Unlike those of mammals, reptile kidneys cannot concentrate urine to save on water intake.

Insufficient secretion of vasopressin underlies diabetes insipidus, a condition in which the body loses the capacity to concentrate urine.

Leaky nephrons may compromise the ability of kidneys to concentrate urine leading to frequent urination and dehydration.

Desert mammals also have longer loops of Henle, structures whose efficiency in concentrating urine is directly proportional to their length.

This causes an inability to concentrate urine, leading to consequent loss of body water and thirst.

An important potential consequence of long-term lithium use is the development of renal diabetes insipidus (inability to concentrate urine).

The ability to concentrate urine is also present in birds, but involves another mechanism which is not comparable.

They have evolved a number of mechanisms to overcome this, but most retain their water by using highly efficient kidneys, that can concentrate urine.

"The fact that you can concentrate urine is not reason not to take out your kidneys."

The kangaroo's kidneys are also great at concentrating urine, particularly during summer.