|MadSci Network: Medicine|
Nikkii, This interesting question is a bit complicated and depends on the type of kidney trouble. Some kidney trouble may be minor and short lived, other renal troubles may be a bit more tenacious. For the sake of our understanding, let’s start with a normal urinary color profile and progress through to the possible disease states that may have a role in black urine excretion. The normal color of urine is primarily from the pigment, urochrome. Urine color ranges from a very light yellow to dark amber, depending on the dilution of urine. Dilution is dependent on the amount of water excreted and is related to the amount consumed. Urine may turn several different colors, Pink, Red, Orange, Blue and Brown/Black. Each of these colors may be caused by a number of different reasons. Any deviation in the color of a patient’s normal urine requires a visit to a physician. Usually a careful patient history, simple dipstick test, a bacteriological smear or urinalysis of a clean catch urine sample will rule out most etiologies of colored urines. The patient usually presents to the clinic as fearful and anxious concerning the unusual coloring of their urine. Upon calming, the patient reports other history: trauma(bull-riding?), urinary urgency, frequency, burning pain with urination(infection?), or colicky, sharp, stabbing pains(stones?), as well as any food colorings, over-the-counter or prescription medications, or diagnostic dyes recently ingested. Posture and circumstances of visualizing the urine may implicate contamination, for example, antiseptic(povidone/iodine) or douche contamination. A controlled ingestion study, full pelvic examination and catheterized urine specimen is often necessary to rule out contamination and toxic effects issues. Brown or black urine which is not due to muscle and blood tissue damage may be caused by ingestion of medications and/or foods or a disease state. There is no general “black color”. The actual chemical causing the black color is a chromogen as the result of the metabolic defect. Copper, phenacetin, phenol poisoning or medications that cause excessive L-dopa or melanin excretion will cause black urine.. Ingestion of large amounts of rhubarb, fava beans, or aloe can cause dark brownish black urine. Many medications(see reference) may cause brown or brown-black urine. Black urine may be associated with the following disease states: Melanoma may cause melanin and melanogen excretion and will darken standing urine.. Alcaptonia, a rare hereditary disease, may cause urine to turn dark after being exposed to the air over a period of time. Urinary tyrosinosis will also cause urine to be brown-black in color. In porphyria cutanea tarda, the urine will appear reddish brown in natural light but fluoresces pink under ultraviolet light. More urological details and links may be found in the references. Hope this helps! Peter 1.) Terris, M.D.; http://urol ogy.stanford.edu/articles/abnormal_urine.html 2.) http://www.ncemi.org/cse/cse070 3.htm
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