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Tissue stains used during gastrointestinal endoscopy

Stain type	What is stained	Mechanism of staining	Positive staining	Clinical uses in GI
Vital stains
Lugol's solution (iodine + potassium iodide)	Normal glycogen containing squamous cells	Binds iodine in non-keratinized cells	Dark brown	1) Squamous cell esophageal cancer (non-staining)
				2) Columnar epithelium in the esophagus, including residual Barrett's esophagus following mucosal ablation (non-staining)
				3) Reflux esophagitis (non-staining)
Methylene blue (methylthionine chloride)	Small or large intestinal cells or intestinal metaplasia	Active absorption into cells	Blue	1) Specialized epithelium (intestinal metaplasia) in Barrett's esophagus*
				2) Intestinal metaplasia in the stomach
				3) Early gastric cancer^¶
				4) Gastric metaplasia in the duodenum (non-staining)
				5) Celiac and tropical sprue
Toluidine blue (tolonium chloride or dimethylamino-toluphenazothioni-chloride)	Nuclei of columnar (gastric and intestinal-type) cells	Diffuses into cell	Blue	1) Squamous cell carcinoma of the esophagus
				2) Gastric or intestinal metaplasia in Barrett's esophagus
Reactive stains
Congo red (biphenylene-napthadene sulfornic acid)	Acid-containing gastric cells	Acid pH <3.0 results in color change	Turns red to dark blue or black	1) Acid-secreting gastric mucosa (including ectopic locations)
				2) Gastric cancer (nonstaining); (may be combined with methylene blue to outline intestinal metaplasia)
Phenol red (phenolsulfonphthalein)	H. pylori-infected gastric cells	Alkaline pH (from hydrolysis of urea to NH3 and CO2 by urease) results in color change	Turns yellow to red	Diagnose Helicobacter pylori infection (positive color change) and map its distribution in the stomach
Contrast stain
Indigo carmine^Δ	Cells are not stained	Pools in crevices and valleys between mucosal projections	Blue (indigo)	1) Colon, gastric, duodenal, esophageal lesions
				2) Barrett's esophagus

* Methylene blue does not stain non-specialized or gastric metaplasia; specialized columnar epithelium stains blue, but highly dysplastic or malignant specialized columnar epithelium in Barrett's esophagus generally takes up little to no dye; low grade dysplasia in Barrett's esophagus may or may not take up stain.
¶ With or without Congo red.
Δ Also used in combination with high resolution or high magnification endoscopy; may be used with or without crystal violet (for early colorectal cancers).

Graphic 68885 Version 9.0