Study Of256-Multidetector-row Computed Tomography Enterography (MDCTE) In Clinical Application

Multidetector-row computed tomographic enterography (MDCTE) is an emerging alternative to traditional fluoroscopy for the assessment of disorders of the small bowel. The greatly improved spatial and temporal resolution provided by multidetector CT scanners, combined with good luminal distention provided by negative oral contrast agents and with good bowel wall visualization, have made CT enterography the main imaging modality not only for investigating proved or suspected inflammatory bowel disease but also for detecting occult gastrointestinal tract bleeding, small bowel neoplasms, and mesenteric ischemia. CT enterography is particularly useful for differentiating between active and fibrotic bowel strictures in patients with Crohn disease, thus enabling selection of the most appropriate treatment (medical management or intervention) for an improved outcome. CT enterography allows excellent visualization of the entire thickness of the bowel wall and depicts extraenteric involvement as well, providing more detailed and comprehensive information about the extent and severity of the disease process.The objectives of this review are fourfold. First, we aimed at describing the technique of CT enterography, including the optimal position of choice. Second, we wished to make the reader more familiar with the imaging of normal mesenteric small bowel.Third,we decided to discuss the utility of CT enterography for evaluating diseases of the small bowel.Fourth,we wanted to touch briefly on potential developments of mesenteric small bowel imaging that may be anticipated.PART I Optimization of Patient’s Different Position in abdominal256Multidetector-row Computed Tomography Enterography (MDCTE)Purpose:The aim of this study was to evaluate the optimization of patient’s position, the width of the enteric cavity and bowel wall thickness in256-MDCTE.Materials and methods:A total of60healthy volunteers (male29; female31; mean age48.3years) underwent256-MDCTE using oral neutral enteral and intravenous contrast. Thirty-five of60(58.3%) patients had prone scan and35/60(41.7%) had supine study.The width of the enteric cavity and bowel wall thickness was measured through the transverse section and multiplanar, on-the-fly reconstruction. Results:Duodenum was measured to the maximum width and bowel wall thickness. No significant differences were observed between the2group regarding the following parameters at the patient level:bowel wall thickening, bowel wall enhancement49cases were distended well with oral administration of2.5%mannitol.Prone position allows a better and more subtle visualization of the bowel loops because of their better distribution.Conclusions:Slight structure of the small bowel was demonstrated well in MDCTE.Prone position can be superior to supine position in demonstrating bowel loops and clinical work. PART ⅡMDCTE manifestations of normal small bowelPurpose:To evaluate MDCTE manifestations of normal small bowel with enhancement after large dose isosmotic mannitol (2.5%) was oral administered.Materials and methods:A total of60healthy volunteers (male29; female31; mean age48.3years) underwent256-MDCTE using oral neutral enteral and intravenous contrast.Bowel wall thickening and enhancement, bowel lumen, mesenteric vessels, abdominal nodes and perivisceral fat can be evaluated with the transverse section and multi-planar reconstruction.Results:The256-MDCTE method used the oral intake of large volumes of neutral contrast agents and rapid intravenous administration of iodinated contrast to improve visualization of the small bowel wall and its mural features. Slight structure and the enhancement of the bowel wall was demonstrated well and better reflect in the vein of early (60s). With multi-planar reconstruction,MDCTE showed the radiologist and gastroenterologist not only the mucosal surface, but also the mural and extralumenal features of the bowel wall.Conclusions:MDCTE has the capability of helical scanning and three-dimensional post-processing techniques, can demonstrate the intestinal wall and extra-luminal structure clearly,which makes it optimal method of choice of small bowel examination. PARTIII Application of256Multidetector-row computed tomography enterography (MDCTE) in small bowel diseasesPurpose:To discuss the utility of MDCTE for evaluating diseases of the small bowel.Materials and methods:At our institution,118patients (male53; female65; mean age48.5years) with symptoms of suspected small bowel diseases underwent256-MDCTE.Pertinent MDCTE and histopathology reports were reviewed. The CT appearances characteristic of small-bowel tumor, inflammatory bowel disease and other conditions affecting the small bowel are described and illustrated in detail. Associated complications and extraenteric manifestations also are described.Results:Of118MDCTEs performed,the sensitivity, specificity, positive and negative predictive values and accuracy of visual assessment for small bowel disease were78.87%(56/71),100%(47/47),100%(56/56),75.80%(47/62), and87.29%((56+47)/118), respectively.There were15cases of small intestinal tumor, including5cases of adenocarcinoma, with the CT signs of lobular mass and obstruction in proximal terminal. There were3cases of GIST, in which there were masses rich in blood supplying without obstruction;1case of lymphoma showing intestinal wall thickened variously in different part with mild enhancement,and1case of leiomyoma,exhibiting bowel wall thickening with slight enhancement.The remaining5cases of mesenteric metastasis demonstrating the presence of lymphadenopathy, ascites and so on.There were25cases of small bowel imflammation. In all16cases of Crohn’s diseases, small bowel involvement was typically transmural, with characteristic skip lesions. CT features of active Crohn disease include mucosal hyperenhancement, irregular wall thickening, mural stratification with a prominent vasa recta (comb sign), and mesenteric fat stranding.3cases of ulcerative colitis characterized by a continuous pattern of bowel wall involvement, starting from the rectum, without evidence of skip lesions. Ulcerative colitis predominantly involved the large bowel but may extend to the terminal ileum.Extraintestinal manifestations may occur but were uncommon. Mucosal hyperenhancement along with circumferential and symmetric bowel wall thickening was present. There was mural stratification with enhancement of the inner mucosa and outer muscularis propria.Mesenteric hyperemia was present in the pericolonic fat; MDCTE demonstrated findings suggestive of intestinal tuberculosis in one patient by depicting ulcero-nodular with strictures, edema and thickening of the ileocecal region, the presence of necrotic mesenteric lymph nodes that were adjacent to a small-bowel thickening. There was1case of viral gastroenteritis and7cases of generalized small bowel enteritis with non-specific MDCTE features include bowel thickening and submucosal edema appreciable in the entire intestine. Mesenteric vessels were regularly opacified. There were22cases of small bowel obstruction. MDCTE depicting the features include simple obstruction patterns (single abrupt transition zone, beak sign,"fat notch" sign), patterns of closed-loop obstruction (two adjacent beaks, C-shaped bowel, radial distribution of mesenteric vessels), the location of the obstruction in the abdominal cavity, and the presence of a whirl sign and a "small-bowel feces".There were3cases of small bowel vascular lesions. One case of superior mesenteric artery occlusion and1case of superior mesenteric vein occlusion; the former demonstrated the twist, thin,irregular arteries,and the number of branches decreased.The latter showed widely longitual filling defect,bowel wall thickening, and the mensenterium edema.The remaining1case of angiodysplasia with non-specific CT features present. Some other rare small-bowel cases were also present in our study.Conclusion:Our results demonstrated that MDCTE with peroral and intravenous contrast is useful in assessing small bowel diseases;however, further studies are needed to determine and validate the full diagnostic and clinical potential of bowel imaging at MDCTE. PART IV Future trends in imaging of small bowel diseasesEarly diagnosis of mesenteric small bowel diseases is a diagnostic challenge for both clinicians and radiologists.CT-enterography is an invaluable technique for the evaluation of various small bowel diseases. This technology, coupled with modern workstations that have complex post processing capabilities, allows creation of multiplanar and three-dimensional reformations with a resolution similar to that obtained with axial images. During the same time, combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, MR-enterography is being used more frequently. However, the superior spatial resolution of CT enterography still makes it the initial imaging modality of choice in many adult patients. In this review, we decided to introduce current imaging tests that can be used for the detection and the characterization of some diseases of the mesenteric small bowel. Then, explain the rationale for selecting one examination instead of another for a specific indication.