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Some etiologies
- Alcohol, cholelithiasis, trauma, iatrogenic, hyperlipidemia, hypercalcemia, viral infections (CMV, mumps), drugs, idiopathic
Clinical diagnosis
Needs at least 2 of the 3 below:
- Abdomen pain strongly pointing to acute pancreatitis
- Serum amylase and or lipase at least 3 times upper limit
- Characteristic imaging findings
Revised Atlanta Classification (2008)
Two morphological types: interstitial edematous and necrotising pancreatitis
Edematous pancreatitis
- Edema and swelling of gland, no necrosis
- Seen in 70-80% of pancreatitis
- US usually normal, or mildly hypoechoic gland
- Mild peripancreatic fluid may be seen
Necrotising pancreatitis
- Cell death and fat necrosis
- Necrosis determines morbidity and mortality
- US is poor in detecting necrosis
Clinical grading using Ranson’s, APACHE-II, BISAP score
Modified CT severity index currently used which has better correlation with clinical outcome. CT scoring system DOES NOT supersede clinical scoring systems.
| Prognostic indicator | Points |
| Pancreatic inflammation | |
| Normal pancreas | 0 |
| Intrinsic pancreatic abnormalities with or without inflammatory changes in peripancreatic fat | 2 |
| Pancreatic or peripancreatic fluid collection or peripancreatic fat necrosis | 4 |
| Pancreatic necrosis | |
| None | 0 |
| <30% of parenchyma | 2 |
| >30% of parenchyma | 4 |
| Extra pancreatic complications (>1 of pleural effusion, ascites, vascular or parenchymal complications, GI tract involvement) | 2 |
| Classification of disease severity | Points (sum) |
| Mild | 0-2 |
| Moderate | 4-6 |
| Severe | 8-10 |
- Ultrasound usually suffices in mild pancreatitis
- Contrast enhanced ultrasound is the pillar of suspected or confirmed acute pancreatitis
- CT in first 24 hours will not pick any necrosis. Necrosis is evident after 48-72 hours
- Single venous phase study with contrast injected at 4ml / sec with fixed delay of 70s is sufficient. Unenhanced and arterial phase imaging not necessary
- MRCP has a role in biliary pancreatitis and quite often can help avoid doing an ERCP pre operatively. ERCPs are a difficult thing to do especially during pancreatitis. MRCP has a 100% negative predictive value for biliary tree stones
Imaging in acute pancreatitis
Interstital edematous pancreatitis
- Streaking of perpipancreatic fat
- Mild swollen appearance of gland
- Peripancreatic fluid is called acute peripancreatic fluid collections (APFC): seen next to pancreas, no solid material, no discernible wall.
- Pseudocyst: >4 weeks since diagnosis. Seen in 20% of patients. Low attenuation content with enhancing fibrous capsule. Fluid is rich in amylase and lipase with no solid debris. Pseudocysts extend into pancreatic parenchyma only when there is pancreatic trauma and duct rupture. 70% of cysts resolve spontaneously. Sometimes can rupture, get infected or bleed. In such instances, do a percutaneous drain.
Necrotising pancreatitis
- Classified into 3 types:
- Pancreatic and peri pancreatic necrosis (80%) of cases
- Peri pancreatic necrosis alone
- Pancreatic necrosis alone
- Peripancreatic necrosis alone has a better prognosis
- Acute necrotic collection (ANC): necrotic glandular tissue, seen as area of non enhancement. Contains necrotic parenchyma and fat fluid debris.
- Two CT features pointing to mortality: necrosis of >1 part (head/body/tail). Distal fluid collections (posterior para renal space or paracolic gutter)
Walled-off necrosis
- Mature ANC after 4 weeks
- Thick wall between necrosis and adjacent tissue
- Can involve parenchyma, peripancreas or peripancreas fat
- Contains non-liquefied material
- May get infected: gas bubbles within favor infection
- Infected necrosis responsible for 80% mortality
- Necrosectomy should be reserved for patients with concomitant complications. Surgical removal is associated with more morbidity than conservative management
Complications
- Infected necrosis vs an abscess: difficult to distinguish both by imaging. Use clinical markers to make the distinction.
- Splenic vein thrombosis
- Splenic infarct or hemorrhage
- Splenic or gastroduodenal artery pseudoaneurysm
- Direct extension of inflammation to stomach or duodenum
- Bowel extension: edema, necrosis or perforation
- Vascular complication can lead to bowel ischemia