Could be culturally diet influenced as well.

My urologist after I had my first oxalate kidney stone said "you can drink a litre of water a day, or you can pay for my yacht upgrade. It's your choice" -but the main thing was to limit oxalate rich foods or take adequate citric acid alongside/soon after. Obv there are many kinds of kidney disease aside from stones, but the commonality here about 'use it or lose it' with heat, fluids, work strikes me.

The best guesses are both chronic rather than single acute injuries. High heat, dehydration, hard work, exposure to nitrites and who knows what else.

It’s mysterious because the specific etiology is unclear and therefore hard to prevent, since telling field workers not to work in the heat will be ignored by all involved.

I'm not a doctor, but if its sudden onset, all in a similar socio-economic-cultutal group, i would assume there was some sort of toxin they were all exposed to, perhaps at work.

*they said crying

[1] https://www.linkedin.com/posts/davereddick_mysterious-kidney...

[2] Most labouring job sites I've been at in the 00s at least always had a very prominent chart regarding urine colour and the dangers of dehydration, and heat stroke. As such most workers at various sites I've worked at being much more aware of urine colour regarding dehydration than most of the medical staff I encountered at the hospital my Mum died in.