Although ileocolonoscopy is a proven sensitive method to detect mucosal injury and diagnose disease activity, it is limited by its maximal extent and inability to detect transmural complications as well as limited ability to assess deep bowel wall involvement .
Several imaging methods including computed tomography (CT), magnetic resonance (MR), and ultrasound (US) were described as essential tests for assessing different mural changes as well as extra-intestinal disease complications .
As modern imaging techniques has been improved to detect and quantify mucosal injury, CT enterography (CTE) was described as an imaging modality for small bowel disease assessment over the recent years and has a main role in the diagnosis and evaluation of patients with inflammatory bowel disease (IBD) with a performance comparable to ileocolonoscopy .
In current study, we did not use positive oral contrast as it would obscure subtle mucosal changes seen in mild/early disease such as mucosal hyper-enhancement, which is a matching study done by Schindera ST et al.  who also stated that positive oral contrast agent (containing iodine) is not routinely used for CTE.
In this study, we observed that the earliest radiological finding of Crohn’s disease activity at CTE was mucosal hyper-enhancement, which was also described by Min JP and Joon SL , who suggested that mural hyper-enhancement is a sensitive finding in detecting early disease activity. It is very important to compare the bowel loops with similar degree of distension because normal collapsed loops show greater attenuation than distended bowel loops.
As the disease progresses, mural thickening was noticed combined with mucosal hyper-enhancement and that was also noticed by Booya et al.  who stated that mural thickening and hyper-enhancement are the most diagnostic computed tomography enterography (CTE) findings that suggest active inflammatory Crohn’s disease.
Bilaminar mural stratifications refer to mucosal hyper-enhancement and decreased intra-mural attenuation. In current study, it was seen in 13 patients (26%) while tri-laminar mural stratification refers to alternating high and low attenuation areas that occurs due to mucosal and serosal hyper-enhancement with low intramural attenuation. It was seen in 8 patients (16%). Low intramural attenuation can represent edema, inflammatory infiltrates, or fat. Hara et al.  concluded that intramural edema represented by mural stratification is much more indicative of active disease as compared to homogenously enhanced intestinal wall. However, Madureira AJ  stated that mural stratification is not specific for Crohn’s disease and may be also seen with other small bowel diseases, such as ischemia, ulcerative colitis, and radiation enteritis. Inflamed bowel segments are commonly absent at endoscopy and histopathologic analysis. Trilaminar enhancement is often identified more with MR enterography than in CT enterography, probably due to the superior contrast resolution at MR enterography .
Engorgement of vasa recta “comb sign” refers to congested vasa recta that penetrate the small bowel wall perpendicular to bowel lumen, simulating the appearance of a comb; it is another indicator of disease activity and was found in 38 patients (76%) in this study. Colombel et al.  also described increased attenuation of the mesenteric fat in combination with the “comb” sign are common CT findings seen in active Crohn’s disease. The “comb sign” is also reported to be associated with higher C-reactive protein (CRP) levels than for patients with normal vasculature .
Extension of the inflammatory process across serosal surface into adjacent mesentery or structures leads to fistula, sinus tract, and/or abscess formation. In this study, three cases showed abscess formation as an extra-enteric complication of active Crohn’s disease. Detection of extra-intestinal complications is very important as it affects the decision to treat medically or surgically, and it also affects the method of surgical approach either laparoscopic or open. Booya et al.  also reported the importance of detection of clinically unsuspected penetrating disease on CTE examinations as it leads to alteration in therapy regimen in up to 61% of patients with Crohn’s disease.
CTE is not also used to assess medical treatment response, which manifests as decreasing mural hyper-enhancement, bowel wall thickening and improvement of the engorged vasa recta, but it also can detect disease recurrence after remission or even after surgical treatment. In this study, one case which was surgically treated represented with recurrence of clinical symptoms including abdominal pain and diarrhea, CTE showed segment of mural thickening and enhancement suggesting disease activity and that was proved by endoscopy results. Wu et al.  also reported that CTE findings have high correlation with clinical symptoms before and after treatment.
Although CT enterography (CTE) is optimized to detect intestinal damage and extra-intestinal findings and complications, this study faced some limitations such as limited number of patients, lack of radiological correlation with treatment protocols, and the obtained radiological findings are not specific to Crohn’s disease so some cases gave false positive results and were not pathologically proved to be Chron’s disease by endoscopy and histopathology.