In our large cohort of patients admitted to the emergency department of our hospital, CT-scan examination was performed in 24% of visits for digestive symptoms.
Patient characteristics are comparable to those reported in the literature for disease localization, phenotype and surgery [11,12,13,14]. The percentage of patients with a diagnosis between 17 and 40 years was high at 75.1% compared to literature where a percentage of 55% has been reported [13, 14]. However, the mean age at diagnosis of our cohort is comparable to other studies .
Our results show that CT-scan detected a penetrating (abscess, fistula, perforation) or stricturing complication (bowel obstruction) in 60% of cases, in contrast with the rates of complications reported in literature of only 23 to 36% [7,8,9, 15, 16].
Univariate analysis of our data evidenced that predictive factors of complications using CT-scan (perforation, abscess, fistula, stenosis) were history of abdominal surgery (OR, 2.9) and stricturing phenotype (OR, 3.42). No independent predictive factor was identified with multivariate analysis, may be due to our small sample size (141 CT-scans). In studies with higher sample sizes, independent predictive factors of abnormal findings using abdominopelvic CT-scan in CD patients presenting to an emergency department were history of abdominal surgery (OR, 2.2) , history of bowel obstruction (OR, 3.8), history of intraabdominal abscess (OR, 2.6)  and stricturing or penetrating phenotype (OR, 2.72) . Nowadays, there is no available predictive score validated in independent population of CD’s patients for the diagnosis of complications. Clinical examination remains the predominant criteria for addressing the patient to the imaging unit.
The percentage of abdominopelvic CT-scans during visits for digestive system symptoms in patients with CD was 23.7% in our study. The study of Kerner et al. showed a significant increase of the rate of CT-scans performed in patients with CD admitted to emergency department: 47.1% in 2001 and 77.5% in 2009 . A more frequent use of CT-scan was reported for all patients who were admitted to an emergency department for abdominal pain . This is most probably due to the improved availability of CT-scans. Various studies reported rates from 49 to 71% for the use of CT-scan for abdominal pain in emergency departments [5, 7,8,9]. Therefore, the rates of CT-scan use that we report (23.7%) are relatively low, probably due to adequate patient selection in a tertiary center and 24-h availability of a gastroenterologist.
According to these results, the indication of CT-scan in emergency department for patients of our cohort appeared to be most often appropriate (low rates of CT-scans performed at admission and high rates of complications detected). Indeed, patients with CD are frequently irradiated for diagnosis purposes and it is necessary to limit their exposition to X-rays . Recent studies in children showed that early exposure to radiations of CT-scan was associated to an increased risk of brain tumor and leukemia . Several studies evidenced that CD patients received large cumulative doses (> 100 mSv) during their follow-up and were exposed to CT-scan radiations up to 2–3 times per year [19, 21,22,23].
According to the 2017 guidelines from the European Crohn’s and Colitis Organisation (ECCO), there is no indication for abdominopelvic CT-scan in suspected CD . In this case, ileocolonoscopy and biopsies for microscopic evidence of CD are recommended as first-line procedure for the diagnosis. CT-scan, together with magnetic resonance imaging and trans-abdominal ultrasonography, are considered as complementary methods to endoscopy. Guidelines recommend to consider radiation exposure when selecting detection methods and especially for the follow-up . The study of Kroeker et al. showed that 30% of the exposure to X-rays of patients with inflammatory bowel disease occurred during the admission to emergency unit including 75% with CT-scan .
Our low rate of CT in this clinical condition (CD’ patients consulting in emergency) could also have local explanation. All physicians in the emergency department could easily access to the total medical history of patients via our hospital computer network. Physicians in this department are well aware of the importance to limit X-Ray exposure in these patients. Hospitalization in a dedicated unit in gastroenterology is also a possibility for them, associated to a senior advice the next day and/or if required in a middle term an MR-enterography. Moreover, some patients went twice to the emergency department and CT could have been done at the second visit for persisting symptoms.
Education of patients on their condition could be a useful tool for limiting the number of admissions to emergency department and the exposition of CD patients to X-ray. Thus, the Spanish study of Casellas et al. reported that among patients with intestinal bowel disease that consulted in an emergency department, 20% of them considered that their visit could have been avoided if they had received a better information on their condition and 18% if they had disposed of the direct phone number of the gastroenterology department . Only 37% considered that the information they received on their disease (evolutive potential, possible complications) was adequate. In CD, some studies showed that telephone follow-up led to a decrease of the number of hospitalizations and admission to emergency department .
The first limitation of our study was the limited sample size. This study has also some others limitations. Some of them are related to the retrospective design. For some parameters (e.g., smoking status, familial history), the rate of missing data was high and was a limitation for the analysis. This study was monocentric and was performed in a tertiary center. As a consequence, the cohort could not reflect all patients with CD. Some patients were not followed in our hospital at the onset of the disease. Therefore, visits to an emergency department during this early period could not be considered. However, the number of patients concerned is probably limited because most of severe CD or with complications were managed in our University Hospital. Biological data at the admission were not studied as predictive data because mechanical complication was also a potential diagnosis (37% of patients).
In conclusion, in CD patients consulting in emergency department, CT-scan examination was performed in 24% of visits for digestive symptoms and complications were found in 60%. Complications were more frequent in patients with stricturing phenotype and previous surgery. Clinical examination and medical history via hospital network remain important data for decision making in order to limit X-ray exposure.