Small bowel MRI in adult patients: not just Crohn's disease-a tutorial

Small Bowel Imaging from Stepchild of Roentgenology to MR Enterography: Part I: Guidance in Performing and Observing Normal and Abnormal Imaging Findings

MRE has become a standard imaging test for evaluating patients with small bowel pathology, but the indications, interpretation of imaging findings, methodology, and appropriate use must be standardized and widely known. Several signs of small bowel damage in inflammatory and non-inflammatory small bowel pathology include strictures, abscess, inflammatory activity, sinus tract, wall edema, fistula, mucosal lesions, and mesentery fat hypertrophy, all of which are widely and accurately explained by MRE. MRE is a non-invasive modality that accurately assesses the intra-luminal, parietal, and extra-luminal small bowel. The differential MRE appearance allows us to distinguish between different small bowel pathologies, such as neoplastic and non-neoplastic small bowel diseases. The purpose of this paper is to present the MRE technique, as well as the interpretation of imaging findings, through the approach of a rigorous stepwise methodology.

Diagnostic approach to small-bowel wall thickening: Beyond Crohn's disease and cancer

Although small-bowel wall thickening is a common manifestation of Crohn's disease and tumors, many other entities can give rise to similar imaging findings. The small bowel is difficult to access by endoscopy, so radiologic imaging tests play an essential role in the diagnosis of conditions involving the small bowel. The main objectives of this paper are to explain the definition of small-bowel wall thickening, analyze the patterns of involvement seen in multidetector computed tomography (MDCT) with intravenous contrast administration, and provide an image-based review of the different causes of small-bowel wall thickening. The differential diagnosis must include many entities because wall thickening can result from immune-mediated, infectious, or vascular causes, as well as from toxicity and other lesser-known entities. As the imaging appearance of many of these conditions overlap, clinical and laboratory findings are necessary to support the imaging diagnosis.

Mimicking conditions of intestinal Crohn's disease: magnetic resonance enterography findings

Crohn's disease is a chronic inflammatory condition characterized by a transmural involvement of intestinal walls. Its diagnosis comes from a combination of clinical data, imaging findings and, above all, endoscopy with biopsy results, which are mandatory for achieving a definitive diagnosis. Even so, endoscopy information may be unavailable, for instance due to technical impairments or patient intolerance. On the radiological side, Magnetic Resonance Enterography is currently considered the imaging technique of choice for Crohn's disease assessment, either at first diagnosis or follow-up. Nevertheless, the lack of radiation exposure as well as invasiveness has made this imaging approach suitable also for the evaluation of a number of small and large bowel diseases over recent years. However, it is important to remember that Magnetic Resonance Imaging findings are non-specific and that a wide overlap exists among Crohn's disease and other intestinal conditions. The aim of this work was to provide a series of intestinal affections evaluated through Magnetic Resonance Enterography that resemble Crohn's disease and that can be helpful in avoiding misinterpretation, especially when endoscopy data are missing.

Diagnostic approach to small-bowel wall thickening: beyond Crohn's disease and cancer

Although small-bowel wall thickening is a common manifestation of Crohn's disease and tumors, many other entities can give rise to similar imaging findings. The small bowel is difficult to access by endoscopy, so radiologic imaging tests play an essential role in the diagnosis of conditions involving the small bowel. The main objectives of this paper are to explain the definition of small-bowel wall thickening, analyze the patterns of involvement seen in multidetector computed tomography (MDCT) with intravenous contrast administration, and provide an image-based review of the different causes of small-bowel wall thickening. The differential diagnosis must include many entities because wall thickening can result from immune-mediated, infectious, or vascular causes, as well as from toxicity and other lesser-known entities. As the imaging appearance of many of these conditions overlap, clinical and laboratory findings are necessary to support the imaging diagnosis.

Clinical significance of isolated abnormal intestinal findings in magnetic resonance enterography in patients with suspected small bowel disease

PURPOSE

Magnetic resonance imaging (MRE) is a well-established adjunct diagnostic tool for the diagnosis of Crohn's Disease (CD), as ileocolonoscopy can sometimes be falsely reassuring when CD skips distal terminal ileum. We aimed to determine the frequency and clinical significance of isolated abnormal small bowel findings in MRE with normal ileal view in ileoscopy.

METHODS

We retrospectively reviewed findings from 1611 MRE studies that were conducted between 2012 and 2018 to detect patients bearing abnormal intestinal findings and having full ileocolonoscopy. After exclusion of normal or repetitive MRE scans and previously known CD, 147 patients with abnormal MRE detected. MRE scans were categorized as suspicious of CD and non-specific findings.

RESULTS

Out of 147 patients with abnormal MRE, 122 (83%) had terminal ileum involvement in MRE consistent with ileoscopy findings. Twenty-five (17%) patients were found to have solitarily abnormal intestinal findings in MRE with normal ileoscopy. Only 3 (12%) were diagnosed with CD initially, and all had MRE findings suspicious of CD. The remainder 40% (n = 10) were diagnosed with non-Crohn's small bowel disease after further investigation, while in the other 48% (n = 12) abnormal MRE findings could not be explained with any organic disease in the follow-up.

CONCLUSION

The present study demonstrated that only a small portion of patients with isolated abnormal intestinal findings in MRE is CD, and more than that are non-crohn's small bowel diseases. These findings, even if they carry the suspicion of CD, do not transform to CD in the long-term follow-up.

Shortened oral contrast preparation for improved small bowel distension at MR enterography

Purpose

Adequate small bowel distension in MR enterography is important for the evaluation of disease activity in Crohn’s disease patients. While distension of the distal small bowel can be achieved using standard oral contrast preparation, proximal small bowel distension remains a common impediment. The aim of this study was to compare small bowel distension between a 60-min oral contrast preparation and a 45-min oral contrast preparation.

Methods

Fifty retrospectively included patients with a 60-min oral preparation protocol and 50 prospectively included patients with a 45-min three-portion oral preparation protocol were included in the study. Both groups gradually ingested a total of 1600 mL 2% Mannitol solution during the preparation time. Two observers independently graded distension of the stomach, duodenum, jejunum, ileum, and (neo-) terminal ileum. Total small bowel distension was calculated as the sum of all small bowel segment scores. Individual and averaged observer distension scores were compared between both groups of patients using χ² test for ordinal variables.

Results

Significant differences in distension for one of both observers in favor of the 45-min protocol were found for the stomach (p = 0.04), duodenum (p = 0.02), jejunum (p = 0.02), and total small bowel (p = 0.02). When distension scores were averaged between observers, the stomach, jejunum, and total small bowel showed a significant difference in favor of the 45-min protocol (p = 0.04, 0.02, and 0.02, respectively).

Conclusion

We advise to use a 45-min three-portion oral preparation protocol for MR enterography for improved overall small bowel distension, proximal small bowel distension, and especially jejunal distension.

Intestinal tuberculosis versus crohn's disease: Clinical and radiological recommendations

Intestinal tuberculosis is a common clinical problem in India. The clinical features of this disease are nonspecific and can be very similar to Crohn's disease. Radiological evaluation of the small bowel has undergone a paradigm shift in the last decade. This long tubular organ that has traditionally been difficult to evaluate can now be well-visualized by some innovative imaging and endoscopic techniques. This article highlights the state-of-the-art evaluation of ulceroconstrictive diseases of the bowel and provides recommendations for the differentiation of intestinal tuberculosis from Crohn's disease.

The Role of Magnetic Resonance Enterography in the Evaluation of Non-Crohn׳s Pathologies

In the young patient population, magnetic resonance enterography is fast becoming a preferred imaging tool for the investigation of patients with non-Crohn׳s small bowel and mesenteric pathologies. Its advantages include lack of ionizing radiation and high-contrast resolution. This review discusses the range of small bowel and mesenteric pathologies that can be easily demonstrated with this technique.

Diffusion-weighted imaging for the detection of mesenteric small bowel tumours with Magnetic Resonance--enterography

PURPOSE

To retrospectively investigate the added value of diffusion-weighted MR imaging (DWI) for detecting mesenteric small bowel tumours (MSBTs) via MR-enterography.

MATERIALS AND METHODS

MR-enterographies of 98 patients with suspected MSBTs were blindly analyzed by two independent readers for the presence of MSBTs. Four imaging sets including "standard" (Haste and TrueFisp), "standard + DWI," "standard + gadolinium-enhanced" and "standard + DWI + gadolinium-enhanced" were reviewed. Diagnostic performance of different readings were compared with McNemar's test.

RESULTS

Twenty-nine MSBTs were pathologically confirmed. For R1 (junior radiologist) sensitivity, specificity, PPV, NPV and accuracy for the detection of MSBTs via standard MRI were 52 % [95 % CI: 34 %-70 %] (15/29), 94 % [95 % CI: 89 %-100 %] (65/69), 79 % [95 % CI: 61 %-97 %] (15/19), 82 % [95 % CI: 74 %-91 %] (65/79) and 82 % [95 % CI: 74 %-89 %] (80/98), respectively. For R2 (senior radiologist) they were 76 % [95 % CI: 60 %-91 %] (22/29), 96 % [95 % CI: 91-100 %] (66/69), 88 % [95 % CI: 75 %-100 %] (22/25), 90 % [95 % CI: 84 %-97 %] (66/73) and 90 % [95 % CI: 84 %-96 %] (88/98), respectively. Adding DWI they were 72 % [95 % CI: 56 %-89 %] (21/29), 91 % [95 % CI: 85 %-98 %] (63/69), 78 % [95 % CI: 62 %-94 %] (21/27), 89 % [95 % CI: 81 %-96 %] (63/71) and 87 % [95 % CI: 80 %-94 %] (85/98) for R1 and 79 % [95 % CI: 65 %-94 %] (23/29), 97 % [95 % CI: 93 %-100 %] (67/69), 92 % [95 % CI: 81 %-100 %] (23/25), 92 % [95 % CI: 86 %-98 %] (67/73) and 92 % [95 % CI: 86 %-97 %] (90/98) for R2. Sensitivities for tumour detection were higher after adding DWI to standard MRI, although only for R1 was this significant (P = 0.03). Adding DWI to standard + gadolinium-enhanced MRI did not significantly increase MR performance.

CONCLUSION

DWI improves MSBT detection via MR-enterography compared to standard unenhanced MR-enterography, especially for unexperienced readers.

KEY POINTS

• MR-enterography is accurate for the detection of mesenteric small-bowel tumours. • Diffusion-weighted sequencing helps inexperienced readers detect small-bowel tumours with MR-enterography. • Diffusion-weighted sequencing adds value to standard MR-enterography when gadolinium is contraindicated.

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.