The body adjusts kidney function to meet current demands using hormones and the nervous system. When the kidneys are dysfunctional, they are less responsive to hormones. Low blood sodium can be caused by abnormal kidney function, due to lack of response to aldosterone, a hormone produced by the adrenal glands.
Regulation of Blood Sodium
Sodium regulation is important because it influences water distribution in the body; for example, increased sodium concentrations in the blood results in increased blood volume and blood pressure. Adequate release of aldosterone from the adrenal glands and appropriate response from the kidneys is necessary for the maintenance of normal blood sodium levels. Aldosterone is released when levels of blood sodium are low; it causes increased reabsorption of sodium in the kidneys, thereby resulting in increased water retention.
Causes of Abnormal Kidney Function
The amount of blood flowing into the kidneys determine kidney function; when blood flow to the kidneys is decreased, such as in severe blood loss, low blood pressure and dehydration, there is decreased urine formation. Kidney failure results when the kidneys are incapable of adequately filtering the blood, which can result from decreased blood flow to the kidneys, damage the kidneys by certain medications or blockage of urine outflow. In kidney failure, the kidneys are actually dying and the extent of damage sustained by the kidneys depends on the cause and duration of insult; regardless, the body begins to lose control of the kidneys.
Sources of Sodium
Dietary sodium intake should be appropriate to maintain optimal levels of sodium in blood; but when sodium intake is low, the kidneys compensate by holding onto sodium, which slows water excretion. Dysfunctional kidneys cannot compensate for low sodium intake, eventually low blood sodium results. Table salt, or sodium chloride, is a popular source of sodium because it is commonly used in cooking, to enhance the flavor of food. Small amounts of sodium naturally occur in drinking water. Other sources of sodium include milk, celery, condiments and seasoning. Processed meats, such as ham and sausage, are also major sources of sodium.
Management of Kidney Dysfunction
According to the "Harrison's Principles of Internal Medicine," when kidney dysfunction results from hypotension, or low blood pressure, normal blood volume must initially be restored via the administration of intravenous fluids or solutions that boosts the volume of blood without causing changes to electrolyte concentrations in the blood. When a medication is suspected as cause of kidney dysfunction, it must be discontinued or switched to a suitable alternative. When outflow is obstructed, such as in prostate enlargement, the obstruction must be addressed for normal kidney function to be restored.
References
- MayoClinic.com: Nutrition and Healthy Eating
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper M.D., et al.; 2005
- "Davidson's Principles & Practice of Medicine; Nicholas A. Boon; 2006
