Urine Transparency

Freshly voided urine is clear and transparent. Cloudy urine may be caused by crystals, deposits, white cells, red cells, epithelial cells or fat globules. Further evaluation with centrifugation, microscopic examination, heating or with ether generally determines the cause of the turbidity.

Substances that cause cloudiness but that are not considered unhealthy include mucus, sperm and prostatic fluid, cells from the skin, normal urine crystals, and contaminants such as body lotions and powders.

Causes of Turbid Urine

Amorphous Phosphates A normal constituent in alkaline or neutral urine
They dissolve upon addition of a dilute acid (e.g. acetic acid).
Amorphous Urates A normal constituent in acid urine
They often appear as yellow crystals
May be pink crystals (“brick dust”) as a result of increased uroerythrin.
They dissolve upon warming to 40°C.
Bacteria Often seen as seen as a uniform cloud
They cannot be removed by ordinary filtration or centrifugation
Confirmed on microscopic examination
Blood (red blood cells) Usually associated with a reddish-brown, smoky appearance to the urine
Confirmed on microscopic examination or chemical tests for hemoglobin
Pus (white cells) May resemble amorphous phosphates to the naked eye
Microscopic examination confirms leucocytes.
Mucus and Epithelial Cells Appear as a faint cloud (“nubecula“) of mucus, leucocytes and epithelial cells upon cooling and standing
The nubecula of normal urine is probably due to nucleoprotein (phosphoprotein) and not a mucin or mucoid (glycoprotein)
Nebecula usually settles to the bottom, but in urine of high specific gravity may float near the middle.
Colloidal Particles Cannot be cleared from urine by filtration, centrifugation or ether
These particles are not visible on microscopic examination
Fat Globules Usually give a milky appearance to urine
Confirmed on microscopic examination and can be removed by ether.
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