Pancreatic Lesions Part 1

Review of pancreatic lesions for radiology board exams. After part 2 is posted, a free study guide on this topic will be available at theradiologyreview.com. Prepare to succeed!

Show Notes/Study Guide:

Within what timeframe are post-pancreatitis fluid collections considered acute?

Peripancreatic fluid collections are considered to be acute for 4 weeks following pancreatitis. 

What are some basic differences between an acute necrotic collection and an acute peripancreatic fluid collection? 

An acute necrotic collection is a non-encapsulated collection of heterogeneous though non-liquified material within 4 weeks following necrotizing pancreatitis.

An acute peripancreatic fluid collection is a non-encapsulated fluid collection within 4 weeks following non-necrotizing interstitial edematous pancreatitis.

Note that acute peripancreatic fluid collections classically have no well-defined wall on CT and often resolve spontaneously.

If an acute peripancreatic fluid collection persists longer than 4 weeks and becomes encapsulated, this fluid collection is termed what?

A pancreatic pseudocyst. 

If an acute necrotic collection persists beyond 4 weeks and becomes encapsulated, what is this termed?

Walled-off necrosis.

True or False: Pancreatic infected necrosis has a high mortality rate?

True.  The most common cause of death in patients with acute pancreatitis is infected necrosis.  Pancreatic abscesses may be found in the acute setting or greater than 4 weeks following pancreatitis. If you see air contained within the pancreatic fluid collection that will often be thick-walled pancreatic abscess/infected necrosis is a diagnostic consideration. One reason why you may wait to see if an acute pancreatic fluid collection or an acute necrotic collection resolve on their own is that percutaneous or surgical drainage have a high risk of introducing infection which should be avoided. 

What are some common causes of splenic vein thrombosis?

Common causes of splenic vein thrombosis include acute and chronic pancreatitis, pancreatic malignancy, aneurysms of the celiac and/or splenic arteries, and retroperitoneal fibrosis.  Note also that pancreatitis can cause pseudoaneurysms of the pancreaticoduodenal artery which are often treated with coil embolization by interventional radiology.  Note that splenic vein thrombosis can lead to gastric varices.  Therefore, pancreatitis can indirectly cause gastric varices by means of first causing splenic vein thrombosis.

What are some of the classic features of a mucinous cystic pancreatic tumor?

A mucinous cystic pancreatic tumor is a low-grade but potentially malignant tumor that is classically found in middle-aged women.  These are loculated, often large thick-walled cystic masses most commonly arising from the pancreatic tail.  Mural nodules and papillary projections may be present.

What is the mechanism by which afferent loop syndrome can cause pancreatitis?

In afferent loop syndrome, you often see a closed-loop bowel obstruction and this causes obstruction of biliary and pancreatic drainage from dilation of the afferent limb post-billroth 2, which can cause pancreatitis.

True or False: Ectopic pancreatic rests can cause a small bowel target sign?

True.  Other causes of the small bowel target sign can be GISTs, lymphoma, melanoma, and primary bowel adenocarcinoma.  If there are multiple small bowel target signs, think lymphoma or melanoma metastatic disease first.

On MRI, what is the expected normal T1 signal of the pancreas?

The pancreas should be extremely bright on T1-weighted MRI due to the high enzyme content of the pancreas. 

If a patient presents with painless jaundice what are common tumors that can cause this presentation?

Cholangiocarcinoma and pancreatic adenocarcinoma. 

Which of these involves the pancreas: primary or secondary hemochromatosis?

Primary hemochromatosis involves the pancreas and spares the spleen and is an inherited disease that causes increased iron absorption.

Secondary hemochromatosis results from multiple transfusions and/or chronic inflammation and classically involves the spleen and spares the pancreas. 

Both primary and secondary hemochromatosis involve the liver. 

What is “bronze diabetes”?

This is when the pancreas becomes sufficiently damaged from primary hemochromatosis that the patient develops diabetes. 

What are different types of annular pancreas?

Annular pancreas occurs when the ventral pancreatic bud does not adequately rotate with the duodenum during development, causing duodenal encasement.  This can be complete or incomplete and extramural or intramural.  Complete means there is complete encasement of the duodenum. Extramural has pancreatic tissue from the ventral bud that drains into the main pancreatic duct.  Intramural has pancreatic tissue from the ventral bud draining via its own small ducts into the duodenum.  Complications from annular pancreas can include duodenal obstruction and pancreatitis.

What are some common features of pancreatic divisum?

Pancreatic divisum occurs when the drainage of the pancreas into the duodenum is split or divided, hence “divisum”.  This is the result of failure of the dorsal and ventral pancreatic anlages to fuse. With pancreatic divisum the main drainage of the pancreas occurs through the dorsal pancreatic duct through the minor or accessary papilla which is more superiorly located and small compared to drainage through the major papilla.  This potentially predisposes to development of pancreatitis. Treatment is usually conservative but if severe symptoms like recurrent pancreatitis develop and for treatment the minor papilla can be dilated or stented. 

True or False: Dorsal pancreatic agenesis is associated with polysplenia?

True.  There is also a risk for diabetes due to beta cell loss in the pancreatic tail.

What are key features of autoimmune pancreatitis?

Autoimmune pancreatitis has an IgG4 association with classic imaging appearance of a sausage shaped pancreas. Clinical presentation, unlike other forms of pancreatitis, is not often associated with an acute onset of inflammation and abdominal pain but rather things like jaundice, new onset diabetes, weight loss and other autoimmune diseases such as inflammatory bowel disease.  Importantly, this disease can regress with steroid treatment.  Laboratory testing often shows elevated IgG and antinuclear antibody levels.

What are key features of paraduodenal aka groove pancreatitis?

This is a chronic pancreatitis affecting the space “groove” between the pancreatic head, duodenum, and common bile duct.  Classic history is that of a middle aged male with chronic alcohol abuse.  Classic symptoms are recurrent episodes of upper abdominal pain, nausea, and vomiting secondary to marked duodenal stenosis and reduced duodenal motility that is worse after fatty meals.  The etiology is fibrosis and scar tissue within the pancreaticoduodenal groove and space superior to the pancreatic head with scarring and fibrosis also involving the duodenal wall causing stenosis of the duodenum. On imaging look for thickening of the duodenal wall which may have some associated cystic changes and a sheet like mass between the pancreatic head and duodenum.