My anecdote is that I was diagnosed with stage 3 kidney disease, likely as a result of years of very high blood pressure. Four years later, using medication to get the blood pressure down to near-normal, and following a high-fat/keto diet, my kidneys were operating perfectly in the normal range. (I didn't tell my doctor about my diet, because I needed him to prescribe the BP meds and didn't want him nagging me about diet. One mention of "healthy grains" was enough.)

The "your kidneys will fall out" nonsense has been circulating since I first started hanging out on alt.support.diet.low-carb in the mid-90s. Probably since Atkins first published his book. It's superstition.