Water Reabsorption

Definition

The physiological process by which the kidneys reabsorb water from the glomerular filtrate to return it to the blood and concentrate urine.

How it works

Water reabsorption occurs mainly in the proximal convoluted tubule (approximately 65%), the loop of Henle (15%), and the collecting tubule (20%). It is an osmotic process dependent on electrolyte concentration gradients and regulated by the antidiuretic hormone (ADH). In the collecting tubule, ADH increases water permeability by inserting aquaporins into the apical membrane. Without effective reabsorption, the body would quickly lose its hydration reserves. Inadequate reabsorption causes diabetes insipidus with polyuria.

Role

Conserves body water by reabsorbing it from the original urine.

Examples

• Basal reabsorption of 99% of filtered water
• Concentration of urine in case of dehydration
• Production of low volumes of concentrated urine
• Regulation by ADH

Recommendations

Ensure adequate hydration to support optimal renal function. Avoid chronic dehydration that forces the kidneys to excessively concentrate urine.

Key takeaway

Renal water reabsorption is crucial for conserving body hydration reserves.

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