Complex sentence: Its metabolism produces calcium oxalate, which crystallizes in the brain, heart, lungs, and kidneys, damaging them; if untreated, death by acute kidney failure can result within 72 hours.
Split into simpler sentences: Its metabolism produces calcium oxalate, which crystallizes in the brain, heart, lungs, and kidneys, damaging them. If untreated, death by acute kidney failure can result within 72 hours.