To the editors of The Journal of the Canadian Association of Gastroenterology,
I have found something relatively easy and inexpensive that may help others in differentiating and identifying polyps during colonoscopy.
It is a common practice to use chromoendoscopy during colonoscopy for chronic colitis because it helps identify subtle polyps or other raised lesions that need to be removed. Methylene blue is most often used for this. There has been some resistance to performing chromoendoscopy, especially in an outpatient clinic setting. It can be relatively costly in relationship to the time it takes and the equipment required, including the dye. Extra time is needed to go back and forth through the colon when using methylene blue. A catheter is required to inject the dye during the colonoscopy, which adds to the cost. Furthermore, although rare, side effects can occur. Methylene blue has a potential to cause hemolysis in persons with glucose-6-phosphate dehydrogenase deficiency.
As an alternative to methylene blue, for several years I have been using regular blue food colouring—which can be purchased at any grocery store—in the waterjet bottle during routine colonoscopies. I found that this helps to identify the edges of polyps and to differentiate adenomatous from hyperplastic polyps. The mucosal pattern is more easily seen than when using white light alone.
Four to six drops of blue food colouring is added to a litre of water in the spray bottle and is sprayed through the water jet channel. As the walls of the colon are flushed normally, the blue food colouring at this concentration is translucent, but provides enough contrast to visualize the mucosal patterns (Figures 1–3). Subtle disruption of the mucosal fold pattern will often identify sessile or flat polyps. No extra catheters are necessary, and spraying along the colon while flushing allows for the food colouring to spread across mucosa. One pass through the colon is all that is needed.
Figure 1.
(A) Before blue dye. (B) After blue dye.
Figure 3.
(A) Polpy in white light. (B) Edge seen spreading out with blue dye.
Figure 2.
(A) TI in white light. (B) fine detail more easily seen with blue dye.
The only side effect from the blue dye is that it may stain the patient’s clothing as it may leak out after the colonoscopy. A small bottle costs approximately $4 and lasts several weeks.
Along with careful and thorough observation, even if using blue food colouring helps only on occasion to find an additional polyp or helps to define the borders of a sessile polyp, it is so simple and inexpensive to use, I think it is worthwhile and would suggest others try this during routine colonoscopy, not just for chronic colitis or IBD.
Sincerely,
Dr. Mark Atin