Health Library

Overview of Kidney Disorders

How do the kidneys work?
Illustration of the anatomy of the kidney
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The body takes nutrients from food and converts them to energy. After the body has used all the food components that it needs, waste products are left behind in the bowel and in the blood.

The kidneys and urinary system help to excrete the waste products  and also keep chemicals, such as potassium and sodium, and water in balance by removing a type of waste, called urea, from the blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys. The kidneys also control the fluid and acid-base balance in the body

Two kidneys, a pair of purplish-brown organs, are located below the ribs toward the middle of the back. Their function is to:

  • Remove liquid waste from the blood in the form of urine

  • Keep a stable balance of salts and other substances in the blood

  • Produce erythropoietin, a hormone that aids the formation of red blood cells

The kidneys remove urea from the blood through tiny filtering units called nephrons. There are about one million nephrons in each kidney, located in the medulla and the cortex. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule.

Once the urine is formed, it passes through the nephrons and down the renal tubules of the kidney. Urine collects in the calyces and renal pelvis and moves into the ureter, where it flows down into the bladder.

In addition to filtering waste from the blood and assisting in the balance of fluids and other substances in the body, the kidneys perform other vital functions. These functions include:

  • Production of hormones that help to regulate blood pressure and heart function

  • Production of corticosteroids that help to regulate kidney function and the body’s inflammatory response system

  • Assisting in converting vitamin D into a form that can be used by the body’s tissues

What is nephrology?

Nephrology is the branch of medicine concerned with the diagnosis and treatment of conditions related to the kidneys, and doctors who specialize in kidney disease are called nephrologists. Other health professionals who treat kidney problems include primary care doctors, pediatricians, transplant specialists, and urologists.

What causes problems with the kidneys?

Problems with the kidneys may include conditions, such as kidney failure, kidney stones, and kidney cancer. These problems with the kidneys may be caused by the following:

  • Aging. As we age, changes in the structure of the kidneys can cause them to lose some ability to remove wastes from the blood, and the muscles in the ureters, bladder, and urethra tend to lose some of their strength. However, this alone does not cause chronic kidney diseases.

  • Illness or injury. Damage to the kidneys caused by illness or an injury can also prevent them from filtering the blood completely or block the passage of urine.

  • Toxicity. The kidneys may be damaged by substances, such as certain medications, a buildup of some substances in the body, or toxic substances such as poisons.

About kidney and urogenital diseases

Diseases of the kidney and urinary tract remain a major cause of illness and death in the United States. The National Kidney Foundation states that more than 26 million Americans are affected by kidney and urologic diseases, and millions more are at risk.

What are the symptoms of kidney disease?

The following are the most common symptoms of kidney disease. However, each individual may experience symptoms differently. Symptoms may include:

  • Frequent headaches

  • Fatigue

  • Itchiness all over the body

  • Blood in the urine

  • Loss of appetite

  • Nausea and/or vomiting

  • Puffiness around eyes and/or swelling of hands and feet

  • Skin may darken

  • Muscle cramps or pain in small of back just below the ribs (not aggravated by movement)

  • High blood pressure

The symptoms of a kidney disease may resemble other conditions or medical problems. Always consult your doctor for a diagnosis.