Case e -  Pancreatitis with multiple complications

This is a complicated case with many findings. 

First the chronic findings.  The patient has had prior surgery.  Can you tell which type?  There are clips at the expected location of the gastric pylorus but the distal stomach is not present.  The proximal jejunum has been brought superiorly and attached to the proximal stomach in a side to side manner.  This is a Bilroth II subtotal gastrectomy and gastrojejunostomy.  This surgery was discussed earlier.  Review the schematic and make sure you can identify the gastrojejunostomy.  Follow both the afferent and efferent loops.

There is some fluid around the body of the pancereas, which appears full, suggesting pancreatitis.  There is fluid surrounding the gall bladder which is collapsed.   This surrounding fluids is probably pericholecystic fluid but could represent gall bladder wall edema since it is extends to the gall bladder neck. Pericholecystic fluid ususally remains confined to the space between the gall bladder and the liver.  Notice how the gall bladder mucosa enhances.  This combination of findings might make you suspicious for cholecystitis.  However, the gall bladder is tensely distended in acute cholecystitis.  This gall bladder is collapsed.  There are multiple loculated fluid collections in the abdomen:  two in the left upper quadrant, one along the posterior aspect of the stomach, and one in the lesser sac.  Scroll through these areas to see their complex interconnections.  Within or adjacent to the lesser sac collection is an ovoid area of enhancement!  This is a pseudoaneurysm.  Lastly, there is a filling defect in the portal vein.

Now to discuss these findings one at a time.

First we will discuss the pseudoaneurysm.  Pseudoaneurysms are seen as complications of pancreatitis, trauma, and vascular interventions.  They mirror the density of arteries on all scans and usually have smooth rounded contours.  Here I am only showing the portal venous phase because this is what you see on routine ER scans.  Active arterial bleeding secondary to trauma also appears as a region of extravascular enhancement mirroring the density of contrast in the arteries.  So how do you tell them apart?  This is very important.  Active extravasation bleeds into a surrounding hematoma (the blood has to go somewhere) and on delayed scans the contrast dissipates into the hematoma.  On even more delayed scans the hematoma will increase in size.  A pseudoaneurysm is not surrounded by hematoma.  In this case the paeudoaneurysm is surrounded by a small low density collection.  Acute hematomas are higher density with HU > 30.  Also, pseudoaneurysms usually have a smooth round or ovoid shape.  If you scroll up and down through the pseudoaneurysm you can see a small feeding vessel.  This can be connectected to the left gastric artery.  A coronal MIP shows this.  A selective left gastric angiogram confirms the finding.  Injections of the splenic, hepatic, and superior mesenteric arteries were normal.  Compare the schematics for a pseudoaneurysm and for active arterial extravasation.

The three fluid collections (1, 2, 3) probably represent pseudocysts.  Pseudocysts are loculated fluid collections that persist six weeks after the onset of acute pancreatitis.  They ususally have relatively thin, enhancing walls and can appear anywhere in the abdomen.  Review of this patient's history showed multiple prior episodes of pancreatitis so the 6 week criteria is met.  It is possible that these collections are post-operative from the Bilroth II gastrectomy.  You have to take my word for it that the surgery was 20+ years ago and older scans show that these collections are relatively new. What is the clinical significance of pseudocysts?  Most resorb without intervention.  Some become infected and are a chronic source of bacteremia.  You can imagine the frustration of constantly draining multiple collections, never knowing which one is infected.  Surgical treatment includes resection or anastamosis of the pseudocyst to the jejunum or pancreatic duct.

The filling defect within the portal vein is characteristic of a portal vein thrombosis.  Note that the thrombosis is not occlusive, i.e. contrast passes around and distal to the clot.  An acute venous thrombosis is usually more hypodense than the thrombus in this example.  Acute thromboses also expand the vessel.  This portal vein is nonexpanded and the thrombus is probably subacute to chronic.  This appearance could be mistaken for a mixing artifact.  However, all the feeding veins are well opacified (SMV, splenic vein) so mixing cannot be the explanation. 

This case has all three major complications of pancreatits:  venous thrombosis, pseudoaneurysm, and pseudocyst.

Notice the nice cortical phase of enhancement in the kidneys.