The renal tubules absorb less water, urine output increases, and total body water declines Disorders of Water Balance Fluid Deficiency Volume depletion occurs when proportionate amounts of water and sodium are lost without replacement. Total fluid volume declines but osmolarity remains normal. Volume depletion occurs during hemorrhage, severe burns, and chronic vomiting or diarrhea. The simplest cause of dehydration is a lack of drinking water. Dehydration from diarrhea is a major cause of infant mortality, and can be a serious problem for elderly or bedridden people who depend on others to provide them with water.
Dehydration affects all fluid compartments.
As the blood loses water its osmolarity rises and water from the tissue fluid enters the bloodstream to balance the loss. This raises the osmolarity of the tissue fluid, and water moves out of the cells to balance that. Fluid Excess Fluid excess is less common than fluid deficiency because the kidneys are highly effective at compensating for excessive intake by excreting more urine. Fluid Sequestration Fluid sequestration is a condition in which excess fluid accumulates in a particular location. The most common form of sequestration is edema, the accumulation of tissue fluid in the interstitial spaces.