Case 19 - Introduction to pancreatitis

The head of the pancreas is larger than the body and tail.  There is fatty stranding around the head of the pancreas making its margins fuzzy and blurry.  Since the pancreas has no serosa the abdominal fat normally insinuates with pancreatic tissue.  When this fat is inflamed, you lose the sharp margins of the pancreatic tissue.  Most importantly, however, there is thickening of Gerota's fascia (the anterior perirenal fascia) bilaterally.  The pancreas lies in the anterior pararenal space, anterior to Gerota's fascia.  When it becomes inflamed enzymaytic juices leak into the pararenal space and track along the fascia.  Inflammation can also track into the pericholecystic space.  It is important to notice that the inflammation is not centered on the gall bladder.  This helps you differentiate this from cholecystitis.  Stranding can also track into the root of the mesentery along the SMA and SMV.  It does not do so in this case.

Pancreatitis is diagnosed on CT by an enlarged or "full" appearing pancreas.  In this case the changes are focal.  In other cases the entire gland is enlarged.  Stranding along Gerota's fascia is an early finding.  In bad cases there is also stranding in the lesser sac. 

By the time you get to look at the scan the patient's blood test results have usually returned from the lab.  Changes on CT lag behind an elevated amylase and lipase.  Thus, the pancreas can appear normal in early or mild pancreatitis.  You can occasionally identify an offending CBD stone in the head of the pancreas.  The duct should be fluid density.  A soft tissue density within the duct suggests a stone.  Most gall stones are not calcified.  In this case the duct appears enlarged but no soft tissue densities are seen within.

Pancreatitis CTs can be performed with and without contrast.  The non-contrast scan allows you to look for calcifications in the gland that would suggest chronic pancreatitis.  You need the contrast enhanced scans to look for the complications of pancreatitis which are dicusses in a separate case.

Did you notice the hypoattenuating lesion in the liver.  Without contrast it is impossible to characterize.  This could be a cyst, hemangioma, or tumor.

Take home points

• Pancreatic edema and peripancreatic stranding is indicates pancreatitis.
• CT appearance can lag behind symptoms and elevated pancreas enzymes.
• Inflammation will track along Gerota's, into the lesser sac, into the porta hepatis, and into the root of the mesentery.