Different forms of lipid in the urine:
(1) oval fat bodies (renal tubular epithelial cells showing accumulation of cytoplasmic lipid)
(2) fat droplets or cholesterol
(3) fatty casts
Disorders associated with lipid in the urine:
(1) nephrotic syndrome, with markedly increased urine protein (typically >= 3.5 g per day; many patients with the nephrotic syndrome have hyperlipidemia)
(2) fat emboli following trauma with multiple fractures
(3) hyperalimentation
(4) hyperlipidemia
(5) chyluria, from a fistula between lymphatics and the urinary system (with filariasis, after trauma, possibly with tumors)
(6) after poisoning (ethylene glycol, phosphorus, carbon monoxide, mercury)
(7) renal disease without the nephrotic syndrome, including polycystic kidney disease, severe diabetic nephropathy, lupus nephropathy, amyloidosis, interstitial nephritis, acute tubular necrosis, etc.
(8) pseudo-lipiduria (catheter lubricants, vaginal lubricants or creams, oils, cells from vaginal secretions or seminal vesicles)
(9) occasionally in persons without demonstrable pathology
Demonstration:
(1) staining with Sudan III or IV
(2) staining with oil red O
(3) examination under polarized light or phase contrast
Differential diagnosis:
(1) air bubbles
(2) yeast
(3) erythrocytes
(4) starch granules (also may give a Maltese cross appearance under polarized light)
Workup:
(1) clinical history, especially trauma, nutritional support and use of lubricants
(2) history of exposure to toxins, with measurement for mercury if indicated
(3) urine protein
(4) serum renal panel
(5) renal ultrasonography or other imaging studies
