(EN) The present invention provides a novel liquid composition in the form of an emulsion or microemulsion for rectal administration comprising at least one dye, at least one emulsifier, and at least one physiologically acceptable excipient, and its use in a diagnostic endoscopic procedure of sigmoid colon and/or rectum. Preferably, said diagnostic endoscopic procedure of sigmoid colon and/or rectum is an anoscopy, a proctoscopy, a rectoscopy and/or a sigmoidoscopy.