To the Editor.—Recently we encountered a blue colon at autopsy (Figure). The recently published article by Boutilier et al1 and their photograph illustrating a green colon were instrumental in determining the probable origin of the unusual finding of this bright blue colon. The autopsy was performed on a 50-year-old diabetic woman who was status postnephrectomy for xanthogranulomatous pyelonephritis. She had been in the surgical intensive care unit for 34 days prior to her death. During this time she received enteral feeding by the aspiration detection protocol calling for 0.5 mL of blue food color per 250 mL of food given. The active ingredient in this product is FD&C Blue No. 1 (Warner-Jenkinson, St Louis, Mich), also commonly known as “brilliant blue.” This patient had a similarly colored bright blue colon and some less intensely stained patchy blue areas in the small intestine. No other organs were blue. Similar to the cases with green colons, the entire length of the colon was blue and the mucosa was as brightly stained as the serosa. No other abnormality was found in the colon, and the patient had no history of significant gastrointestinal symptoms. Histologic examination of the colon did not show blue discoloration or abnormalities, with the exception of moderate autolysis.
FD&C Blue No. 1 was hypothesized to have caused refractory hypotension and metabolic acidosis in 2 patients who died.2 The Food and Drug Administration approved the blue food coloring based on experiments performed on healthy animals, which demonstrated the dye to be nonabsorbable. Now there are case reports of humans in which the dye may have been absorbed.2,3 Absorbed dye is likely excreted by the kidneys.4 Our patient had 1 remaining kidney, which was found on histologic examination to have nodular and diffuse glomerulosclerosis consistent with diabetic nephropathy. However, she did not have any clinical evidence of renal insufficiency. Due to the lack of information on the effects of FD&C Blue No. 1 given to patients with renal disease, it is not possible to determine if the blue color of the bowel was related to nephropathy or was merely an incidental finding. Clearly there is a need for more research on the safety of FD&C Blue No. 1 in critically ill patients. Pathologists can make an important contribution by thoroughly documenting any unusual discoloration found at autopsy.
The photograph was taken by Scott Sharples, fourth-year medical student at Baylor College of Medicine, Baylor, Tex.