ANATOMY

Detailed explanation-1: -Increased urine concentration may be due to different conditions, such as: Heart failure. Loss of body fluids (dehydration) from diarrhea or excessive sweating. Narrowing of the kidney artery (renal arterial stenosis)

Detailed explanation-2: -When you have not drank enough fluids your kidneys try to save as much water as they can and cause your urine to be darker in colour (more concentrated). Dark yellow urine is a sign that you are dehydrated and that you must drink more fluids to prevent dehydration.

Detailed explanation-3: -During whole-body dehydration, urochrome concentration increases as antidiuresis is stimulated via increased arginine vasopressin production, thus increasing water reabsorption from the collecting duct of the nephron. This physiological response to dehydration results in darker and more concentrated urine (3, 4).

Detailed explanation-4: -When water intake is large enough to dilute blood plasma, a urine more dilute than blood plasma is produced; when water intake is so small that blood plasma is concentrated, a urine more concentrated than blood plasma is produced.