Imaging Inflammation and Infection in the Gastrointestinal Tract

Abstract

A variety of seemingly non-specific symptoms manifest within the gastrointestinal (GI) tract, particularly in the colon, in response to inflammation, infection, or a combination thereof. Differentiation between symptom sources can often be achieved using various radiologic studies. Although it is not possible to provide a comprehensive survey of imaging gastrointestinal GI tract infections in a single article, the purpose of this review is to survey several topics on imaging of GI tract inflammation and infections. The review discusses such modalities as computed tomography, positron emission tomography, ultrasound, endoscopy, and magnetic resonance imaging while looking at up-an-coming technologies that could improve diagnoses and patient comfort. The discussion is accomplished through examining a combination of organ-based and organism-based approaches, with accompanying selected case examples. Specific focus is placed on the bacterial infections caused by Shigella spp., Escherichia coli, Clostridium difficile, Salmonella, and inflammatory conditions of diverticulitis and irritable bowel disease. These infectious and inflammatory diseases and their detection via molecular imaging will be compared including the appropriate differential diagnostic considerations.

Keywords: gastrointestinal tract; infection; inflammation; molecular imaging.

Figure 1

CT imaging used to identify C. diff. with an axial CT scan demonstrates low-attenuation wall thickening involving the entire length of the colon with intense mucosal enhancement (white arrow, (a)); the enhancing mucosa is stretched over the edematous haustral folds, resembling an accordion even in the absence of intra-luminal contrast (black arrow, (b)). A large amount of ascites is also present (dashed arrow, (c)) [59].

Figure 2

Evaluation of lower abdomen of pediatric patient with Salmonella enterocolitis using transverse ultrasound. There is thickening of the sigmoid colon which results predominantly from submucosal edema (arrow) observed as the thick hyperechoiclayer. S = sigmoid colon [72].

Figure 3

¹⁸F-FDG PET/CT scan of ulcerative colitis (UC) patient. Extent of disease is seen on the left and in areas indicated by arrows in the right panel [124].

Figure 4

Multispectral optoacoustic tomography (MSOT) (A–C) and colonoscopic (D–F) images of murine colitis progression. Images were taken at t = 0, 2, and 7 days after bacterial inoculation. Yellow arrows indicate areas of inflammation correlating with colitis [67].