Lipiduria, also termed Lipuria, is the presence of lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s in the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

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Lipuria is most frequently observed in nephrotic syndrome

Nephrotic syndrome

Nephrotic syndrome is a nonspecific disorder in which the kidneys are damaged, causing them to leak large amounts of protein from the blood into the urine....

 where it is passed as lipoprotein

Lipoprotein

A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...

s along with other proteins.

Lipuria has also been reported as a sign following fat embolism

Fat embolism

A fat embolism is a type of embolism that is often caused by physical trauma such as fracture of long bones, soft tissue trauma and burns.-Presentation:...

.

When lipiduria occurs, these cells contain endogenous fats. When filled with numerous fat droplets, such cells are called oval fat bodies. Oval fat bodies exhibit a "Maltese cross

Maltese cross

The Maltese cross, also known as the Amalfi cross, is identified as the symbol of an order of Christian warriors known as the Knights Hospitaller or Knights of Malta and through them came to be identified with the Mediterranean island of Malta and is one of the National symbols of Malta...

" configuration under polarized light microscopy.

This Maltese cross is because of its liquid-crystalline structure giving it a double refraction (birefringence

Birefringence

Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...

.)