A 53-year-old-man with prostate cancer underwent prostate brachytherapy one month ago. Since then, he has experienced increased urinary frequency, dysuria, perineal discomfort, re-duced urinary stream velocity, and nocturia. The patient was prescribed the following medications to relieve his urinary fre-quency and dysuria: sulfamethoxazole/trimethoprim, ciprofloxa-cin, tamsulosin, methylprednisolone, ibuprofen, and Phosphasal. He denied any special diet. Urinalysis and culture results were normal except for the blue-green color of the urine. Urinary mi-croscopic examination revealed 3 red blood cells per high-power field. His serum PSA was 7.4 µg/L. The questions were raised as: A) What caused this urine color change? B) What other conditions could cause this urine discol-oration? C) Can this discoloration be pathological or cause any test interference? The normal color of urine ranges from light yellow to dark am-ber, depending on the concentration of solutes in the urine. Pa-tients may be quite frightened at any unusual urine color, espe-cially with accompanying symptoms such as frequent urination and burning pain with urination. Food dyes and additives are the most common causes of blue or green urine. A few foods, especially asparagus, can cause a greenish discoloration. Cer-tain medications can cause blue or green urine, including ami-triptyline, doxorubicin, indomethacin, cimetidine, phenergan, triamterene, rinsapin, propofol, Prosed DS, sildenafil, and B vi-tamins [1, 2]. A number of medical conditions, such as familial hypercalcemia, indicanuria, and pseudomonas infection, may cause urine to become blue or green. Blue or green urine may be caused by a blue dye such as methylene blue, which has weak antiseptic properties and is a component in several medications (Trac Tabs, Urised, Uroblue) used to reduce symptoms of bladder inflammation or irritation [1, 2]. The Phosphasal this patient was given for his dysuria con-tains methylene blue, which contributed to the blue-green urine color [2]. Methylene blue is increasingly used in cancer chemo-therapy regimens. Methylene blue is well absorbed by the gas-trointestinal tract and rapidly reduced to leukomethylene blue, which is stabilized in some combination form in the urine and excreted mostly in unchanged form. It peaks approximately 2-6 hr after oral administration and remains detectable in 24 hr [3]. The blue-green urine is a normal side effect of this medication and is harmless. Urine discoloration due to diet or medication is unlikely to be harmful. If it is due to a medication, the patient should be ad-vised of potential side effects other than urine color change. Methylene blue may cause falsely increased blood methemoglo-bin levels by co-oximetry and other colorimetric assays such as glucose and protein [1, 4]. If the patient has not ingested a food or medication known to change urine color, further investigation is warranted to rule out medical conditions or infection.
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Jan 1, 2018
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