The colonoscopy is the reference examination for the diagnosis of neoplastic lesions in the colon and rectum. Mass screening assessment studies have shown that colonoscopic detection and removal of adenomas in patients selected through fecal occult blood test reduces colorectal cancer incidence and mortality. However, the literature has reported interval cancer cases or adenomas, probably "missed" by the colonoscopy. In theory, using coloured warm water could improve colon preparation by mobilizing the residual faeces, decreasing the colic spasm and increasing the visualization of the pit pattern. Preliminary American studies, led by Leung et al, have shown a very clear increase in the adenoma detection rate.

The investigators' study involves 1 000 patients, treated in the Rhône-Alpes / Auvergne region. The patients present an indication for colonoscopy following a positive fecal occult blood test or symptoms or personal and family histories of pre-cancerous colonic lesions. They will be randomized into two study groups:one of both groups of study: Group 1: patients undergoing a colonoscopy wtih instillation of tepid water tinged with blue (Indigo Carmin®) Group 2: patients undergoing a standard colonoscopy with insufflation of air. The main objective is to show that the colonoscopy with blue water (Indigo Carmin®) enable detection of more lesions than standard colonoscopy with insufflation of air. The two techniques will be also compared in terms of tolerance, of duration of colonoscopy and type of detected lesions.

In case of improved detection of colorectal lesions, the blue water instillation technique of could dramatically change gastroenterologists' practice by becoming the reference method. The expected clinical benefits are potential revealing of more neoplastic lesions and improvement in abdominal discomfort after colonoscopy.

Inclusion Criteria:

• Male or female patients 18 years of age or older

• Scores 1 to 3 in ASA (American Society of Anesthesiologists) classification

• Patient having an indication for of colonoscopy to detect colorectal neoplastic lesions, which meet at least one of the following conditions:

  • Positive fecal occult blood Test
  • 1st degree family history of colorectal cancer or adenoma before 60 years of age
  • Personal history of colorectal adenomas or colorectal cancer
  • Unexplained digestive symptoms after 50 years of age or those not responding to symptomatic treatment: modification of bowel movements, abdominal pains
  • Isolated or repeated rectal bleeding after 50 years of age or occult bleeding
  • Acromegaly
  • Infectious endocarditis with digestive bacteria

• No coagulation anomalies or no taking of medicine affecting coagulation

• Signing of informed consent form before the performance of any procedure related to the study

Exclusion Criteria:

• Known inflammatory or infectious colorectal disease
• Hereditary Non Polyposis Colorectal Cancer disease (Lynch syndrome) or family history of adenomatous polyposis
• Histories of colorectal surgical resection
• Known hypersensitivity to indigo Carmin® or to one of the preparation components
• Pregnant or breastfeeding women, or those likely to become pregnant without effective contraception
• patient not affiliated with a social security care system or who do not benefit from such a system
• Patient over 18 years of age protected by the Law, under guardianship or curators
• Concomitant participation in an interventional biomedical research trial