Definition of Nephropathy

nephropathyNephropathy – Progressive, irreversible damage to the KIDNEYS that occurs as a result of systemic health conditions or disease processes.

Nephropathy is the main cause of END-STAGE RENAL DISEASE (ESRD) and the leading reason for KIDNEY TRANSPLANTATION.

Doctors diagnose more than 100,000 Americans with nephropathy every year.

DIABETES and HYPERTENSION (high BLOOD PRESSURE) are the leading cause of nephropathy in the United States. These conditions damage the delicate glomeruli, the capillary networks that feed BLOOD through the nephrons, the filtering structures of the kidneys.

Each kidney contains more than a million nephrons and can tolerate the loss of about two thirds of them before symptoms of kidney failure become apparent. By such time, however, damage to the kidneys is usually profound.

Types of Nephropathy

Nephropathy of Diabetes

Diabetes accounts for 45 percent of kidney failure among Americans. The elevated GLUCOSE (sugar) levels in the blood that occur with diabetes are particularly damaging to the blood vessels and the nerves that serve them. For reasons researchers do not understand, African Americans, Hispanic Americans, and Native Americans who have diabetes are significantly more likely to develop nephropathy of diabetes (sometimes called diabetic nephropathy).

About 40 percent of people who have diabetes develop some degree of nephropathy, half of whom eventually progress to ESRD. Nephropathy is more likely in type 1 diabetes.

Nephropathy of Hypertension

Hypertension accounts for 25 percent of nephropathy among Americans. Chronically elevated blood pressure places considerable stress against the walls of the glomeruli, causing microscopic ruptures and scarring (fibrosis).

As with nephropathy of diabetes, nephropathy of hypertension (sometimes called hypertensive nephropathy) is significantly more likely to develop in African Americans, Hispanic Americans, and Native Americans. The progression to ESRD (End-Stage Renal Disease) can be rapid in poorly controlled or untreated hypertension.

IgA Nephropathy

In IMMUNOGLOBULIN A (IgA) nephropathy, a dysfunction of the IMMUNE SYSTEM results in deposits of gA, a protein, accumulating within the tubules of the nephrons. The kidneys have no process for removing these deposits, which eventually clog the tubules and prevent them from transporting filtrate.

IgA nephropathy typically is ongoing for 20 years or longer before causing enough damage to result in symptoms. Many people who have IgA nephropathy also have a systemic autoimmune disorder such as SYSTEMIC LUPUS ERYTHEMATOSUS (SLE)RHEUMATOID ARTHRITIS, or ANKYLOSING SPONDYLITIS. Treating the underlying autoimmune disorder often slows the progression of the nephropathy.

Toxic Nephropathy

Many drugs and chemicals are nephrotoxins, substances that damage the kidneys. Toxic nephropathy typically develops as a result of chronic exposure though can occur with limited though substantial exposure (such as DRUG overdose). Common nephrotoxins include heavy metals (such as lead and cadmium), organic solvents (such as benzene), and certain ANTIBIOTIC MEDICATIONS (notably gentamicin and streptomycin, which are sometimes the only antibiotics effective against life-threatening infections such as bacterial MENINGITIS).

Worrisome culprits are the NONSTEROIDAL ANTIINFLAMMATORY DRUGS (NSAIDS). DEHYDRATION in combination with NSAID use, which occurs among people who compete in ENDURANCE activities, is a particular risk. Long-term, daily use of other painrelief medications, notably codeine and combination products that contain CAFFEINE with acetaminophen or aspirin, also can cause this form of toxic nephropathy, commonly called analgesic nephropathy.

People who have conditions of chronic PAIN are most susceptible to analgesic nephropathy. People who have diabetes or congestive HEART FAILURE, have other kidney disease, engage in heavy ALCOHOL consumption, or are age 70 or older also have increased risk for analgesic nephropathy, in part because many people do not understand the danger regular analgesic use poses for the kidneys. These circumstances reduce kidney function, increasing the likelihood that further damage to the kidneys will result in kidney failure.

Symptoms and Diagnostic Path

Nephropathy generally does not show symptoms until damage to the kidneys is fairly advanced. One of the earliest indications of nephropathy is ALBUMINURIA, a consequence of protein leaking from the glomeruli into the filtrate. Doctors often detect albuminuria through urinalysis done as part of a routine medical examination. When symptoms do appear, they often include

  • frothy URINE during URINATION (indicates albuminuria)
  • edema (fluid accumulation in the tissues), most noticeable upon awakening and often affecting the face and the feet
  • fatigue
  • loss of APPETITE in combination with increased weight (weight gain results from edema)
  • HEADACHE

Some forms of nephropathy also cause painless HEMATURIA (bloody urine). The diagnostic path includes further urine tests as well as BLOOD tests to assess kidney function. The nephrologist may perform a kidney biopsy to examine the nephrons under the microscope, which reveals the microscopic damage of nephropathy. The nephrologist may also conduct diagnostic imaging procedures such as COMPUTED TOMOGRAPHY (CT) SCAN and INTRAVENOUS PYELOGRAM (IVP) to examine kidney structure and function.

Treatment Options and Outlook

Treatment targets the underlying condition with the aim of slowing progression of the nephropathy and preserving remaining kidney function. It is critically important for people who have diabetes or hypertension (or both) to maintain effective control of these conditions through medication therapy and lifestyle measures.

Some people are able to successfully manage the underlying condition and the nephropathy to avoid ESRD, though often nephropathy progresses to require RENAL DIALYSIS. Whether kidney transplantation is a viable treatment option for ESRD resulting from nephropathy depends on multiple factors, including co-existing health conditions, age, and overall health status.

Risk Factors and Preventive Measures

Diabetes and hypertension combined cause more two thirds of nephropathy in the United States. The risk for nephropathy is particularly high for people who have both these conditions. Preventing these conditions and appropriately and diligently treating them when they develop mitigates the risk for nephropathy.

People who take longterm NSAIDs to treat chronic conditions such as OSTEOARTHRITIS should have regular blood and urine tests to screen for early indications of nephropathy, and work with their doctors to find the lowest effective DOSE and least nephrotoxic medication to manage the condition and its symptoms.

See also HEAVY-METAL POISONINGHEPATORENAL FAILURE; NEPHRITIS; NEPHRONNEPHROTIC SYNDROMERETINOPATHY.

Nephropathy – Diabetes, Hypertension – Definiton, Infotmation
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