No specific Oil Red O staining procedures are available and validated for staining urine sediment. Below are instructions for preparing the stock and working solutions for use in staining tissue sections. Preparing the stock and working solutions should be the same as if staining tissue sections. It may be necessary to dry the urine sediment onto the slide before use. If the urine sediment has not dried, it is possible the lipid might get washed off the slide during the staining procedure. Do not attempt to fix the urine sediment to the slide using alcohol. If fixation is required, use 10% Neutral buffered formalin as it is considered an aqueous fixative.
Below are instructions for staining tissue sections. If the urine sediment is attached to the glass slide, the same procedure should be suitable for urine sediment.
Stock Solution.
Prepare a saturated (approximately 1%) stock solution of oil red O in 99% isopropanol. Mix well to dissolve.
Working Solution
Mix 6 parts of stock solution with 4 parts of deionized water. Let stand for 10 minutes and filter. Working solution stable for 1 - 2 hours.
Technique
1. If the urine sediment has been fixed to the slides with 10% Neutral Buffered Formalin, gently rinse sections in deionized water.
2. Stain in working oil red O solution for 6 - 15 minutes.
3. Clear background if necessary using 60% isopropanol.
4. Wash in deionized water.
6. Coverslip using an aqueous mounting medium or simply use water for the coverslipping.
Results
Lipids - orange to red
It is also possible to view lipids in urine sediment by using polarized microscopy. Another option might be to use a method for fecal fats since the urine sediment would not need to be attached to the glass slide prior to staining.