Urinary concentrating ability of the kidney is increased by:
The kidney has the ability to form urine that is more concentrated than the plasma.
When there is contraction of ECF volume, the urinary concentrating ability of kidney increases and it firms a concentrated urine with a smaller volume, thereby maintaining homeostasis.
ECF volume concentration.
Increase in renal blood flow.
Reduction of medullary hyperosmolarity.
Increase in GFR.