Fat particles in urine vary in size and are usually round in shape. These droplets consist of cholesterol or triglycerides. When cholesterol is present, they show a characteristic Maltese cross pattern under polarized light.

Fat in the urine can be of biological origin, for example in nephrotic syndrome, where oval fat bodies (oval fat bodies), fatty cylinders (fatty casts) and proteinuria are often found. However, contamination is also possible, for example through the use of oiled catheters or genital creams. In addition, fatty casts can sometimes be observed in severe hematuria, probably from degeneration of erythrocyte membranes.

Finding fat particles is pathological, provided contamination is ruled out.