All that is red is not blood!

A 62-year-old woman presented for screening colonoscopy after a 24-hour clear-liquid diet and Colyte preparation. Frank blood was noted from the point of colonoscope insertion up to the terminal ileum ([Fig. 1 a]). Aspirate tested negative with the hemoccult card. Using narrow-band imaging (NBI) the “red liquid” appeared cyan blue ([Fig. 1 b]). Upon further questioning during recovery, the patient reported eating red jello.

NBI is an alternative light-wavelength capture system that filters light in the visible spectrum, except for narrow bands in the blue and green wavelengths (415 nm and 540 nm, respectively) [1] ([Fig. 3]). The peak absorption spectrum of red dye is 502 – 518 nm and appears as a cyan color whereas oxyhemoglobin is absorbed at 415 nm and appears as dark maroon. As shown in [Figs. 1 a] and [2 a], red jello and post-polypectomy bleeding appeared indistinguishable under white light. Even the most sophisticated of tools, NBI, has demonstrated here a simple clinical use in differentiating between blood and other red substances. We suspect that this is not the first or the last case of “red jello stool” [2].

Fig. 1 Screening colonoscopy following ingestion of red jello. a Red liquid in colon lumen seen under white light. b Under the blue light of narrow-band imaging, the red dye in the jello (dye No. 40) appears blue–green.

Fig. 2 Bleeding from recent polypectomy site. a Seen under white light. b Seen under blue light; note the dark maroon color of the blood.

Fig. 3 Maximum absorptive capacity of hemoglobin at a wavelength of 415 nm. Adapted with permission from Olympus Europe (www.olympus-europa.com).

Competing interests: None

Endoscopy_UCTN_Code_CPL_1AJ_2AI

References

• 1 Kuznetsov K. Narrow-band imaging: potential and limitations.  Endoscopy. 2006;  38 76-81
• 2 Sullivan S N. Red jello stool and red dye-arrhea.  J Clin Gastroenterology. 1993;  16 178