Green urine in a postoperative patient.

To cite: Hadi HIA, Williamson JS, Bhowmick AK. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2014204986 DESCRIPTION An 85year-old man underwent reversal of loop ileostomy. The integrity of the anastomosis was tested by an injection of methylene blue into the bowel lumen. Postoperatively the patient voided ‘green urine’ and alarmed the nursing staff and junior duty doctor (figure 1). Routine microscopic examination and culture of urine revealed no abnormality. Liver function test and full blood count was also normal. This discolouration of urine resolved spontaneously in the next few days. Methylene blue is commonly used to test the integrity of the gastrointestinal tract following anastomosis. This substance is also used for diagnostic tests such as localisation of parathyroid adenoma during surgery and identification of fistula tracts, as a therapeutic agent for the treatment of methemoglobinaemia or refractory hypotension and as a mild antimicrobial agent. This dye is converted into leucomethylene blue by gastrointestinal bacterial flora and mostly excreted in the urine. The yellow colour of urine is attributed to the compound urochrome. When it combines with methylene blue, a harmless compound is formed which creates a green or greenish blue colour. The intensity of the green colour in urine is the dose related. Some medications such as propofol, cimetidine, promethazine, metoclopramide, amitryptiline and indomethacin can also cause green urine. Careful history, physical examination and awareness of this self-limiting condition are important to avoid anxiety and unnecessary investigations on such urine samples.