Can Pan-Colonic Chromoendoscopy (PCC) Improve Adenoma Detection Rate in FIT-Positive-Patients: A Randomized Study

Eligible subjects with positive screening FIT test referred to the Department of Gastroenterology, Singapore General Hospital will be approached and recruited. The included patients will be randomised to either a) Group A- Chromoendoscopy or b) Group B- high definition white light based evaluation.

Hypothesis:

The investigators hypothesize that application of non-absorbable dye during colonoscopy would enhance the mucosal contrast, delineate the border and surface patterns by accumulating in the innominate grooves and, thereby, enhance the detection of adenoma during colonoscopy

Procedure:

Pan-colonic chromoendoscopy and high-definition white light endoscopy will be performed by five experienced endoscopist, and hospital sedation guidelines will be followed. The colonoscopy will be performed using Olympus (CF-HQ190) or Fujifilm (EC-590) colonoscopies. Indigo carmine dye will be used for pan-colonic chromoendoscopy. Two ampules of Indigo carmine (0.8%, 5ml/ampule) will be dissolved in 250 ml of water and sprayed through the waterjet channel by using the auxiliary foot pump upon reaching the caecum.

The colonoscopy insertion will be performed using high-definition white light, and the scope will be advanced till the caecum. The quality of the bowel preparation will be rated according to the validated Boston bowel preparation score. Participants with inadequate bowel preparation score (Score <6) will be excluded from the study. The fecal residue will be washed, suctioned and cleared during insertion to improve visibility. No special care will be taken to look for lesions during the insertion. Assessment for colonic lesions will only be performed during withdrawal of the endoscope. The minimum withdrawal time was set at 7 minutes. Randomization: Once the caecum is intubated and if the bowel preparation is adequate, the participants will be randomized to pan-colonic chromoendoscopy based withdrawal or high-definition while light based withdrawal. In the pan-colonic chromoendoscopy group, the indigo carmine was sprayed by pressing the auxiliary foot pump, and dye was delivered systematically to coat the entire colonic mucosa. In both, the groups, the lesion size, number, location, morphology will be documented during withdrawal. The investigators characterized the morphology of the lesion according to the established Paris classification. The investigators characterized the lesion as flat neoplasm if the lesion project <2.5mm or polypoid lesion if lesion project >2.5mm into the lumen. The investigators measured the size of the lesions using an open biopsy forceps when needed.

In both the groups, the identified polyps will be removed using the standard techniques, and the tissue will be placed in separate formalin bottles and sent for histology assessment. The histology of the polyps was assessed by dedicated pathologist trained in gastrointestinal pathology. Both the endoscopists and the pathologist will not be blinded to the study technique. The investigators defined advanced adenoma as any adenoma >10 mm in size or with >25% villous histology or high-grade dysplasia. The investigators classified hyperplastic polyps and sessile serrated polyps (SSA) as serrated lesions, The investigators excluded hyperplastic lesions in the rectum from the analysis as such lesions are frequently encountered in the rectum