Tony writes:

The QED of that is to look at what goes on with patients who are given
fluids IV. Your model of lesser night time renal function would suggest
the collection bags would not get as full at night.

I only know what the medical textbooks say. Renal activity, like most
other types of body activity, does decline during the night. That's
why most people can go all night without getting up to urinate, unless
they drink a substantial amount of fluid just before going to sleep.

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