FIT in Diverticulitis

What is the purpose of the study? The main aim of this study is to see if a faecal immunochemical test (FIT), could be used as an alternative to currently used follow-up investigations, of colonoscopy, flexible sigmoidoscopy or CT (computerised tomography) colonography, for patients who have an episode of acute diverticulitis to exclude a colorectal cancer (CRC). As stated in the ASCPGBI consensus guidelines 2021 the risk of CRC in those with CT diagnosed uncomplicated diverticulitis is 1.6-1.9% and in those with complicated diverticulitis 7.8-10.9%. Our primary aim is to determine whether single, or multiple faecal haemoglobin and faecal calprotectin results after an episode of acute diverticulitis can be used to risk stratify for further investigations to exclude colorectal cancer. Our secondary aims are: To determine whether single, or multiple faecal haemoglobin and faecal calprotectin results after an episode of acute diverticulitis could be used to risk stratify for further investigations to exclude other colonic findings such as high-risk adenoma? Would including demographic factors such as age or anaemia allow better risk stratification? Assess the faecal microbiome in patients with acute diverticulitis and how it changes as inflammation settles. Any antibiotic treatment will also be recorded and the effect on the faecal microbiome analysed. Inclusion criteria: Computerised tomography diagnosis of acute diverticulitis Participants capable of giving informed consent Aged ≥ 18 years Planned for colonoscopy, flexible sigmoidoscopy or CT colonoscopy after diverticulitis diagnosis Exclusion criteria: Paediatric patients (\<18 years) Not provided at least 1 FIT sample Unable to/unwilling to provide informed consent Withdrawal of consent for inclusion in study Previous pan-proctocolectomy, subtotal colectomy surgery, or presence of stoma Diagnosed with colorectal cancer Mental health illness limiting compliance Treated in hospital with colonic resection Did not have colonoscopy, flexible sigmoidoscopy or CT colonoscopy Recruitment: Patients who attend hospital with a diagnosis of acute diverticulitis confirmed on a CT scan and who have had a clinical decision to follow-up with either a colonoscopy, flexible sigmoidoscopy or CT colonography will be approached for written consent to participate. Patients will then be posted a patient information leaflet and a pack with collection devices to take samples at home and post back. The results of their follow-up investigation (colonoscopy, flexible sigmoidoscopy or CT colonography + any histology) will be collected when completed Involvement for patients will involve collecting and posting back in pre-paid envelopes faecal samples on their first solid stool (or as soon as possible after diagnosis) and at 3 and 6 weeks post-diagnosis. Sample size: 275 - Estimated using available data on diverticulitis and stratified data from FIT use in 2WW patients.