SpeckleDust
You’re talking about kidney damage.
Broadly, a high protein diet is known to worsen kidney function in existing kidney disease. Kidney disease patients may be advised to cut their protein intake.
In healthy subjects, studies of increased protein intake in humans and mammals, including dogs, mice and rats, have shown changes in renal function - increased glomerular filtration rate and hypertrophy.
The question is whether those changes cause long term damage. Generally research indicates that in healthy people with no risk of kidney disease, these changes may not result in any long term detrimental impact. However there isn’t a huge amount of research on the subject.
And of course you may not know if you’re at risk. Risk factors include - family tendency, race - African Americans, Asian and Hispanic, diabetes, obesity, hypertension, long term use of NSAIDs and post-streptococcal glomerularnephritis.
A recent study on rats over 12 weeks from the University of Granada found the following:
Rats on a high-protein diet lost 10% of their body weight. But the weight of the kidneys in these rats increased by 22%, the capillaries filtering blood to the kidneys increased in size by 13%, and the collagen around the capillaries by 32%
The citrate levels in the rats' urine was 88% lower and their urinary pH was 15% more acidic.
A low amount of citrate in the urine and swollen kidneys are risk factors for kidney stone formation. High urinary pH is also a symptom of kidney failure and kidney tubular acidosis, among other conditions.
One of the studies’ authors emphasised that results of experiments on rats, despite their physiological and metabolic similarity to humans, should be taken with caution. However she noted:
“Studies developed in humans have also observed very similar results in plasma and urine to what we observed in rats.... We just showed a less favorable renal profile, which could bring long-term renal complications in some individuals most prone to or at increased risk of renal disease."
In other words, a less favourable renal profile, not simply in people with existing kidney disease, but also in people prone/at risk of it.