I have a urine taste in mouth, sometimes oversalted-like, with caustic effect on my tongue. Kidney and liver tests are ok. What might that be?

Hard to know, but. If you test medically normal, then possibly when patients have 2 different types of metal fillings in their mouth and have acidic saliva, they can set up a galvanic reaction (battery effect). Do you have silver amalgam fillings and gold or other metal restorations? If this is the case, simple remedy, place 1teaspoon baking soda in small glass of water & rinse 1 minute & spit out, see if this help.