Abnormal Urine Color

Ryan D. Aycock, MD, MS; Dara A. Kass, MD

Disclosures

South Med J. 2012;105(1):43-47. 

In This Article

Red Urine

The first problem we encounter with word "red" is that the term is broad enough to encompass the colors pink, shades of red, orange, brown, or black, depending on which clinician views the sample.[4] Whenever a patient develops red urine, the physician should always order a urine dipstick and urinalysis to look for the presence of red blood cells or hemoglobin. If blood is truly present, then the differential is broad and includes disorders of the renal collecting system[5] and hematologic system,[6,7] and contamination from menstrual blood. Additional workup will be guided depending on the patient's history and physical examination. A computed tomography scan may elucidate an anatomical problem such as entrapment of the left renal vein between the superior mesenteric artery and the aorta, also known as Nutcracker syndrome.[8] A transfusion reaction, glucose-6 -phosphate dehydrogenase deficiency,[9,10] sickle cell anemia, or thalassemia can lead to a hemolytic anemia and darken the urine to a deep reddish color.

Even without the presence of blood, dark red urine could be an ominous sign. The classification of diseases collectively known as porphyria can present with dark urine,[11] abdominal pain, photosensitive rashes, or neuropsychiatric complaints.[12] The disease is difficult to detect because it is rare. In addition, many hospital laboratories are ill equipped to perform porphyrin analysis on urine, further delaying treatment.

A relatively new development in US toxicology practice is the use of hydroxocobalamin for cyanide poisoning.[13] The traditional treatments for cyanide poisoning—amyl nitrite, sodium nitrite, and sodium thiosulfate—can induce methemoglobinemia, further reducing the oxygen-carrying capacity of red blood cells. Hydroxocobalamin works by combining with cyanide to form cyanocobalamin (vitamin B[12]).[14] An unintended yet benign consequence of its administration is to color the skin and urine red.[15] The effects usually wear off after a few days.[16]

Other medications associated with red urine development include warfarin,[17] phenazopyridine,[18] rifampin,[19] ibuprofen, and deferoxamine.[20] Certain foods such as carrots (carotene),[21] blackberries, and beets can occasionally cause red urine.[22,23] Curiously, beeturia seems to be linked to the co-ingestion of oxalate-containing foods such as rhubarb, spinach, and oysters.[24]

Finally, a patient with factitious disorder may present with red urine from adding blood or another red-colored material directly to his or her sample.[25–27] These patients may present with otherwise nonspecific complaints and will undergo an extensive but futile workup. Malingering is difficult to diagnose and may require repeat urine samples obtained under direct observation to finally uncover the disorder.

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