Lipiduria or lipuria is the presence of lipids in the urine. Lipiduria is most frequently observed in nephrotic syndrome where it is passed as lipoproteins along with other proteins.[1][2] It has also been reported as a sign following fat embolism.[3]
When lipiduria occurs, epithelial cells or macrophages contain endogenous fats. When filled with numerous fat droplets, such cells are called oval fat bodies. Oval fat bodies exhibit a "Maltese cross" configuration under polarized light microscopy.[4] The Maltese cross appearance occurs because of its liquid-crystalline structure giving it a double refraction (birefringence).