What Is Kidney Disease?

Kidney disease, or renal disease, happens if the kidneys are not removing waste and excess water from the blood as efficiently as they normally do. Some of the most common types of kidney disease include chronic kidney disease (CKD), kidney infections, and kidney stones.

Symptoms vary by type. Some people may not even know they have kidney disease. Late-stage CKD, for example, causes symptoms like headache, loss of appetite, muscle cramps, and swelling. A healthcare provider can diagnose kidney disease using blood and urine samples. Treatment typically includes managing risk factors, such as blood pressure and blood sugar. Kidney failure, or the last stage of CKD, requires dialysis or a kidney transplant.

Some of the most common causes of kidney disease are diabetes and high blood pressure. About 37 million adults in the U.S. have kidney disease. Kidney disease is one of the leading causes of death in the U.S.

Types

There are several types of kidney disease, including:

• Chronic kidney disease (CKD): Kidney function is gradually lost and can result in complications like high blood pressure, bone problems, and heart disease. CKD can eventually lead to kidney failure, which can be fatal without dialysis or a kidney transplant.
• Glomerulonephritis (GN): Each nephron contains filters called glomeruli, or tiny blood vessels. Inflammation of and damage to glomeruli is called glomerulonephritis.
• Immunoglobulin A (IgA) nephropathy (Berger's disease): This is when deposits of the IgA antibody build up in the kidneys. IgA nephropathy has no cure, so treatment focuses on slowing kidney damage.
• Kidney cancer: This is cancer that begins in the kidneys. Kidney cancer is diagnosed in more than 81,000 adults each year and affects more men than women. The average age of diagnosis is 64.
• Kidney cysts: These are fluid-filled sacs in the kidneys caused by diseases like polycystic kidney disease (PKD). PKD impairs kidney function and can lead to kidney failure. Another type is acquired cystic kidney disease (ACKD), a complication of CKD.
• Kidney infections: This is a type of urinary tract infection (UTI) called pyelonephritis. Bacteria or viruses infect one or both kidneys to cause pyelonephritis. Kidney infections require antibiotic treatment.
• Kidney stones: Kidney stones form when the saturation of certain minerals in the urine exceeds their solubility. They are most common in men. Smaller stones may be asymptomatic. Larger ones can cause extreme pain while urinating, bloody urine, lower back pain, nausea, and vomiting.

What Are the Signs of Kidney Disease?

What Is the Leading Cause of Kidney Disease?

Chronic Kidney Disease (CKD)

Kidney Disease Symptoms

Most adults with kidney disease are unaware they have it. You may have varying symptoms depending on what type of kidney disease you have. 

The following are symptoms of CKD, which usually appear during the advanced stages when the kidneys have lost most of their ability to function: 

• Chest pain
• Dry, itchy skin
• Headache
• Increased urination
• Loss of appetite and weight loss
• Muscle cramps
• Nausea and vomiting
• Swelling of the legs, ankles, feet, face, and hands
• Tiredness
• Trouble focusing

What Causes Kidney Disease?

Kidney disease affects the nephrons, or tiny structures within the kidneys that filter waste. You have a pair of kidneys below your ribcage in the middle of your back, with one sitting on each side of your backbone. Each kidney is the shape of a bean and the size of a fist. Nephrons remove waste from your blood. You excrete this waste and excess fluids from your body as urine.

Damage to the nephrons causes the kidneys to be unable to filter and remove waste from your blood. Some of the most common causes of this damage include genetics, injuries, and certain medications.

Risk Factors

One-third of adults in the U.S. are at risk for kidney disease. That's because diabetes and hypertension (high blood pressure), two of the most common risk factors for CKD, are so prevalent among American adults. Diabetes and hypertension account for three-fourths of new diagnoses of CKD.

Diabetes is a health condition that causes high blood sugar and abnormal glucose metabolism, which can increase the rate of kidney dysfunction. Diabetes also damages blood vessels.

High blood pressure also damages blood vessels, stymying the flow of oxygen and nutrients to nephrons. This ultimately impairs their blood-filtering ability. Hypertension can eventually narrow or weaken the arteries around the kidneys, preventing adequate blood flow to the organs.

Other risk factors include:

• Autoimmune disorders (e.g., lupus)
• Certain medications and toxic chemicals
• Kidney injuries
• Kidney stones
• Malformations during fetal development
• Recurrent UTIs
• Reflux nephropathy, or when urine flows backward and into the kidneys

Diagnosis

 It's likely you will not experience any symptoms in the early stages of kidney damage. Talk to a healthcare provider about testing your kidney function if you have health conditions that put you at risk for kidney disease. 

A healthcare provider might administer diagnostic tests like:

• Biopsy: A healthcare provider removes a small sample of kidney tissue to determine the cause and severity of kidney disease.
• Blood creatinine: This blood test can be a marker for the severity of kidney disease.
• GFR: This blood test examines your glomerular filtration rate (GFR). These are the clusters of small blood vessels that filter your blood. An optimal GFR is 60 or more.
• Imaging: An ultrasound or CT scan can provide an image of your kidneys to assess their size and look for kidney stones or tumors.
• Urine albumin: Albumin is a protein marker in the urine that signals kidney damage.
  

The 5 Stages of Kidney Disease

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Stages of Kidney Disease

There are five stages of CKD, the last being end-stage renal failure (ESRF), or kidney failure. A healthcare provider stages CKD based on how well your kidneys remove waste from your blood.

The stages of CKD include:

• Stage I: The kidneys do not work well, and you have mild kidney damage. You likely will not have symptoms, but a urine test may reveal a protein in the urine that signals CKD.
• Stage II: The kidneys still function well and show little signs of physical damage. You might notice swelling of the hands and feet due to fluid build-up.
• Stage III: The kidneys are unable to remove waste as they normally would, causing an imbalance of calcium and phosphorus. These minerals support bone health, so you might develop bone disorders that increase fracture risk.
• Stage IV: This is the last stage before kidney failure, in which the kidneys are severely damaged. One of the most common symptoms of stage IV CKD is breath that smells like ammonia (urine-lik or fishy).
• Stage V (ESRF): You are in kidney failure if your kidneys cannot work as they normally do. If untreated, kidney failure causes waste to build up in the blood and is fatal.

Treatment

Damage to the kidneys can be permanent. Being diagnosed early can prevent kidney failure. The goal of treatment for CKD is to stop further kidney damage to prevent the progression of the disease.

You can treat CKD by:

• Blood sugar management: Proper treatment for prediabetes or diabetes helps keep blood sugar levels stable. This might include insulin therapy or lifestyle changes. 
• Blood pressure control: This might include eating a heart-healthy diet, limiting your sodium intake, staying physically active, and taking medication.
• Dialysis: Kidney failure occurs when the kidneys lose most of their ability to remove waste from your blood. Dialysis sends your blood through a filter outside of your body. This procedure can be done in a dialysis center or at home.
• Diet changes: A healthcare provider may recommend a low-sodium, heart-healthy diet that emphasizes smaller portions of proteins if you have CKD. You might also have to limit the amount of phosphorus and potassium in your diet.
• Kidney transplant: This is a surgical procedure in which a donor kidney is placed in your body. A transplant can help you feel better and is one of the definitive treatments for end-stage kidney failure.
• Symptom management: A healthcare provider may prescribe medications to treat fluid retention, weak bones, and other symptoms.

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Prevention

Kidney disease prevention starts with lifestyle habits that keep your blood pressure and blood sugar levels in check. These habits include:

• Diet: Focus on whole, minimally processed foods (e.g., vegetables, fruits, whole grains, legumes, nuts and seeds, lean protein, fish, and heart-healthy fats). Stick to the recommended sodium limit of no more than 2,300 milligrams (mg) per day.
• Do not smoke and limit alcohol: Drink alcohol moderately if you consume it. This is one drink per day for women and two for men.
• Exercise: Regular physical activity helps maintain weight and improve blood flow.
• Sleep: Get seven to eight hours of sleep per night. 

You'll want to follow a healthcare provider's advice on managing diabetes or hypertension if you have one of these health conditions. See a healthcare provider if you have kidney stones or UTIs to prevent kidney infections or damage. 

Related Conditions

CKD is linked to several health conditions that you are likelier to have or develop if you have the disease. These include:

• Anemia: This is a low red blood cell count, resulting in fatigue and weakness. Anemia can develop as a result of the kidneys' inability to produce the hormone erythropoietin. About one in seven people with CKD have anemia.
• Bone disease: You might have an increased risk of fractures due to abnormal changes in the bones due to chronic kidney disease that causes the bones to be more brittle.
• Dementia: Research has shown that people with CKD have a high risk of cognitive decline. Confusion, depression, and problems with memory and thinking are common side effects of CKD.
• Heart disease and stroke: CKD, heart disease, and stroke share several risk factors, including high blood pressure, sugar, and cholesterol.
• Infections: CKD can weaken your immune system, leaving you more susceptible to infections.

Living With Kidney Disease

The prognosis of kidney disease depends on several factors, including the type, severity, and access to treatments. Stage V CKD, for example, has a life expectancy of five to 10 years with dialysis after diagnosis. Some people, however, live for up to 30 years on dialysis.

Research has shown that CKD disproportionally affects racial and ethnic minority groups. Black adults, for example, have a 3.4-fold greater risk of kidney failure than White adults. This is because Black adults are less likely to receive life-saving treatment, including less access to kidney transplants. It's important to expand access to home dialysis to racial and ethnic minority groups and lower out-of-pocket costs for this treatment.

Researchers are continuously looking for new ways to diagnose CKD and expand treatments. Novel ways to diagnose and treat CKD include immunotherapy and gene therapy.