1. Colorful Urine
Presentation
The patient may complain or be frightened about the color of his urine; color may be
one component of some urinary complaint, or the color may be noted incidentally on
urinalysis.
What to do:
• Ask about symptoms of urinary urgency, frequency, and crampy pains
(suggesting stones), as well as any food colorings, over-the-counter or
prescription medications, or diagnostic dyes recently ingested. Ascertain the
circumstances surrounding noticing the color: Did the color only appear after the
urine contacted the container, or the water in the toilet bowl? Did the urine have
to sit in the sun for hours before the color appeared?
• Obtain a fresh urine sample for analysis. Persistent foam suggests protein or
yellow foam bilirubin, which should also show up on a dipstick test. A positive
dipstick for blood implies the presence of red cells, free hemoglobin, or
myoglobin, which can be double-checked by examining the urinary sediment for
red cells and the serum for hemoglobinemia. In patients with normal renal
function, hemoglobinuria can be distinguished from myoglobinuria by drawing a
blood sample, spinning it down, and looking at the serum. Free hemoglobin
produces a pink serum which will test positive with the dipstick. Myoglobin is
cleared more efficiently by the kidneys, usually leaving a clear serum which tests
negative with the dipstick.
• If the urine is red and acidic but does not contain hemoglobin, myoglobin, or red
blood cells, suspects an indicator dye such as phenolphthalein (the laxative in
ExLax) in which case the red should disappear when the urine is alkalinized with
a few drops of KOH. People with a particular metabolic defect produce red urine
whenever they eat beets. Blackberries can turn acidic urine red, while rhubarb,
anthraquinone laxatives, and some diagnostic dyes will redden urine only when it
is alkaline.
• Orange urine may be produced by phenazopyridine (Pyridium) or ethoxazene
(Serenium), both of which are used as urinary tract anesthetics to diminish
dysuria. Rifampin will also turn urine orange.
• Blue or green urine may be caused by a blue dye such as methylene blue, a
component in several medications (Trac Tabs, Urised, Uroblue) used to reduce
symptoms of cystitis. A blue pigment may also be produced by Pseudomonas
infection
• Brown or black urine (not due to myoglobin or bilirubin) may be caused by L-
dopa, melanin, phenacetin, or phenol poisoning. Metabolites of the
antihypertensive methyldopa (Aldomet) may turn black on contact with bleach
(which is often present in toilet bowls). Contamination with povidone-iodine
(Betadine) solution or douche can turn urine brown. Melanin and melanogen,
found in the urine of patients with melanoma, will darken standing urine from
the air-exposed surface downward.

2. What not to do:
• Do not allow the patient to alter his urine factitiously. Have someone observe
urine collection and inspect the specimen at once.
• Do not let a urine dipstick sit too long in the sample (allowing chemical indicators
to diffuse out) or hold the dipstick vertically (allowing chemicals to drip from one
pad to another and interfere with reagents).
• Do not be misled by dye in urine interfering with dipstick indicators. Pyridium can
make a dipstick appear falsely positive for bilirubin, while contamination with
hypochlorite bleach can cause a false positive test for hemoglobin. Also the
urobilinogen dipstick (or Erlich reaction) is not adequate for diagnosing
porphyria.
Discussion
Porphyrins or eosin dyes fluoresce under ultraviolet light. Eosin turns urine pink or red
but fluoresces green.