The kidneys are two bean-shaped organs found in your lower back. They have many functions. One is to filter waste products produced by normal bodily processes (for example, protein breakdown). Another is to maintain the balance of acids and bases and many other chemicals (for example, electrolytes such as sodium, potassium and chloride) in your blood and tissues. The kidneys also eliminate fluid and byproducts of foods or medicines that your body does not need through the urine. In addition, the kidneys play important roles in controlling blood pressure and producing red blood cells.
The basic working component of each kidney is a structure called a nephron. Healthcare professionals who specialize in the care of people with kidney (renal) diseases are called nephrologists.
What are Kidney Diseases?
For about one-third of older people, kidney (also called renal) function remains steady throughout life. But for the rest of us, kidney function gradually starts to decline around age 35, sometimes worsening quickly in later years with increasing structural and hormonal changes. Our kidneys are normally more than capable of meeting the body’s demands, so there is a built-in reserve of kidney function even as we age. Older kidneys, however, may not be as resilient as younger ones if they have been stressed. The result may be a higher risk of fluid imbalances, a build-up of waste products (such as urea), and other serious consequences in later years. Doses of medications must also be reduced if kidney function has declined, since your body can accumulate “overdose” levels if your kidneys cannot get rid of drugs efficiently.
Because the kidneys are important in regulating a variety of bodily functions, you may eventually develop problems requiring medical attention if your kidneys are not working well. These problems from kidney disease may include:
- Fluid and electrolyte imbalance – for example, having too much or too little sodium, potassium, or water in your body
- A build-up of waste products in your body—for example, urea or acids
- Loss of protein through your kidneys
- High blood pressure from too much fluid in your body
- Anemia (low blood counts)
- Brittle bones
If these problems become severe enough or don't recover, you may end up needing dialysis – a procedure that uses a machine to wash out your blood to make up for the loss of kidney function.
What are the types of kidney diseases and how common are they?
Chronic kidney disease (CKD) refers to kidney damage that lasts for more than three months. It is classified into five stages based on how well your kidneys are able to filter your blood. In stage one, your kidneys retain much of their ability to filter out wastes. In stage five, however, the filtration rate is inadequate and your kidneys are considered to have failed.
CKD afflicts more than 20 million adults in this country. It affects 35% of patients with diabetes and about 20% of adults with high blood pressure.
Electrolyte imbalances, such as sodium concentrations that are either too high or too low, are found in about one-quarter of all older people arriving at the emergency department. Older patients in hospitals are very likely to have abnormally low sodium levels. More than one in five residents of long-term care facilities have this problem. Even when mild, low sodium concentrations are associated with problems with attention and gait (the way you walk), falls, and increased fracture risk in older adults. Fluid imbalances are also common in older people, leading to dehydration, swelling, or other harmful conditions.
Nephrotic syndrome is a kidney disease common in older adults. Nephrotic syndrome causes your kidneys to excrete too much protein into your urine due to damage of tiny kidney blood vessels. Nephrotic syndrome occurs in various forms, which can be seen by examining a biopsy of your kidneys under a microscope, including:
- Membranous nephropathy (when the body’s immune system attacks the filtering membranes in the kidney)
- Diabetic nephropathy (damage from diabetes over time)
- Amyloidosis (accumulation of special proteins around blood vessels in the kidney)
- Glomerulonephritis (inflammation of the filtering structures in the kidney)
- Minimal change syndrome (damage to the filtering structures in the kidney)
Renovascular disease is a disease of the blood vessels that supply the kidneys. It occurs mostly in older adults, especially in people with heart and circulatory diseases and those who smoke. Healthcare professionals have found this condition in 25% of patients who have a common heart test called an angiogram.
Acute (sudden) kidney failure is increasingly common in older people, occurring about twice as often as end-stage kidney disease, with as many as 200,000 cases annually in the US. This is a condition in which there is a more sudden decrease in kidney function. There are many causes for this, but most commonly can be because of dehydration or use of medications that can place stress on the kidneys (see the Causes section).
End-stage renal (kidney) disease (ESRD) is diagnosed in over 100,000 new patients each year in the US. Almost 600,000 people are currently being treated for ESRD. The incidence is highest in adults over the age of 65 years, and in African Americans and Hispanic Americans. Every year, almost 400,000 ESRD patients are maintained on dialysis, about 18,000 receive a kidney transplant, and close to 90,000 patients with ESRD die.
Last Updated August 2020