Human metabolism is a delicate balance of chemistry that requires inputs from the environment and creates outputs, some of which are considered waste. Accumulation of the waste created by human metabolism in the blood can become toxic if not dealt with, therefore, the body requires a system of filtration.
The kidneys are responsible for waste filtration from the blood and are a vital component of metabolic health in the human body. Their importance cannot be understated with regards to body function. The most common blood scan administered by medical professionals is called a complete metabolic panel (CMP), which includes indicators of kidney function.
Urinalysis is another tool used by medical professionals, because accumulation of certain products in the urine indicates potential disease.
General health is vital for the health of the kidneys. It has been estimated that the two most common causes of kidney disease are type II diabetes and hypertension (high blood pressure).
5 Interesting Facts about Kidneys: 
- Blood flow through the kidneys is greater than the heart, brain, and liver.
- The kidneys can process about 15 gallons of blood every hour.
- The kidneys filter the bodies entire volume of blood 400 times a day.
- The kidneys work with the liver to activate vitamin D
- The kidneys can stimulate red blood cell production when oxygen levels drop.
There are two kidneys located on the left and right side of the abdomen just below the stomach, directly associated with the inferior (below the heart) aorta and vena cava, which are the two primary blood vessels associated with the circulatory system. The kidneys look “bean” shaped and can be separated into the cortex (outer portion) and medulla (inner portion).
The major function of the kidneys occurs in the medulla region. Located in structures called renal pyramids, a collection of the basic unit of filtration clears the blood of metabolic waste products and any environmental toxin that has accumulated.
The basic unit is called the nephron and it consists of specialized capillary beds called the glomerulus and a network of tubes that collect the filtered plasma and concentrate it for removal from the body as urine.
The total number of functioning nephrons has been linked to kidney health and it has been estimated that the adult kidney contains between 250K and 1.8 million units.  The plasma filtered by the glomerulus is passed through the network of tubes which reabsorb mainly water, sodium, and bicarbonate.
The kidney can serve a variety of functions, most of which relate to blood filtration. The body is exposed to a variety of toxic materials that can accumulate and become harmful. The majority of the urine content filtered by the kidneys are byproducts of metabolism; however, inputs from the environment such as toxins, drugs, drug metabolites, and bacterial remnants are also filtered. 
Glomerular Filtration Rate (GFR) is a measure of the efficiency for the kidneys. This can be affected by the number of functional units a kidney has.  Each unit separates the plasma from the blood cells by increasing the blood pressure of the capillary beds.  The plasma is then shipped through the tubes of the nephron.
Hydration level, sodium intake, and diet influence what the kidneys reabsorb from the plasma extract. As the fluid moves through the tubes, water is primarily reclaimed, which helps to concentrate the urine waste.
The resulting urine becomes more concentrated as it is emptied into collecting ducts, which is then shuttled to the bladder for excretion.
A secondary function of the kidney is to aid the liver with gluconeogenesis, which is the new production of glucose by the body in response to low blood sugar levels. During fasting periods—stretches of times without food—blood sugar levels will drop.
The liver acts as an acute responder by releasing stored glucose and new glucose it produces. When the fast is prolonged (4 days and beyond), the kidneys will begin gluconeogenesis to aid the liver with maintaining blood sugar levels. 
The kidneys will also begin gluconeogenesis following a meal. The theory is that to assure full glucose stores in the liver and the muscle are completely replenished, that gluconeogenesis in the kidney helps supply a large amount for those tissues to take up. 
The final major function of the kidneys is the regulation of water volume and blood pressure. Specialized cells in the glomerulus can sense changes in blood pressure. The change triggers the release of the hormone renin. This event sets into motion a cascade of events that increases water retention.
Chronic kidney disease (CKD) has been estimated to be prevalent in 13 percent of the US population.  The progression of CKD is measured by a stage system, with stage 5 being the most severe and often referred to as End Stage Renal Failure (ESRF).  The diagnosis of CKD is dependent on GFR rate.
There are a variety of conditions that contribute to the progression of kidney disease. The most common include nephrotic syndrome, glomerulonephritis, glomerulosclerosis, and amyloidosis.  Each of these conditions affect the efficiency of kidney filtration, which can lead to accumulation of toxic wastes in the blood or loss of important materials from the blood. 
Another common kidney issue is the development of kidney stones. The prevalence of kidney stones has been estimated to be 9 percent in the United States.  Several minerals and bi-products of metabolism can accumulate and form hardened crystals, which can be extremely painful as they are forced down the narrow tubes from kidney to bladder, and then during urination.
pH balance is an important function of the kidney. There is a condition called metabolic acidosis which causes a drop in blood pH (usually around neutral pH 7) below the narrow range that is suited for health. Death can occur quickly when one has metabolic acidosis. 
Primary kidney cancer is generally called Renal Cell Carcinoma (RCC). The prognosis for RCC depends on early detection, as it is the most common type of kidney cancer.  The survival rates drop significantly from stage 1 RCC to stage 4 RCC.
The health of the kidneys can play a major part in the health of the entire body, but the body’s overall health can also impact the health of the kidneys. There are a variety of measurements a physician can do to determine the health of the kidneys as well as isolate specific causes. 
Protecting the kidney from potentially harmful factors requires a commitment to overall health and diet. It has been estimated that 50 percent of individuals who have chronic kidney disease (CKD) also report type II diabetes and hypertension (high blood pressure). 
Metabolic syndrome has been significantly linked to the onset and progression of CKD. Its defining traits include obesity, hypertension, high glucose or diabetes, and high cholesterol/triglycerides. Individuals with at least one trait of metabolic syndrome are twice as likely to form CKD and that value becomes greater if an individual has at least 3 traits. 
With obesity and hypertension being the most common causes of CKD, to achieve kidney health an individual must alter diet to reduce body weight, which can have a lasting effect on blood pressure as well.
A few practices can greatly reduce the strain on the kidneys:
Drinking a Healthy Amount of Pure Water 
Depending on the health of the kidneys, water intake should be modified for the stage of CKD that may be present. Healthy individuals should consume one-half to one gallon (8-16 cups) of pure water a day.
This also means reducing intake of sugary drinks, like processed soft drinks and processed juices. Diet soft drinks that use artificial sweeteners may also put one at risk for CKD. A study in 2011 found a link between diet soda consumption and CKD progression, though the specifics of which artificial sweeteners may be culprits was not given. 
A Balanced Diet that Reduces Sugar and Sodium Consumption
High sugar leads to excessive excretion, which may cause damage to the glomerulus. Sodium intakes that exceed current recommendations cause the kidneys to excrete excessive calcium which may lead to glomerular damage or form crystals capable of developing a kidney stone.
Reducing intake of processed foods is a great start to improve kidney health, as sugar and sodium are very high in processed foods. Many food additives also are found in processed foods, with non-table-salt sodium products being some of the highest. Chemical-containing sodium products act as preservatives in processed foods and are a common ingredient.
Phosphorus-containing chemicals are also found in processed foods and are also linked to the progression of CKD.  Everyone should familiarize themselves with the generally recognized as safe list provided by the FDA , a list of all the approved food additives allowed in the United States.
Exercise Helps to Improve Kidney Health Before and After CKD Appears
There are studies that show participation in regular physical activity can reduce the loss of kidney function in those that have advanced to stages 3 and 4. 
The kidneys play a vital role in the proper function of the body. A healthy diet comprised of whole foods and plenty of water, coupled with regular physical activity, is the best option for kidney health. Consuming numerous fresh fruits and vegetables, coupled with moderate protein and complex carbohydrates, is the best approach. Exercise is a great way to improve kidney health both before and after CKD appears.