Inflammatory bowel disease (IBD) includes both Crohn's disease (CD) and ulcerative colitis (UC). In comparison with the general population, it primarily affects young people, significantly affecting their quality of life and raising morbidity .
MRE is useful to assess bowel inflammation and complications such as perforation, fibrosis, and stenosis during the disease course .
The current study had a mean patient age of 32 years, which agrees with most of the evidence published in the literature that IBD had a peak incidence during the second and third decades of life with a rare incidence in the 6th decade of life .
The affected parts of the intestine as detected by MRE were mainly ileocecal junction in (5/30, 16.7%) cases and descending colon in (5/30, 16.7%), followed by distal ileum in (4/30, 13.3%) and recto-sigmoid in (4/30, 13.3%) cases.
These findings are agreeing with Esmat et al. , who found that the most commonly affected part of the colon in patients diagnosed with UC is mainly the left-sided colon (65%) followed by the recto-sigmoid area (18.5%) and finally whole colon (16.3%) as reported by Egyptian gastroenterologists. Also, Petagna et al.  have stated that CD mainly affects the ileocecal junction followed by the distal ilium, and this agrees with many authors who correlated the extent of affection of ileum with CD as a part of its pathogenesis where it affects the Peyer's patches which defined as a group of lymphoid follicles in the mucous membrane that lines the small intestine.
In the present study, MRE showed advancement in the assessment of the length of the affected loop of the intestine which was significantly higher in colonoscopy with a mean of 48 ± SD 44 cm versus 15.8 ± SD 19.7 cm, with a p value of 0.0001. We assume that the higher length of ileo-colonoscopy is not as accurate as MRE.
There was a concordance of findings between both imaging modalities in terms of: mural enhancement/hyperemia, loss of haustral/vascular pattern, polyps/pseudo-polyps, backwash ileitis, fat smudging, skip lesions, stagnation, stricture/narrowing, mass lesions, fistulous tracts, perforation, and related vascular congestion with p values > 0.05 each.
Mucosal edema/hyperemia was reported in (18/30, 60%) of cases by ileo-colonoscopy, and this was corresponding to mucosal edema/hyperenhancement in MRE which was reported in (15/30, 50%) of cases; however, this difference was not statistically significant with P value 0.50.
Loss of vascular and haustral pattern was reported in (6/30, 20%) of cases by ileo-colonoscopy, while it was only detected in (5/30, 16.7%) of cases by MRE with one false-negative case; however, this difference was not statistically significant with P value 1.0.
In the present study, MRE was defective in the detection of mucosal lesions, such as pseudo-polyps and polyps as MRE only reported (1/30, 3.3%) cases with pseudo-polyps, while ileo-colonoscopy was positive in (5/30, 16.7%) cases; however, this difference was not statistically significant with p value 0.12.
In the present study, extraluminal affection such as fat smudging, abscess formation, related vascular congestion, and regional lymphadenopathy was only detected by MRE in (4/30, 13.3%), (1/30, 3.3%), (2/30, 6.7%), and (22/30, 73.3%) of cases, respectively, versus no cases by colonoscopy with p value 0.0001 for the abscess formation and the regional lymphadenopathy, and P value 0.12 and 0.50 for fat smudging and related vascular congestion, respectively. Agreeing with Kim et al.  as they have mentioned that MRE is a noninvasive diagnostic tool that assesses both small and large bowel affection in IBD, as well as, can identify intraluminal and extraluminal adverse events. And with Langan et al. , who have stated that although endoscopy has distinct advantages, it cannot be used to assess extraintestinal abnormalities and can be limited when strictures impede the passage of the endoscope and thus prevent completion of the examination.
According to Neumann et al.  who had added that in addition to the lack of extraintestinal visualization using ileo-colonoscopy, as it is mainly limited to the luminal visualization, standard endoscopy may have technical restrictions that hinder the examination of all colon hidden parts. This is because traditional endoscopes only have a 170° field of view due to the use of a complementary metal oxide semiconductor (CMOS) or charge-coupled device (CCD) optics. New developments have been made to improve visualization using seven light-emitting diodes. Particularly, the FUSE colonoscopy's multiple CCD chips, which enable a field of view of up to 330°.
In the present study, paired comparison of both modalities showed that ileo-colonoscopy had a higher detection rate of diseased areas than detected by MRE; however, this difference was not significant with a p value of 0.12. MRE showed a sensitivity of 88.5%, a specificity of 75%, a negative predictive value of 95.8%, a positive predictive value of 50%, and overall diagnostic accuracy of 86.7% in detecting diseased areas within the intestine.
These results are confirmed by a large prospective study conducted by Taylor et al.  in the UK where they included all patients diagnosed with IBD and they were assessed using conventional ileo-colonoscopy, MRE, and ultrasound. Results showed that the sensitivity of MRE in the detection of IBD is 97% and for detection of the extent of the disease is 80%; however, specificity in the detection of disease extent was 95% which was higher than reported in our study.
Monitoring the patient's reaction to anti-inflammatory treatment is another possible application for MRE, which would allow for more accurate and less invasive ways of surveillance .
Due to the failure of prior therapeutic methods to alter the course of CD, novel therapeutic objectives such as early intervention with effective treatment, treat to target, tight disease control, and surveillance can help patients achieve improved outcomes. These objectives involve regular and timely patient evaluations to monitor clinical (Patient Reported Outcomes, PRO), endoscopic (mucosal healing), and radiographic outcomes so that proactive therapy can be optimized .
There was a progression in radiologic evaluation from barium enema investigations to advanced cross-sectional imaging procedures like MR enterography. Endoscopy and magnetic resonance (MR) enterography are complementing diagnostic procedures for the evaluation of inflammatory bowel disease (IBD), as stated by Sahi et al. , and Gallego et al. . It has been demonstrated that MR enterography correlates well with endoscopy in predicting disease activity, particularly in Crohn's disease.
Importantly, a higher risk of complications may exist even with lower cumulative radiation exposures . Therefore, imaging techniques that are not using ionizing radiation, such as MRE, are especially appealing in a population of young patients who are susceptible to recurrent imaging .
According to Lanier et al. , magnetic resonance enterography (MRE) has become the imaging modality of choice for the assessment of IBD activity in both adults and children.
A systematic review and meta-analysis on the role of MRI in the detection of Crohn's disease activity concluded its effectiveness as an alternative to CT enterography as it has good diagnostic accuracy without radiation exposure .
The most important findings that detect disease exacerbation and activity are: mucosal hyperenhancement/hyperemia, mural thickening, related lymph node enlargement, and mucosal erosions/ulcerations as well as related vascular congestion of the mesenteric arteries [30,31,32,33].
Mucosal hyperemia/enhancement was detected by MRE with a sensitivity of 80% and specificity of 60%. MRE could estimate the mural thickening with a mean of 4.1 ± SD 5.1 mm. Yet, mural thickening could not be detected by ileo-colonoscopy at all, with a significant difference; the p value was 0.001.
In the current study, MRE could detect related lymphadenopathy in (22/30, 73.3%) cases versus (0/30, 0%) cases by ileo-colonoscopy with a significant difference of P value of 0.0001. DWI was useful in the detection of lymphadenopathy, which is an important marker of disease exacerbation; lymph nodes with restricted DWI were of good value in the detection of the active inflammatory process. According to the literature, DWI with parallel imaging permits the detection of inflammation in Crohn's disease patients, and the lower ADC values in the inflamed bowel segments indicate restricted diffusion .
However, mucosal erosions and ulcerations could not be detected by MRE in this study, while using ileo-colonoscopy could detect (18/30, 60%) of cases, with mucosal erosions and ulcerations, versus (0/30, 0%) of cases by MRE, with a significant difference P value 0.0001. According to Sinha et al. , superficial aphthous ulcers might appear on T2WI when there is good distention of the lumen. It appears as an intermediate signal on T2WI, surrounded by a focal area of bright T2WI signal. This might have been apparent in UC cases with a lack of proper colonic distension in the MRE. They have also stated that deep ulcers would appear as thin lines penetrating the bowel wall that appears bright in T2 W sequences with fat suppression. These deep ulcers might complicate to become penetrating fistulae . The current study included (2/30, 6.7%) cases with fistulae/sinus tracts that were detected equally by MRE and ileo-colonoscopy.
On the other hand, Dulai et al.  have stated that MRE has a low negative predictive value for the detection of mucosal pathology because it may exclude the presence of active inflammation or ulceration when it is present, and further endoscopic assessment may still be necessary for patients with persistent symptoms despite the appearance of normal mucosa on MRE.
Related vascular congestion of the mesenteric arteries (vasa recta) was detected by MRE in (2/30, 6.7%) of cases, while it was not detected by ileo-colonoscopy. With a P value of 0.50, this was described by Tolan et al.  as a sign of active illness when combined with intestinal wall edema and enhancement.
In the present study, we were limited by the lack of long-term follow-up of patients to assess the patterns of disease activities. Also, we only assessed patients with CD and UC and disregarded patients with idiopathic inflammatory bowel disease, so our results cannot be generalized over all types of IBD.
Our study showed some MRE examination difficulties that include prolonged examination time and patients with associated spine and sacroiliac joint inflammation who have found difficulty in the prolonged supine position during examination.
Although the MRE was reported by an expert radiologist with 12 years of experience in GIT sub-specialty who was blinded to the ileo-colonoscopy results, it would have been better if it was reported by two radiologists.
The use of 3 T MR operators will provide a more reasonable evaluation for dynamic contrast-enhanced and diffusion-weighted MR images to better detect active versus chronic stages of the disease. It will also allow a faster scanning time about 15–20 min rather than the standard 30–60 min while utilizing a 1.5 T MR operator.