Both urinary system and digestive system works to conserve water in the human body by way of shutting off the flushing of water when the body is being dehydrated and water is needed to remain in the body.
The body has receptors whereby the receptors estimates the amount of water in the cells and in blood. Receptors sends the information to the brain through the neurons.
All liquids are being absorbed and put in the bloodstream through the digestive system. It is through the bloodstream where water is being spread to all other body parts then cells absorbs it.
Electrolytes and water are reabsorbed and filtered when the blood which passes to the other parts of the body goes to the kidney.
If there is low circulation of liquids in the body, and the brain gets the signals it activates hormones which then influences both urinary system and digestive system.