Whether a student still in training or a veteran of the job, this blog is dedicated to refreshing the mind with all that relates to the field of Clinical Laboratory Sciences.

Saturday, June 12, 2010

Urine Coloration

Within the clinical setting a routine urinalysis is performed to determine the health of a patient. This particular test can tell a physician how well a patient’s kidneys are functioning. The test can show not only if infection is present, but it can also show if other organ systems such as the rest of the digestive tract are performing properly. A urinalysis consists of two parts, a urine dipstick test and a urine microscopic test. The urine dipstick tests for the presence of leukocytes, nitrite, urobilinogen, protein, pH, blood, specific gravity, ketones, bilirubin, and glucose. During the microscopic scan a technologist looks for cellular material including white blood cells, red blood cells, bacteria, crystals, casts, epithelial cells, and other foreign materials that would not normally be found in urine. It is also necessary to report out urine color and clarity. These two mostly overlooked results help to complete the picture presented to the physician by a urinalysis report.

Urine can come in many different colors that amaze and excite the medical technologist (and not the patient), however in a normal healthy individual it should be a straw yellow color. The straw yellow color is attributed to urochrome, a pigment excreted into the urine as a result of hemoglobin degradation. Clear urine with little to no yellow color is an indicator of very dilute urine. This can be due to drinking too much water, taking diruetics, or diabetes insipidus. On the other hand dark yellow urine could be a sign that urine is over concentrated. This could be due to dehydration or due to an overproduction of the waste materials that give pigmentation to urine. Red cell destruction in the body (i.e. hemolytic anemia) would cause an increase in the concentration of urochrome pigment in the urine. Hepatitis can cause bilirubin to spill over into the urine in various amounts causing different shades of urine from yellow to brown. The next color in line is orange colored urine. While this could be a result of severe dehydration, it is most likely due to some other factor. The orange coloration of urine can be caused by bilirubin and urobilinogen being spilled over into the urine due to liver or other gastrointestinal diseases. Other less alarming causes of orange urine include food and drug sources. Rifampicin (antibiotic), coumadin, pyridium, and some chemotherapy drugs can all produce various shades of orange urine. Foods that can stain urine orange include vitamin C tablets, large amounts of carrots, and winter squash. The carotene in these vegetables is what discolors the urine and can discolor the palms of hands and soles of feet when eaten in large amounts. Pink colored urine is not very common. Usually it is indicative of a light amount of hematuria. Infrequent sightings of pink urine can be caused by anything from trauma received to the urinary tract when catheterized to intense exercising. Problems with the kidneys, bladder, and prostate are looked at more closely when the passing of pink urine becomes more frequent. Propofol (diprivan), a popular anesthetic, will also cause pink urine. In this case the chemical is a uricosuric agent and favors uric acid crystal formation. Urine from these patients is full of uric acid crystals, which gives it a reddish-pink hue. Red urine which is much more common than pink urine is usually a sure sign of gross hematuria. Common causes of hematuria include kidney stones, infection, and cancer. Keep in mind that the presence of blood in urine can also be due to menstruation or other contaminant bleeds from outside the body. Red urine can also be caused by benign factors such as food and drugs. Foods such as beetroot, rhubarb, and even blackberries can turn urine red. About 10-14% of the population will pass red urine after eating beetroot. Medications that will turn urine red include anisindione (anticoagulant), cerubidine (chemo), phenolphthalein (laxative), prochlorperazine (antipsychotic), senna (laxative), and thorazine (antipsychotic). Chronic lead or mercury poisoning can also turn urine red. In this case the red color of the urine is due to the porphyrins being excreted into the urine from the toxic effects of the metals. Brown or tea-colored urine can have a variety of causes. First and foremost the color can be caused by oxidized hemoglobin and myoglobin. Patients with major bleeds or trauma can produce this color urine due to build up of excess myoglobin and urochrome in the urine. Severe hepatitis or cirrhosis can cause urine to turn brown due to large amounts of biliruin. Other lesser known causes for brown urine include eating large amounts of foods such as fava beans, rhubarb, and aloe. There are several medications that will also turn urine brown. These medications include primaquine (antimalarial), metronidazole (antibiotic), nitrofurantoin (antibiotic), and methocarbamol (muscle relaxant). Blue to green colored urine, while pretty, is fairly rare. There are several medical and non medical causes that can be attributed to this color of urine. Medically speaking urinary tract infections can produce greenish colored urine due to pus buildup. Bile leakage from diarrhea can also tint urine a greenish color. Urinary tract infections caused by Pseudomonas aeruginosa will sometimes cause green colored urine if the pigment pyocyanin is produced. In very rare cases a baby might have what is known as blue diaper syndrome, where blue urine is found in the diaper. This is caused by a rare inherited disorder called familial hypercalcemia that causes the patient to have higher than normal levels of calcium. One of the traits of this disease is urine that turns blue upon contact with air. These strange colors can also be caused by foods and drugs. Eating large amounts of asparagus can lead to greenish colored urine. Drugs that can lead to blue or green urine include rinsapin (antibiotic), indomethacin, amitriptyline, triamterene (diuretic), listerine, tagamet, and phenergan (anti-nausea). Another strange and unusual color is purple. Purple urine has a select few known causes and all are medical. The classic cause is Hartnup disease which is a rare defect of tryptophan transport that results in purplish-blue urine. The other cause is urinary tract infections, most often in nursing home patients, caused by Klebsiella pneumoniae, E. coli, Proteus species, Morganella species, Enterobacter species, Pseudomonas species, and Providencia species. Most patients with these types of multiple organism urinary tract infections will also have intestinal stasis. Stasis of the intestines causes tryptophan to be oxidized to the pigment indican by bacterial flora. Once the indican is passed into the urine the bacteria in the urine ferment it using sulfatase and phosphatase. The pigments that give purple urine its color are indigo and indirubin. Once the urinary infection is treated the color of the urine returns to normal. The final abnormal color that can be found in urine is black. This is extremely rare. The first cause is a condition called alkaptonuria. This is caused by a genetic disorder where a patient is deficient in the enzyme homogentisic oxidase causing homogentisic acid to build up all over the body in the tissues. Homogentisic acid is expelled in the urine and once the urine becomes alkaline this acid oxidizes producing a black color. Patients with disseminated melanoma and rarely Addison’s disease can produce melanogens (melanin) which can be excreted in urine and cause black discoloration once urine becomes alkaline. The antihypertensive drug α-methyldopa also produces melanogens which can cause black colored urine. Whatever a person’s urine color may be, if it is frequently abnormal it is worth getting checked out by a physician.

The other half of the picture is urine clarity. While different labs have different gradients for determining the turbidity of urine there are really only two states of clarity; clear and cloudy. Normal urine is clear, meaning there is no particulate matter floating in it. It can have some bubbles to it but it should not be overly foamy. Foamy urine is a sign that the urine is heavy with protein materials and can occur in either clear or cloudy urine. Cloudy or “milky” urine can be a sign of several issues. The most obvious cause of cloudy urine is an infection. Bacteria and white blood cells will cause urine to become cloudy. Turbidity can also be due to light amounts of red cells. Other cellular material such as casts and crystals when excreted in high amounts can cause urine to cloud. Urine with high lipid content will look cloudy. On rare occasions vaginal contamination or semen discharge will be the culprit. Whatever the case may be a microscopic examination will clear up any questions concerning the cause of cloudy urine.

Just looking at a urine sample and determining its color and clarity can give a person a very good general idea of their state of health. It is a simple act that anyone can do. It only takes a minute but it can impact our health habits greatly. Urine gives us information about our dietary habits and tells us how well our bodies have processed what we have put into it. If the kidneys are the filters of the body, then urine should be the first place to look for indicators of disease in the event something goes awry in any of the other systems. Checking the color and clarity is just the first easy step towards creating the big diagnostic picture of a patient’s state of health.


• Urine Colors (2010). XebWeb Network. Retrieved on January 9, 2010 from http://www.urinecolors.com/
• Foot, C., Fraser, J. (2006). Uroscopic rainbow:modern matula medicine. Postgraduate Medical Journal, 82(964), 126-129. Retrieved on January 9, 2010 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596703/
• Health Topics (2009).Ohio Health. Retrieved on January 9, 2010 from http://www.ohiohealth.com/bodymayo.cfm?xyzpdqabc=0&id=6&action=detail&ref=4046
• Hanrun, N., Nainar, S., Chong, V. (2007). Purple Urine Bag Syndrome: A Rare and Interesting Phenomenon. Southern Medical Journal, 100(10), 1048-1050. Retrieved on January 9, 2010 from http://medscape.com/viewarticle/565078

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