Urinary discoloration after rectal instillation of methylene blue dye

Methylene blue is a vital dye that is used in the treatment of methaemoglobinaemia. It is also used to delineate tissues to facilitate identification during surgery. Discoloration of the urine is known after oral and intravenous administration of the dye. We have used it routinely to detect the presence of defects after colorectal anastomosis. However, there have not been any previous reports of urinary discoloration after brief rectal instillation of the dye. We report a case of self-limiting urinary discoloration after anterior resection with colorectal anastomosis.