo spin-echo T2 weighted (HASTE) image with fat-suppression shows the homogeneously increased T2 signal of the peripancreatic fluid much better. The fluid extends into the lesser sac (arrowheads) between the gallbladder and the pancreatic head.

Figure 4.

Small pancreatic pseudocyst in a 43-year-old male more than 4 weeks after the onset of acute pancreatitis a, Axial; and b, coronal CECT, arterial phase images, show a 3 cm, thin-walled ovoid collection (asterisks) with attenuation identical to that of the stomach, indicating it is a cyst. Note the mild rim enhancement typical of pancreatic pseudocysts (arrows). c, Axial; and d, coronal turbo spin-echo T2 weighted (HASTE) images with fat-suppression. e, Axial pre-contrast; and f, post-contrast portal venous-phase 3D-GRE T1 weighted image with fat-suppression. The small ovoid lesser sac cyst (asterisks) is bright on T2 weighted images, with slight non-enhancing layering material dark on T2 weighted images, typical of fluid (arrowhead). Rim enhancement helps demarcate the pseudocyst from the more ventral stomach (arrows).

Figure 5.

Severe necrotising pancreatitis with fluid collection in a 39-year-old male a, Axial; and b, coronal CECT, arterial phase images, show a huge well-defined multi loculated inhomogeneous fluid collection partially containing solid tissue (arrows), which replaces most of the pancreas. The absence of any appreciable enhancement of the remaining pancreatic gland (asterisks) is consistent with necrotising pancreatitis.

Figure 6.

Walled-off necrosis in 63-year-old male 8 weeks after the onset of severe necrotising pancreatitis a, Axial; and b, coronal CT, non-contrast; c, coronal turbo spin-echo T2 weighted (HASTE) image. d, Axial pre-; and e, post-contrast arterial phase; and f, portal venous-phase 3D-GRE T1 weighted images with fat-suppression. There is a sausage-shaped encapsulated mass (arrows) in the pancreatic body and tail. On CT, the collection appears partially fatty and is inhomogeneous consistent with walled-off necrosis (asterisks). There is a patchy, lace-like hypointense area on T2 which is hyperintense on T1 images and does not enhance, consistent with necrotic tissue or haemorrhagic areas (asterisks). The head and neck of the pancreas have been auto-digested and are no longer visible.

Figure 7.

A 63-year-old male who developed infected necrosis following acute pancreatitis a, Axial CECT, arterial phase images; and b, coronal CE-CT, portal venous phase images, show a large, thick-walled, rim-enhancing collection in the pancreatic bed (arrows). Several air bubbles within the fluid collection and a large air-fluid level (arrowhead) are suspicious for an infected necrosis replacing the entire pancreatic gland. Fine-needle aspiration confirmed the diagnosis. Minimal peri-pancreatic stranding is present. Note the stomach ventral to the infected necrosis (asterisk).

Figure 8.

Signs of advanced chronic pancreatitis in two different patients a, Axial; and b, coronal non-enhanced CT in a 17-year-old male. Diffuse parenchymal atrophy and calcification consistent with severe chronic pancreatitis. MRI of a 35-year-old male patient with advanced chronic pancreatitis. c, Axial turbo spin-echo T2 weighted (HASTE) image with fat-suppression shows moderate dilatation and diffuse irregularity of the MPD with a few visible side-ducts (arrows) and atrophy of the pancreatic gland. d, Coronal oblique maximal intensity projection image of a 3D MR cholangiopancreatogram shows generalised irregularity and marked dilatation of the MPD with multiple massively dilated side-branches (arrows), classified as Cambridge 4. e, Pre-contrast axial 3D- GRE T1-weighted image with fat-suppression shows markedly decreased signal intensity of the pancreatic body compared to that of the tail (asterisk). f, Contrast-enhanced, portal venous phase, axial, T1- weighted images show the atrophied pancreas with lobular disappearance and mild MPD dilation, as well as diminished contrast enhancement of the body more than the tail.

Figure 9.

Focal chronic pancreatitis in a 56 year old male mimicking pancreatic cancer. a, Axial non-contrast; and b, axial contrast-enhanced arterial-phase 3D- GRE T₁ weighted images with fat-suppression show a well-circumscribed, 3 cm pancreatic head mass of decreased signal intensity with strong early enhancement (thick arrow). c, Coronal T₂ weighted HASTE image shows the non-obstructed MPD in the pancreatic neck and body (arrow). d, Coronal oblique maximal intensity projection image of a 3D MR cholangiopancreatogram shows that the pancreatic duct is narrowed in the head, but neither obstructed nor dilated. The duct passes through the mass, joining the CBD in the major papilla, the so-called duct penetrating sign (arrow).

Figure 10.

A 46-year-old female with signs of acute pancreatitis exacerbating underlying early-stage chronic pancreatitis a, Non-contrast CT axial shows punctate calcifications within the pancreatic body (arrows). b, CECT, arterial phase, axial shows mild swelling of the gland with a residual lobular pattern and inhomogeneous diminished enhancement (asterisk). c, Coronal oblique thick-slab MR cholangiopancreatogram image eight minutes after administration of secretin (S-MRCP). Mild dilatation of the PD in the tail suggests stenosis or obstruction (arrowheads). d, MRCP repeated four months after ERCP. There is a recurrent short-segment stenosis in the main PD (thick arrow) and mild irregularity along the entire MPD with multiple dilated side-branches, classified as Cambridge 3. e, Pre-contrast axial 3D- GRE T₁ weighted image with fat-suppression shows mild signal intensity decrease with incipient atrophy and early loss of lobulation. f, DWI, b 50, shows increased signal intensity of the pancreas, indicating diffuse oedema from the bout of acute on chronic pancreatitis. DWI, diffusion-weightedimage

Figure 11.

Biopsy-proven groove pancreatitis in a 44-year-old female a, Axial non-contrast; and b, axial contrast-enhanced arterial-phase; and c, portal venous-phase 3D- GRE T1 weighted images with fat-suppression; and d, axial DWI, b-value = 50; and E, axial turbo spin-echo T2 weighted (HASTE) image with fat-suppression. There is mild duodenal thickening and oedema associated with a sheet-like mass in the pancreaticoduodenal groove that extends to the pancreatic head (arrowheads), plus multiple tiny bright cystic lesions in the pancreatico-duodenal groove (arrows) (a). Decreased pancreatic parenchymal T1 signal and diminished enhancement on post-contrast images (d). f, Coronal, oblique, thick-slab MR cholangiopancreatogram image after administration of secretin (S-MRCP) shows normal calibre of the entire MPD (thick arrow) as it goes through the mass (duct penetrating sign), excluding malignancy. MRCP, MRcholangiopancreatography.

Figure 12.

Autoimmune pancreatitis of the pancreatic body and tail in an 83-year-old male. The diagnosis was made at follow-up, by good response to steroid therapy, since repeated biopsies were equivocal. a, Axial non-contrast; and b, axial post-contrast, arterial-phase; and c, portal venous-phase 3D-GRE T₁ weighted images with fat-suppression show marked swelling and loss of lobules and signal intensity in the pancreatic body and tail (asterisk). Moderate enhancement seen with contrast (arrowheads). d, Axial DWI, b 300, with fat-suppression, shows high signal intensity limited to the swollen distal gland (black asterisk). e, Axial non-contrast 3D-GRE T₁ weighted image six weeks after steroid therapy confirms the diagnosis of AIP. There is near-complete resolution of distal pancreatic swelling, with only mild residual decreased signal intensity. DWI, diffusion-weightedimage