Pancreatitis
Review of pancreatitis for radiology board exams. Download the free study guide on this episode by clicking here.
Show Notes/Study Guide:
What are classic causes of pancreatitis to remember for radiology board exams?
A useful mnemonic for remembering causes of pancreatitis is "I GET SMASHED", with the first four letters—Idiopathic, Gallstones, Ethanol, Trauma—representing the most common causes. The full mnemonic includes:
· I: Idiopathic
· G: Gallstones, Genetic (e.g., cystic fibrosis)
· E: Ethanol (alcohol)
· T: Trauma
· S: Steroids
· M: Mumps (and other infections), Malignancy
· A: Autoimmune
· S: Scorpion stings/Spider bites
· H: Hyperlipidemia, Hypercalcemia, Hyperparathyroidism
· E: ERCP
· D: Drugs (e.g., tetracyclines, furosemide, azathioprine, thiazides)
What are classic complications of acute pancreatitis to remember for board exams?
Complications of acute pancreatitis are classified based on the presence or absence of necrosis. In cases without necrosis (interstitial edematous pancreatitis), early complications include acute peripancreatic fluid collections (APFCs), which occur within the first four weeks, and pseudocysts, which are encapsulated fluid collections that develop after four weeks. When necrosis is present (necrotizing pancreatitis), acute necrotic collections (ANCs) may form within the first four weeks, while walled-off necrosis (WON) refers to encapsulated collections that appear after four weeks.
Necrotizing pancreatitis may involve liquefactive necrosis of pancreatic tissue, leading to increased morbidity and mortality, especially if secondarily infected, such as in emphysematous pancreatitis.
Vascular complications include hemorrhage from vessel erosion, pseudoaneurysm formation due to autodigestion of arterial walls by pancreatic enzymes, splenic and/or portal vein thrombosis.
Additional complications include fistula formation with pancreatic ascites due to leakage of pancreatic enzymes into the peritoneal cavity, abdominal compartment syndrome, and progression to chronic pancreatitis.
What are some potential CT findings in acute pancreatitis?
CT findings in acute pancreatitis can include diffuse pancreatic enlargement and peripancreatic edema. In milder cases, the pancreatic parenchyma may enhance uniformly without evidence of necrosis. In more advanced cases necrosis and the various complications described above may be present.
How is the severity of acute pancreatitis on CT often graded?
Severity grading of acute pancreatitis on CT can be done using the Balthazar grading system and the CT severity index.
CTSI (Computed Tomography Severity Index) Summary:
CTSI = Balthazar score (0–4) + Pancreatic necrosis score (0–6)
Total score range: 0–10
· Balthazar Score:
o A: Normal pancreas – 0
o B: Enlarged pancreas – 1
o C: Inflammation in pancreas/peripancreatic fat – 2
o D: One fluid collection – 3
o E: Two or more fluid collections – 4
· Pancreatic Necrosis:
o None – 0
o ≤30% – 2
o 30–50% – 4
o 50% – 6
How does pancreatic necrosis appear on CT? When is the optimal time to evaluate for it?
Pancreatic necrosis on CT appears as a focal or diffuse area of nonenhancing pancreatic parenchyma. Evaluation of necrosis is best performed 48–72 hours after onset, and late arterial phase imaging has the highest sensitivity for detection.
What are common complications of acute pancreatitis that can be visualized on CT?
Fluid collections are a common complication. Peripancreatic fluid may resolve or evolve into a peripancreatic abscess or pseudocyst.
How does a pancreatic pseudocyst appear on CT? How long does it typically take to mature?
A pancreatic pseudocyst on CT is a collection of pancreatic enzymes and fluid enclosed by a fibrous wall, which usually takes 4-6 weeks to mature.
How does a pancreatic abscess appear on CT, and what is a key feature that may help differentiate it from a pseudocyst?
A pancreatic abscess on CT is a purulent collection featuring thicker, more irregular walls compared to a pseudocyst. Gas locules may be present within the abscess.
What are some potential findings of acute pancreatitis on ultrasound? How does the echogenicity of the inflamed pancreas compare to the liver?
On ultrasound, the pancreas may appear diffusely enlarged and relatively hypoechoic due to edema in acute pancreatitis. Notably, on ultrasound, an inflamed pancreas will be hypoechoic (edematous) when compared to the liver (opposite of normal).
What is the general utility of ultrasound in evaluating complications of acute pancreatitis like necrosis or fluid collections? How well can it detect a pseudocyst?
Ultrasound has limited utility in evaluating complications of pancreatitis such as pancreatic necrosis or peripancreatic fluid collections. However, a pancreatic pseudocyst is usually detectable by ultrasound. Its primary use is to identify gallstones as a potential underlying cause. It is also valuable in diagnosing vascular complications, such as thrombosis. Ultrasound can sometimes help detect areas of pancreatic necrosis, which appear as hypoechoic regions. Beyond pancreatitis, it assists in assessing other conditions that may present similarly to an acute abdomen, helping to narrow the differential diagnosis.
What is a normal finding for the pancreas on T1-weighted MRI, and how might this be altered in acute pancreatitis?
Normally, the pancreas should be extremely bright on T1-weighted MRI due to its high enzyme content. In acute pancreatitis, there might be reduction in intrinsic pancreatic T1 signal intensity. Diffusion-weighted imaging typically reveals hyperintense signal in affected pancreatic tissue, along with reduced ADC values.
What are key imaging findings of chronic pancreatitis?
Dilation and beading of the pancreatic duct with calcifications are characteristic findings of chronic pancreatitis.
What finding on imaging is considered pathognomonic for chronic pancreatitis?
Calcifications in the distribution of the pancreatic duct are pathognomonic for chronic pancreatitis. These can be seen on abdominal radiographs and CT.
How might the pancreas appear on ultrasound in chronic pancreatitis? What ductal changes and other features might be seen?
On ultrasound, the classic appearance of chronic pancreatitis is an atrophied gland, with diffuse calcifications and a dilated and beaded distal pancreatic duct. Calculi within the pancreatic duct may also be seen.
What vascular complication can be associated with both acute and chronic pancreatitis?
Splenic vein thrombosis is a potential complication of both acute and chronic pancreatitis.
What is a typical imaging appearance of autoimmune pancreatitis on contrast-enhanced CT and T1-weighted MRI?
Autoimmune pancreatitis can have a segmental region of low attenuation enlargement on contrast-enhanced CT, with loss of normal ductal architecture. T1-weighted unenhanced MRI may show a corresponding segmental loss of the normal T1-hyperintense pancreatic signal. The typical appearance is diffuse “sausage-shaped” enlargement of the entire pancreas.
What are typical imaging findings in groove pancreatitis?
Groove pancreatitis may show thickening of the duodenal wall with cystic changes and a sheet-like mass between the pancreatic head and duodenum on imaging.