Kidney Disease

Kidney disease refers to any condition affecting how well the kidneys work. Kidney diseases range from mild infections that can be treated with antibiotics to chronic (long-lasting) diseases that cause the kidneys to deteriorate and ultimately to stop working.

The kidneys are a pair of bean-shaped organs located in the back of the abdominal cavity right above the waist. One lies on each side of the spinal column, and each kidney holds about a million nephrons (NEF-rons). The nephrons perform one of the kidneys’ primary jobs: filtering waste out of the blood. Each nephron contains a tiny blood vessel, or capillary, called a glomerulus (glom-ER-you-luss). The glomerulus sits inside a chamber that is known as Bowman's capsule, and the capsule lies within a tangle of small tubes, or tubules. Blood enters the glomerulus, and water and small molecules (including ions) filter out of the blood and into Bowman's capsule. From there, this fluid of water and small molecules moves into the tubule system, specifically the part known as the proximal convoluted tubule. While the fluid travels through this tubule, the blood reabsorbs, or resorbs, the nutrients and much of the water from the liquid. At this point, the liquid is known as urine. The urine then travels from the proximal tubule into the loop of Henle (HEN-lee), which is a section of tubule that has a hairpin turn. The loop of Henle removes additional water and ions from the urine, making the urine even more concentrated. From there, the urine enters the next part of the tubule system, the distal convoluted tubule. The urine eventually exits the tubule system and flows into a larger collecting tube, called the ureter (yu-REE-ter), and then on to the bladder. The bladder stores the urine until it empties out of the body when the person urinates.

When the kidneys are damaged by disease, some or all of these functions can be impaired. If both kidneys do not function properly, a person can become very ill. When they fail to function at all, a person will die without treatment. Fortunately, the human body has two kidneys, and if one is damaged or even missing, the other is capable of performing all of the functions quite well. Most people who have only one healthy kidney can live a normal life. Some people with only one kidney develop slightly higher blood pressure, however, so a doctor may want to monitor them a bit more carefully than those people who have two kidneys.

Kidney disease is a major health problem in the United States. The Centers for Disease Control and Prevention reported that as of 2014 more than 10 percent of adults in the United States (more than 20 million people) had chronic kidney disease. According to a 2011 study by the United States Renal Data System (USRDS), the incidence of chronic kidney disease (CKD) in people ages 65 and older more than doubled between 2000 and 2008. In 2013 kidney disease ranked number 9 in cause of death with 47,112 deaths.

At the end of 2009, more than 871,000 people were being treated for end-stage renal disease (ESRD); 398,861 ESRD patients were being treated with some form of dialysis; and 172,553 ESRD patients had a working transplanted kidney. Between 1980 and 2009, the prevalent rate for ESRD increased nearly 600 percent, from 290 to 1,738 cases per million. ESRD rates are more than three times higher for African Americans than for Caucasians.

Kidney diseases are divided into three categories: congenital disorders (that appear at the time of birth), chronic disorders (that may develop gradually over many years), and acute disorders (that occur suddenly).

Some people are born with a kidney disorder, which is called a congenital disease. They may have one kidney missing, two on one side, or two ureters (the tube that carries urine from the kidney to the bladder) for one kidney. In some cases, the two kidneys may be connected at their base to form a single horseshoe-shaped kidney. The human body can usually adjust to these abnormalities because it can function with only one kidney.

Chronic kidney diseases are very serious conditions because they cause the kidneys to deteriorate over time. Glomerulonephritis (glom-er-u-lo-ne-FRY-tis) is a condition in which the glomeruli (glom-ER-you-li)—the plural of glomerulus—become inflamed. It often accompanies other diseases such as diabetes * and high blood pressure, or it can develop as the result of a bacterial infection or a disease that affects the immune system. The immune system makes proteins called antibodies to fight infection. In glomerulonephritis, these antibodies become trapped in the glomeruli, causing them to become inflamed. Glomerulonephritis is treatable under certain circumstances, but in other cases it may progress and cause severe kidney damage.

Many people who have kidney disease develop anemia, a condition in which an individual has too few of the red blood cells that carry oxygen to cells and organs in the body. This condition occurs when the kidneys do not make enough of the hormone erythropoietin (ee-rith-ro-po-EE-tin). Erythropoietin stimulates the bone marrow to produce the right amount of red blood cells. Anemia can also result when a patient loses blood from hemodialysis.

In addition, cancer or tumors in the kidneys or a condition called polycystic kidney disease (PKD) can stop the kidneys from functioning properly over time. PKD is a genetic disorder that results in the growth of numerous liquid-filled sacs, called cysts, in the kidneys. These cysts can take the place of functioning kidney tissue and prevent the kidneys from doing their job. Eventually, many of these diseases lead to ESRD, a condition in which the kidneys shut down.

Acute, or sudden, kidney failure can result from many factors, including injury that greatly reduces blood flow, severe dehydration, exposure to chemicals and drugs that are poisonous to the kidneys, infections, tumors, and kidney stones.

Pyelonephritis (PY-el-o-ne-FRY-tis), or infection of the kidney, is a common type of acute kidney disease. Its symptoms can include pain in the back or abdomen, fever, and frequent or painful urination. Medical professionals can treat it effectively with antibiotics. Another well-known condition is kidney stones, which are hard crystals made of chemicals that separate from the urine and build up in the kidney. Small kidney stones can pass out of the body without medical assistance, but larger stones require a procedure that breaks them into smaller pieces so that they can leave the body in the urine. People may recover from these kidney diseases without permanent damage to the kidneys. If left untreated, however, these diseases can cause permanent damage and kidney failure.

The treatment for kidney disease varies based on the underlying cause. For example, an infection might require antibiotics, whereas a tumor would demand surgical removal. Medical professionals can treat chronic conditions with drugs to reduce symptoms in cases in which the disease cannot be cured. A restricted diet also may help alleviate symptoms. Complete kidney failure requires dialysis two or three times per week or a kidney transplant.

See also Glomerulonephritis • Kidney Stones • Nephrotic Syndrome

* diabetes (dye-uh-BEE-teez) is a condition in which either the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.

* MRI, short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.