Lipiduria Pathophysiology 1) Damaged glomerular basement membrane allows plasma lipids to escape into Bowman's space and enter the glomerular filtrate. 2) Lipids are absorbed by renal tubular epithelial cells. 3) Lipid molecules coalesce into lysozomes, forming cytoplasmic droplets. 4) Lipid-filled RTE cells slough and become oval fat bodies. Because oval fat bodies are clinically significant (a marker of glomerular basement membrane damage), they should be reported quantitatively (i.e., number per high-power field). Macrophages filled with lipid are found in lipid storage diseases such as Fabry disease. They can mimic oval fat bodies and are distinguished by their large size or by immunocytochemical methods. The lipid in casts and RTE cells can be composed of either cholesterol or neutral fat (triglycerides). Under polarized light, cholesterol produces a "Maltese cross" appearance. Both types of fat are positive by Sudan Ill or IV stains (oil red O stain is #Lipiduria #Pathophysiology #nephrology
