First aid with color atlas for the use of intestinal ultrasound for inflammatory bowel disease in daily clinical practice

Abstract

Intestinal ultrasound (IUS) is a promising modality for the management of inflammatory bowel disease (IBD) and has the potential to particularly contribute in monitoring disease activity, an advantage crucial for optimizing the therapeutic strategy. While many IBD physicians appreciate and are interested in the use of IUS for IBD, currently only a limited number of facilities can employ this examination in daily clinical practice. A lack of guidance is one of the major barriers to introducing this procedure. Standardized protocols and assessment criteria are needed such that IUS for IBD can be considered a feasible, reliable examination in clinical practice, and multicenter clinical studies can be conducted for further clinical evidence of the application of IUS in IBD for best patient care. In this article, we provide an overview of how to start IUS for IBD and introduce basic procedures. Furthermore, IUS images from our practice are provided as a color atlas for understanding sonographic findings and scoring systems. We anticipate this "first aid" article will be helpful to promote IUS for IBD in daily practice.

Keywords: Color atlas; Inflammatory bowel disease; Intestinal ultrasound; Sonographic parameters.

Fig. 1.

Examination of the colon using transabdominal ultrasound. We start from the middle lower area to examine the rectum. The rectum cannot be sufficiently assessed with transabdominal ultrasound. Then, we trace the colon counterclockwise. In some cases, the transverse colon descends from the middle to the lower abdominal area.

Fig. 2.

Sonographic images of the normal large and small bowel. (A) The overall B-mode image of the colon and small intestine. The colon exhibits the haustra, whereas the Kerckring’s fold is observed in the small intestine. During an examination, distinguishing the difference in peristalsis (lesser in the large bowel than in the small bowel) is also helpful. (B) The bowel has a 5-layer wall stratification: The 1st layer (hyperechoic) is the surface of the mucosa (superficial mucosa); 2nd layer (hypoechoic), the mucosa (deep mucosa) or muscularis mucosae; 3rd layer (hyperechoic), the submucosa; 4th layer (hypoechoic), the muscularis propria; and 5th layer (hyperechoic), the serosa.

Fig. 3.

The landmark for identifying the sigmoid colon. At the left lower quadrant, the iliopsoas muscle and iliac blood vessels can be landmarks in identifying the sigmoid colon. The image is that of a patient with ulcerative colitis.

Fig. 4.

Examination of the small intestine. (A) Ileocecal valve is identified while observing the ascending colon and cecum and then the terminal ileum can be followed from the ileocecal valve. At the right lower quadrant, the iliopsoas muscle and iliac blood vessels can be landmarks in identifying the sigmoid colon. This image is that of a patient with Crohn’s disease. (B) We screen the small bowel in the entire abdomen by moving the sonographic probe.

Fig. 5.

Bowel wall thickness. The bowel wall thickness should be measured vertically to the wall (yellow line). These images are that of a patient with ulcerative colitis, which represents a thickened colon wall with a thickened submucosa.

Fig. 6.

Bowel wall flow. The bowel wall flow is generally assessed using color Doppler. The machine setting is crucial for appropriate examination. (A) Normal bowel wall thickness without color Doppler signal. (B) Thickened bowel wall without color Doppler signal. (C) Point-like, short color Doppler signals. (D) Linear-appearance color Doppler signals. (E) Long color Doppler signals extending the bowel wall and the surrounding mesenteric tissue. The velocity range of color Doppler for these images was 4.2 cm/s. IBUS-SAS, International Bowel Ultrasound Segmental Activity Score.

Fig. 7.

Bowel wall stratification. (A) The normal 5-layer stratification. The yellow line represents bowel wall thickness. (B) The pink line indicates the area with uncertain bowel wall stratification. (C) The blue line indicates the area with loss of stratification. This image represents a focal loss of stratification (≤3 cm). (D) The blue line indicates the area with loss of stratification. This image represents an extensive loss of stratification (>3 cm). IBUS-SAS, International Bowel Ultrasound Segmental Activity Score.

Fig. 8.

Haustration of the colon. Both panels are identical sonographic images, and the yellow line in the lower panel indicates the haustration structure.

Fig. 9.

Mesenteric proliferation (inflammation of mesenteric fat). Both panels are identical sonographic images, and the yellow area in the right panel indicates the hyperechogenic mesenteric tissue compared with the surrounding areas.

Fig. 10.

Peri-intestinal lymph nodes. Both panels are identical sonographic images, and the yellow arrowheads in the right panel indicate lymph nodes surrounding the intestine.

Fig. 11.

Thickened submucosa. The total bowel wall (yellow line) and the 3rd layer, i.e., the submucosa (pink line), are thickened. The ratio of the submucosa to the total bowel wall increases.

Fig. 12.

Ulcer. (A) Both panels are identical sonographic images. The bottoms of the ulcers are observed inside the wall (yellow arrowheads). The orange line indicates the luminal surface. (B) The bowel wall appears thin due to the loss of wall tissues in the area with broad deep ulcers (blue line). The yellow arrowheads indicate ulcers.

Fig. 13.

An example image of perineal intestinal ultrasound. The dorsal wall thickness of the rectum can be measured (pink line). This case with Crohn’s disease shows a perianal fistula (yellow arrowheads). The velocity range of the color Doppler for this image was 4.2 cm/s.

Fig. 14.

Intestinal complications observed using ultrasound examinations. (A) The fistula between the terminal ileum and skin is shown (yellow arrowheads). An adhesion can be observed between the terminal ileum and cecum. (B) This perineal ultrasound image shows a perianal fistula (yellow arrowheads). The hyperechoic objects compatible with gas are observed in the fistula (blue arrowheads). (C) The hypoechoic area surrounded by yellow arrowheads is an abscess. Some hyperechoic objects compatible with gas (blue arrowheads) are observed inside the abscess. (D) This perianal ultrasound image shows a perianal abscess (surrounded by yellow arrowheads). Color Doppler signals are detected around the abscess. (E) Both panels are identical sonographic images. The dilation of the ileum (yellow arrowheads) occurs due to terminal ileum stenosis. The velocity range of color Doppler for images (B) and (D) was 4.2 cm/s.

Fig. 15.

Hand-drawn report format in our facility. (A) Each format is used mainly for ulcerative colitis and Crohn’s disease. (B) An example illustration of the ileocecal area extracted from a hand-drawn report. In this patient with Crohn’s disease, inflammation is observed in the oral side of the ascending colon and the cecum, and these parts appear distorted with inflammatory fat and the local collection of ascites. With distortion, the ileocecal valve is observed at the ventral side of the cecum, and adhesion is detected between the terminal ileum and ventral side of the cecum (yellow arrowheads). The ileum is also inflamed, showing loss of stratification with mesenteric proliferation.