Intestinal Ultrasound for the Pediatric Gastroenterologist: A Guide for Inflammatory Bowel Disease Monitoring in Children: Expert Consensus on Behalf of the International Bowel Ultrasound Group (IBUS) Pediatric Committee

Abstract

Crohn disease and ulcerative colitis are chronic inflammatory bowel diseases (IBD) often diagnosed in childhood. A strict monitoring strategy can potentially alter the disease course and facilitate early effective treatment before irreversible bowel damage occurs. Serial colonoscopy in children, the gold standard for monitoring, is impractical. Accurate, real-time, noninvasive markers of disease activity are needed. Intestinal ultrasound is an accurate, noninvasive, real-time, point-of-care, cross-sectional imaging tool used to monitor inflammation in pediatric IBD patients in Europe, Canada, and Australia. It is now emerging in a few expert centers in the United States as a safe, non-radiating, inexpensive, bedside tool used by the treating gastroenterologist for real-time decision-making. Unlike the standard biomarkers of pediatric IBD activity, C-reactive protein, and fecal calprotectin, intestinal ultrasound (IUS) facilitates disease localization, characterizes severity, extent, and accurately detects complications. Perhaps most importantly, IUS may enhance shared understanding and ease the burden of treatment decision-making for both the gastroenterologist and the patient. There is a lack of standardization for bedside IUS among pediatric gastroenterologists. The purpose is to outline a standardized approach to pediatric bedside IUS, including basic equipment requirements and technique, patient selection, preparation and positioning, technical considerations and limitations, documentation of mesenteric and luminal features of IBD, characterization of penetrating disease and strictures, and provide a proposed pediatric IUS monitoring algorithm to guide care.

FIGURE 1.

(A) The sigmoid colon (SC) is identified by the iliac artery (IA) and vein as it lies directly over the iliac vessels as identified with the transducer in the patients left lower quadrant. (B) The descending colon (DC) can be visualized, often on the patients left flank, by moving the transducer towards the spleen and rib cage from the left lower quadrant and then moving the transducer onto the patients left flank and further towards the back if necessary. (C) The transverse colon (TC) can be identified by locating the aorta through the application of color Doppler, and then moving the transducer upward towards the patient’s xyphoid process. Note the haustral folds of the colon that may differentiate the transverse colon from under or overlying proximal small bowel. (D) The ascending colon (AC) can be found on the child’s right abdomen, by identification of the liver and then moving the transducer downward. (E) The terminal ileum (TI) identified in the child’s right lower quadrant, identified as lying just above the iliac artery and vein.

FIGURE 2.

Schematic on the left identifying the bowel wall layers and optimal points to measure bowel wall thickness beginning at the lumen-mucosa interface to the muscularis propria-serosa interface. On the right, a still ultrasound frame with an inflamed terminal ileum is shown with measurement of bowel wall thickness with blue arrows.

FIGURE 3.

(A) Ultrasound still frame showing loss of bowel wall stratification shown in the terminal ileum with disruption between the bowel layers in a thickened terminal ileum. (B) Ultrasound still frame displaying increased color Doppler signal representing increased bowel wall hyperemia in the terminal ileum encased in surrounding hyperechoic inflammatory fat. (C) Ultrasound still frame highlighting inflamed terminal ileum with a stricture characterized by luminal narrowing and proximal bowel dilation. (D) Ultrasound still frame highlighting a fistula tract from an inflamed terminal ileum leading to an intraabdominal wall abscess.

FIGURE 4.

Proposed ultrasound monitoring algorithm. Ultrasound performed at baseline (time of colonoscopy or diagnosis) and/or when making a treatment change. Repeat ultrasound performed post-induction or 4–12 weeks after a treatment change and if no significant improvement on ultrasound in bowel wall thickness and hyperemia, treatment should be escalated/optimized or therapy change should be considered if there is evidence of worsening on ultrasound. The ultrasound should ultimately be repeated at treat-to-target colonoscopy and can then be utilized for serial monitoring moving forward every 3–6 months if targets achieved.