National Centre for Ultrasound in Gastroenterology, Haukeland University Hospital / Department of Clinical Medicine, University of Bergen
High-resolution ultrasonography has greatly improved the diagnostic potential of ultrasound in the assessment of Crohn’s disease. Ultrasonography is not only a method used by radiologists, but also a clinical tool that can be applied to evaluate the patient bedside. The GI wall is most often visualized as a layered structure normally consisting of 3-9 layers, depending on the frequency applied, but usually 5 layers are observed. When examining the intestines, it is preferable to use frequencies above 7.5 MHz to enable optimal visualisation of wall layers, thickened bowel walls and target lesions. Ultrasound can be used to study disease activity in Crohn’s disease using bowel wall thickness and Doppler measurements as a marker of inflammation. By adding CEUS enhancement in different wall layers can be evaluated and quantified in Crohn’s disease and this correlates to clinical activity index （CDAI） with good sensitivity and specificity. Quantitative measurements of bowel enhancement obtained by CEUS also correlate with severity grade determined at endoscopy. In patients with a stricture of the bowel and resultant bowel obstruction, it is important to determine if there is active inflammation at the site of stricture or if the obstructed segment is fibrotic. Preliminary studies indicate that CEUS appears to be useful in the recognition of a cicatricial stenosis in patients with Crohn’s disease. Using CEUS, the active inflammatory components will enhance whereas the fibrotic stricture will enhance less. Furthermore, one may apply elastography to evaluate stiffness of the stenotic area, thus providing more clues to the fibrous content of the stricture. Distinguishing abscesses from inflammatory infiltrates is an important clinical task in the management of Crohn’s disease. If the tissue close to an affected bowel loop is completely devoid of microbubble signals, most likely this lesion represents avascular abscesses rather than inflammatory infiltrates. In these cases, peri-intestinal tissue enhancement indicates infiltrate rather than abscess. In conclusion, US is a useful clinical tool in the management of patients with Crohn’s disease, particularly to diagnose the complications of the disease. 【References】 1.Kim Nylund, Svein Ødegaard, Geir Folvik, Gülen Arslan, Trygve Hausken, Ivan Viola, Helwig Hauser and Odd Helge Gilja. Sonography of the small intestine. World J Gastroenterol 2009 Mar 21;15（11）:1319-30. 2.Nylund K, Hausken T, Gilja OH. Ultrasound and inflammatory bowel disease. Ultrasound Q. 2010 Mar;26（1）:3-15. 3.Postema M, Gilja OH. Contrast-enhanced and targeted ultrasound. WJG 2011;7,17（1）:28-41. 4.Kolar R, Jirik R, Harabis, V, Nylund K, Gilja OH. Registration of ultrasound Contrast images for perfusion analysis. IEEE Proc Ultrason & Ferroelect & Freq contr 2009;1251-1254. 5.Angeleli P, Nylund K, Gilja OH, Hauser H. Interactive Visual Analysis of Contrast-Enhanced Ultrasound Data based on Small Neighborhood Statistics. Computers and Graphics 2011;35:218-226. 6.Jirık R, Nylund K, Taxt T, Mezl M, Harabiˇs V, Kol′aˇr R, Standara M, Gilja OH. Ultrasound Perfusion Analysis Combining Bolus Tracking and Replenishment. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 2013 Feb;60（2）:310-9. doi: 10.1109/TUFFC.2013.2567. 7.Nylund K, Jirik R, Mezl M, Leh S, Hausken T, Pfeffer F, Odegaard S, Taxt T, Gilja OH. Quantitative Contrast-Enhanced Ultrasound Comparison Between Inflammatory and Fibrotic Lesions in Patients With Crohn’s Disease. Ultrasound Med Biol. 2013 Apr 30. doi:pii: S0301-5629（13）00053-7. 10.1016/j.ultrasmedbio.2013.01.020. PMID:23643057. 8.Piscaglia F, Nolsøe C, Dietrich CF, Cosgrove DO, Gilja OH, Bachmann Nielsen M, Albrecht T, Barozzi L, Bertolotto M, Catalano O, Claudon M, Clevert DA, Correas JM, D’Onofrio M, Drudi FM, Eyding J, Giovannini M, Hocke M, Ignee A, Jung EM, Klauser AS, Lassau N, Leen E, Mathis G, Saftoiu A, Seidel G, Sidhu PS, Haar GT, Timmerman D, Weskott HP. The EFSUMB Guidelines and Recommendations on the Clinical Practice of Contrast Enhanced Ultrasound （CEUS）: Update 2011 on non-hepatic applications. Ultraschall Med. 2012 Feb;33（1）:33-59; Epub 2011 Aug 26. PMID: 21874631.