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NIHR Signal MRI and ultrasound scans are both helpful in assessing Crohn’s disease; MRI is slightly more accurate

Published on 8 January 2020

doi: 10.3310/signal-000858

Two types of scan, MRI and ultrasound, work well when used for staging and monitoring Crohn’s disease. MRI is more accurate.

Researchers compared a form of magnetic resonance (MR) imaging that includes an oral contrast agent, with ultrasound scans. They aimed to see which was better able to detect the presence and extent of active disease in the small bowel. The trial, carried out in eight NHS hospitals, involved 284 participants who had both MR and ultrasonography. While both tests performed well, MR was 10% more accurate for correctly classifying small bowel disease.

Patients were more likely to rate ultrasonography as acceptable or fairly acceptable. The tests were similar in terms of value for money. Clinicians were helped equally by the two tests in making potential treatment decisions.

The study suggests either MRI or ultrasound scans are acceptable tests to use for the management of Crohn’s disease.

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Why was this study needed?

Management of Crohn’s disease depends on the extent and severity of active disease.

While ileocolonoscopy is the gold standard diagnostic test, it can only see a short way into the small bowel, so is less useful for assessing the extent of small bowel disease. It is also invasive and uncomfortable for patients. Both ultrasound and magnetic resonance imaging have been used to assess the small bowel at the start of the disease and when a flare-up is suspected.

Magnetic resonance (MR) enteroscopy is a newer technique that uses conventional MR scanners after the patient has been given an oral ‘biphasic’ contrast agent that distends the bowel and allows better assessment of mucosal folds and wall thickness.

While ultrasound scanners are more widely available, their accuracy may be more dependent on operator performance.

There have been questions about the quality of the previous research into the accuracy of these techniques and so this multi-centre study was designed to compare the performance of the tests in a prospective cohort design, primarily of patients with small bowel disease.

What did this study do?

The METRIC cohort study analysed a final cohort of 284 participants, 133 of whom were newly diagnosed with Crohn’s and 151 who were suspected of having relapses. 82% had small bowel disease and 45% had colonic disease. Participants in the original sample of 335 who were found not to have Crohn’s disease were excluded from the analysis.

Participants underwent both ultrasonography and MR enteroscopy, along with any other clinically-indicated investigations. For the reference standard, against which the scans were compared, a panel of clinicians reviewed all data about the participants, including their clinical course over six months. They recorded their opinion about the presence and activity of disease. 

What did it find?

  • MR enteroscopy had a sensitivity of 80% for extent of small bowel disease (95% confidence interval [CI] 72% to 86%), while ultrasonography had a sensitivity of 70% (95% CI 62% to 78%). Specificity was 95% for MR enteroscopy (95% CI 85% to 98%) and 81% for ultrasonography (95% CI 64% to 91%).
  • For detecting the presence of small bowel disease, MR enteroscopy had a sensitivity of 96% (95% CI 86% to 99%) and ultrasonography had a sensitivity of 84% (95% CI 65% to 94%). 
  • For colonic Crohn’s disease presence or extent, there was no overall significant difference in sensitivity or specificity between the tests.
  • Both imaging techniques were acceptable to patients as 99% of participants said they tolerated ultrasonography ‘well or fairly well’ as did 88% for MR enteroscopy.

What does current guidance say on this issue?

NICE published a guideline on the management of Crohn’s disease in May 2019. However, this guideline does not include information or advice on the use of MR enteroscopy or ultrasonography for monitoring disease.

What are the implications?

This study suggests that clinicians can use either MR or ultrasound to assess and monitor the progress of Crohn’s disease, as an adjunct to diagnostic ileocolonoscopy.

While MR is more sensitive, both tests perform well and ultrasound may be more acceptable to patients.

Citation and Funding

Taylor SA, Mallett S, Bhatnagar G et al. Magnetic resonance enterography compared with ultrasonography in newly diagnosed and relapsing Crohn's disease patients: the METRIC diagnostic accuracy study. Health Technol Assess. 2019;23(42).

This project was funded by the NIHR Health Technology Assessment Programme (project number 11/23/01).

Bibliography

NICE. Crohn’s disease: management. NG129. London: National Institute for Health and Care Excellence; 2019.

Why was this study needed?

Management of Crohn’s disease depends on the extent and severity of active disease.

While ileocolonoscopy is the gold standard diagnostic test, it can only see a short way into the small bowel, so is less useful for assessing the extent of small bowel disease. It is also invasive and uncomfortable for patients. Both ultrasound and magnetic resonance imaging have been used to assess the small bowel at the start of the disease and when a flare-up is suspected.

Magnetic resonance (MR) enteroscopy is a newer technique that uses conventional MR scanners after the patient has been given an oral ‘biphasic’ contrast agent that distends the bowel and allows better assessment of mucosal folds and wall thickness.

While ultrasound scanners are more widely available, their accuracy may be more dependent on operator performance.

There have been questions about the quality of the previous research into the accuracy of these techniques and so this multi-centre study was designed to compare the performance of the tests in a prospective cohort design, primarily of patients with small bowel disease.

What did this study do?

The METRIC cohort study analysed a final cohort of 284 participants, 133 of whom were newly diagnosed with Crohn’s and 151 who were suspected of having relapses. 82% had small bowel disease and 45% had colonic disease. Participants in the original sample of 335 who were found not to have Crohn’s disease were excluded from the analysis.

Participants underwent both ultrasonography and MR enteroscopy, along with any other clinically-indicated investigations. For the reference standard, against which the scans were compared, a panel of clinicians reviewed all data about the participants, including their clinical course over six months. They recorded their opinion about the presence and activity of disease. 

What did it find?

  • MR enteroscopy had a sensitivity of 80% for extent of small bowel disease (95% confidence interval [CI] 72% to 86%), while ultrasonography had a sensitivity of 70% (95% CI 62% to 78%). Specificity was 95% for MR enteroscopy (95% CI 85% to 98%) and 81% for ultrasonography (95% CI 64% to 91%).
  • For detecting the presence of small bowel disease, MR enteroscopy had a sensitivity of 96% (95% CI 86% to 99%) and ultrasonography had a sensitivity of 84% (95% CI 65% to 94%). 
  • For colonic Crohn’s disease presence or extent, there was no overall significant difference in sensitivity or specificity between the tests.
  • Both imaging techniques were acceptable to patients as 99% of participants said they tolerated ultrasonography ‘well or fairly well’ as did 88% for MR enteroscopy.

What does current guidance say on this issue?

NICE published a guideline on the management of Crohn’s disease in May 2019. However, this guideline does not include information or advice on the use of MR enteroscopy or ultrasonography for monitoring disease.

What are the implications?

This study suggests that clinicians can use either MR or ultrasound to assess and monitor the progress of Crohn’s disease, as an adjunct to diagnostic ileocolonoscopy.

While MR is more sensitive, both tests perform well and ultrasound may be more acceptable to patients.

Citation and Funding

Taylor SA, Mallett S, Bhatnagar G et al. Magnetic resonance enterography compared with ultrasonography in newly diagnosed and relapsing Crohn's disease patients: the METRIC diagnostic accuracy study. Health Technol Assess. 2019;23(42).

This project was funded by the NIHR Health Technology Assessment Programme (project number 11/23/01).

Bibliography

NICE. Crohn’s disease: management. NG129. London: National Institute for Health and Care Excellence; 2019.

Magnetic resonance enterography compared with ultrasonography in newly diagnosed and relapsing Crohn's disease patients: the METRIC diagnostic accuracy study

Published on 21 August 2019

Taylor SA, Mallett S, Bhatnagar G, Morris S, Quinn L, Tomini F et al.

Health Technology Assessment Volume 23 Issue 42 , 2019

Background Magnetic resonance enterography and enteric ultrasonography are used to image Crohn’s disease patients. Their diagnostic accuracy for presence, extent and activity of enteric Crohn’s disease was compared. Objective To compare diagnostic accuracy, observer variability, acceptability, diagnostic impact and cost-effectiveness of magnetic resonance enterography and ultrasonography in newly diagnosed or relapsing Crohn’s disease. Design Prospective multicentre cohort study. Setting Eight NHS hospitals. Participants Consecutive participants aged ≥ 16 years, newly diagnosed with Crohn’s disease or with established Crohn’s disease and suspected relapse. Interventions Magnetic resonance enterography and ultrasonography. Main outcome measures The primary outcome was per-participant sensitivity difference between magnetic resonance enterography and ultrasonography for small bowel Crohn’s disease extent. Secondary outcomes included sensitivity and specificity for small bowel Crohn’s disease and colonic Crohn’s disease extent, and sensitivity and specificity for small bowel Crohn’s disease and colonic Crohn’s disease presence; identification of active disease; interobserver variation; participant acceptability; diagnostic impact; and cost-effectiveness. Results Out of the 518 participants assessed, 335 entered the trial, with 51 excluded, giving a final cohort of 284 (133 and 151 in new diagnosis and suspected relapse cohorts, respectively). Across the whole cohort, for small bowel Crohn’s disease extent, magnetic resonance enterography sensitivity [80%, 95% confidence interval (CI) 72% to 86%] was significantly greater than ultrasonography sensitivity (70%, 95% CI 62% to 78%), with a 10% difference (95% CI 1% to 18%; p = 0.027). For small bowel Crohn’s disease extent, magnetic resonance enterography specificity (95%, 95% CI 85% to 98%) was significantly greater than ultrasonography specificity (81%, 95% CI 64% to 91%), with a 14% difference (95% CI 1% to 27%). For small bowel Crohn’s disease presence, magnetic resonance enterography sensitivity (97%, 95% CI 91% to 99%) was significantly greater than ultrasonography sensitivity (92%, 95% CI 84% to 96%), with a 5% difference (95% CI 1% to 9%). For small bowel Crohn’s disease presence, magnetic resonance enterography specificity was 96% (95% CI 86% to 99%) and ultrasonography specificity was 84% (95% CI 65% to 94%), with a 12% difference (95% CI 0% to 25%). Test sensitivities for small bowel Crohn’s disease presence and extent were similar in the two cohorts. For colonic Crohn’s disease presence in newly diagnosed participants, ultrasonography sensitivity (67%, 95% CI 49% to 81%) was significantly greater than magnetic resonance enterography sensitivity (47%, 95% CI 31% to 64%), with a 20% difference (95% CI 1% to 39%). For active small bowel Crohn’s disease, magnetic resonance enterography sensitivity (96%, 95% CI 92% to 99%) was significantly greater than ultrasonography sensitivity (90%, 95% CI 82% to 95%), with a 6% difference (95% CI 2% to 11%). There was some disagreement between readers for both tests. A total of 88% of participants rated magnetic resonance enterography as very or fairly acceptable, which is significantly lower than the percentage (99%) of participants who did so for ultrasonography. Therapeutic decisions based on magnetic resonance enterography alone and ultrasonography alone agreed with the final decision in 122 out of 158 (77%) cases and 124 out of 158 (78%) cases, respectively. There were no differences in costs or quality-adjusted life-years between tests. Limitations Magnetic resonance enterography and ultrasonography scans were interpreted by practitioners blinded to clinical data (but not participant cohort), which does not reflect use in clinical practice. Conclusions Magnetic resonance enterography has higher accuracy for detecting the presence, extent and activity of small bowel Crohn’s disease than ultrasonography does. Both tests have variable interobserver agreement and are broadly acceptable to participants, although ultrasonography produces less participant burden. Diagnostic impact and cost-effectiveness are similar. Recommendations for future work include investigation of the comparative utility of magnetic resonance enterography and ultrasonography for treatment response assessment and investigation of non-specific abdominal symptoms to confirm or refute Crohn’s disease.

Expert commentary

Ileocolonoscopy is the gold standard for the diagnosis of Crohn's disease.

The findings from the NIHR-funded METRIC study showing that MR and ultrasound can identify the presence, site and activity of Crohn's disease in over 80% of cases will encourage clinicians to use MR and ultrasound to complement ileocolonoscopy in assessing patients with Crohn's disease.

Both the tests also hold promise for identifying Crohn's disease in patients with relevant symptoms. Although ultrasound is more readily available, the expertise for bowel ultrasound is patchy in the NHS and hence MR may be used more often by clinicians. It is reassuring to note that there was no difference in costs and both are well accepted by patients.

Professor Shaji Sebastian, Consultant Gastroenterologist, Hull University Teaching Hospitals NHS Trust

Dr Charlie Lees, Consultant Gastroenterologist, MRC Institute of Genetics and Molecular Medicine, Centre for Genomic and Experimental Medicine, The University of Edinburgh

The commentators declare no conflicting interests