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Stains/Dyes Used in Endoscopy
Using stains or dyes at the time of endoscopy can enhance diagnosis of GI lesions. Currently, three stains, Lugol’s solution, methylene blue and indigo carmine, are commonly and safely used by doctors to distinguish suspicious areas of gastrointestinal tract. Lugol’s solution is an iodine-based absorptive stain that has an affinity for glycogen in normal esophageal epithelium. Early squamous esophageal cancer, inflammation which is depleted of glycogen are usually unstained or weakly stained (Fig 1). Methylene blue stains the normal absorptive epithelium of the small bowel and colon (Fig 2) and also stains abnormal epithelium of the esophagus and stomach. Indigo carmine, a dark bluish dye that is non-absorptive to GI epithelium, has been used in several settings throughout the gastrointestinal tract and is the most widely used endoscopic technique for the detection, predict the size and limits of minute, flat, or depressed colorectal polyps and neoplasms more accurately(Fig 3,4,5). It can also help doctor to detect small gastric cancers, to evaluate villous atrophy in patients suspected of having malabsorption, to study the surface appearance of colonic crypts and discriminate between different polyps. It can also aid in detection of dysplastic changes in patients with ulcerative colitis undergoing surveillance colonoscopy. With the development of technology, a high-resolution endoscopic technique called narrow band imaging (NBI) is coming into practice, which could enhance the fine structure of the mucosal surface without the use of dyes.
 
Fig 1. A superficial esophageal cancer (arrow) before (A) and after(B) lugol’s stain
 
Fig 2. An adenoma before (A) and after (B) staining with indigo carmine
 
Fig 3.A hyperplastic colonic polyp before (A) and after (B) using indigo carmine
 
Fig.4 Small bowel villae before (A) and after (B) staining with indigo carmine
 
Fig.5 A small flat adenoma (white arrow) before (A) and after (B) indigo carmine
By Dr. Bo Sun |
