Pancreas (for PBR 2) Flashcards
Two morphologic types of pancreatitis
Interstitial edematous
Acute necrotizing pancreatitis
Imaging finding of interstitial edematous pancreatitis
CE CT:
Localized or diffuse enlargement of the pancreas with normal homogeneous parenchymal
Slightly heterogeneous enhancement due to edema
Mild fat stranding and peripancreatic inflammatory changes may be present with varying fluid volumes of peripancreatic fluid
Acute necrotizing pancreatitis is divided into three forms by CT appearance
- Pancreatic parenchymal necrosis with peripancreatic necrosis
- Peripancreatic necrosis alone
- Pancreatic parenchymal necrosis alone
Most common form of acute necrotizing pancreatitis
Pancreatic parenchymal necrosis with peripancreatic necrosis
Imaging finding of pancreatic parenchymal necrosis with peripancreatic necrosis
Lack of parenchymal enhancement associated with nonliquefied heterogeneous areas of nonenhancement in peripancreatic tissues, most commonly in the lesser sac and retroperitoneum
Pancreatic necrosis is best determined by CT at approximately how many hours following onset of symptoms?
72 hours
Collections associated with interstitial pancreatitis
Initial 4 weeks as nonencapsulated, nonenhancing, low attenuation, liquid collections without solid components
Walls are imperceptible
Acute peripancreatic fluid collections
These are defined as simple collections with perceptible walls seen after 4 weeks
Pseudocyst
Collections associated with necrotizing pancreatitis seen in the first 4 weeks
Acute necrotizing collections
Heterogeneous collections containing hemorrhage, fat, or necrotic fat within or surrounding necrotic pancreatic parenchyma
An enhancing wall may develop around an acute necrotic collection and seen after 4 weeks -
What is the term of the collection?
Walled-off necrosis
WONs appear heterogeneous in attenuation and complex because of variable necrotic tissues and debris
This is caused by recurrent and prolonged bouts of acute pancreatitis that cause parenchymal atrophy and progressive fibrosis
Chronic pancreatitis
Both exocrine and endocrine function of the pancreas may be impaired
Most common cause of chronic pancreatitis
Alcohol abuse (70%)
Biliary stone disease (20%)
Morphologic changes and imaging findings of chronic pancreatitis
- Dilation of the pancreatic duct (usually in a beaded pattern of alternating areas of dilation and constriction)
- Decrease in visible pancreatic tissue because of atrophy
- Calcifications (finely stippled to coarse)
- Focal-mass-like enlargement of the pancreas (owing to benign inflammation and fibrosis)
- Stricture of the bile duct (because of fibrosis or mass in the pancreatic head resulting in proximal bile duct dilation)
- Fascial thickening and chronic inflammatory changes in surrounding tissues
Also known as lymphoplasmacytic sclerosing pancreatitis
Unique form of pancreatitis caused by autoimmune disease associated with elevation of IgG4
Autoimmune pancreatitis
Extrapancreatic manifestations of autoimmune pancreatitis
Inflammatory bowel disease (ulcerative colitis)
Long segment bile duct strictures
Lung nodules
Lymphadenopathy
Lymphocytic infiltrates in the liver and kidneys
Retroperitoneal fibrosis
Sjogren syndrome
Findings that favor diagnosis of autoimmune pancreatitis over adenocarcinoma
- Diffuse or focal swelling of the pancreas with characteristic halo of edema
- Extensive peripancreatic stranding and edema are absent
- Diffuse or segmental narrowing of the pancreatic duct and/or the common bile duct
- Absence of dilation of the pancreatic duct and absence of parenchymal atrophy proximal to the pancreatic mass (theses findings are typically present with adenocarcinima)
- Fluid collections and parenchymal calcifications are typically absent
- Peripancreatic blood vessels are usually not involved
- Kidneys are involved in 1/3 of cases (round-wedge-like , or diffuse peripheral patchy areas of decreased contrast enhancement)
This is an uncommon form of pancreatitis that may also mimic adenocarcinoma
Fibrosis in the groove between the head of the pancreas, the descending duodenum, and the common bile duct produces an inflammatory mass that obstructs the common bile duct
Groove pancreatitis
Characteristic finding of groove pancreatitis
- Sheet-like mass in the pancreaticoduodenal groove
- Atrophy and fibrotic changes in the pancreatic head
- Small cysts along the wall of the duodenum
- Duodenal wall thickening and luminal narrowing
- Tapering stenosis of the common bile and pancreatic ducts
- Widening of the space between the distal ducts and the wall of the duodenum (rarely seen with adenocarcinoma)
- Enhancement is delayed but progressive
Signs of resectability of pancreatic adenocarcinoma
- Isolated pancreatic mass with or without dilation of the bile or pancreatic ducts
- No extrapancreatic disease
- No encasement of celiac axis or SMA
Signs of potential resectability
- Absence of involvement of the celiac axis or SMA
- Occlusion of the superior mesenteric or portal vein without a technical option for reconstruction
- Liver, peritoneal, lung, or any other distant metastases
Evidence of arterial encasement that indicates unresectability
- Tumor abutting >180 degrees of the circumference of the artery
- Tumor abutment focally narrowing the artery
- Occlusion of the artery by tumor
These tumors may be functioning producing hormones resulting in distinct clinical syndromes, or may be nonfunctional and grow to large size before presenting clinically
Neuroendocrine (islet cell) tumors
Different types of neuroendocrine (islet cell) tumors
Insulinomas Gastrinomas Glucagonoma Somatostatinoma VIPoma
80% of nonfunctioning tumors are:
a. benign
b. malignant
Malignant
Imaging findings of nonfunctioning neuroendocrine tumors
Coarse calcifications Cystic degeneration Necrosis Local and vascular invasion Metastases
CT scan finding of lymphoma
Homogeneous, of lower attenuation than muscle, and show limited enhancement
Lesions can be localized, well-defined mass, or be infiltrating diffusely enlarging or replacing gland
Attenuation may be so lows as to appear cystic
Types of fatty lesions of the pancreas
Diffuse fatty infiltration (associated with aging and obesity and is seen with pancreatic atrophy)
Focal fatty infiltration (between the lobules of pancreatic parenchyma)
Focal fatty sparing (in diffuse infiltration may simulate a pancreatic mass, especially when it involves the head or uncinate process
Lipoma
Most common pancreatic cystic lesions
Pancreatitis-associated fluid collections
Findings of pancreatitis-associated fluid collections
- Fluid-density unilocular cyst
(associated with findings of acute or chronic pancreatitis) - Complex cystic mass
(with internal hemorrhage, infection, or gas) - Most are round or oval with a thin or thick wall that may enhance
(however, cyst contents do not enhance) - Septations and lobulated contours (unusual and more often associated with serous cystadenoma)
- Some lesions may be infected showing the presence of gas and debris within the lesion
- Serial imaging usually shows involution of noninfected collections
What are the three major appearances of serous cystadenomas
- Honeycomb microcyst (microcystic adenoma) with innumerable cysts 1 mm to 2 cm size - MOST COMMON
- Macroscropic form with larger cysts
- Innumberable tiny cysts
Lesions do not communicate with the pancreatic duct
Classification of cystic mucinous neoplasms of the pancreas
Papillary mucinous neoplasm
Mucinous cystic neoplasm
In cystic mucinous neoplasms:
“Worrisome features”
- Cysts >3 cm diameter
- Enhancing thickened cyst walls
- Main pancreatic duct diameter 5 to 9 mm
- Mural nodules without enhancement
- Abrupt narrowing of main pancreatic duct w/ proximal atrophy of pancreatic parenchyma
- Regional lymphadenopathy
In cystic mucinous neoplasms:
“High-risk stigmata”
- CBD obstruction w/ jaundice associated w/ cystic tumor in pancreatic head
- Enhancement of solid components
- Main pancreatic duct >10 mm
Intraductal papillary mucinous neoplasms are classified into 3 morphologic types
Branch duct (BD-IPMN) Main duct (MD-IPMN) Mixed type
Type of IPMN :
Most common in the uncinate process arising in branches of the main pancreatic duct to form grape-like collections of small cysts (5- to 20-mm diameter) that communicate with the ductal system
Branch duct - IPMN
Some lesions consist of a single unilocular cyst
Cyst have thin walls w/ flat or papillary lining that produces tenacious mucin
Invasive carcinoma - 17%
Type of IPMN :
This is characterized by diffuse or segmental dilation of the main pancreatic duct >5-mm diameter without evidence of other causes of obstruction
Main duct - IPMN
Diffusely or partially dilated, tortuous and irregular, main pancreatic duct is filled with mucin produced by tumor cells
Presence of ovarian stroma in addition to mucin-producing epithelial tumor cells is specific to this pancreatic tumor
Occurs nearly always in women
Do not arise from or communicate with the pancreatic duct
Mucinous cystic neoplasm
Imaging finding of mucinous cystic neoplasm
- Cystic lesion larger than 2 cm nearly always in the pancreatic tail
- Tumors are multilocular with a few compartments or uncommonly unilocular
- Papillary projections of solid tumor are common
- Peripheral eggshell calcification - uncommon but highly specific finding
This is a rare low-grade pancreatic malignancy that presents as a large encapsulated mass with a mixture of fluid, hemorrhagic, necrotic, and solid components
It is not truly papillary or cystic
Solid pseudopapillary tumor
Pseudopapillae are formed by layers of epithelial cells that cover a fibrovascular core
Imaging finding of a solid pseudopapillary tumor
CT shows a heterogeneous well-encapsulated tumor with variable cystic and solid components
Solid areas, usually in the periphery, enhance
Peripheral calcifications may be present
Cystic change in neuroendocrine tumors are a result of what process?
Tumor degeneration
Cystic change in adenocarcinoma is the result of what process?
Necrosis, hemorrhage, or formation of pseudocysts adjacent to the neoplasm
