Role of Intestinal Ultrasound for IBD Care: A Practical Approach

Abstract

Intestinal ultrasound (IUS) has recently become the imaging technique of choice for patients with different types of intestinal inflammation. IUS has a high sensitivity, specificity, positive predictive value, and negative predictive value when diagnosing Crohn's disease or ulcerative colitis. Further, it is now the preferred imaging modality for routine IBD reevaluations because of its non-invasiveness, cost-effectiveness, availability (at least in Europe), and reproducibility in all age groups. However, the clinical success of IUS requires IUS training for doctors and technicians who perform IUS with a standardised description of ultrasound findings of the terminal ileum and entire colon. Complications such as abscess formation, fistulae, and stenosis can be detected by either conventional IUS or contrast-enhanced ultrasound (CEUS). Lately, several disease activity scores have been proposed for Crohn's disease, postoperative Crohn's disease, and ulcerative colitis both in adults (including elderly) and in children. IUS was successfully used in randomised clinical trials in order to measure the treatment response. Therefore, IUS now plays a central role in clinical decision making.

Keywords: Crohn’s disease; diagnostic algorithm; imaging; standardised reporting; therapeutic algorithm; ulcerative colitis.

Figure 1

Intestinal ultrasound: normal colon. The transverse (a) and longitudinal (b) section of a normal colonic wall are shown. On the transverse section (a), the white arrows show the inner and outer margin with five layers in between (the white interface, the dark mucosa, the white submucosa, the dark muscularis propria, and the white serosa as the outer layer). On the longitudinal section (b), the normal haustration is indicated by the turquoise arrows.

Figure 2

Variants of bowel wall stratification (BWS) and bowel wall thickness (BWT) in IBD: (a) normal BWS on a longitudinal colonic wall section with normal BWT (white arrows). The lumen is indicated by the turquoise arrow; (b) preserved layers with increased BWT due to a markedly thickened submucosa in a transverse section of the colonic wall; (c) complete loss of BWS in a longitudinal section of the descending colon. White arrows indicate the BWT and green arrows the total bowel diameter; (d) variants of BWS in a longitudinal section of a colonic wall (yellow: blurred BWS, white: preserved BWS); (e) asymmetric BWS in a transverse section of a transverse colonic wall.

Figure 3

Variants of bowel wall vascularisation in IBD using colour Doppler signalling of colonic walls. Shown are typical examples employing the modified Limberg classification: (a) transverse section of the descending colon showing preserved layers with increased BWT but no signals on CDS employing superb microvascular imaging (SMI) (Limberg 1); (b) longitudinal section of the right transverse colon with orange dots within the blurred intestinal wall using SMI (Limberg 2); (c) oblique section of the sigmoid colon with preserved BWS, increased BWT and stretches of blood vessels within the intestinal wall using colour Doppler signalling indicated by the turquoise arrow (Limberg 3); (d) longitudinal section of the descending colon with markedly increased vascularity in the intestinal wall extending into the pericolonic echoenhanced tissue (turquoise arrow) using SMI (Limberg 4).

Figure 4

Variants of colonic wall haustration in IBD using B-mode ultrasound. Typical examples are shown as follows: (a) longitudinal section of the left transverse colon showing preserved haustration (turquoise arrows); (b) longitudinal section of the descending colon with increased BWT (yellow markers, number 1), preserved BWS, thickened submucosa (yellow markers, number 2), no hypervascularity (Limberg 1), and complete loss of haustration; (c) longitudinal section of the left transverse colon with increased BWT, thickened mucosa, and reduced haustration (turquoise arrows).

Figure 5

Variants of intestinal and extraintestinal complications of Crohn’s disease. (a) Longitudinal section of the terminal ileum in Crohn’s disease. Shown is a stricture with prestenotic dilatation (red arrows), luminal narrowing (yellow arrows), and increased BWT (white arrows). (b) Longitudinal section of a 7.2 cm long ileal stricture. (c) Intestinal fibrosis indicated by spiculates extending from the submucosa towards the serosa (red arrows) with increased BWT (white arrows); the lumen is indicated by the turquoise arrow. (d) A fistula (indicated by the turquoise arrow) extends from the sigmoid colon to an underlying abscess, which is shown by the red arrows. Fibrofatty proliferation is indicated by the yellow arrow leading to increased echogenicity. (e) B-mode image of an extra-intestinal abscess indicated by the red arrows. The yellow arrow shows the hyperechogenic surrounding inflammation. (f) Adherent, inflammatory small bowel loops form a pseudotumor (green arrows) with surrounding fat wrapping (yellow arrow).

Figure 6

Additional extraintestinal ultrasound findings in IBD. (a) Shown is a round hypoechoic lymph node next to the thickened wall of the descending colon in hyperechoic tissue (fat wrapping) (yellow arrow). (b) The tissue surrounding the thickened strongly hypervascularised colonic wall (Limberg 4) is hyperechoic known as fat stranding, fat wrapping, or inflammatory fat (i-fat) (yellow arrow). (c) Ascites shown as an anechoic area indicated by a turquoise arrow. (d) Patient with Crohn’s disease showing all three additional extraintestinal signs, i.e., fat wrapping (yellow arrow), pericolonic lymph node (red arrow), and small amount of ascites (turquoise arrow).

Figure 7

Diagnostic algorithm in suspected inflammatory bowel disease (IBD). EGD = esophagogastroduodenoscopy, IUS = intestinal ultrasound, ICS = ileocolonoscopy, MRE = magnetic resonance enterography.

Figure 8

IUS-based therapeutic and follow-up algorithm. IBD = inflammatory bowel disease; UC = ulcerative colitis; CD = Crohn’s disease; ASA = amino-salicylic-acid; IUS = high resolution intestinal ultrasound; BUD = budesonide; BIOL = biologicals; JAKi = JAK inhibitor; CS = corticosteroids; IS = immunosuppressants, i.e., azathioprin; mo = months; H&CE = history and clinical examination; Q = every.