New Concepts in Intestinal Imaging for Inflammatory Bowel Diseases
2011; Elsevier BV; Volume: 140; Issue: 6 Linguagem: Inglês
10.1053/j.gastro.2011.02.013
ISSN1528-0012
AutoresJoel G. Fletcher, Jeff L. Fidler, David H. Bruining, James E. Huprich,
Tópico(s)Microscopic Colitis
ResumoIn the last decade, multiple imaging technologies have been developed that improve visualization of the mucosal, mural, and perienteric inflammation associated with inflammatory bowel diseases. Whereas these technologies have traditionally been used to detect and stage suspected enteric inflammation, we review new, emerging roles in detecting clinically occult inflammation (in asymptomatic patients) and inflammatory complications, predicting response prior to therapy, assessing response after therapy, and enteric healing. We compare the relative performance of these technologies in detecting inflammation, focusing on their advantages and disadvantages and how they might complement each other. We also discuss their potential benefits for patients and clinical trials, reviewing technologic developments and areas of research that could provide important insights into the pathophysiology of inflammatory bowel diseases-related enteric inflammation. In the last decade, multiple imaging technologies have been developed that improve visualization of the mucosal, mural, and perienteric inflammation associated with inflammatory bowel diseases. Whereas these technologies have traditionally been used to detect and stage suspected enteric inflammation, we review new, emerging roles in detecting clinically occult inflammation (in asymptomatic patients) and inflammatory complications, predicting response prior to therapy, assessing response after therapy, and enteric healing. We compare the relative performance of these technologies in detecting inflammation, focusing on their advantages and disadvantages and how they might complement each other. We also discuss their potential benefits for patients and clinical trials, reviewing technologic developments and areas of research that could provide important insights into the pathophysiology of inflammatory bowel diseases-related enteric inflammation. View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)In the past 2 decades, there have been unprecedented advances in methods for imaging the intestine and in our understanding of the unique information these technologies provide resulting in increased imaging demand for patients with inflammatory bowel diseases (IBDs). Improvements in the temporal and spatial resolution of computed tomography (CT) and magnetic resonance (MR) imaging and the development of enteric agents to distend the bowel have led to routine visualization of the small bowel lumen, wall, and perienteric tissues using CT and MR enterography.1Gourtsoyiannis N. Papanikolaou N. Grammatikakis J. et al.MR enteroclysis: technical considerations and clinical applications.Eur Radiol. 2002; 12: 2651-2658PubMed Google Scholar, 2Lauenstein T. Schneemann H. Vogt F. et al.Optimization of oral contrast agents for MR imaging of the small bowel.Radiology. 2003; 228: 279-283Crossref PubMed Scopus (84) Google Scholar, 3Mako E.K. Mester A.R. Tarjan A. et al.Enteroclysis and spiral CT examination in diagnosis and evaluation of small bowel Crohn disease.Eur J Radiol. 2000; 35: 168-175Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar, 4Mazzeo S. Caramella D. Battolla L. et al.Crohn disease of the small bowel: spiral CT evaluation after oral hyperhydration with iosotonic solution.J Comput Assist Tomo. 2001; 24: 612-616Crossref Scopus (44) Google Scholar, 5Paulsen S.R. Huprich J.E. Fletcher J.G. et al.CT enterography as a diagnostic tool in evaluating small bowel disorders: review of clinical experience with over 700 cases.Radiographics. 2006; 26: 641-662Crossref PubMed Scopus (166) Google Scholar, 6Rollandi G.A. Curone P.F. Biscaldi E. et al.Spiral CT of the abdomen after distention of small bowel loops with transparent enema in patients with Crohn's disease.Abdom Imaging. 1999; 24: 544-549Crossref PubMed Scopus (75) Google Scholar, 7Young B.M. Fletcher J.G. Booya F. et al.Head-to-head comparison of oral contrast agents for cross-sectional enterography: small bowel distention, timing, and side effects.J Comput Assist Tomogr. 2008; 32: 32-38Crossref PubMed Scopus (31) Google Scholar, 8Fidler J. MR imaging of the small bowel.Radiol Clin North Am. 2007; 45: 317-331Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar Capsule endoscopy (CE) studies have revealed the limitations of conventional fluoroscopic imaging to detect mucosal lesions in patients with Crohn's disease (CD).9Costamagna G. Shah S.K. Riccioni M.E. et al.A prospective trial comparing small bowel radiographs and video capsule endoscopy for suspected small bowel disease.Gastroenterology. 2002; 123: 999-1005Abstract Full Text Full Text PDF PubMed Scopus (635) Google Scholar, 10Buchman A.L. Miller F.H. Wallin A. et al.Videocapsule endoscopy versus barium contrast studies for the diagnosis of Crohn's disease recurrence involving the small intestine.Am J Gastroenterol. 2004; 99: 2171-2177Crossref PubMed Scopus (105) Google Scholar, 11Eliakim R. Suissa A. Yassin K. et al.Wireless capsule video endoscopy compared with barium follow-through and computerised tomography in patients with suspected Crohn's disease—final report.Dig Liver Dis. 2004; 36: 519-522Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar The development of effective biologic and immunomodulator therapies has increased the need for intestinal imaging, to detect fistulizing disease, determine treatment strategies, reduce complications, and reproducibly and accurately track inflammation beyond the reach of the endoscope. Successful therapy for CD requires detection and treatment of the inflammation when it still can be reversed;12Cosnes J. Cattan S. Blain A. et al.Long-term evolution of disease behavior of Crohn's disease.Inflamm Bowel Dis. 2002; 8: 244-250Crossref PubMed Google Scholar to achieve this goal, we must improve our understanding of inflammatory healing.13D'Haens G.R. Fedorak R. Lemann M. et al.Endpoints for clinical trials evaluating disease modification and structural damage in adults with Crohn's disease.Inflamm Bowel Dis. 2009; 15: 1599-1604Crossref PubMed Scopus (36) Google Scholar Patients with CD are evaluated by imaging technologies that allow physicians to objectively detect, stage, and classify inflammatory, obstructive, and fistulizing disease; select treatment; assess response to therapy; and determine subsequent risk. Clinical indices such as the CD Activity Index incorporate symptoms and other clinical parameters14Sandborn W.J. Feagan B.G. Hanauer S. et al.A review of activity indices and efficacy endpoints for clinical trials of medical therapy in adults with Crohn's disease.Gastroenterology. 2002; 122: 512-530Abstract Full Text Full Text PDF PubMed Google Scholar but rely on subjective assessments of patients and can underestimate biologic activity in patients with fistulizing disease.14Sandborn W.J. Feagan B.G. Hanauer S. et al.A review of activity indices and efficacy endpoints for clinical trials of medical therapy in adults with Crohn's disease.Gastroenterology. 2002; 122: 512-530Abstract Full Text Full Text PDF PubMed Google Scholar, 15Irvine E. Usual therapy improves perianal Crohn's disease as measured by a new disease activity index McMaster IBD study group.J Clin Gastroenterol. 1995; 20: 27-32Crossref PubMed Scopus (111) Google Scholar, 16Present D. Rutgeerts P. Targan S. et al.Infliximab for the treatment of fistulas in patients with Crohn's disease.N Engl J Med. 1999; 340: 1398-1405Crossref PubMed Scopus (1613) Google Scholar Additionally, clinical indices do not correlate with endoscopic or serum markers of inflammation,17Cellier C. Sahmoud T. Froguel E. et al.Correlations between clinical activity, endoscopic severity, and biological parameters in colonic or ileocolonic Crohn's disease A prospective multicentre study of 121 cases. The Groupe d'Etudes Therapeutiques des Affections Inflammatoires Digestives.Gut. 1994; 35: 231-235Crossref PubMed Google Scholar and active enteric inflammation is often present in patients without symptoms.18Solem C.A. Loftus Jr, E.V. Tremaine W.J. et al.Correlation of C-reactive protein with clinical, endoscopic, histologic, and radiographic activity in inflammatory bowel disease.Inflamm Bowel Dis. 2005; 11: 707-712Crossref PubMed Scopus (191) Google Scholar Endoscopic imaging does not detect transmural inflammation or penetrating disease (ie, fistulas, sinus tracks, or abscesses that arise from fistulas) in the presence of mucosa of normal appearance.17Cellier C. Sahmoud T. Froguel E. et al.Correlations between clinical activity, endoscopic severity, and biological parameters in colonic or ileocolonic Crohn's disease A prospective multicentre study of 121 cases. The Groupe d'Etudes Therapeutiques des Affections Inflammatoires Digestives.Gut. 1994; 35: 231-235Crossref PubMed Google Scholar, 19Lee S.S. Kim A.Y. Yang S.K. et al.Crohn disease of the small bowel: comparison of CT enterography, MR enterography, and small-bowel follow-through as diagnostic techniques.Radiology. 2009; 251: 751-761Crossref PubMed Scopus (130) Google Scholar, 20Siddiki H.A. Fidler J.L. Fletcher J.G. et al.Prospective comparison of state-of-the-art MR enterography and CT enterography in small-bowel Crohn's disease.AJR Am J Roentgenol. 2009; 193: 113-121Crossref PubMed Scopus (132) Google Scholar We review technologies for imaging IBDs, discussing their roles in detecting symptomatic and clinically occult disease, mural and perienteric healing, and response to therapy. We also summarize trends in technology, comparing benefits and risks of different approaches. Before CT and MR enterography are performed, enteric contrast agents are given to patients to distend the bowel lumen. These agents contain sugar alcohols or osmotic laxatives to prevent absorption of water and provide diagnostically acceptable images, compared with enteroclysis.2Lauenstein T. Schneemann H. Vogt F. et al.Optimization of oral contrast agents for MR imaging of the small bowel.Radiology. 2003; 228: 279-283Crossref PubMed Scopus (84) Google Scholar, 7Young B.M. Fletcher J.G. Booya F. et al.Head-to-head comparison of oral contrast agents for cross-sectional enterography: small bowel distention, timing, and side effects.J Comput Assist Tomogr. 2008; 32: 32-38Crossref PubMed Scopus (31) Google Scholar, 21Wold P.B. Fletcher J.G. Johnson C.D. et al.Assessment of small bowel Crohn disease: noninvasive peroral CT enterography compared with other imaging methods and endoscopy—feasibility study.Radiology. 2003; 229: 275-281Crossref PubMed Scopus (201) Google Scholar, 22Negaard A. Paulsen V. Sandvik L. et al.A prospective randomized comparison between two MRI studies of the small bowel in Crohn's disease, the oral contrast method and MR enteroclysis.Eur Radiol. 2007; 17: 2294-2301Crossref PubMed Scopus (101) Google Scholar, 23Negaard A. Sandvik L. Berstad A.E. et al.MRI of the small bowel with oral contrast or nasojejunal intubation in Crohn's disease: randomized comparison of patient acceptance.Scand J Gastroenterol. 2008; 43: 44-51Crossref PubMed Scopus (29) Google Scholar The enteric contrast agents used to study IBD typically have low attenuation or signal, to improve detection of segments of inflamed bowel, which have high attenuation and signal when contrast agents are given intravenously. Patients typically ingest 1300–1800 cc of enteric contrast agent over 30 to 60 minutes, with imaging typically performed 60 minutes after the beginning of ingestion.7Young B.M. Fletcher J.G. Booya F. et al.Head-to-head comparison of oral contrast agents for cross-sectional enterography: small bowel distention, timing, and side effects.J Comput Assist Tomogr. 2008; 32: 32-38Crossref PubMed Scopus (31) Google Scholar Among patients with CD, CT and MR enterography findings are similar and have been well described.5Paulsen S.R. Huprich J.E. Fletcher J.G. et al.CT enterography as a diagnostic tool in evaluating small bowel disorders: review of clinical experience with over 700 cases.Radiographics. 2006; 26: 641-662Crossref PubMed Scopus (166) Google Scholar, 20Siddiki H.A. Fidler J.L. Fletcher J.G. et al.Prospective comparison of state-of-the-art MR enterography and CT enterography in small-bowel Crohn's disease.AJR Am J Roentgenol. 2009; 193: 113-121Crossref PubMed Scopus (132) Google Scholar, 24Fletcher J.G. Huprich J. Loftus Jr, E.V. et al.Computerized tomography enterography and its role in small-bowel imaging.Clin Gastroenterol Hepatol. 2008; 6: 283-289Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar, 25Hara A.K. Leighton J.A. Heigh R.I. et al.Crohn disease of the small bowel: preliminary comparison among CT enterography, capsule endoscopy, small-bowel follow-through, and ileoscopy.Radiology. 2006; 238: 128-134Crossref PubMed Scopus (159) Google Scholar, 26Prassopoulos P. Papanikolaou N. Grammatikakis J. et al.MR enteroclysis imaging of Crohn disease.Radiographics. 2001; 21: S161-S172Crossref PubMed Google Scholar Findings are either confined to the bowel wall or extraenteric. In patients with active CD, bowel wall findings reflect acute and chronic mural inflammation; they include mural hyperenhancement, bowel wall thickening, and stratification (Figure 1). Mural hyperenhancement means segmental increases in the enhancement of bowel wall (either transmurally or to the inner lining of the bowel wall) and is identified by comparing the affected bowel segments with adjacent segments. Using this approach, mural hyperenhancement correlates with inflammation at histology and is the most sensitive imaging finding reflecting active disease.21Wold P.B. Fletcher J.G. Johnson C.D. et al.Assessment of small bowel Crohn disease: noninvasive peroral CT enterography compared with other imaging methods and endoscopy—feasibility study.Radiology. 2003; 229: 275-281Crossref PubMed Scopus (201) Google Scholar, 27Bodily K.D. Fletcher J.G. Solem C.A. et al.Crohn disease: mural attenuation and thickness at contrast-enhanced CT enterography—correlation with endoscopic and histologic findings of inflammation.Radiology. 2006; 238: 505-516Crossref PubMed Scopus (159) Google Scholar Segmental mural hyperenhancement is a nonspecific finding that is also associated with other inflammatory conditions; however, the presence of asymmetrical mural enhancement and thickening is virtually pathognomonic for CD (Supplementary Figure 1). Mural thickening is present when the thickness of the bowel wall is greater than 3 mm in a bowel loop that is distended with fluid; in CD, it is often asymmetric and prominent along the mesenteric border. Mural stratification refers to the laminated appearance of the thickened bowel wall and can accompany bowel wall thickening. Many healthy patients have mural stratification with intramural fat in the terminal ileum but not accompanied by other signs of inflammation. Evaluating images for the combination of segmental hyperenhancement and wall thickening improves the detection of mural inflammation.28Baker M.E. Walter J. Obuchowski N.A. et al.Mural attenuation in normal small bowel and active inflammatory Crohn's disease on CT enterography: location, absolute attenuation, relative attenuation, and the effect of wall thickness.AJR Am J Roentgenol. 2009; 192: 417-423Crossref PubMed Scopus (19) Google Scholar, 29Siddiki H. Fletcher J.G. Hara A.K. et al.Validation of a lower radiation computed tomography enterography imaging protocol to detect Crohn's disease in the small bowel.Inflamm Bowel Dis. 2011; 17: 778-786Crossref PubMed Scopus (15) Google Scholar Because CD is a transmural inflammatory process, inflammation can extend into the adjacent perienteric fat and small bowel mesenteric tissues. Increased density in the perienteric fat results from extension of the inflammatory process outside the bowel wall and is associated with increased serum levels of C-reactive protein (CRP).30Colombel J.F. Solem C.A. Sandborn W.J. et al.Quantitative measurement and visual assessment of ileal Crohn's disease activity by CT enterography: correlation with endoscopic severity and C-reactive protein.Gut. 2005; 55: 1561-1567Crossref Scopus (111) Google Scholar Fibrofatty proliferation refers to an increased deposition of fat, which can be metabolically active, along the mesenteric border of the bowel; it is detected by surgery or imaging.31Desreumaux P. Ernst O. Geboes K. et al.Inflammatory alterations in mesenteric adipose tissue in Crohn's disease.Gastroenterology. 1999; 117: 73-81Abstract Full Text Full Text PDF PubMed Scopus (157) Google Scholar The comb sign is the appearance of an engorged vasa recta (Supplementary Figure 2); it correlates with increased levels of CRP and erythrocyte sedimentation rates and risk for aggressive treatment during flares of CD.32Lee S. Ha H. Yang S. et al.CT of prominent pericolic or perienteric vasculature in patients with Crohn's disease: correlation with clinical disease activity and findings on barium studies.Am J Roentgenol. 2002; 179 (17941029)Google Scholar Extension of inflammation into the mesentery can cause mesenteric arterial and venous thrombosis: in acute cases, this appears as a clot within an enlarged vessel, and in chronic cases, as vessel narrowing with collateral formation.33Aguas M. Bastida G. Nos P. et al.Septic thrombophlebitis of the superior mesenteric vein and multiple liver abscesses in a patient with Crohn's disease at onset.BMC Gastroenterol. 2007; 7: 22Crossref PubMed Scopus (14) Google Scholar, 34Sanghavi P. Paramesh A. Dwivedi A. et al.Mesenteric arterial thrombosis as a complication of Crohn's disease.Dig Dis Sci. 2001; 46: 2344-2346Crossref PubMed Scopus (11) Google Scholar Penetrating disease causes fistulas, sinus tracts, phlegmons, and abscesses in up to 20% of patients with CD.35Bruining D.H. Siddiki H.A. Fletcher J.G. et al.Prevalence of penetrating disease and extraintestinal manifestations of Crohn's disease detected with CT enterography.Inflamm Bowel Dis. 2008; 14: 1701-1706Crossref PubMed Scopus (41) Google Scholar When imaged by CT, fistulas appear as enhancing extraenteric tracts that sometimes contain air or fluid and frequently arise from inflamed bowel loops (Supplementary Figure 3).36Booya F. Akram S. Fletcher J. et al.CT enterography and fistulizing Crohn's disease: clinical benefit and radiographic findings.Abdom Imaging. 2009; 34: 467-475Crossref PubMed Scopus (25) Google Scholar Patients with IBD can develop neoplasms of the small bowel, particularly adenocarcinomas and lymphomas and, in rare instances, carcinoid tumors. Imaging also detects primary sclerosing cholangitis, sacroiliitis, renal stones, cholelithiasis, and avascular necrosis (from steroid therapy).35Bruining D.H. Siddiki H.A. Fletcher J.G. et al.Prevalence of penetrating disease and extraintestinal manifestations of Crohn's disease detected with CT enterography.Inflamm Bowel Dis. 2008; 14: 1701-1706Crossref PubMed Scopus (41) Google Scholar Following intravenous administration of contrast agent, CT enterography can be used to identify segmental bowel hyperenhancement and fistulas. CT imaging is generally performed about 50 seconds after contrast injection when enhancement of the normal bowel wall is maximal (ie, the "enteric phase"),37Schindera S.T. Nelson R.C. DeLong D.M. et al.Multi-detector row CT of the small bowel: peak enhancement temporal window—initial experience.Radiology. 2007; 243: 438-444Crossref PubMed Scopus (33) Google Scholar but imaging later during the hepatic phase of enhancement (∼65 seconds) also effectively displays bowel inflammation.38Vandenbroucke F. Mortele K.J. Tatli S. et al.Noninvasive multidetector computed tomography enterography in patients with small-bowel Crohn's disease: is a 40-second delay better than 70 seconds?.Acta Radiol. 2007; : 1-9PubMed Google Scholar Multiplanar images are reconstructed, with slice thicknesses generally of 3 mm or less. Automatic exposure control is used to modulate the x-ray tube current according to patient size, in order to minimize radiation dose, and optimize image quality. Early studies to assess the ability of CT enterography to detect CD-associated enteric inflammation were generally performed using inadequate reference standards or suboptimal techniques. Studies that used mucosal visualization as a reference standard (such as ileoscopy with biopsy) reported detection of active ileal inflammation with 75%–85% sensitivity.25Hara A.K. Leighton J.A. Heigh R.I. et al.Crohn disease of the small bowel: preliminary comparison among CT enterography, capsule endoscopy, small-bowel follow-through, and ileoscopy.Radiology. 2006; 238: 128-134Crossref PubMed Scopus (159) Google Scholar, 27Bodily K.D. Fletcher J.G. Solem C.A. et al.Crohn disease: mural attenuation and thickness at contrast-enhanced CT enterography—correlation with endoscopic and histologic findings of inflammation.Radiology. 2006; 238: 505-516Crossref PubMed Scopus (159) Google Scholar, 29Siddiki H. Fletcher J.G. Hara A.K. et al.Validation of a lower radiation computed tomography enterography imaging protocol to detect Crohn's disease in the small bowel.Inflamm Bowel Dis. 2011; 17: 778-786Crossref PubMed Scopus (15) Google Scholar, 39Booya F. Fletcher J.G. Huprich J.E. et al.Active Crohn disease: CT findings and interobserver agreement for enteric phase CT enterography.Radiology. 2006; 241: 787-795Crossref PubMed Scopus (82) Google Scholar, 40Solem C.A. Loftus Jr, E.V. Fletcher J.G. et al.Small-bowel imaging in Crohn's disease: a prospective, blinded, 4-way comparison trial.Gastrointest Endosc. 2008; 68: 255-266Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar, 41Voderholzer W.A. Beinhoelzl J. Rogalla P. et al.Small bowel involvement in Crohn's disease: a prospective comparison of wireless capsule endoscopy and computed tomography enteroclysis.Gut. 2005; 54: 369-373Crossref PubMed Scopus (188) Google Scholar, 42Hassan C. Cerro P. Zullo A. et al.Computed tomography enteroclysis in comparison with ileoscopy in patients with Crohn's disease.Int J Colorectal Dis. 2003; 18: 121-125PubMed Google Scholar The specificity of CT enterography with endoscopic reference standards for detection of CD-associated inflammation is about 90%.20Siddiki H.A. Fidler J.L. Fletcher J.G. et al.Prospective comparison of state-of-the-art MR enterography and CT enterography in small-bowel Crohn's disease.AJR Am J Roentgenol. 2009; 193: 113-121Crossref PubMed Scopus (132) Google Scholar Using only ileoscopy as a reference standard can result in underestimation of the diagnostic performance of enterography because patients with stenotic ileoceal valves are excluded from analysis and those with inflammation proximal to the endoscope or mural inflammation, with normal overlying ileal mucosa, are classified as false positive (Figure 2).19Lee S.S. Kim A.Y. Yang S.K. et al.Crohn disease of the small bowel: comparison of CT enterography, MR enterography, and small-bowel follow-through as diagnostic techniques.Radiology. 2009; 251: 751-761Crossref PubMed Scopus (130) Google Scholar, 20Siddiki H.A. Fidler J.L. Fletcher J.G. et al.Prospective comparison of state-of-the-art MR enterography and CT enterography in small-bowel Crohn's disease.AJR Am J Roentgenol. 2009; 193: 113-121Crossref PubMed Scopus (132) Google Scholar, 29Siddiki H. Fletcher J.G. Hara A.K. et al.Validation of a lower radiation computed tomography enterography imaging protocol to detect Crohn's disease in the small bowel.Inflamm Bowel Dis. 2011; 17: 778-786Crossref PubMed Scopus (15) Google Scholar Taking these factors into account, the sensitivity of CT enterography to detect CD-associated enteric inflammation improves to about 90%.19Lee S.S. Kim A.Y. Yang S.K. et al.Crohn disease of the small bowel: comparison of CT enterography, MR enterography, and small-bowel follow-through as diagnostic techniques.Radiology. 2009; 251: 751-761Crossref PubMed Scopus (130) Google Scholar, 29Siddiki H. Fletcher J.G. Hara A.K. et al.Validation of a lower radiation computed tomography enterography imaging protocol to detect Crohn's disease in the small bowel.Inflamm Bowel Dis. 2011; 17: 778-786Crossref PubMed Scopus (15) Google Scholar Prospective studies to compare CT enterography with CE in patients with CD have been complicated by exclusion of patients with strictures or partial small bowel obstructions.40Solem C.A. Loftus Jr, E.V. Fletcher J.G. et al.Small-bowel imaging in Crohn's disease: a prospective, blinded, 4-way comparison trial.Gastrointest Endosc. 2008; 68: 255-266Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar, 41Voderholzer W.A. Beinhoelzl J. Rogalla P. et al.Small bowel involvement in Crohn's disease: a prospective comparison of wireless capsule endoscopy and computed tomography enteroclysis.Gut. 2005; 54: 369-373Crossref PubMed Scopus (188) Google Scholar For patients with nonstricturing disease, CE detects ileal inflammation with greater levels of sensitivity than CT enterography.25Hara A.K. Leighton J.A. Heigh R.I. et al.Crohn disease of the small bowel: preliminary comparison among CT enterography, capsule endoscopy, small-bowel follow-through, and ileoscopy.Radiology. 2006; 238: 128-134Crossref PubMed Scopus (159) Google Scholar, 40Solem C.A. Loftus Jr, E.V. Fletcher J.G. et al.Small-bowel imaging in Crohn's disease: a prospective, blinded, 4-way comparison trial.Gastrointest Endosc. 2008; 68: 255-266Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar, 41Voderholzer W.A. Beinhoelzl J. Rogalla P. et al.Small bowel involvement in Crohn's disease: a prospective comparison of wireless capsule endoscopy and computed tomography enteroclysis.Gut. 2005; 54: 369-373Crossref PubMed Scopus (188) Google Scholar In a study that excluded patients with symptoms of obstruction, Solem et al40Solem C.A. Loftus Jr, E.V. Fletcher J.G. et al.Small-bowel imaging in Crohn's disease: a prospective, blinded, 4-way comparison trial.Gastrointest Endosc. 2008; 68: 255-266Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar found that CT enterography diagnosed ileitis with a greater specificity than CE (89% vs 53%, respectively) and, unlike CE, could be performed in all patients. The overall sensitivity of CT enterography for detecting active inflammation of the colon has been estimated to be 74%43Johnson K.T. Hara A.K. Johnson C.D. Evaluation of colitis: usefulness of CT enterography technique.Emerg Radiol. 2009; 16: 277-282Crossref PubMed Scopus (13) Google Scholar; the test is generally considered to be complementary to ileocolonoscopy. Vogel et al estimated that CT enterography detected fistulas and abscess or phlegmon with accuracies of 94% and 97%–100%, respectively, on a per-patient basis in a surgical series (86% specificity in identification of individual fistulas).44Vogel J. da Luz Moreira A. Baker M. et al.CT enterography for Crohn's disease: accurate preoperative diagnostic imaging.Dis Colon Rectum. 2007; 50: 1761-1769Crossref PubMed Scopus (51) Google Scholar In comparison to optimal fluoroscopic techniques, CT identifies significantly more fistulas (36% vs 16%).45Sailer J. Peloschek P. Schober E. et al.Diagnostic value of CT enteroclysis compared with conventional enteroclysis in patients with Crohn's disease.AJR Am J Roentgenol. 2005; 185: 1575-1581Crossref PubMed Scopus (49) Google Scholar Patients undergoing MR enterography generally receive oral enteric contrast agents, similar to CT enterography, but some physicians use nasojejunal intubation to administer the agent and improve jejunal distention.46Lawrance I.C. Welman C.J. Shipman P. et al.Small bowel MRI enteroclysis or follow through: which is optimal?.World J Gastroenterol. 2009; 15: 5300-5306Crossref PubMed Scopus (5) Google Scholar MR enterography involves delivery of multiple, complementary pulse sequences in the axial and coronal planes, summarized in Table 1 (Figure 3).8Fidler J. MR imaging of the small bowel.Radiol Clin North Am. 2007; 45: 317-331Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar, 47Fidler J.L. Guimaraes L. Einstein D.M. MR imaging of the small bowel.Radiographics. 2009; 29: 1811-1825Crossref PubMed Scopus (61) Google Scholar Fat is also usually suppressed to improve identification of inflammation. Ultrafast gradient echo sequences are performed after gadolinium has been injected to assess enhancement characteristics of the bowel wall to identify areas of active inflammation. Spasmolytic agents are used to reduce motion artifact from peristalsis (eg, glucagon, hyoscine butylbromide). Most centers perform MR enterography with torso coils at 1.5T to aide access and reproducibility of image quality. 3T can improve the signal and spatial resolution but is limited by the dielectric effect and banding and pulse-sequence related artifacts. Several trials have shown that MR enterography detects small bowel inflammation with greater sensitivity than barium studies and also improves detection of penetrating complications.48Albert J.G. Martiny F. Krummenerl A. et al.Diagnosis of small bowel Crohn's disease: a prospective comparison of capsule endoscopy with magnetic resonance imaging and fluoroscopic enteroclysis.Gut. 2005; 54: 1721-1727Crossref PubMed Scopus (165) Google Scholar, 49Schreyer A.G. Seitz J. Feuerbach S. et al
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