MR imaging of the small bowel

Small-bowel radiology has undergone dramatic changes in the past 2 decades. Despite important recent advances in small-bowel endoscopy, radiologic imaging remains important for patients suspected of having or with established small-bowel disease. Cross-sectional imaging techniques (computed tomography and magnetic resonance [MR] imaging), used to investigate both extraluminal abnormalities and intraluminal changes, have gradually replaced barium contrast examinations, which are, however, still used to examine early mucosal disease. MR imaging techniques clearly highlight endoluminal, mural and extramural enteric details and provide vascular and functional information, thereby enhancing the diagnostic value of these techniques in small-bowel diseases. Two MR imaging based techniques are currently utilized: MR enteroclysis and MR enterography. In enteroclysis, enteric contrast material is administered through a nasoenteric tube, whereas in enterography, large volumes of enteric contrast material are administered orally. MR enteroclysis ensures consistently better luminal distention than does MR enterography in both the jejunum and the ileum and more accurately depicts endoluminal abnormalities and early disease, particularly at the level of the jejunal loops. Moreover, MR enteroclysis provides a high level of accuracy in the diagnosis and exclusion of small-bowel inflammatory and neoplastic diseases and can be used for the first radiologic evaluation, while MR enterography may effectively be used to follow up both Crohn disease patients without jejunal disease and in pediatric patients where nasogastric intubation might be a problem. MR enteroclysis may also reveal subtle transition points or an obstruction in the lower small bowel, which may escape detection when more routine methods, including enterography, are used. MR imaging offers detailed morphologic information and functional data of small-bowel diseases and provides reliable evidence of normalcy, thereby allowing the diagnosis of early or subtle structural abnormalities and guiding treatment and decisions in patient care.     

MR imaging of the small bowel

Cross-sectional imaging techniques such as CT and MR imaging have advantages over traditional barium fluoroscopic techniques in their ability to visualize superimposed bowel loops better and to improve visualization of extraluminal findings and complications. This article discusses MR imaging of the small bowel with enterography and enteroclysis techniques. It reviews the advantages, limitations, technique, and indications and reviews the results that have been obtained in evaluating different disease processes.     

Diagnostic imaging of inflammatory bowel disease

This article considers the possibilities of different image acquisition techniques in the study of inflammatory bowel disease, with special emphasis on the roles of tomodensitometry and magnetic resonance imaging. Although these techniques are not superior to barium follow through studies or conventional enteroclysis at depicting the mucosa in detail, they are very useful in the evaluation of the characteristics of the walls of the bowel loops and in the detection of possible extraluminal complications, such as abscesses, adenopathies, and mesenteric involvement. Magnetic resonance shows great potential for the study of the small bowel and is likely to play an important role in the study of inflammatory bowel disease in the near future. This recurring disease affects young patients with long life expectancies in whom exposure to ionizing radiation needs to be minimized. We explain the radiologic findings through a physiopathologic approach to the sequence of events (aphthoid ulcers, fissuring and penetrating ulcerations, formation of fistulous tracts, abscesses, mesenteric involvement) that give rise to them. We propose an objective classification based on the imaging findings that is useful for therapeutic decision making, and we describe the important role of the radiologist in the follow-up as well as in the diagnosis of this entity.     

Cross-sectional imaging of small bowel malignancies

Small bowel malignancies are rare neoplasms, usually inaccessible to conventional endoscopy but detectable in many cases by cross-sectional imaging. Modern multidetector computed tomographies permit accurate diagnosis, complete pretreatment staging, and follow-up of these lesions. In this review, we describe the cross-sectional imaging features of the most frequent histologic subtypes of the small bowel malignancies.     

Diagnostic imaging in the diagnosis of small bowel Crohn's Disease – A literature review

Crohn's Disease can be imaged using Barium sulphate studies, ultrasound, magnetic resonance imaging, computerised tomography and nuclear medicine. However, the radiological pathway used for the diagnosis and management of this disease can vary from hospital to hospital. By evaluating the literature a broad picture can be developed regarding the sensitivity and specificity of each modality. It is often the case that the sensitivity and specificity of a modality can change due to the level of skill of the operator. Barium sulphate studies are still considered to be the recognised route for diagnosing Crohn's Disease, but it is apparent that newer studies are concerned with trying to find a more patient tolerant, less invasive method of radiological diagnosis. It is also important to consider when evaluating a pathway, the availability of each modality within each individual hospital setting.     

MR imaging of the small bowel in Crohn's disease

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 advantage of these techniques over tradition barium fluoroscopic examinations secondary 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 [Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med 2007;357:2277–84]. 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 [Froehlich JM, Patak MA, von Weymarn C, Juli CF, Zollikofer CL, Wentz KU. Small bowel motility assessment with magnetic resonance imaging. J Magn Reson Imaging 2005;21:370–75]. A recent study showed that certain subgroups of patients with Crohn's disease may be exposed to higher doses of radiation; those diagnosed at an early age, those with upper tract inflammation, penetrating disease, requirement of intravenous steroids, infliximab or multiple surgeries [Desmond AN, O’Regan K, Curran C, et al. Crohn's disease: factors associated with exposure to high levels of diagnostic radiation. Gut 2008;57:1524–29]. Therefore it has been suggested that techniques that can reduce or eliminate radiation exposure should be considered for imaging [Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med 2007;357:2277–84]. Owing to the excellent softtissue contrast, direct multiplanar imaging capabilities, new ultrafast breath-holding pulse sequences, lack of ionizing radiation and availability of a variety of oral contrast agents, MR is well suited to play a critical role in the imaging of small bowel disorders. In this article we will review the technical issues related to the performance of MR enterography and enteroclysis and discuss the role and controversies of using MR in the assessment of inflammatory bowel disease.     

Current concepts in imaging of small bowel obstruction

The diagnosis and treatment of small bowel obstruction continue to evolve. The imaging approach in the work-up of patients with known or suspected small bowel obstruction and the timing of surgical intervention in this disease have undergone considerable changes over the past two decades. This article examines the current concepts related to the use of imaging technology in the diagnosis and management of patients with small bowel obstruction. The meaning of frequently used but poorly defined terms in describing intestinal obstruction is clarified and illustrated.     

MR imaging of small bowel with water administration

We performed MR imaging of the small bowel (MRSB) in 20 patients using water as an oral contrast agent, to improve the demonstrability of pathologic conditions without a large amount of intestinal fluid. Bowel lumen and folds were clearly visualized: duodenum in 13(65%), jejunal loops in 14 (70%), ileal loops in 15(75%), and ileocecum in 8 (40%) cases. Furthermore, conventional enteroclysis was performed in 16 of 20 patients, and the MRSB findings were comparable with those of conventional enteroclysis. If conventional enteroclysis is used as the gold standard, MRSB visualized luminal stenosis in 11 of 13(84.6%), displacement or extrinsic compression in 4 of 5(80%), polypoid lesion in 3 of 4(75%), and fistula formation in one of one cases. None of four ulcerative lesions could be visualized by MRSB. Our MRSB technique is a noninvasive, easy method that does not require a long time. Accordingly, MRSB can be used in addition to the conventional MR sequence. MRSB has potential usefulness for evaluating small-bowel disease without radiation exposure.     

Crohn's disease at the small bowel imaging by the ultrasound-enteroclysis

SUMMARY: Crohn's disease is more likely a systemic disease governed by a shift in the immune response, thus affecting the whole MALT system. Its treatment should be as conservative as possible and surgery is usually taking place after complications like indolent fistulations, stenoses, bleeding, or bowel perforation started. Standard radiological methods to check the extent of the disease are loaded either with certain radiation exposure (enteroclysis, CT) or lack standardization (ultrasound). The aim of this small study was to evaluate the worth of ultrasound-enteroclysis in detecting the extent and complications of the Crohn's disease in surgically treated patients. MATERIAL AND METHODS: Since 1997, when we started with the ultrasound-enteroclysis, 246 surgical performances were involved into our study. Out of them, 181 had conventional abdominal intestinal ultrasound as well as conventional enteroclysis within 1 week. Remaining 65 cases were diagnosed by the ultrasound-enteroclysis. Intestinal ultrasound was performed on the Ultramark 3000 HDI device with autofocussable convex 5 MHz and linear 7.5 MHz probes or nowadays ATL 5000 HDI, 7-12 MHz linear probe. No contrast enhancement was used. Enteroclysis was done with the Micropaque suspension diluted 1:1 with HP-7000 300 ml with its application rate up to 75 ml/min followed by HP-7000 solution 2000 ml, application rate of 120 ml/min. The patients with ultrasound-enteroclysis were applied HP 7000 solution only (2000 ml, rate 100ml/s) via an enteroclysis catheter. All investigations were video-recorded. RESULTS: Consent with the per-operative finding was reached in 162 from 181 enteroclyses and in 169 of 181 ultrasounds. Ultrasound-enteroclysis was precise in 61 cases from 65. Among these, 60 patients had the recurrence during the treatment proved by clinical and laboratory results. This re-activation was clearly revealed in 38 from 43 cases by enteroclysis, 41 from 43 by US and in 16 from 17 by ultrasound-enteroclysis. From 30 patients that developed acute complication non-responding to the conservative therapy (abscesses, fistulas and intestinal obstructions) there were 18 from 20 accurately diagnosed by enteroclysis, only 12 from 20 by US and 9 from 10 by US-enteroclysis. The differences were either statistically non-significant or there were too small numbers to give sensible statistical results, but low sensitivity of ultrasound in complications (p=0.05). CONCLUSION: US-enteroclysis seems to became the standard examination of patients with Crohn's disease mainly in those with unclear conventional ultrasound. The most important fact is that this examination significantly decreases the radiation load when maintaining high sensitivity. This is very important namely in patients with Crohn's disease that require life-long observation and repeated examinations. This examination is much more easy to standardize than the conventional US.     

Diagnostic performance of 64-MDCT for blunt small bowel perforation

ObjectiveThe objective was to assess the diagnostic performance of 64-multidetector computed tomography (CT) for blunt small bowel perforation (BSBP).Materials and methodsThe study included 106 CT examinations of surgically proven blunt bowel and mesentery injuries (78 of BSBP and 28 of non-BSBP). CT diagnosis was based on detection of bowel wall discontinuity or extraluminal gas.ResultsAccuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT diagnosis were 84.0%, 79.5%, 96.4%, 98.4%, and 62.8%, respectively. Bowel wall discontinuity and extraluminal gas were detected on 19.2% and 74.4% examination, respectively.ConclusionCT diagnosis of BSBP is highly specific but not sensitive.     

Diagnostic imaging of renal tumors of small dimensions

The incidence of small renal tumors (less than cm 3) has increased in the past few years. Reasons for the increased number of reports are related to the contribution of Sonography and Computed Tomography--which enable a greater number of kidneys to be examined and allow a more detailed study of renal parenchyma. In order to assess the diagnostic value and role of the various imaging techniques in this pathology, the authors reviewed all renal tumors observed between 1982 and 1987. Nineteen cases presented with the characteristics of small renal tumors with "solid" findings on both US and CT. Sixteen cases were histologically proven (15 adenocarcinomas, 1 oncocytoma). Three recent, unoperated, cases are included since their features are the same as in the other cases. Metastases and other kinds of tumors (i.e. angiomyolipomas) are not included in this series. Ivp was performed in 14/19 cases; US and CT were always performed. CT proved to be the most sensitive technique, being positive in all cases. Ivp was positive in 9/14 cases (64%) and US in 14/19 (73%). A significant increase in the number of small renal tumors detected was observed, mainly in 1985-1987. This increase is correlated with the increase in the total number of abdominal examinations which US and CT have made possible. Most patients were asymptomatic; in fact, 15/19 cases were incidentally discovered with US and CT of the upper abdomen. US and CT appear to give a substantial contribution to an early diagnosis of small renal tumors, which may have a significant impact on both surgery and prognosis.     

小肠腺癌的气钡双对比造影诊断

本文搜集经病理手术证实的小肠腺癌20例,进行分析,旨在探讨小肠气钡双重造影对小肠腺癌的诊断价值.1 材料与方法1.1 临床资料搜集我院2004年～2009年临床及影像资料完整经病理证实的小肠腺癌20例,其中十二指肠10例,空肠4例,回肠6例.男12例,女8例,年龄48～80岁,平均年龄67.5岁.     

OMOM 胶囊内镜对小肠疾病的诊断价值

目的：探讨胶囊内镜（ capsule endoscope ,CE）在小肠疾病中的诊断价值。方法回顾性分析196例行CE检查患者的临床资料,按不同症状归类,分析CE对各类症状组检出疾病的阳性率。结果195例完成检查,胶囊内镜回盲瓣通过率为86．6％（169/195）,123例发现小肠病变（63．0％）,消化道出血组小肠病因检出率80．9％（68/84）,明显高于其他各组（P均＜0．01）。其他各组小肠疾病检出率为腹泻组64．7％,腹痛组51．7％,消瘦组50％和腹胀组38．4％。结论国产OMOM胶囊内镜安全,顺应性好,可用于小肠疾病,尤其是不明原因消化道出血的诊断。     

Optimization of oral contrast agents for MR imaging of the small bowel

Effect on small-bowel distention of additives to water as contrast agents for magnetic resonance (MR) imaging was assessed. Oral contrast agents included water and water in combination with mannitol, a bulk fiber laxative, locust bean gum, and a combination of mannitol and locust bean gum. Filling of the small bowel was quantified on coronal images obtained with two-dimensional true fast imaging with steady-state precession sequence; bowel diameters were measured. Ingestion of water with locust bean gum and mannitol provided the best distention of the small bowel. MR imaging of the small bowel with oral administration of water can be improved with addition of osmotic and nonosmotic substances that lead to decreased water resorption.     

Classification of small bowel Crohn's subtypes based on multimodality imaging

This article has reviewed the imaging features that correspond to and support the classification of patients into clinical subtypes of Crohn's disease. One study showed that radiologic features on barium studies closely correlated with the Crohn's Disease Activity Index, and another study indicated that CT findings changed patient management in up to 29% of cases. Knowledge of the location, severity, and presence of complications assist in providing patients with appropriate treatment options. Reports of radiologic studies in Crohn's disease should include the presence or absence of imaging features that support these different subtypes. An additional advantage of the use of a reproducible imaging classification that emphasizes morphologic features would be improved comparison of the results of different investigators and treatment protocols. Whatever method of radiologic investigation is employed, it should be targeted to answer questions relevant to patient management. The imaging modalities used should be able to classify the small bowel Crohn's subtypes and should be reflected in the radiologists' reports.