P-156 Shear Wave Velocity Measurement in Bowel Wall Using ARFI Ultrasound for Prediction of Response to Medical Therapy in Crohnʼs Disease

Abstract

Crohn’s disease (CD) is a chronic inflammatory disease necessitating surgical bowel resection in 60% of patients due to stricturing. CD stricturing is the result of bowel wall thickening composed of a mixture of inflammatory and fibrotic intestinal wall changes. Over time, cycles of inflammation and healing shift the stricture pathology from largely inflammatory to primarily fibrotic. Predominantly fibrotic strictures are unresponsive to anti-inflammatory therapies and require endoscopic dilation or surgery. Decisions between medical and surgical therapy are plagued by the difficulty of determining whether bowel wall thickening is the result of inflammation or fibrosis. The current practice of empirically using anti-inflammatory therapy in most patients with CD-related bowel wall thickening and obstructive symptoms in the hope of success leads to many unnecessary side effects, infections, worse surgical outcomes, and long delays of appropriate surgical intervention when significant fibrostenotic disease is already present. Ultrasound stiffness imaging, using acoustic radiation force impulse imaging (ARFI), provides real-time non-invasive bedside elastography of bowel wall reported as shear wave velocity (SWV). We hypothesize that AFRI SWV of luminal stricturing disease will stratify medically responsive (inflammatory) from non-responsive (predominantly fibrotic) ileal Crohn’s disease; we present the interim analysis. Subjects with established ileal Crohn’s disease hospitalized for small bowel obstruction (defined as CT evidence of small bowel dilation >3.5cm) and scheduled to receive methylprednisone were enrolled. Within 48 hours of admission subjects underwent bedside ultrasound using Acuson S3000 with ARFI Virtual-Touch software package (Siemens, USA). SWV of the lateral, anterior, and medial portions of diseased ileum at 0% and 10% strain were collected in triplicate at baseline and Day 3. Subject demographic data, medical history, laboratory values and Harvey Bradshaw Index (HBI) were assessed at both time points. Ultrasound SWV values were compared to a primary outcome of surgical bowel resection for obstructive disease within 90 days. In 10 subjects with complete follow up to date, 4/10 have undergone surgical bowel resection within 90 days. Patient demographics, BMI, anti-TNF and immunomodulator use, and prednisone use prior to hospitalization did not significantly differ between surgical and non-surgical groups. Mean SWV at 0% strain (no freehand force) did not discriminate those requiring surgery within 90 days (1.42 [1.28–1.53] versus 1.56 [1.44–1.73] m/s, P = 0.154). When applying 10% freehand strain to the affected segment, baseline SWV yielded improved discrimination between those requiring surgery within 90 days (2.20 [1.74–2.39] m/s) versus subjects avoiding surgery (1.81 [1.54–2.09] m/s), although statistical significance was not reached at this interim point of the study, P = 0.066. No significant difference in SWV change between baseline and day 3 of methylprednisone was observed between the surgical and non-surgical cohorts. Ultrasound stiffness imaging by ARFI elastography demonstrates a trend of increasing shear wave velocities in subjects with obstructive ileal Crohn's requiring near-term surgical resection, although at this interim analysis point trends have not reached statistical significance. The data presented suggests that SWV non-invasive bowel wall stiffness measurements at higher strain values (20%-30%) may better predict the success or futility of medical therapy in subjects with obstructive Crohn's disease.