Hydrostatic stress is made via the pumping action of the guts, plus the result of gravity to the blood within the blood vessels (Scales and Pilsworth, 2008);
When recording urine output with a fluid balance chart, It's https://biobodyboost.co.uk/products/fluid-balance-electrolyte-hormone-water-blend?_pos=1&_psq=fluid&_ss=e&_v=1.0