why is adrenaline placed above the kidneys?
This is because the adrenal gland and kidney works together to carry out certain functions.
The adrenal gland secretes a hormone called aldosterone that travels to the kidney, where it causes the kidney to retain sodium by not excreting it into the urine. Thus aldosterone, by acting on the kidneys, controls the salt content of the body — by which means it also indirectly controls the blood pressure. The amount of aldosterone produced is controlled by other substances, including a protein from the kidney known as renin.
Sodium and chloride are electrolytes regulated by the kidneys and adrenal glands.