GI Radiology > Small Bowel > Anatomy > Pattern Analysis

Anatomy

Pattern Analysis

In pattern analysis, evaluation of an abnormality (after deciding that one is present) is characterizing it. Patterns that should be assessed when evaluating the small bowel include:

1.      Location of the abnormality

 In the broadest sense, diseases can be divided into two categories: diffuse or focal. Diffuse diseases include those that affect all or a large portion of the small bowel (i.e. small bowel obstruction) or represent multiple abnormalities (i.e. metastatic disease). Focal diseases, on the other hand, represent solitary abnormalities. This should immediately narrow down your differential diagnosis. For example, primary malignancies of the small bowel are usually solitary, but metastatic lesions are most often multiple. Therefore, if you see multiple masses on a small bowel follow-through, you should think of metastatic disease before you think of primary neoplasm such as leiomyoma.

In addition, the location of an abnormality (i.e. duodenum vs. jejunum vs. ileum) is important. Most abnormalities have a site predilection that should be taken into consideration when contemplating differential diagnoses. For example, a filling defect (mass) in the duodenum is much more likely to be a primary adenocarcinoma than a carcinoid. However, the opposite is true in the distal ileum.

 

2.      Caliber of the lumen

 

The bowel lumen can only be three things… normal, dilated, or narrowed. Dilatation usually represents a diffuse process, while luminal narrowing usually represents a more focal finding. In addition, dilatation can be CAUSED by focal narrowing, as seen in small bowel obstruction (SBO).

 

3.      Mucosal contour

 

The mucosal contour is best evaluated with fluoroscopic studies. The most common contour abnormalities include filling defects (masses), ulceration, diverticula, and fistulas. These entities will be discussed in detail in later sections.

 

4.      Fold pattern.

 

Fold thickening, which represents infiltration of the bowel wall, occurs when folds are thicker than 3mm. Fold thickening can have two appearances, smooth or nodular. Smooth thickening occurs as a result of either hemorrhage or edema into the bowel wall. This type of thickening is often referred to as “thumbprinting”. Nodular thickening, however, occurs as a result of cellular infiltration, as is seen in neoplastic and infectious processes.

 

5.      In fluoroscopy studies, the character and transit time of the contrast material should also be evaluated.

 

Rapid transit times and barium dilution is often seen in hypersecretory states.

 

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