Renal failure due to hypertension
Renal failure due to hypertension
Renal failure (kidney failure) is caused primarily by chronic high blood pressure (hypertension) over many years. Hypertension is the second major cause, after diabetes, of end stage renal disease (ESRD) and is responsible for 25–30% of all reported cases. In addition, many people with diabetes also have hypertension, thus high blood pressure plays an even larger role in kidney failure.
About 398,000 people were diagnosed with end-stage renal disease in 1998. Of these, about 83,000 had hypertension and about 133,000 had diabetes. That same year, approximately 63,000 people with ESRD passed away. Most people with ESRD have had symptoms for a long time and may have had kidney disease (nephropathy) for as many as 20 years or more prior to experiencing kidney failure.
It is believed that most cases of hypertension leading to kidney failure have a genetic element. Finding a genetic link is complicated by the fact that nearly half of all people with renal failure have three or more serious disorders, such as diabetes. Animal studies have been done to find genetic linkages to hypertension and kidney failure, but genetic studies on humans are in their infancy. A recent breakthrough came in a study of African American subjects with hypertensive end-stage renal disease. Researchers found a significant association between severe hypertension and mutations on the HSD11B2 gene . This is a gene that plays a role in sodium retention and related factors. Their data suggested that the 16q22.1 chromosome region was the location of the mutation.
In another study, researchers studied an Israeli family of Iraqi-Jewish origin whose members suffered from hypertension and renal failure. The researchers found a genetic locus at 1q21 that was autosomal dominant. They also hypothesized that the gene encoding atrial natriutetic peptide receptor-1 (NPR1) was the disease gene that led to the hypertension/renal failure.
Other families with high rates of hypertension have also been studied. For example, researchers observed a family of Old Order Amish in Lancaster, Pennsylvania and found a genetic link for hypertension to chromosome 2q31-34. The subjects were not experiencing kidney failure, thus, further study would be needed to determine if the identified genetic locus also coded for ESRD.
People of all ages, races, and both sexes may develop kidney failure due to hypertension. However, some groups are at much greater risk than others. African Americans are at particularly high risk for both hypertension and renal failure and have four times the number of ESRD cases as Caucasians. They also experience kidney failure at a younger age, with an onset at about age 56 compared to an onset at age 62 for Caucasians. African Americans also have a higher rate of diabetes than non-African Americans, another reason for their increased risk for kidney failures. Native Americans and Alaskan Natives are also at high risk for ESRD. There are about the same number of males and females with newly diagnosed ESRD.
In general, according to the National Institutes of Health, the risk for ESRD increases with age, and those who are over age 65 are at greatest risk for ESRD. The United States Renal Data Service (USRDS) of the National Institutes of Health tracks kidney failure statistics in the United States. According to the USRDS, in 1998, the rate of new cases for those under age 20 was just 13 per million, and the rate increased to 109 for those ages 20–44. A sharp upturn of five times that rate occurred in the 45–64 age group, when the rate is 545 per million people. The rate for those over 65 is about double, at 1,296 per million people. The mean age for individuals with ESRD was 62 years in 1998.
Signs and symptoms
Universal symptoms of ESRD are severe fatigue, fluid retention (edema), and elevated blood pressure readings. Other symptoms include a failure to eat (anorexia) and skin color changes such as a change to a yellow-brown skin color. Urea from perspiration may appear on the skin as whitish crystals, similar to frost. Pruritis (severe itching of the skin) is common. Patients may have muscle cramps and convulsions. Many have malnutrition from anorexia and vomiting. Gastric ulcers are common, as are cardiac symptoms stemming from the retention of sodium and water. Anemia (low levels of iron in the blood) is also common.
Diagnosis is based on the results of a physical examination and laboratory blood and urine tests. A patient who has end stage renal disease looks very ill and has obvious fluid retention and clear indicators of severe disease. Anemia is common. Blood pressure is elevated, and even patients who did not have hypertension prior to the onset of ESRD will develop hypertension. Patients also usually have massive amounts of protein in the urine and high levels of serum creatinine. Urea levels are also raised.
Treatment and management
Once physicians diagnose end stage renal disease, they must make a plan for dialysis. In addition, patients may be placed on restricted fluids. Anemia is treated and transfusions are given if anemia is severe. ACE inhibitor drugs may be prescribed at low doses to treat cardiac symptoms. Diuretics may be prescribed to reduce fluid retention. Multivitamins may be recommended because of food restrictions.
All patients with kidney failure, despite the cause of the failure, must receive kidney dialysis or kidney transplantation. Eventually, those on dialysis will require transplantation of a kidney, either from a recently deceased person or a live donor. (Each person has two kidneys and can live normally with only one kidney.) About 13,000 kidney transplants are performed in the United States each year and about 47,000 people wait for a donated kidney per year.
There are two types of dialysis. The most common type of treatment is "hemodialysis," a procedure that uses a machine called a dialyzer to clean and filter the blood, since the kidneys can no longer perform that function. A connection from the machine is made to the patient's bloodstream and the blood travels through the dialyzer where it is cleaned for 2–4 hours. This procedure is generally performed three times a week. Patients must also change their diets to carefully limit the amount of salt, potassium, and fluids that are consumed, among other dietary restrictions that are given.
Peritoneal dialysis is another option for patients with kidney failure. In this procedure, the patient's own abdominal lining (the peritoneal membrane) is used to help clean the blood. Rather than the patients own blood traveling to a machine, as with a dialyzer, a cleansing solution is transferred through a special tube (catheter) directly into the body. The catheter remains in the body. The number of treatments and time to perform the cleansing procedures vary.
Most patients will eventually need a transplanted kidney to continue to live. The survival rate for those on kidney dialysis after one year is about 80% and after two years, about 66%. However, the five year survival rate with dialysis is 29% and the 10 year survival rate is only 8%.
In contrast, the survival rate for those who receive a transplanted kidney from a deceased person is 94% after one year, 92% after two years and 80% after five years. The 10 year survival rate with a cadaver transplantation is 57%. The survival rates are higher when the kidney is from a live donor; for example, the survival rate after 5 years with a live donor kidney is 89% and about 77% after 10 years.
Beers, Mark H. MD, and Robert Berkow, MD, eds. The Merck Manual of Diagnosis and Therapy. 1999. Available at <http://www.merck.com/pubs/manual/>.
National Institutes of Health. "Chronic Kidney Disease." In Healthy People 2010. National Institutes of Health, 2000.
"Patient characteristics at the beginning of ESRD." 2000 Atlas of ESRD in the United States. U.S. Renal Data System, 2000
Cohn, Daniel H., et al. "A locus for an autosomal dominant form of progressive renal failure and hypertension at Chromosome 1q21." American Journal of Human Genetics 67 (2000): 647-651.
Hsueh, Wen-Chi, PhD., et al. "QTL influencing blood pressure maps to the region of PPH1 On Chromosome 2q31-34 in Old Order Amish." Circulation 101 (2000): 2810.
Watson Jr., Bracie, et al. "Genetic association of 11B-hydroxysteroid dehydrogenase type 2 (HSD11B2) flanking microsatellites with essential hypertension in blacks." Hypertension 28 (1996): 478-482.
American Association of Kidney Patients. 100 S. Ashley Dr., Suite 280, Tampa, FL 33602. (800) 749-2257. <www.aakp.org>.
American Kidney Fund. Suite 1010, 6110 Executive Blvd., Rockville, MD 20852. (899) 638-8299.
National Kidney and Urologic Disases Information Clearinghouse. 3 Information Way, Bethesda, MD 20892-3560.
"Entry 161900: Renal Failure, Progressive, with Hypertension." OMIM—Online Mendelian Inheritance in Man. <http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?161900>.