MRI in the diagnosis of small bowel disease: use of positive and negative oral contrast media in combination with enteroclysis

Imaging of Gastrointestinal Tract Ailments

Gastrointestinal (GI) disorders comprise a diverse range of conditions that can significantly reduce the quality of life and can even be life-threatening in serious cases. The development of accurate and rapid detection approaches is of essential importance for early diagnosis and timely management of GI diseases. This review mainly focuses on the imaging of several representative gastrointestinal ailments, such as inflammatory bowel disease, tumors, appendicitis, Meckel's diverticulum, and others. Various imaging modalities commonly used for the gastrointestinal tract, including magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT), and photoacoustic tomography (PAT) and multimodal imaging with mode overlap are summarized. These achievements in single and multimodal imaging provide useful guidance for improved diagnosis, staging, and treatment of the corresponding gastrointestinal diseases. The review evaluates the strengths and weaknesses of different imaging techniques and summarizes the development of imaging techniques used for diagnosing gastrointestinal ailments.

Challenges and Strategies to Optimising the Quality of Small Bowel Magnetic Resonance Imaging in Crohn’s Disease

Magnetic resonance enterography (MRE) is one of the most highly utilised tools in the assessment of patients with small bowel Crohn’s disease (CD). As a non-invasive modality, it has both patient and procedure-related advantages over ileocolonoscopy which is the current gold standard for Crohn’s disease activity assessment. MRE relies upon high-quality images to ensure accurate disease activity assessment; however, few studies have explored the impact of image quality on the accuracy of small bowel CD activity assessment. Bowel distension and motion artifacts are two key imaging parameters that impact the quality of images obtained through MRE. Multiple strategies have been employed to both minimise the effects of motion artifacts and improve bowel distension. This review discusses the definitions of bowel distension and motion artifacts within the literature with a particular focus on current strategies to improve bowel distension and limit motion artifacts in MRE.

Benign Uterine Disease: The Added Role of Imaging

Benign uterine diseases are very common gynecologic conditions that affect women mostly in reproductive age. Ultrasound examination is the first-line imaging technique, but MRI is more accurate for diagnosis, characterization, and patient management. In this review, we especially highlight the added value of MRI in the diagnosis of benign uterine disease, discuss their imaging characteristics, and describe the therapeutic options and the added value of MRI in the treatment planning.

Manganese threonine chelate-a new enteric contrast agent for MRI: a pilot study on rats

Enteric contrast agents are important in gastrointestinal MRI. However, no currently available agent is well established as the standard of care. In this study, in vitro relaxivities of manganese threonine chelate (Mn-Thr), a common nutritional food supplement, were measured at 1.5 T and 3 T with further investigation of its efficacy and safety in vivo as an enteric contrast agent. According to the calculated relaxivities, T₁ W and T₂ W TSE sequences of Mn-Thr solutions at different concentrations were acquired, and the optimal concentration for dark lumen imaging on both T₁ W and T₂ W images was determined in vitro. To validate the optimal concentration in vivo, eight Sprague-Dawley rats were randomly divided into two groups. Each group received rectal injection of either 2.00 g/L (about 3.80 mM) Mn-Thr or saline as an enteric contrast agent and underwent MRI. After a time interval of one week, the same procedures were repeated with the alternative contrast agent. Animals were sacrificed after the second MRI. Tissue manganese quantification and histopathological examination were obtained. Qualitative MR image quality assessments were performed and compared between Mn-Thr and saline. Measured T₁ and T₂ relaxivities of Mn-Thr were significantly higher than those of MnCl₂ in vitro (p < 0.05). At the concentration of 2.00 g/L (about 3.80 mM), Mn-Thr produced a dark lumen on T₁ W and T₂ W images both in vitro and in vivo. Compared with saline, Mn-Thr showed significantly more homogenous luminal signal and increased bowel wall conspicuity in image quality assessments. Tissue manganese concentrations were not significantly different between two groups. Histopathological examinations were normal in both groups. Our data suggest that Mn-Thr possesses favorable paramagnetic properties and can create a homogenous dark lumen on T₁ W and T₂ W images without obvious side effects in healthy rats. As a commercially available nutritional food supplement, Mn-Thr appears to be a promising enteric contrast agent for MRI.

Ingestible Contrast Agents for Gastrointestinal Imaging

Gastrointestinal (GI) ailments cover a wide variety of diseases involving the esophagus, stomach, small intestine, large intestine, and rectum. They bring about many inconveniences in daily life in chronic diseases and can even be life threatening in acute cases. Rapid and safe detection approaches are essential for early diagnosis and timely management. Contrast agents for GI imaging can enhance contrast to distinguish abnormal lesions from normal structures. Computed tomography and magnetic resonance imaging are two important diagnostic tools for the evaluation of GI conditions. This review mainly involves several common GI diseases, including inflammatory diseases, intestinal tumors, diarrhea, constipation, and gastroesophageal reflux diseases. Selected contrast agents, such as barium sulfate, iodine-based agents, gadolinium-based agents, and others, are summarized. Going forward, continued endeavors are being made to develop more emerging contrast agents for other imaging modalities.

Magnetic Resonance Enterography for Inflammatory and Noninflammatory Conditions of the Small Bowel

Magnetic resonance enterography (MRE) is an effective noninvasive tool for evaluation of inflammatory and noninflammatory conditions of the small bowel. MRE allows for repeated evaluation of patients with Crohn disease without exposure to ionizing radiation, and can be used to assess disease status and direct management. MRE also allows evaluation of neoplastic and other nonneoplastic conditions of the small bowel. Adequate patient preparation and acquisition techniques are required for optimal image quality.

Endoluminal contrast for abdomen and pelvis magnetic resonance imaging

Magnetic resonance (MR) imaging of the abdomen and pelvis can be limited for assessment of different conditions when imaging inadequately distended hollow organs. Endoluminal contrast agents may provide improved anatomic definition and detection of subtle pathology in such scenarios. The available routes of administration for endoluminal contrast agents include oral, endorectal, endovaginal, intravesicular, and through non-physiologic accesses. Appropriate use of endoluminal contrast agents requires a thorough understanding of the clinical indications, available contrast agents, patient preparation, and interaction of the contrast agent with the desired MR imaging protocol. For example, biphasic oral enteric contrast agents are preferred in MR enterography as their signal properties on T1- and T2-weighted imaging allow for evaluation of both intraluminal and bowel wall pathology. In specific situations such as with MR enterography, MR defecography, and accurate local staging of certain pelvic tumors, the use of an endoluminal contrast agent is imperative in providing adequate diagnostic imaging. In other clinical scenarios, the use of an endoluminal contrast agent may serve as an indispensable problem-solving tool.

Abdominal MRI without Enteral Contrast Accurately Detects Intestinal Fibrostenosis in Patients with Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD) presenting for surgical evaluation require thorough small bowel surveillance as it improves accuracy of diagnosis (ulcerative colitis versus Crohn's) and differentiates those who may respond to nonoperative therapy, preserving bowel length. MRI has not been validated conclusively against histopathology in IBD. Most protocols require enteral contrast. This study aimed to 1) evaluate the accuracy of MRI for inflammation, fibrosis, and extraluminal complications and 2) compare MRI without enteral contrast to standard magnetic resonance enterography. Adults with Crohn's disease or ulcerative colitis who underwent abdominal MRI and surgery were retrospectively reviewed. Of 65 patients evaluated, 55 met inclusion criteria. Overall sensitivity and specificity of MRI for disease involvement localized by segment were 93 per cent (95% confidence interval = 89.4–95.0) and 95 per cent (95% confidence interval = 92.3–97.0), respectively (positive predictive value was 86%, negative predictive value was 98%). Sensitivity and specificity between MRI with and without oral and rectal contrast were similar (96% vs 91% and 99% vs 94%, P > 0.10). As were positive predictive value and negative predictive value (85% vs 96%, P = 0.16; 97% vs 99%, P = 0.42). Magnetic resonance is highly sensitive and specific for localized disease involvement and extraluminal abdominal sequelae of IBD. It accurately differentiates patients who have chronic transmural (fibrotic) disease and thus may require an operation from those with acute inflammation, whose symptoms may improve with aggressive medical therapy alone. MRI without contrast had comparable diagnostic yield to standard magnetic resonance enterography.

Systematic review with meta-analysis: magnetic resonance enterography signs for the detection of inflammation and intestinal damage in Crohn's disease

BACKGROUND

In the treatment of Crohn's disease (CD), mucosal healing has become a major goal, with the hope of avoiding intestinal damage from chronic inflammation. Magnetic resonance enterography (MRE) has emerged as a non-invasive means of monitoring inflammation and damage.

AIMS

As part of the development of MRE-based multi-item measures of inflammation and damage for paediatric studies, we carried out a systematic review and meta-analysis to identify MRE variables used to describe these two distinct concepts.

METHODS

2501 studies of MRI and CD were identified. Studies written in any language reporting individual MRE signs for patients diagnosed with CD were included. Two-hundred-and-forty-four studies were fully reviewed and 62 were included (inflammation, n = 51; damage, n = 24). Sensitivity, specificity and associated confidence intervals were calculated, and hierarchical summary ROC curves were constructed for each MRE sign.

RESULTS

A total of 22 MRE signs were used to reflect inflammation, and 9 to reflect damage. Diagnostic accuracy of MRE signs of inflammation and damage was heterogeneous; however, wall enhancement, mucosal lesions and wall T2 hyperintensity were the most consistently useful for inflammation (most sensitivities >80% and specificities >90%), and detection of abscess and fistula were most consistently useful for damage (most sensitivities >90%, specificities >95%).

CONCLUSIONS

Identifying the best MRE variables to reflect inflammation and damage will maximise the utility of this rapidly emerging technique and is the first stage of constructing MRE-based indices for evaluating inflammation and intestinal damage.

Diagnostic imaging in Crohn's disease: what is the new gold standard?

Historically Barium and isotope studies been used for imaging of inflammatory bowel disease (IBD) but carry risk of radiation exposure. Use of Barium is declining resulting in fewer radiologists that have the necessary expertise. Isotopes studies lack anatomical definition but 18F - fludeoxyglucose (FDG) positron emission tomography (PET) shows promise in accurate assessment of disease compared to endoscopy. Computerised tomography (CT) is particularly useful in assessment of complications of Crohn's disease (CD) but radiation exposure is high. CT enterography (CTE) has improved visualisation of small bowel mucosal disease and allows assessment of disease activity. Ultrasound is increasingly used for preliminary assessment of patients with potential IBD. Although widely available and economically attractive, the expertise required is not widespread. Finally magnetic resonance imaging (MRI) is proving to be the most accurate tool for assessment of disease extent and distribution. MRI of the pelvis has superseded other techniques in assessment of peri-anal fistulation.

Evolving role of MRI in Crohn's disease

MR enterography is playing an evolving role in the evaluation of small bowel Crohn's disease (CD). Standard MR enterography includes a combination of rapidly acquired T2 sequence, balanced steady-state acquisition, and contrast enhanced T1-weighted gradient echo sequence. The diagnostic performance of these sequences has been shown to be comparable, and in some respects superior, to other small bowel imaging modalities. The findings of CD on MR enterography have been well described in the literature. New and emerging techniques such as diffusion-weighted imaging (DWI), dynamic contrast enhanced MRI (DCE-MRI), cinematography, and magnetization transfer, may lead to improved accuracy in characterizing the disease. These advanced techniques can provide quantitative parameters that may prove to be useful in assessing disease activity, severity, and response to treatment. In the future, MR enterography may play an increasing role in management decisions for patients with small bowel CD; however, larger studies are needed to validate these emerging MRI parameters as imaging biomarkers.

Noninflammatory conditions of the small bowel

Magnetic resonance (MR) imaging has been playing an evolving role in evaluating noninflammatory small-bowel conditions, such as tumors and malabsorption syndrome. MR imaging has shown to be superior to other diagnostic methods in identifying tumors of the small bowel. MR enterography and MR enteroclysis are both valid for studying noninflammatory conditions of the small intestine, although MR enteroclysis may be considered the modality of choice because of its accuracy in the diagnosis of small-bowel neoplasms. Intraluminal and extraluminal MR findings, combined with contrast-agent enhancement and functional information, help to make an accurate diagnosis and consequently to characterize small-bowel diseases.

MR imaging techniques of the bowel

Due to advances in technology, magnetic resonance is an increasingly popular method for evaluating the small bowel and colon because of the lack of radiation, wealth of information provided by the images, and growing demand from gastroenterologists, surgeons, and oncologists. Careful attention to proper technique, however, is necessary to obtain high-quality images. Factors that need to be considered for successful magnetic resonance of the bowel include method for administration of oral or rectal contrast, patient positioning, need for antiperistaltic medication, and imaging sequences and planes.

Small Bowel Imaging: Clinical Applications of the Different Imaging Modalities—A Comprehensive Review

In the last years, MR and CT techniques have been optimized for small bowel imaging and are playing an increasing role in the evaluation of small bowel disorders. In comparison to traditional barium fluoroscopic examinations, spatial and temporal resolution is now much more improved partially thanks to modern bowel distending agents. However, there is a 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. Owing to the excellent soft tissue 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.

Magnetization transfer for the assessment of bowel fibrosis in patients with Crohn's disease: initial experience

OBJECT

To assess the feasibility of magnetization transfer (MT) imaging of the bowel wall in patients with Crohn's disease (CD), and to evaluate its utility for the detection of intestinal fibrosis.

MATERIALS AND METHODS

In this prospective study, 31 patients (age 39.0 ± 13.2 years) with CD were examined in a 1.5T MR scanner. To establish a standard of reference, two independent readers classified the patients in different disease states using standard MR enterography, available clinical data and histological findings. In addition to the standard protocol, a 2D gradient-echo sequence (TR/TE 32 ms/2.17 ms; flip angle 25°) with/without 1,100 Hz off-resonance prepulse was applied. MT ratios (MTR) of the small bowel wall were computed off-line on a pixel-by-pixel basis.

RESULTS

The MT sequences acquired images of sufficient quality and spatial resolution for the evaluation of the small bowel wall without detrimental motion artefacts. In normal bowel wall segments, an intermediate MTR of 25.4 ± 3.4 % was measured. The MTR was significantly increased in bowel wall segments with fibrotic scarring (35.3 ± 4.0 %, p < 0.0001). In segments with acute inflammation, the mean MTR was slightly smaller (22.9 ± 2.2 %).

CONCLUSION

MT imaging of the small bowel wall is feasible in humans with sufficient image quality and may help with the identification of fibrotic scarring in patients with CD.

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.

Gadolinium-chitosan nanoparticles as a novel contrast agent for potential use in clinical bowel-targeted MRI: a feasibility study in healthy rats

BACKGROUND

MRI is of increasing importance in the diagnostic evaluation of gastrointestinal diseases, with depiction of mucosal enhancement obtained with conventional intravenous contrast. Routine clinical use of contrast agents has been carried out using intravenous injection for mucosal imaging. Contrast agents that specifically target the intestinal mucosa are therefore needed to improve clinical imaging of the mucosal surface.

PURPOSE

To synthesize a novel contrast agent for gadopentetic acid (Gd-DTPA)-loaded chitosan nanoparticles and observe the absorption of the nanoparticles in the colon wall of healthy rats by MR imaging in vivo.

MATERIAL AND METHODS

A contrast agent was successfully synthesized by a modified emulsion coalescence method, and the resulting agents were characterized in detail by dynamic light-scattering spectroscopy and inductively coupled plasma emission spectroscopy. The cytotoxicity of Gd-chitosan nanoparticles was evaluated by an MTT assay. Gadolinium-chitosan (Gd@chitosan) nanoparticles were administered to the colon mucosa of healthy rats by rectal administration, and MRI scans in vivo were carried out with a 3.0 T imaging scanner at various time points.

RESULTS

The prepared Gd@chitosan nanoparticles were ~420 nm in diameter with a 74.4% Gd-DTPA content. The MTT assay indicated little cytotoxicity. MRI results showed that nanoparticles can be retained in both the stratum submucosum and epithelial cells of the colon for almost 80 min. Transmission electron microscopy images further revealed that Gd@chitosan nanoparticles were localized inside the mucosal cells or intercellular space, while tissue from Gd-DTPA aqueous solution administration showed nothing. Due to the infusion of Gd@chitosan nanoparticles, the MR signal intensity of colon mucosa increased from about 6% to 35%, and the contrast enhancement was highest at 20 min after administration.

CONCLUSION

Gd@chitosan nanoparticles with high Gd-DTPA content were successfully prepared for use as a novel MRI contrast agent. All results indicated that rectally administered Gd@chitosan nanoparticles have the potential for MRI diagnosis of colon mucosal disease.

Manifestations of small bowel disease in pediatric Crohn's disease on magnetic resonance enterography

BACKGROUND

We report the manifestations of Crohn's disease (CD) observed on magnetic resonance enterography (MRE) in a pediatric population at the time of CD diagnosis.

METHODS

MRE of 95 consecutive pediatric patients with inflammatory bowel disease (IBD) examined in 2006-2009 were retrospectively analyzed, with documentation of findings based on type and location of the small bowel (SB) disease.

RESULTS

In all, 51 were boys and 44 girls. 54 had CD, 31 non-CD IBD, and 10 no IBD. The most common site of SB involvement in CD was the terminal ileum seen in 29 (53.7%) patients, followed by ileum in 10 (18.5%) and jejunum in 9 (16.7%) patients. Solitary jejunal inflammation (3.7%), SB stenoses (1.9%), fistula formation (0.95%), and abscess (0.95%) were much less common. Perienteric lymphadenopathy was seen in 30 (55.6%) patients and fatty proliferation in 9 (16.7%). The most common manifestation of SB inflammation was increased contrast enhancement of bowel wall (93.5%), thickening of the bowel wall (90.3%), and derangement of bowel shape with saccular formations (25.8%).

CONCLUSIONS

MRE in the pediatric population often demonstrates increased contrast uptake, bowel wall thickening, and perienteral lymphadenopathy in CD. More chronic small bowel changes seen commonly in adults and solitary jejunal involvements are less commonly seen.

MR enterography with a new negative oral contrast solution containing maghemite nanoparticles

AIM

The aim of this study was to test an oral contrast solution with maghemite for the magnetic resonance imaging of small bowel diseases.

PATIENTS AND METHODS

The study sample included 3 cohorts: 17 healthy volunteers (group A), 22 patients with small bowel disease (group C). Both groups underwent MR enterography and 24 patients with small bowel disease (group B) underwent magnetic resonance cholecystopancreaticography. Various concentrations in 1000 ml vs 500 ml of experimental solution were tested. All cohorts completed questionnaires evaluating the solution characteristics and side-efects during and after drinking.

RESULTS

A maghemite concentration of 800 mg /4 g bentonite in 1000 ml solution was sufficient for proper intraluminal lay-out. An experimental solution of 500 ml was sufficient for magnetic resonance cholecystopancreaticography and 1000 ml for MR enterography. There were no statistically significant differences between groups for taste, taste characteristic or appearance of the experimental solution. Side-effects experienced during drinking were: nausea (29.4%) and eructation (29.4%) in group A, in group B (42%) and diarrhoea (27.3%) in group C. Side-effects 2 h after drinking occured in group A (nausea 17.6%) and in group C (diarrhoea 47%). The best tolerance of experimental solution was found in group B with a higher median patient age than groups A and C. The experimental solution was evaluated more favorably in the older subjects (age over 50 years).

CONCLUSION

The experimental oral solution with maghemite was well tolerated in all 3 groups. Our study supports its use in magnetic resonance practice.

Small bowel imaging in Crohn's disease

Imaging of Crohn's disease of the small bowel is gradually moving away from barium fluoroscopy and towards cross-sectional modalities. This review explores the strengths and limitations of various techniques, and focuses on several current questions in small bowel imaging, such as the comparison between oral ingestion or nasojejunal intubation and enteroclysis for introduction of contrast, the use of computerised tomography (CT) versus magnetic resonance (MR) and the likely changes over the next decade.

Small intestine contrast ultrasonography (SICUS) for the detection of small bowel complications in crohn's disease: a prospective comparative study versus intraoperative findings

BACKGROUND

In Crohn's disease (CD) patients, small intestine contrast ultrasonography (SICUS) accurately assesses small bowel lesions. Its diagnostic role is not known in the assessment of intraabdominal CD complications. The aim was to assess the value of SICUS to detect intestinal complications in patients with CD.

METHODS

Forty-nine CD patients (21 female, mean age 37.7 years; range 12-78 years) underwent resective bowel surgery and were included in this study. The accuracy of SICUS to preoperatively detect number, site, and length of strictures, fistulas, and abscesses was compared with surgical and pathological findings by kappa statistics.

RESULTS

SICUS identified at least one stricture in 39/40 and excluded it in 9/9 (97.5% sensitivity, 100% specificity, k = 0.93); two or more strictures in 9/12 (75% sensitivity, 100% specificity, k = 0.78). The agreement by k-statistics between SICUS and surgery in identifying proximal and distal small intestine site of stricture was 1 and 0.92, respectively. The extension of strictures was 6.8 ± 5.4 cm at surgery, 6.6 ± 5.4 cm at SICUS (NS). Fistulas were correctly identified in 27/28 patients and excluded in 19/21 patients (96% sensitivity, 90.5% specificity, k = 0.88). Intraabdominal abscesses were correctly detected in 10/10 patients and excluded in 37/39 patients (100% sensitivity, 95% specificity, k = 0.89).

CONCLUSIONS

SICUS is an accurate method for the detection of small intestinal complications in CD. Noninvasive SICUS is valuable as a primary investigative method for evaluating and planning proper treatment in patients with severe CD of the small bowel.

Diagnostic accuracies of MR enterography and CT enterography in symptomatic Crohn's disease

OBJECTIVE

In patients, with symptomatic Crohn's disease (CD), valid information about the presence or absence of small bowel disease activity and stenosis is clinically important. Such information supports decisions about medical or surgical therapy and can be obtained with MR enterography (MRE) or CT enterography (CTE).

MATERIALS AND METHODS

A total of 50 patients with symptomatic pre-existing CD and a demand for small bowel imaging to support changes in treatment strategy were included in this prospective and blinded study. MRE and CTE were performed on the same day in alternating order and subsequently compared with the gold standard: pre-defined lesions at ileoscopy (n = 30) or surgery with (n = 12) or without (n = 3) intra-operative enteroscopy.

RESULTS

A total of 35 patients had active small bowel CD (jejunum 0, ileum 1, (neo)-terminal ileum 34) and 20 had small bowel stenosis. The sensitivity and specificity of MRE for detection of small bowel CD was 74% and 80% compared to 83% and 70% with CTE (p ≥ 0.5). MRE and CTE detected small bowel stenosis with 55% and 70% sensitivities, respectively (p = 0.3) and 92% specificities.

CONCLUSIONS

MRE and CTE have comparable diagnostic accuracies for detection of small bowel CD and stenosis. In symptomatic patients with CD and high disease prevalence, positive predictive values are favorable but negative predictive values are low. Consequently, MRE and CTE can be relied upon, if a positive result is obtained whereas a negative enterography should be interpreted with caution.

Diffusion-weighted MRI: role in detecting abdominopelvic internal fistulas and sinus tracts

PURPOSE

To retrospectively determine the incremental value of diffusion-weighted MR-imaging (DW-MRI) to T2-weighted (T2w) images in diagnosis of internal fistulas (IFs) and sinus tracts (STs).

MATERIALS AND METHODS

Fourteen patients with 25 IFs and STs arising from the small bowel (20), colon (4) and biliary tract (1) were included. Two independent observers reviewed T2w images, T2w+DW-MRI images and T2w+contrast enhanced T1-weighted (CE T1w) images at three sessions to detect IF/ST based on a confidence scale of five. Sensitivity and confidence score of each session was compared.

RESULTS

10/25 (40%) and 9/25 (36%) IFs and STs were detected on T2w images by observer 1 and 2, respectively. Both observers detected 19/25 (76%) and 24/25(96%) IFs and STs on T2w+DW-MRI and T2w+CE T1w images, respectively. Detection rate and confidence score improved significantly by combining T2w images with DW-MRI or CE T1w images (reader 1 + 2: P ≤ 0.01). There was no significant difference between the IF/ST detection rate of T2w+DW-MRI and T2w+CE T1 image combinations. Confidence scores with T2w+CE T1w images were significantly greater than DW-MRI+T2w images (reader 1:P = 0.01; reader 2: P = 0.03).

CONCLUSION

DW-MRI showed additional value to T2w imaging for diagnosis of IF and ST. DW-MRI can be a useful adjunct, especially for patients with renal failure.

MR enterography of Crohn disease: part 2, imaging and pathologic findings

OBJECTIVE

The purpose of this article is to review MR enterography technique and imaging findings suggestive of Crohn disease on these examinations. This article will also allow the reader to self-assess and improve his or her skills in the performance and interpretation of MR enterography examinations.

CONCLUSION

This article reviews the technique of performing MR enterography examinations. MRI plays a valuable role in providing accurate information about severity of and complications related to Crohn disease and can help in guiding surgical or medical treatment.

MRI in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) affects ≈1.4 million people in North America and, because of its typical early age of onset and episodic disease course, IBD patients often undergo numerous imaging studies over the course of their lifetimes. Computed tomography (CT) has become the standard imaging modality for assessment of IBD patients because of its widespread availability, rapid image acquisition, and ability to evaluate intraluminal and extraluminal disease. However, repetitive CT imaging has been associated with a significant ionizing radiation risk to patients, making MRI an appealing alternative IBD imaging modality. Pelvic MRI is currently the imaging gold standard for detecting perianal disease, while recent studies indicate that MRI bowel-directed techniques (enteroclysis, enterography, colonography) can accurately evaluate bowel inflammation in IBD. With recent technical innovations leading to faster and higher resolution body MRI, the role of MRI in IBD evaluation is likely to continue to expand. Future applications include surveillance imaging, detection of mural fibrosis, and early assessment of therapy response.

Diagnosis of small-bowel disease: comparison of magnetic resonance enteroclysis and conventional enteroclysis

In this prospective study, 32 patients with symptoms suggestive of small-bowel disease underwent conventional enteroclysis and magnetic resonance (MR) enteroclysis. Image quality, luminal distension, wall thickening, homogeneity of luminal opacification, the presence of artefacts and extraluminal changes were assessed. Small-bowel pathologies were subsequently proved surgically and by follow-up examinations in 19 (59.4%) of the patients. Abnormal findings were detected by MR enteroclysis in 11 of these 19 patients (57.9%). Normal findings on MR enteroclysis were found in eight of the 19 patients (42.1%) whereas conventional enteroclysis detected abnormal findings in these patients. Abdominal lesions outside the small bowel, comprised renal cysts, cholelithiasis, ovarian cysts and horseshoe kidney, and were detected by MR enteroclysis in two, one, four and one, respectively, of these normal patients but not by conventional enteroclysis. Excluding lesions outside of the small bowel, a higher rate of false-negative results and the missing of superficial lesions occurred with MR enteroclysis. It is, therefore, suggested that MR enteroclysis should not be used as a primary way of evaluating small-bowel disease and its use should be restricted to follow-up examinations of known disease.

Malignant tumours of the small intestine: a review of histopathology, multidetector CT and MRI aspects

Small bowel neoplasms, including adenocarcinoma, carcinoid tumour, lymphoma and gastrointestinal stromal tumours, represent a small percentage of gastrointestinal cancers, yet are among those with the poorest prognosis compared with other gastrointestinal malignancies. Unclear clinical scenarios and difficult radiological diagnosis often delay treatment with negative effects on patient survival. Recently, multidetector CT (MDCT) and MRI have been introduced as feasible and accurate diagnostic techniques for the identification and staging of small bowel neoplasms. These techniques are gradually replacing conventional barium radiography as the tool of choice. However, the inherent technical and physiological challenges of small bowel imaging require a familiarity with patient preparation and scan protocols. Adequate knowledge of the histopathology and natural evolution of small bowel neoplasms is also important for differential diagnosis. The aim of this article is to review MDCT and MRI protocols for the evaluation of small bowel tumours and to provide a concise yet comprehensive guide to the most relevant imaging features relative to histopathology.

Inflammatory bowel disease

This review focuses on the prominent etiological and pathogenetic aspects of inflammatory bowel disease (IBD), with particular attention being paid to the mucosal immune response to commensal micro-organisms in health and disease. Pathogenetic implications for target therapy will also be discussed. The clinical presentation, diagnostic aspects, and currently recommended therapeutic options for the two main types of IBD are also taken into consideration, including manifestations of these conditions in the oral cavity.

Imaging of malignant neoplasms of the mesenteric small bowel: new trends and perspectives

This article describes the recent advances in radiological imaging of malignant neoplasms of the mesenteric small bowel and provides an outline of new trends and perspectives that can be anticipated. The introduction of multidetector row technology, which allows the acquisition of submillimeter and isotropic voxels, has dramatically improved the capabilities of computed tomography in the investigation of the mesenteric small bowel. This technology combined with optimal filling of small bowel loops through the use of appropriate enteral contrast agents has markedly changed small bowel imaging. Computed tomography-enteroclysis, which is based on direct infusion of enteral contrast agent into the mesenteric small bowel through a naso-jejunal tube, provides optimal luminal distension. By contrast, computed tomography-enterography is based on oral administration of enteral contrast agent. These two techniques are now well-established ones for the detection and the characterization of small bowel neoplasms. During the same time, combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, magnetic resonance imaging has gained wide acceptance for the evaluation of patients with suspected small bowel neoplasms. Rapid magnetic resonance imaging sequences used in combination with specific enteral contrast agents generate superb images of the mesenteric small bowel so that magnetic resonance-enteroclysis and magnetic resonance-enterography are now considered as effective diagnostic tools for both the detection and the characterization of neoplasms of the mesenteric small bowel. Recent improvements in image post-processing capabilities help obtain realistic three-dimensional representations of tumors and virtual enteroscopic views of the small bowel that are useful for the surgeon and the gastroenteroenteologist to plan surgical or endoscopic interventions. Along with a better knowledge of the potential and limitations of wireless capsule endoscopy and new endoscopic techniques, these recent developments in radiological imaging reasonably suggest that substantial changes in the investigation of small bowel tumors may be anticipated in a near future, thus potentially create a new paradigm shift after standard small bowel follow-through study has been universally abandoned.

MR enterography with polyethylene glycol as oral contrast medium in the follow-up of patients with Crohn disease: comparison with CT enterography

BACKGROUND

To compare magnetic resonance enterography (MRE) and computed tomography enterography (CTE) in detecting inflammatory bowel disease activity (IBD) in patients with Crohn's disease (CD).

METHODS

A total of 29 patients (M 20; F 9; mean age 43.8 ± 15.9) with known CD underwent MRE. MRE was performed at 1.5 T using phased-array sense body coil, after oral administration of 1.5-2 L of PEG solution as oral contrast agent. MRE protocol included T1-weighted, sSShT2, sBTFE and gadolinium-enhanced THRIVE sequences acquired on coronal and axial planes. CTE was performed using a 16 multidetector-row computed-tomography before and after intravenous administration of 120 mL of iodinated contrast. MRE images and CTE scans were reviewed by a radiologist for bowel thickness and enhancement, mesenteric lymph nodes, vascular engorgement, fibrofatty proliferation, fistulas and abscesses. The disease activity was also defined by CDAI > 150.

RESULTS

MRE has demonstrated a good sensitivity in detection of CD activity, particularly in depiction of mural thickening, mural enhancement, and vascular engorgement. The level of agreement between the two technique was excellent in evaluating wall thickening with mucosal hyperenhancement (κ = 1), comb (κ = 0.90) and halo signs (κ = 0.86). In detecting fibrofatty proliferation and mesenteric lymph nodes, CTE was superior to MRE (accuracy: P < 0.05), while MRE was superior in visualization of fistulas.

CONCLUSION

MRE is an accurate method in monitoring the activity of CD as compared to CTE and may be considered an alternative to CTE in assessing degree of CD and evaluating therapeutic effectiveness.

MRI for diagnosis and evaluation of inflammatory bowel disease

As a non-invasive and ionizing radiation-free cross-sectional imaging technique, magnetic resonance imaging (MRI) has shown a bright future in following up patients with inflammatory bowel disease (IBD), especially child and young adult patients. The application of new techniques in MRI makes it possible to obtain MRI images that are richer in information and to evaluate the activity of IBD more objectively and quantitatively. This improvement is of great significance for clinical decision-making and evaluation of drug efficacy in IBD patients.

Magnetic resonance follow-through imaging for evaluation of disease activity in ileal Crohn's disease: an observational, retrospective cohort study

BACKGROUND

Magnetic resonance follow-through (MRFT) is a new cross-sectional imaging modality with the potential to accurately stage ileal Crohn's disease (CD), while avoiding ionizing radiation and the discomfort associated with enteroclysis. We aimed to assess the reliability of this technique in assessing the extent and activity of ileal CD, and to assess its influence on subsequent management.

METHODS

Out of a total of 342 patients undergoing MRFT between 2004 and 2008, 221 were performed in 191 patients with confirmed CD. Case notes were reviewed in detail with documentation of all investigations pre- and post-MRFT. Agreement between inflammatory markers, histopathology, and MRFT findings was determined.

RESULTS

Overall, 116/221 (52.5%) of MRFTs showed active ileal CD, and 76/221 (34.4%) quiescent CD, while 29/221 (13.1%) were suboptimal. Overall, 66 strictures and 18 fistulae were identified. There was substantial agreement between active ileal CD on MRFT and histopathology (n = 59; kappa = 0.66; P = 0.0006; sensitivity 85.1%, specificity 85.7%) and fecal calprotectin (n = 14; kappa = 0.72; P = 0.047), while C-reactive protein (CRP) showed moderate agreement (n = 107; kappa = 0.402; P = 0.00028). Management was influenced by MRFT reports following active (52/84, 62% treated medically) or quiescent (48/62, 77.4% managed conservatively) disease. Fibrotic strictures were predominantly treated surgically (7/14, 50%). In all, 13/32 (40.6%) patients with inflammatory ileal strictures required surgery, mostly due to steroid-resistant disease. Overall, 75 MR findings were documented in 221 MRFTs, including 1 renal cancer.

CONCLUSIONS

MRFT provides accurate information on ileal CD activity, with close agreement to inflammatory markers and histopathology. It represents a substantial advance in the staging of CD, while avoiding painful enteroclysis and radiation exposure in young patients.

MR enterographic manifestations of small bowel Crohn disease

Magnetic resonance (MR) enterography is a clinically useful technique for the evaluation of both intraluminal and extraluminal small bowel disease, particularly in younger patients with Crohn disease. MR enterography offers the advantages of multiplanar capability and lack of ionizing radiation. It allows evaluation of bowel wall contrast enhancement, wall thickening, and edema, findings useful for the assessment of Crohn disease activity. MR enterography can also depict other pathologic findings such as lymphadenopathy, fistula and sinus formation, abscesses, and abnormal fold patterns. Even subtle disease manifestations may be detected when adequate distention of the small bowel is achieved, although endoscopic and double-contrast barium small bowel techniques remain superior in the depiction of changes in early Crohn disease (eg, aphthoid ulceration). Further research will be needed to determine whether MR imaging enhancement patterns may reliably help discriminate between active and inactive disease.

Benefits and challenges in bowel MR imaging at 3.0 T

Abdominal imaging at 3.0 T has shown to be challenging because of a number of artifacts and effects related to the physics at higher field strength. For bowel imaging at 3.0 T, artifacts due to magnetic field inhomogeneities, standing waves, increased susceptibility, and greater chemical shift effects are of particular concern because they are likely to affect the assessment of relevant structures and counterbalance the benefits of higher signal-to-noise ratio. Regarding small- and large-bowel magnetic resonance imaging, the benefits of higher field strengths translate mainly in better contrast-to-noise ratio of contrast-enhanced T1-weighted gradient echo and T2-weighted imaging, whereas steady-state free precession sequences seem to suffer from serious degradation of image quality. The present article summarizes the technical challenges in bowel imaging at 3.0 T, provides an overview of performance compared with 1.5 T in small- and large-bowel diseases including the rectum, and revises the current literature.

Magnetic resonance enterography in Crohn’s disease: Standard and advanced techniques

Crohn’s disease (CD) is a chronic autoimmune disorder that affects mainly young people. The clinical management is based on the Crohn’s Disease Activity Index and especially on biologic parameters with or without additional endoscopic and imaging procedures, such as barium and computed tomography examinations. Recently, magnetic resonance (MR) imaging has been a promising diagnostic radiologic technique with lack of ionizing radiation, enabling superior tissue contrast resolution due to new pulse-sequence developments. Therefore, MR enterography has the potential to become the modality of choice for imaging the small bowel in CD patients.

MR imaging of the small bowel

Cross-sectional imaging techniques are playing an increasing role in the evaluation of suspected small-bowel disorders, and a growing awareness of the risks of ionizing radiation exposure has prompted the exploration of alternative imaging techniques. Advantages of magnetic resonance (MR) imaging include a lack of ionizing radiation, the ability to provide dynamic information regarding bowel distention and motility, improved soft-tissue contrast, and a relatively safe intravenous contrast agent profile. Limitations of MR imaging include cost, imager access, variability in examination quality, and lower spatial and temporal resolution compared with those of computed tomography (CT). MR imaging of the small bowel is indicated for patients with Crohn disease, those for whom exposure to radiation is a concern, those with contraindications to CT, and those with low-grade small-bowel obstruction. MR imaging may be performed with enterography or enteroclysis. In enterography, large volumes of fluid are ingested. Several different contrast agents may be used. These agents are classified according to their signal intensity on T1- and T2-weighted images. In enteroclysis, enteric contrast material is administered through a nasoenteric tube. Crohn disease is the primary indication for MR imaging of the small bowel because many patients require multiple follow-up examinations. Findings suggestive of active inflammation include bowel wall thickening and hyperenhancement, ulcerations, increased mesenteric vascularity, and perienteric inflammation. Complications are well depicted and may include penetrating disease and small-bowel obstruction.

Utility of high-resolution MR imaging in demonstrating transmural pathologic changes in Crohn disease

Magnetic resonance (MR) imaging has emerged as an imaging modality that can be used to help diagnose and evaluate Crohn disease of the small and large bowel. MR imaging has high diagnostic accuracy in the detection of Crohn disease, and high-resolution thin-section MR images can demonstrate transmural pathologic changes of Crohn disease from the level of the mucosa to that of the mesentery. High-resolution MR image data also may be used to construct high-quality multiplanar and endoluminal views that may provide additional diagnostic information. Knowledge of the MR imaging findings of Crohn disease and how they correlate with the pathologic features of the disease is important to facilitate accurate diagnosis and detect complications.

Feasibility of MRI in experimentally induced inflammatory small bowel disease: a pilot study in a porcine model

The purpose of this study was to compare the macroscopic and microscopic findings of experimentally induced inflammatory lesions in jejunum and ileum with magnetic resonance imaging (MRI) findings. Inflammatory small bowel lesions were experimentally induced in six pigs. Bowel segments in jejunum and ileum were isolated, and a solution with trinitrobenzenesulfonic acid and ethanol (TNBS-EtOH) was installed. MRI of the small bowel was performed 7 days after surgery. Before the MRI examination, a 6% mannitol solution was installed through a nasogastric tube. The MRI protocol consisted of single-shot turbo spin echo T2 sequences, steady state free precession (BFFE) sequences, and a 3D T1 gradient echo sequence with fat saturation and intravenous contrast. The following image findings were evaluated: increased bowel wall thickness (BWT), increased bowel wall enhancement (BWE), and bowel stenosis. After the MRI examination, the animals were sacrificed. The small bowel was removed and examined macroscopically and microscopically. Inflammatory lesions developed in jejunum and ileum in all animals. The lesions were visible macroscopically and microscopically. The microscopic findings consisted of variable degrees of inflammation, ulcer formation, and fibrosis. In jejunum the inflammatory lesions were not diagnosed with MRI, except in one pig with a bowel necrosis probably caused by an intramural injection or leakage of the TNBS-EtOH solution. In ileum the bowel wall thickness was increased and the inflammatory lesions were diagnosed with MRI. In conclusion, the inflammatory lesions were visible macroscopically and microscopically. Lesions in ileum had increased BWT and were possible to image with MRI. Lesions in jejunum had normal BWT and were not diagnosed with MRI, except in one pig with increased BWT probably caused by complications to the installation of TNBS-EtOH.

Small bowel MRI enteroclysis or follow through: Which is optimal?

AIM: To determine if a nasojejunal tube (NJT) is required for optimal examination of enteroclysis and if patients can be examined only in the supine position.

METHODS: Data were collected from all patients undergoing small bowel (SB) magnetic resonance imaging (MRI) examination over a 32-mo period. Patients either underwent a magnetic resonance (MR) follow-through (MRFT) or a MR enteroclysis (MRE) in the supine position. The quality of proximal and distal SB distension as well as the presence of motion artefact and image quality were assessed by 2 radiologists.

RESULTS: One hundred and fourteen MR studies were undertaken (MRFT-49, MRE-65) in 108 patients in the supine position only. Image artefact was more frequent in MRE than in MRFT (29.2% vs 18.4%), but was not statistically significant (P = 0.30). Adequate distension of the distal SB was obtained in 97.8% of MRFT examinations and in 95.4% of MRE examinations, respectively. Proximal SB distension was, however, less frequently optimal in MRFT than in MRE (P = 0.0036), particularly in patients over the age of 50 years (P = 0.0099). Image quality was good in all examinations.

CONCLUSION: All patients could be successfully imaged in the supine position. MRE and MRFT are equivalent for distal SB distension and artefact effects. Proximal SB distension is frequently less optimal in MRFT than in MRE. MRE is, therefore, the preferred MR examination method of the SB.

Comparison of MR enteroclysis with colonoscopy in Crohn's disease--first locust bean gum study from Turkey

BACKGROUND/AIM

The aim of this study was to compare magnetic resonance enteroclysis (MRE) findings with those of colonoscopy, using locust bean gum (LBG) as an oral contrast agent in the diagnosis and follow-up of patients with Crohn's disease.

MATERIALS AND METHODS

Nine patients with histologically proven Crohn 's disease were enrolled in this study; MRE was performed within a week of colonoscopy. All patients were examined using a 1.5 T MR Scanner after per os administration of 850 mL of a combination of LBG and mannitol. After intravenous administration of 50 mg Eritromisin and 40 mg Scopolamine, images were obtained using a T2-weighted, balanced GRE, fat-suppressed T1-weighted sequence, before and after intravenous gadolinium administration. Bowel wall thickness and enhancement of inflamatory bowel wall were measured.

RESULTS

The oral ingestion of LBG was well tolerated and allowed optimal small and large bowel distention in all patients. MR findings correlated with the colonoscopy results. Additional inflammatory lesions of the colon and mesenteric inflamatory changes such as lymphadenopathy, conglomerate tumor, and fistulas were demonstrated. Contrast enhancement of the affected bowel wall was markedly increased and positive correlation was obtained between bowel wall enhancement and bowel wall thickness.

CONCLUSION

Gadolinium-enhanced MRE with oral locust bean gum is very efficient in the detection and follow-up of the intestinal and extraintestinal findings of Crohn's disease.