Inflamm Bowel Dis. 2014 Sep;20(9):1575-83.

Diffusion-weighted magnetic resonance for assessing ileal Crohn’s disease activity.


Caruso A, DʼIncà R, Scarpa M, Manfrin P, Rudatis M, Pozza A, Angriman I, Buda A, Sturniolo GC, Lacognata C.

Department of Surgical, Oncological and Gastroenterological Sciences, University of Padova, Padova, Italy;



BACKGROUND: Endoscopy and imaging objectively assess Crohn’s disease (CD) activity. Magnetic resonance enterography (MRE) uses no ionizing radiation, carries no significant morbidity, and is highly sensitive in revealing soft tissues inflammation. Diffusion-weighted imaging can distinguish intestinal inflammation from a lower diffusion of water molecules giving rise to a reduced apparent diffusion coefficient. The magnetic resonance index of activity score and, more recently, the Clermont score were recently developed for staging CD activity. The aim of this study was to compare the MRE scores and the Simple Endoscopic Score for CD in identifying ileal CD activity.

METHODS: Fifty-five patients with ileal and ileocolonic CD were consecutively enrolled between June 2012 and June 2013. All patients underwent clinical examination, biochemical tests, MRE, and colonoscopy to assess disease activity.

RESULTS: MRE assessed active ileal disease in 31 patients (56.3%). The Clermont score significantly correlated with the magnetic resonance index of activity score (r = 0.91; P < 0.0001) and the Simple Endoscopic Score for CD (r = 0.76; P < 0.0001). The apparent diffusion coefficient correlated with the Simple Endoscopic Score for CD (r = -0.63; P < 0.0001) especially in unoperated patients.

CONCLUSIONS: The Clermont score and the apparent diffusion coefficient value can stage ileal CD, avoiding the need to use contrast agents.

PMID: 25025715



Magnetic Resonance Enterography (MRE) is a radiological technique useful not only for diagnosing Crohn’s Disease (sensitivity 78%; specificity 85%) but also for evaluating the extent of the disease and its complications. Moreover, MRE has high accuracy for the detection of penetrating lesions and abscesses. The main advantage with respect to Computed Tomography is the absence of ionizing radiation, ideal for young CD patients who need more than one evaluation over time [1]. The technique also has the capability for identifying edema (in T2-fat saturation sequences or DWI with a b value of 50), bowel wall contrast enhancement (perfusion sequences), wall thickening (anatomical sequences), motion (functional sequences), and cellularity (DWI with a b value of 1000).

MRE changes associated with the presence of inflammation include: wall thickening, wall hyper-enhancement after injection of contrast medium, presence of wall edema, presence of ulcers, as well as extramural changes such as presence of comb sign, fat stranding and enlarged lymph nodes. Several studies reported the MRE parameters useful to evaluate disease severity; these include increased contrast uptake and thickening of bowel wall, loss of folds, abscess, and pattern stratification of enhancement of bowel wall [2, 3].

DWI is a MR sequence that can give additional information about the structural organization of the tissue. [4]. DWI measures the Brownian motion of the water molecules in the tissues. In free water the molecules mobility is high and constant. In biological tissues this mobility is restricted by cell density, cell membranes, membrane permeability, vascular structures. Signal intensity of pathologic tissue is strongly influenced by cellular density and increase in diffusion imaging [5]. Measures regarding the mobility of water molecules can provide important information by tissue structure and the presence of pathologic alterations. We showed that the restrict proton motion can be quantified by calculating the Apparent Diffusion Coefficient (ADC) from ADC maps. In inflammatory tissue, cell density increase in comparison with healthy tissue and ADC decreases (restriction of diffusion), as seen in CD patients [6, 7]. DWI is more frequently used in solid organs. In gastrointestinal tract imaging, DWI has not been commonly used because the image quality is dampened by bulk motion artifacts [8]. Recently, with the use of spasmolytic agents, DWI has been applied to gastrointestinal diseases such as colorectal cancer. The increase of DWI signal intensity and decreased ADC value in inflamed bowel segments, could be related to high viscosity. Changes in viscosity are associated with CD mucosal and transmural damage [9]. Moreover, the dynamic contrast-enhancement Magnetic Resonance Imaging (DCE-MRI) and DWI provide a quantitative measure of small bowel inflammation that can differentiate actively inflamed small bowel segments from normal/fibrotic segments [10].

Recently two radiological scores have been validated. The first is the Magnetic Resonance Index of Activity (MaRIA) that evaluates disease activity with the use of contrast medium [11], the other is the Clermont score which uses diffusion sequences [12,13].



Figure 1: In red circle inflamed intestinal loop after contrast medium injection.


The MRE with DWI has two important advantages that make the technique of very useful and safe:

  • It does not use paramagnetic contrast medium that is associated with possible nephrogenic systemic fibrosis.
  • It dose not use ionizing radiation eliminating the risk of radiation damage.

We showed that DWI, without the use of contrast medium, allows a good assessment of ileal disease activity in CD patients with or without previous surgery. The performance of DWI was better in non-operated patients probably because of artifacts due to fibrosis after surgery.

The correlation of DWI with endoscopic scores could allow to use this radiological tool for disease monitoring and evaluation of response to therapy thus reducing the need for the more invasive endoscopic examinations. The correlation of DWI with biochemical parameters (CRP and lactoferrin) shows the accuracy of DWI for the presence of intestinal inflammation.

The ADC value could be helpful to differentiate fibrotic from inflamed stenosis and could guide the choice of surgical vs medical therapy.



Figure 2: ADC map. In red circle inflamed intestinal loop.



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