Extraluminal Air: Pneumatosis Intestinalis & Pneumobilia

00:01 Let's talk a little bit about pneumatosis intestinalis.

00:04 So what is that? That's really air in the bowel wall and this is a sign of bowel necrosis.

00:10 It can be a sign of bowel necrosis.

00:12 So it can be caused by mucosal damage which is caused by lack of blood flow, such as from a volvulus or a superior mesenteric artery or vein thrombosis.

00:19 It can also be seen post-endoscopy due to muscosal disruption and increased luminal pressure.

00:25 It's occasionally seen in patients with COPD and it's due to alveolar rupture with air dissecting into the mediastinum and then extending to the bowel wall through the diaphragmatic hiatus. So from the chest down into the abdomen.

00:38 And occasionally, it can also be seen with steroids and in patients with autoimmune disease and this is due to increase bowel permeability and decreased immunity resulting in bacterial gas that enters the bowel wall.

00:49 So what are some of the imaging findings of pneumatosis intestinalis? It results in a curvilinear lucency that follows the bowel wall and it can be associated with pneumoperitoneum or pneumoretroperitoneum or it may also be associated with the gas in the portal venous system which often indicates bowel necrosis.

01:07 This is an example here of what pneumatosis intestinalis looks like.

01:13 You can see the arrows pointing to a curvilinear area of air which actually represents air within the loop of bowel, that's here.

01:22 This is an example of the same patient on a CT scan, so this is an axial CT image in the pelvis and it demonstrates multiple curvilinear areas of air all within multiple loops of bowel.

01:36 You can see them kind of scattered all throughout the lower abdomen here.

01:39 Let's move on to pneumobilia. So pneumobilia is air in the biliary system.

01:47 It is linear branching lucencies that are found in the right upper quadrant in the region of the liver.

01:53 What are some causes of pneumobilia? It's often cause by prior biliary intervention that results in chronic air within the biliary system and is usually a very benign incindental finding.

02:05 Other causes include gallstone ileus which is erosion of a gallstone through the gallbladder wall into the duodenum and this results in air from the small bowel entering the gallbladder and the biliary system. It can also be caused by gas forming infection of the biliary system. So when you're seeing pneumobilia, it's important to see whether or not the patient has hide any kind other prior biliary intervention and then you'll know whether this is something that you need to worry about and further work up or rather this is just a benign incidental finding from that prior intervention.

02:35 So how can you differentiate portal venous gas versus pneumobilia? Portal venous gas as we mentioned, most often indicates bowel necrosis and it's usually located more peripherally within the liver.

02:46 Pneumobilia is almost often a benign incidental finding and it's most often located centrally within the liver.

02:53 So as you can see one is a very urgent finding while one is a very benign findings.

02:57 So it's important to be able to differentiate between the two.

03:00 So what is this patient have? We see multiple linear areas of air within the liver.

03:09 So here's liver which I'm outlining and then adjacent to the liver, we actually have a little bit of free fluid within the abdomen.

03:16 You can see that it's a bit slightly lower density than the liver is.

03:19 Here is contrast within the stomach, and then again we have these areas of air within the liver.

03:25 Is this portal venous air or is this biliary air? So this is actually air located peripherally within the liver which indicates that it's portal venous air.

03:41 So this is a patient that needs to be further worked up for possible bowel necrosis.

03:45 So we've reviewed multiple different findings of free air within the abdomen both intraperitoneal and retroperitoneal.

03:54 And we've reviewed the differences between pneumobilia and portal venous gas.