Intest Res.  2023 Jul;21(3):385-391. 10.5217/ir.2022.00030.

Submucosal fat accumulation in Crohn’s disease: evaluation with sonography

• Ripollés T
• Martínez-Pérez MJ
• Paredes JM
• Vizuete J
• Martin G
• Navarro L

• KMID: 2544761
• DOI: http://doi.org/10.5217/ir.2022.00030

Abstract

Background/Aims
The study objective is to investigate the ultrasound features that allow suspecting the presence of submucosal fat deposition, called the fat halo sign (FHS), in the intestinal wall of patients with Crohn’s disease.
Methods
Computed tomography (CT) examinations over a period of 10 years were reviewed for the presence of the FHS in the bowel wall. A measurement of less than –10 Hounsfield units was regarded as indicative of fat. We included only patients who had undergone ultrasound examinations 3 months before or after CT. The study cohort group comprised 68 patients. Wall and submucosal thickness were measured on longitudinal ultrasound sections. A receiver operating characteristic curve was constructed to determine the best cutoff of ultrasound submucosal wall thickness value for predicting FHS in the bowel wall determined on CT.
Results
The FHS was present in 22 patients (31%) on CT. There were significant differences between submucosal thickness of patients with FHS and patients without FHS (4.19 mm vs. 2.41 mm). From the receiver operating characteristic curve, a threshold value of 3.1 mm of submucosal thickness had the best sensitivity and specificity to suspect FHS (95.5% and 89.1%, respectively; area under the curve, 0.962), with an odds ratio of 172. All of 16 patients with a submucosal thickness >3.9 mm had FHS.
Conclusions
FHS in patients with Crohn’s disease can be suspected on ultrasound in cases with marked thickening of the submucosa layer. In these cases, the activity of the disease should be measured by other parameters such as the color Doppler.

Keyword

Ultrasonography; Crohn disease; Inflammatory bowel diseases; Fat deposition; Bowel wall thickness

Figure

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  Fig. 1. A 70-year-old woman with longstanding Crohn’s disease. (A) A computed tomography scan reveals thickening of the wall of terminal ileum with prominent low attenuation submucosa (fat halo sign). Note the intense mucosal enhancement in the intestinal segment seen in axial view (–18 HU) and the mild mucosal enhancement in the longer segment (–69 HU). Corresponding axial (B) and longitudinal (C) ultrasound images of the terminal ileum with hyperechoic thickened submucosal layer (asterisks) of the bowel wall (53 and 57 mm), concordant with the fat deposition as shown on computed tomography scan. HU, Hounsfield unit.

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  Fig. 2. A 56-year-old man has diagnosed with Crohn’s disease 3 years ago. (A) Coronal image from an enhanced computed tomography scan shows fat deposition in the submucosa of the terminal ileum. (B) Corresponding longitudinal ultrasound scan of the terminal ileum shows thickened wall (6.6 mm) and hyperechoic thickened submucosal layer (asterisks) (4.5 mm) suggesting submucosal fat deposition.

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