Evaluation of small bowel tumors: MR enteroclysis

Magnetic resonance imaging (MRI) of the small bowel has become widely accepted at centers dedicated to the diagnosis and treatment of inflammatory bowel disease, due to the method’s diagnostic efficacy. MR enteroclysis is an imaging modality that combines the advantages of enteroclysis and multiplanar MR and allows the detection and the manifestations of small bowel diseases wherever they are located (intraluminal, intramural, or extramural). Magnetic resonance enteroclysis (MRE) is an emerging technique used for the detection and evaluation of small bowel neoplasms. This article illustrates the imaging appearances of small bowel tumors on MRI and the usefulness of MR enteroclysis in the diagnosis and categorization of these tumors, also discussing the role of MRE in comparison with other diagnostic modalities.     

Magnetic resonance enteroclysis compared with conventional enteroclysis and computed tomography enteroclysis: a critically appraised topic

Recent advances in CT and MR technology, particularly the advent of multidetector CT (MDCT), the advent of rapidly changing gradients in industry standard MRI scanners, enabling ultrafast sequences, have led to an expansion in the role of cross sectional imaging in the investigation of small bowel disorders. We conducted an evidence-based review of MR enteroclysis (MRE) and how it performs in comparison to CT enteroclysis (CTE) and the gold standard of conventional enteroclysis (CE) for diagnosis of small bowel Crohn’s disease and small bowel neoplasia. We used the standard 5 step evidence-based medicine method of ask, search, appraise, apply and evaluate. We found 3 relevant level 1B studies, and one level 3B study. No studies evaluating MRE in small bowel neoplasia were found. MRE does not perform as well as CE in evaluation of fine mucosal detail, but the additional extraluminal detail, and absence of ionising radiation enhances its overall performance. It was not possible to establish the relative diagnostic performances of MRE and CTE from existing literature. CTE does involve patient irradiation. For patients in whom jejunal intubation and enteroclysis is considered to evaluate the small bowel, MRE should be considered the first-line investigation, local resources and expertise permitting.     

Crohn disease of the small bowel: MR enteroclysis versus conventional enteroclysis

Enteroclysis has been suggested as the technique of choice for the evaluation of Crohn disease of the small intestine. Adequate distention of the entire small bowel with barium suspension allows the radiologic demonstration of mucosal abnormalities and provides functional information by defining distensibility or fixation of the small bowel loops. The principal disadvantage of conventional enteroclysis is the limited indirect information on the state of the bowel wall and extramural extension of Crohn disease, and its effectiveness may be hindered owing to overlapping bowel loops. Moreover, the radiation dose administered to patients, mostly at a young age, should be considered. Magnetic resonance (MR) enteroclysis is an emerging technique for small bowel imaging and was introduced to overcome the limitations of conventional enteroclysis and MR cross-sectional imaging by combining the advantages of both into one technique. MR enteroclysis has the potential to change how the small bowel is assessed because of the functional information, soft tissue contrast, direct multiplanar imaging capabilities, and lack of ionizing radiation.     

Role of computed tomography enterography/magnetic resonance enterography: is it in prime time?

Today, cross-sectional imaging modalities, such as computed tomography enterography (CTE) and magnetic resonance enterography (MRE), are particularly suited to evaluate small bowel diseases, especially Crohn's disease (CD). It is well known that CTE/MRE can provide excellent assessment of disease activity as well as the macroscopic features, extramural abnormalities, and complications of the small intestine in patients with CD. In general, CTE is considered as the first-line modality for the evaluation of suspected inflammatory bowel disease and for long-term assessment or follow-up of these patients. Because of the advantage of lack of radiation, MRE is being used more frequently, especially in children or young patients with CD.     

儿童小肠MR成像临床应用评价

目的分析儿童小肠病变MRI表现,评价小肠MR成像在儿科中的临床应用价值。方法对12例经手术和病理证实的小肠病变患儿进行回顾性分析,检查前让患儿口服2.5%的等渗甘露醇溶液后,静脉注射山莨菪碱0.3mg/kg,随后行MR扫描,扫描方法包括冠状面真稳态进动快速成像(TrueFisp)序列,横断面及冠状面T1WI、T2WI脂肪抑制序列、vibe超薄容积扫描(压脂)序列,然后行带脂肪饱和技术的T1WI横断面及冠状面增强扫描。结果 12例患儿均能接受等渗甘露醇溶液,未发现并发症,其中Crohn病6例,共显示16段炎症肠管,MRI表现为增强后病变肠壁强化明显,病变肠段肠壁增厚(厚度为5～14mm),且多表现环形增厚,肠壁厚薄不均,肠腔变窄。十二指肠球部慢性溃疡、十二指肠球部穿孔、胃肠吻合口溃疡、小肠梗阻(柿石症)、小肠淋巴瘤、肠套叠各1例。小肠MR成像不仅显示了病变本身,还显示了肠壁、肠外血管及肠系膜脂肪的情况。结论小肠MR成像安全、有效、无创、无电离辐射,能全方位多维显示儿童小肠疾病的方法。     

Adult celiac disease: MRI findings

The purpose of our report is to describe a spectrum of findings of celiac disease at MR enterography. MR enterography is a non-invasive, feasible, and reproducible imaging technique for the evaluation of small bowel. Findings on MR enterography, similar to those of conventional barium studies, may suggest a diagnosis of celiac disease.     

口服2.5%甘露醇溶液后小肠超声造影检查诊断小肠克罗恩病及其并发症

目的 观察口服2.5%甘露醇溶液后小肠超声造影检查（SICUS）诊断小肠克罗恩病（CD）及其并发症的价值。方法 前瞻性纳入135例小肠CD患者,根据C反应蛋白（CRP）水平将其分为轻微组（n=66）和严重组（n=69）,对比观察常规肠道超声（IUS）、SICUS及MR小肠造影（MRE）诊断小肠CD及其并发症的效能。结果 对所有135例及轻微组66例患者,SICUS对检出小肠CD 的敏感度均高于IUS而低于MRE（P均<0.05）;对严重组69例患者,SICUS检出小肠CD的敏感度高于IUS（P<0.05）,而与MRE差异无统计学意义（P>0.05）。所有患者中,SICUS检出小肠CD的特异度高于MRE（P<0.05）。SICUS检出小肠CD合并狭窄的敏感度均高于IUS及MRE（P均<0.05）,而其特异度差异均无统计学意义（P均>0.05）。结论 口服2.5%甘露醇溶液后SICUS有助于诊断小肠CD及其并发症,特别是肠腔狭窄;结合MRE可提高检出轻微小肠CD的敏感度。     

CT and MR enterography in evaluating small bowel diseases: when to use which modality?

MR and CT techniques optimized for small bowel imaging are playing an increasing role in the evaluation of small bowel disorders. Several studies have shown the advantages of these techniques over traditional barium fluoroscopic examinations due to improvements in spatial and temporal resolution combined with improved bowel distending agents. The preference of MR vs. CT has been geographical and based on expertise and public policy. With the increasing awareness of radiation exposure, there has been a more global interest in implementing techniques that either reduce or eliminate radiation exposure. This is especially important in patients with chronic diseases such as inflammatory bowel disease who may require multiple studies over a lifetime or in studies that require sequential imaging time points such as in assessment of gastrointestinal motility. MRI has many properties that make it well suited to imaging of the small bowel: the lack of ionizing radiation, the improved tissue contrast that can be obtained by using a variety of pulse sequences, and the ability to perform real time functional imaging. Moreover, MR modalities allow visualization of the entire bowel, without overlapping bowel loops, as well as the detection of both intra- and extraluminal abnormalities.The intra- and extraluminal MR findings, combined with contrast enhancement and functional information, help to make an accurate diagnosis and consequently characterize small bowel diseases.     

Small bowel

MR imaging, using modern equipment and a rigorous technical approach, can offer detailed morphologic information and functional data on the small bowel. The optimal study technique is debatable, although the oral administration of contrast material as a first-line approach is less expensive, faster, easier to perform, and better tolerated by patients. MR enteroclysis might be reserved for selected cases as a second-line study. The major clinical indication is the evaluation of patients who have suspected or known Crohn's disease. The absence of ionizing radiation, considering the young age of most of the patients and the frequency of the examinations, is an important advantage over other techniques (radiograph and CT enteroclysis).     

The peroral pneumocolon revisited: a valuable fluoroscopic and CT technique for ileocecal evaluation

The peroral pneumocolon represents a time-honored but somewhat forgotten and underutilized technique for improved ileocecal evaluation at small bowel fluoroscopy. The peroral pneumocolon entails fluoroscopically guided gaseous insufflation per rectum following the arrival of barium at the cecum at conventional small bowel follow-through examination. In most cases, high-quality double contrast evaluation of the terminal ileum can be achieved, often superior to enteroclysis examination for this critical location. The peroral pneumocolon improves diagnostic confidence, including assessment of disease activity, and may result in a reversal of the diagnostic impression. This simple procedure will be discussed and a spectrum of fluoroscopic findings with CT and endoscopic correlation will be provided to demonstrate the added yield of this technique in the evaluation of known or suspected Crohn’s disease. Application of the pneumocolon technique to CT for combined small and large bowel evaluation (“CT coloenterography”) will also be discussed, which represents an attractive new option for investigating inflammatory bowel disease and other bowel-related conditions. Through the use of automated low-pressure carbon dioxide delivery per rectum, supplemented by IV glucagon for relaxation of the ileocecal valve, a CT-based pneumocolon examination may prove to be a useful hybrid technique for bowel evaluation in the future.     

Small bowel involvement in blue rubber bleb nevus syndrome: MR imaging features

Blue rubber bleb nevus syndrome (BRBNS) is a rare condition which is characterized by multiple venous malformations that may affect several organs. Gastrointestinal lesions, which mostly involve the small bowel and distal colon, may be responsible for gastrointestinal bleeding, causing more frequently chronic anemia. We report herein two cases of BRBNS causing gastrointestinal bleeding which were investigated by means of MR imaging. All venous malformations showed markedly high signal intensity on fat-suppressed T2-weighted MR images. In addition, extraintestinal venous malformations displayed high signal intensity similar to that of small bowel venous malformations. Fat-suppressed T2-weighted TSE images show both small bowel and colonic involvement, thus providing useful information relative to the most appropriate therapeutic approach to be used. MR imaging is especially helpful when capsule endoscopy or enteroscopy are contraindicated or not feasible. In addition, because of lack of radiation, MR imaging can be performed repeatedly to assess the evolution of the disease before a planned surgery or endoscopic resection. Also, because BRBNS is by essence a multifocal condition with extraintestinal involvement, MR imaging appears as an appropriate imaging technique to investigate the multiple locations of the disease in one session, thus replacing multiple examinations.     

Multimodality imaging of small bowel neoplasms

Although the small intestine accounts for over 90% of the surface area of the alimentary tract, tumors of the small intestine represent less than 5% of all gastrointestinal tract neoplasms. Common small bowel tumors typically are well evaluated with cross-sectional imaging modalities such as CT and MR, but accurate identification and differentiation can be challenging. Differentiating normal bowel from abnormal tumor depends on imaging modality and the particular technique. While endoscopic evaluation is typically more sensitive for the detection of intraluminal tumors that can be reached, CT and MR, as well as select nuclear medicine studies, remain superior for evaluating extraluminal neoplasms. Understanding the imaging characteristics of typical benign and malignant small bowel tumors is critical, because of overlapping features and associated secondary complications.

     

Small bowel Crohn’s disease: MR enteroclysis and capsule endoscopy compared to balloon-assisted enteroscopy

New modalities are available to visualize the small bowel in patients with Crohn’s disease (CD). The aim of this study was to compare the diagnostic yield of magnetic resonance enteroclysis (MRE) and capsule endoscopy (CE) to balloon-assisted enteroscopy (BAE) in patients with suspected or established CD of the small bowel. Consecutive, consenting patients first underwent MRE followed by CE and BAE. Patients with high-grade stenosis at MRE did not undergo CE. Reference standard for small bowel CD activity was a combination of BAE and an expert panel consensus diagnosis. Analysis included 38 patients, 27 (71%) females, mean age 36 (20–74) years, with suspected (n = 20) or established (n = 18) small bowel CD: 16 (42%) were diagnosed with active CD, and 13 (34%) by MRE with suspected high-grade stenosis, who consequently did not undergo CE. The reference standard defined high-grade stenosis in 10 (26%) patients. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value of MRE and CE for small bowel CD activity were 73 and 57%, 90 and 89%, 88 and 67%, and 78 and 84%, respectively. CE was complicated by capsule retention in one patient. MRE has a higher sensitivity and PPV than CE in small bowel CD. The use of CE is considerably limited by the high prevalence of stenotic lesions in these patients.     

Contrast-enhanced MRI of the small bowel in Crohn��s disease

Recently, magnetic resonance imaging has emerged as a valuable tool in evaluation of small bowel Crohn’s disease. MRI provides several advantages to other imaging modalities, including the lack of ionizing radiation, multiplanar capability, and functional information. Intravenous contrast administration is a routine portion of MR enterography protocol, and aids in detection of disease extent, extramural complications such as fistula and abscess, and assessment of activity. Additionally, promising techniques such as dynamic contrast-enhanced MRI may provide quantitative measures to assess bowel perfusion, which may enhance evaluation of disease activity. This article will provide an overview of the technical aspects of contrast-enhanced MR enterography, describe common pathologic findings involving the small bowel in Crohn’s disease, summarize its role in determination of activity with an emphasis on endoscopic and histologic correlation, and compare its efficacy with other imaging modalities.     

Internal fistulas in Crohn disease: magnetic resonance enteroclysis

Internal fistulas (IFs) and abscesses are the most common complications of Crohn disease (CD). To reliably diagnose and clearly distinguish inflammatory or fibrostenotic manifestations of CD from its complications is of paramount importance to appropriately guide therapeutic decisions. Magnetic resonance enteroclysis (MRE), a recently introduced technique for small bowel imaging, has proved a high efficacy in the depiction of luminal and extraluminal manifestations of CD and holds great promise as a powerful diagnostic tool in the comprehensive diagnostic workup of this disease. As of yet, the characteristic imaging appearance of IFs on MRE has not been described in detail. This article reviews the performance of conventional imaging techniques and the current potential of MRE in the depiction of IFs in CD. Typical imaging morphology and characteristic imaging findings of IFs on MRE are described in detail and a newly defined and highly indicative imaging finding, the “star-sign,” is presented and discussed.     

Can MR elastography be used to measure liver stiffness in patients with iron overload?

Untreated hepatic iron overload causes hepatic fibrosis and cirrhosis and can predispose to hepatocellular carcinoma. MR elastography (MRE) provides a non-invasive means to measure liver stiffness, which correlates with liver fibrosis but standard gradient recalled echo (GRE)-based MRE techniques fail in patients with high iron due to very low hepatic signal. Short echo time (TE) 2D spin echo echoplanar imaging (SE-EPI)-based MRE may allow measurement of stiffness in the iron loaded liver. The purpose of this study was to describe the use of such an MRE sequence in patients undergoing liver iron quantification by MRI. In our preliminary study of 43 patients with mean LIC of 9.3 mg/g (range 1.8–21.5 mg/g), liver stiffness measurements could be made in 77% (33/43) of patients with a short TE, SE-EPI based MRE sequence. On average, mean LIC in patients with failed MRE was higher than in those with successful MRE (15.9 mg/g dry weight vs. 7.3 mg/g), but a cut-off value for successful MRE could not be established. Seven patients (21% of those with successful MRE) had liver stiffness values suggestive of the presence of significant fibrosis (> 2.49 kPa). A short TE, SE-EPI based MR elastography sequence allows successful measurement of liver stiffness in a majority of patients with liver iron loading, potentially allowing non-invasive screening for fibrosis.

     

Surveillance of patients affected by Peutz-Jeghers syndrome: diagnostic value of MR enterography in prone and supine position

Introduction  

Peutz-Jeghers syndrome (PJS) is a familial polyposis syndrome characterized by multiple hamartomatous polyps throughout the gastrointestinal tract. The aim of our study was to retrospectively determine the diagnostic value of MR enterography (MRE), performed in supine and prone position, in the detection of small bowel polyps in PJ patients.     

Computed Tomography Enterography

Computed tomography enterography (CTE) is an abdominopelvic computed tomography (CT) tailored for evaluation of the small bowel. This multidetector CT examination uses neutral oral contrast to optimally distend small bowel. Patients are scanned after the rapid injection of intravenous contrast during peak bowel wall enhancement. CTE is excellent for the evaluation of many small bowel disorders, particularly Crohn's disease. The purpose of this article is to review CTE indications, contraindications, technique, safety considerations, and imaging findings of common small bowel diseases.     

Current status of small bowel radiography

Background: In the past, small bowel examinations were usually ordered for the sake of ``completeness.' As a result, small bowel radiography was performed casually and without attention to detail. This review examines pertinent clinical issues and the recent contribution of small bowel radiography to the evaluation and management of the patient with suspected small bowel disease. Recommendations for the clinical utilization of small bowel radiography are discussed. Methods: Analysis of pertinent citations addressing valid indications for, and technique of, small bowel radiography from 1980 to July 1995 through a computerized bibliographic search (Medline and Current Contents). Results: Accepted clinical indications for small bowel radiography include (1) unexplained gastrointestinal bleeding, (2) possible small bowel tumor, (3) small bowel obstruction, (4) Crohn disease, and (5) malabsorption. The current literature reflects the limitations of the conventional small bowel follow-through, various modifications to improve its clinical yield, the important contribution of enteroclysis in the workup, and subsequent management of patients with possible small bowel disease. A controversy in the radiology literature exists as to whether to use the small bowel follow-through or enteroclysis as the primary method of examining the small bowel. Conclusion: The thoughtful selection of patients by clinicians for small bowel radiography is essential to make radiologic evaluation cost effective. The incidence of disease of the small intestine is low and is associated with nonspecific symptoms. Because of the inherent difficulty of visualizing numerous loops of an actively peristalsing bowel, a reliable imaging method is needed that not only detects small or early structural abnormality but also accurately documents normalcy. The yield of information provided by enteroclysis and its high negative predictive value suggests that it should be the primary method for small bowel examination. The ``overhead'-based conventional small bowel follow-through should be abandoned. The ``fluoroscopy'-based small bowel follow-through augmented when necessary by the peroral pneumocolon or the gas-enhanced double-contrast follow-through method is an acceptable alternative when enteroclysis is not possible. Received: 0/0/00Accepted: 0/0/00     

MR imaging of the bowel: pediatric applications

Magnetic resonance enterography with oral contrast administration using fast T2-weighted and fat saturated, contrast-enhanced T1-weighted sequences is the most common technique for bowel evaluation. The main indication for bowel MR imaging in children has been evaluation of inflammatory bowel diseases. A less common application is appendicitis. Other potential applications include evaluation of vascular malformations and transplanted bowel.