The use of diuretics is a possible cause of dehydration in kidneys; as the kidneys work to filter blood, water content is important in their function. Dry kidneys is not an official medical term, as the kidney never completely dries out as long as there is blood in the body, but a doctor may use the term to describe volume depletion caused by a lack of fluid or excess sodium to a layperson.
Kidneys act as a filter for the body to remove unwanted byproducts of metabolism and also to maintain water balance. Too much water in the body leads to issues, such as high blood pressure or an increase in cell death. Too little water causes dehydration. Kidneys release hormones that stimulate urination when too much water is present and cause the body to retain water when there is not enough.
A diuretic is any medicine or other substance that stimulates an increase in urination. Diuretics are of use to patients with heart problems, high blood pressure and certain kidney diseases. However, diuretics directly affect water and electrolyte levels in the body. This means that a doctor needs to monitor the kidney function of any patient on diuretics. If water levels in the body become too low, the kidneys hold on to more sodium; the more sodium present outside the cells of the body, the more water the body retains. If a doctor describes kidneys as being dry, it might mean that kidneys are holding on to too much sodium in an attempt to hydrate the body. Lowering the dosage of a diuretic helps put the body's water content back in balance.