The aetiologies of computed tomography-diagnosed acute colitis remain surprisingly unknown. Moreover, no diagnostic tool or clinical score allow to quickly determine or at least stratify the exact cause of colitis in patients admitted at an Emergency Ward and to direct them to the appropriate therapeutic care. The aims of the present study are to describe the presentation and aetiologies of acute colitis, and to develop diagnostic methods to guide patients admitted for acute colitis to the appropriate therapeutic care, notably colonoscopy.

Colitis is the generic term that refers to an inflammation of a segment of the colonic tract confirmed by computed tomography. This pathology represents approximately 100-150 admissions per year in the Division of Digestive Surgery of the University Hospitals of Geneva.

The aetiologies of colitis are numerous and include all pathologies having the ability to cause the inflammation and thickening of the colon wall. Colites are classified according to their aetiologies into: infectious colitis (bacterial, parasitic or viral), inflammatory chronic bowel diseases (ulcerative colitis, Crohn's disease, others), ischaemic colitis and iatrogenic colitis (non-steroidal anti-inflammatory drugs, others). The aetiologies of colitis affect therapeutic care, since patients with infectious colitis will improve with appropriate antibiotics, those with inflammatory chronic bowel disease will require the introduction of an immunosuppressive therapy, and those with ischaemic colitis will only need a supportive treatment and a careful evaluation to detect any progression to bowel perforation that would prompt for surgery.

Therefore, numerous investigations are performed to determine the precise aetiology of colitis.

At the University Hospitals of Geneva, as well as in other centres, a microbiological analysis of faeces (routine PCR assay looking for Shigella spp., Salmonella spp. and Campylobacter spp.; PCR for Clostridium difficile as well as cultures for Vibrio spp. and Yersinia spp. (in option)) are performed in first intention. If these assays yield to the absence of a potential pathogen, a colonoscopy is performed to look for: 1) a tumour, 2) a chronic inflammatory bowel disease or 3) an ischaemic colitis. Patients in whom no aetiology can be found to explain the colonic inflammation are given a diagnosis of undetermined colitis.

However, the respective prevalences of the different aetiologies of colitis remain surprisingly unknown. Similarly, no diagnostic tool or clinical score allow to quickly determine or at least stratify the exact cause of colitis in patients admitted in the Emergency Ward and to direct them to the appropriate therapeutic care. As a consequence, all patients admitted with a diagnosis of computed tomography-proven colitis are subjected to broad-spectrum antibiotics associated with a 5-10 days hospitalisation for monitoring and investigations. Patients with negative microbiological examination of the stools will benefit from an early colonoscopy, a procedure that carries significant risks of complications and generates high costs. Moreover, the difficulties in the early identification of patients requiring endoscopy for suspected inflammatory chronic bowel disease or cancer may delay or even contribute to miss these diagnoses, especially if the acute phase of inflammatory chronic bowel disease has passed.

Considering the lack of evidences regarding the therapeutic care of colitis, we plan to constitute a cohort of 200 patients admitted for a first episode of computed tomography-proven colitis at the University Hospitals of Geneva. We will collect data related to 1) the history, clinical and para-clinical presentations at admission, 2) the results of the aetiological investigations; and we will complete the investigations by performing 3) a detailed microbiological examination of the stools using an accurate and rapid multi-array PCR assay (FilmArray, Biofire Diagnostics, Salt Lake City, USA), as well as 4) a dosage of faecal calprotectin (a marker of bowel inflammation).

The aims of the present study are to describe the presentation and aetiologies of colitis, and to develop diagnostic methods to guide patients admitted for acute colitis to the appropriate therapeutic care, with the objective to generate savings by shortening hospital stays and by better prescribing additional tests, including colonoscopy. We therefore think that an adequate and early patient stratification has important medical and economical values in this setting.

We expect: 1) to diagnose a higher proportion of infectious colitis than currently reported, and this within a shorter turnaround time, a finding that could serve as a basis to discuss and implement a reduction in the rate of colonoscopies, 2) to identify predicting factors, including faecal calprotectin, which would help distinguishing patients who require an endoscopic evaluation from others, among patients with negative microbiological examination of the stools.

Inclusion Criteria:

• ≥18 year old
• French speaking
• Informed consent
• ≥1 symptom compatible with an acute colitis (fever≥38°C ± acute abdominal pain ± diarrhoea) + colon wall thickening at computed tomography

Exclusion Criteria:

• Another diagnostic evoked by the radiologist (diverticulitis, tumor, ...)
• Patient with a positive history for: chronic inflammatory bowel disease ± colorectal cancer ± immunosuppression ± abdominal ascites
• Refusal of investigations

All patients admitted at the Emergency Department with a first diagnosis of computed tomography-diagnosed acute colitis