What is Chronic Kidney Disease?
Chronic kidney disease is a progressive condition that causes the kidneys to function less effectively over time. Kidneys that don’t function correctly are not able to filter waste from blood. There are different types of kidney disease, including disease caused by external factors (lifestyle habits, such as diets) as well as polycystic kidney disease, which refers to kidney cysts that reduce kidney function.
Doctors measure kidney function using a patient’s glomerular filtration rate (GFR), which refers to how much blood a kidney filters every minute. GFR is calculated using a range of factors, including age and race. Normal GFR is about 60 or higher. Anything lower than 60 indicates kidney impairment.
As the condition progresses (gets worse), it can lead to kidney failure, which occurs when the kidneys can only function at 15% or less of their normal capacity (indicated by a GFR of 15). When kidneys do not filter blood properly, waste and fluids build up in the blood.
What are the Causes of Chronic Kidney Disease?
Several conditions can lead to the development or progression of chronic kidney disease. The most common conditions include:
- Diabetes
- Hypertension (high blood pressure)
- Heart disease
- Family history of kidney disease
- Glomerulonephritis (inflammation of the kidneys)
Less common causes include infections, genetic disorders and renal artery stenosis (a narrowing of blood vessels in the kidney).
Diabetes
Diabetes mellitus is a chronic condition that affects the body’s ability to store and break down glucose. Important for cellular energy production, glucose is a vital resource for the body. Normally, the pancreas produces insulin to break glucose down into a usable form.
In people with diabetes, however, the insulin in the body is either ineffective or absent. Type 1 diabetes is characterized by the body’s immune system attacking insulin-producing cells. In type 2 diabetes (the most common type of diabetes, and often caused by lifestyle factors), the pancreas simply doesn’t produce enough insulin. Or, insulin resistance develops, meaning the insulin the body does produce doesn’t work as well as it should.
In either type of diabetes, the body can’t break down glucose. As a result, glucose builds up in the body. These high blood sugar levels can damage healthy tissue. This damage leads to a range of conditions, including neuropathy (nerve damage), eye damage, and heart and blood vessel damage. Damaged blood vessels, in particular, can make it harder for the kidneys to pump and filter blood, causing kidney damage.
Hypertension
Hypertension is a condition characterized by chronic high blood pressure levels. Blood pressure refers to the amount of pressure placed on blood vessels and arteries when the heart pumps blood. People with hypertension have blood pressure levels above 130/80 mmHg (normal blood pressure is around 120/80 mmHg).
While blood pressure is a vital health function, high blood pressure can also lead to many health conditions. Excess force can damage blood vessels and arteries, making it harder for the kidneys to filter blood and remove waste products. Conditions like treatment-resistant hypertension, in particular, are common in people with chronic kidney disease.
Heart Disease
Heart disease refers to a range of health conditions that affect the heart and its ability to pump blood. Some of the most common types of heart disease include the following:
- Coronary artery disease (CAD)
- Heart arrhythmia
- Heart failure
Each of these conditions generally causes the heart to function irregularly or work harder than normal. As a result, heart muscle can weaken, which affects its ability to pump blood effectively.
While heart disease can cause kidney damage, the resulting kidney damage can also worsen existing heart disease. A reduced ability to filter blood through the kidneys, for example, forces the heart to work harder. The harder the heart has to work, the weaker heart muscles can become.
Family History
Many conditions are known to be genetic or inherited. That means people can pass on a health condition to their children. While researchers are still looking at how family history can increase someone’s risk, they generally agree that having a family history of kidney disease increases the risk of developing chronic kidney disease.
Polycystic kidney disease, for example, is a disorder that has a genetic cause.
Glomerulonephritis
Glomerulonephritis refers to inflammation of the parts of the kidney responsible for filtering blood and urine. These tiny filters are called the glomerulus. When the glomerulus fails, the kidneys slowly lose their ability to function correctly. Bacterial infections, toxins and inflammation often cause glomerulonephritis.
What are the Symptoms of Chronic Kidney Disease?
Early-stage disease usually doesn’t cause any symptoms, which is likely why chronic kidney disease is an underdiagnosed condition. In fact, it can sometimes take years to progress to the point of causing symptoms.
End-stage renal (kidney) disease occurs when kidney function is severely impaired. Most of the time, severe kidney impairment can lead to or worsen the following symptoms and conditions:
- Swelling (edemas) due to fluid buildup
- Anemia
- Digestive diseases and conditions, such as nausea/vomiting
- Changes in urination frequency
- Urinary tract infections
- Treatment-resistant hypertension (high blood pressure that is difficult to treat)
Many of these symptoms are the result of fluid buildup in the body. As kidney function decreases, the body holds onto more fluid.
What are the Risk Factors Associated with Chronic Kidney Disease?
While there are many factors associated with higher disease risk, the people most likely to have chronic kidney disease often have one or more of the following characteristics:
- Diabetes
- Hypertension (high blood pressure)
- Heart disease
- A family history of kidney disease
- African, Native or Asian American heritage
- Obesity
Hypertension and diabetes, in particular, are among the more common factors because of their growing prevalence. For example, almost half of U.S adults have hypertension, while about one in ten has diabetes.
What are Complications Associated with Chronic Kidney Disease?
As a progressive condition, chronic kidney disease gets worse over time if left untreated. As a result, it can cause many complications that have lasting consequences. Anemia, for example, is common. In addition, damaged blood vessels in the kidneys can slow the flow of blood through the kidneys, resulting in low numbers of red bloods. Urinary tract infections are also common.
End-stage kidney disease can cause kidney failure, the most severe complication. When this happens, people often have only two options: dialysis or kidney transplant.
Dialysis offers advanced kidney disease patients a way to do what their kidneys cannot: filter blood. Patients who need dialysis are hooked up to a machine, which pulls out their blood, cleans it and puts it back into the body. While dialysis has had some success as an ongoing treatment for patients, it is a very time-consuming treatment for chronic kidney disease. It must be done multiple times a week, for multiple hours at a time. Dialysis is also not able to sustain kidney failure patients forever.
Kidney transplants are an option for people who have reached kidney failure, but getting a new kidney is riddled with challenges and risks.
Chronic kidney disease can also make many of the conditions that cause it worse. This includes conditions like hypertension and heart disease. For example, hypertension damages blood vessels, making it harder to filter blood. Damaged blood vessels cause the heart to work even harder to pump blood, weakening heart muscles and leading to heart failure.