Slide 1

Bowel wall thickening CT-pattern

Dr. Bhishm SevendraBaroda Medical college,gujarat Radiology assistant Radiopaedia

Important features to look for are:

Length of bowel wall involvement

< 5 -10cm involvement.

Adenocarcinoma: usually presents as a short segment of bowel wall thickening. The borders are shouldering unlike in diverticulitis, where the borders are tapering .

Adeno-carcinomaDiverticulitis

10-30 cm involvement:

Ischemia. Submucosal hemorrhage. Radiation. Crohns disease. Infection. Lymphoma.

Diffuse involvement:

Entire colon is involved in ulcerative colitis.

Involvement of both the colon and the small bowel is seen in infectious bowel disease (IBD), edema and SLE.

Enhancement pattern

Type 1 - White Attenuation.

Acute IBD. Shock bowel. Reperfusion after ischemia. Hemorrhage.

Acute IBD

Bright enhancementof the large segment of bowel wall is seen due to vasodilatation in acute inflammatory bowel disease.

Shock Bowel

In patients with a hypovolemic shock, there is a redistribution of the blood flow.

Hypoperfusion results in injury to intramural vessels & increased permeability and increased enhancement.

The slit-like inferior vena cava is seen in hypovolemia.

Hyper enhancing adrenal glands in seen as a result of redistribution of blood flow to adrenal gland, to produce adrenaline in order to manage the shock.

Normal bowel wall enhancement.

The normal bowel will enhance bright especially if the scan is in the late arterial phase, 35-40 seconds post injection.

If the bowel wall is not thickened, this is normal enhancement.

Type 2 - Gray Attenuation

The bowel wall is thick and despite a nice bolus of contrast there is poor enhancement and differentiation of layers of the bowel wall is lost.

This pattern is seen in, ischemia and neoplasm like Adenocarcinoma ,lymphoma and chronic fibrotic Crohn's disease

Mesenteric Ischemia

Bowel ischemia frequently affects the colon and is more frequently seen in the splenic flexure.

It is mostly due to a low flow state like hypovolemic shock or congestive heart failure.

Other causes are superior mesentric artery thrombus & mid gut volvulus.

Ischemia of a large segment of the small bowel due to a closed loop obstruction

An important appearance of a closed loop obstruction is that of a radial array of dilated small bowel loops with the mesenteric vessels converging to a central point.

Tumors

The gray enhancement pattern with loss of differentiation of the layers of the bowel wall can be seen in various tumors like Adenocarcinoma, metastases,lymphoma and GIST.

Type 3 - Water target sign

The most common type of enhancement is the target sign with water density.

The target sign is caused by the enhancing mucosa and muscularis propria with the edematous submucosa in between.

Infection: shigella, salmonella, peudomembranous colitis.

Portal hypertension.

Acute ulcerative colitis & crohns. Typhlitis. AIDS. Ischemia.

Pseudomembranous Colitis

Caused by the bacterium Clostridium difficile due to bacterial overgrowth of the colon in patients who are treated with broad-spectrum antibiotics.

Portal hypertension

Portal hypertension is another cause of the water target sign.

When patient has portal hypertension, the increased pressure is transmitted to the right colon.

This leads to the generation of inflammatory mediators and increased production of nitrous oxide, which induces tissue injury.This produces an isolated right sided colitis.

Type 4 - Fat target sign

Submucosal fat is seen in patients with chronic ulcerative colitis and Crohn's, celiac disease & in obese pt.

In obese patients ,it is seen especially in the. transverse and descending colon

Patients with Crohn's disease have Submucosal fat in the terminal ileum and ascending colon.

if there is isolated fat in the duodenum or in the proximal jejunum, that is very suspicious of celiac disease.

Celiac disease patients also have more pronounced folds in the ileum compared to the jejunum, which is the opposite of the normal finding.

The faeces in celiac ds patients may contain more fat.

CRONIC ULCERATIVE COLITIS

Celiac disease

Type 5 - Gas Pneumatosis

The most concerning pattern is gas within the bowel wall.

Pneumatosis intestinalis is seen in life-threatening situations in patients with ischemia and impending bowel perforation & need immediate therapy.

Portal venous gas

Patient in whom there is no doubt about the diagnosis of pneumatosis intestinalis.

Identifying gas within the mesenteric or portal veins is diagnostic of pneumatosis.

Differentiate it from pneumobilia

Sometimes an air-fluid level can be seen in the portal vein.

Portal venous gas is located peripherally in the liver as opposed to pneumo-bilia which is usually more centrally located.

Pseudopneumatosis

Gas adjacent to the bowel wall can mimick pneumatosis.

Specially in the cecum and ascending colonic gas bubbles can be trapped between fecal debris and the mucosa.

The linear arrangement of the gas bubbles makes it suspective of pneumatosis.

In these cases you have to carefully study all the images and use different window settings.

Give special attention to the non-dependent bowel wall, where there is no feces in contact with the mucosa.

Degree of mural thickening

The benign diseases that cause the largest bowel wall thickening are Crohn's disease and Pseudomembranous colitis (PMC) (3cm).

Mesenteric abnormalities

Patency of the mesenteric vessels

Mesenteric changes:

enlarged lymph-nodesedema and engorgement of vessels

Mesenteric edema

Mesenteric edema in association with bowel wall thickening is seen in:

IschemiaInflammatory bowel disease, especially Crohn's disease

Lumen contents

Blood in the lumen indicates gastrointestinal hemorrhage.

Fat in the colonic lumen sometimes seen in celiac disease.

Thank You