Chronic kidney disease (CKD) is defined as the presence of kidney damage, manifested by abnormal albumin excretion or decreased kidney function, quantified by measured or estimated glomerular filtration rate (eGFR) that persists for more than 3 months.
CKD is typically a progressive disease. It is defined as
- Reduction of kidney function is defined as an eGFR < 60 mL/min/1.73 m2 for > 3 months
- Evidence of kidney damage, including persistent albuminuria is defined as > 30 mg of urine albumin per gram of urine creatinine for > 3 months.
What are kidneys and why are they important?
You have two kidneys. Each kidney is about the size of your fist. They are located near the middle of your back, just below the rib cage. Healthy kidneys do many important jobs. They:
- Regulate the composition and volume of blood, remove metabolic wastes in the urine, and help control the acid/base balance in the body.
- They produce erythropoietin needed for red-blood cell synthesis and activate vitamin D needed for calcium absorption and bone health.
Structure of kidney
Think of your kidneys as a coffee filter. When you make coffee, the filter keeps the coffee grains inside, but allows water to pass through. Your kidneys do something similar. They keep the things you need inside your body, but filter out things you don’t need.
Each of your kidneys has about 1.5 million filters called nephrons. Nephrons remove wastes and extra fluid from your blood in the form of urine. The urine flows through two tubes, called ureters, to the bladder. The urine is stored there until you urinate. The wastes come from the breakdown of what you eat or drink, medicine you take, plus normal muscle activity
Structure of nephron
Staging of CKD
The different stages of CKD form a continuum. The stages of CKD are classified as follows:
Stage 1: Kidney damage with normal or increased GFR (>90 mL/min/1.73 m 2)
Stage 2: Mild reduction in GFR (60-89 mL/min/1.73 m 2)
Stage 3a: Moderate reduction in GFR (45-59 mL/min/1.73 m 2)
Stage 3b: Moderate reduction in GFR (30-44 mL/min/1.73 m 2)
Stage 4: Severe reduction in GFR (15-29 mL/min/1.73 m 2)
Stage 5: Kidney failure (GFR <15 mL/min/1.73 m 2 or dialysis)
History behind CKD
Richard Bright (1789-1858), is widely regarded as the founder of the specialty of nephrology. He gave his name to Bright’s disease, which was used for over 100 years first as a term for any type of kidney disease, and later particularly for glomerular diseases.
About one in ten people have chronic kidney disease. African Americans, American Indians, Hispanics, and South Asians, particularly those from Pakistan, Sri Lanka, Bangladesh, and India, are at high risk of developing CKD. African Americans are at greater risk due to a prevalence of hypertension among them. As an example, 37% of ESKD cases in African Americans can be attributed to high blood pressure, compared with 19% among Caucasians.
Chronic kidney disease was the cause of 956,000 deaths globally in 2013, up from 409,000 deaths in 1990. In Canada 1.9 to 2.3 million people were estimated to have CKD in 2008. The U.S. Centers for Disease Control and Prevention found that CKD affected an estimated 16.8% of U.S. adults aged 20 years and older in the period from 1999 to 2004. UK estimates suggested that in 2007 8.8% of the population of Great Britain and Northern Ireland had symptomatic CKD.
Causes and risk factors of CKD
- High blood pressure
- Prostate or kidney stones
- Pain-killing drugs (analgesics)
- Family history of kidney failure
- 60 years or older
- Obese (body mass index ≥ 30)
- Cardiovascular disease
- HIV infection
- Immunological diseases
Complications of chronic kidney disease
As eGFR declines, complications occur more commonly and are more severe. These may include
- Cardiovascular disease (CVD) and dyslipidemia
- Anemia due to impaired erythropoiesis and low iron stores
- Mineral imbalance and bone disorder (calcium, phosphorus, and vitamin D)
- Metabolic acidosis
- Malnutrition (low serum albumin)
- Fluid and salt retention, often associated with accelerated hypertension
Symptoms of chronic kidney disease
In the later stages of kidney disease, you may:
- Feel tired or short of breath
- Have trouble thinking clearly
- Not feel like eating
- Have trouble sleeping
- Have dry, itchy skin
- Have muscle cramping at night
- Need to go to the bathroom more often, especially at night
- Have swollen feet and ankles
- Have puffiness around your eyes, especially in the morning
Diagnosis of chronic kidney disease
Doctor performs a physical exam, also checking for signs of problems with your heart or blood vessels, and conducts a neurological exam. For kidney disease diagnosis, you may also need certain tests and procedures, such as:
- Blood tests. Kidney function tests look for the level of waste products, such as creatinine and urea, in your blood.
- Urine tests. Analyzing a sample of your urine may reveal abnormalities that point to chronic kidney failure and help identify the cause of chronic kidney disease.
- Imaging tests. Your doctor may use ultrasound to assess your kidneys’ structure and size. Other imaging tests may be used in some cases.
- An ultrasound or CT scan to get a picture of your kidneys and urinary system. These pictures show the size of your kidneys, and whether they are too large or too small. They also show whether you have any tumors, kidney stones, or cysts.
- Removing a sample of kidney tissue for testing. Your doctor may recommend a kidney biopsy to remove a sample of kidney tissue. Kidney biopsy is often done with local anesthesia using a long, thin needle that’s inserted through your skin and into your kidney. The biopsy sample is sent to a lab for testing to help determine what’s causing your kidney problem.
Identifying and Evaluating CKD
Estimated Glomerular Filtration Rate (eGFR)
- eGFR provides an estimate of kidney function.
- eGFR reflects the total filtration by all functioning nephrons.
- As nephrons are damaged or destroyed, eGFR declines.
- The results of eGFR (mL/min/1.73m2) gives the following normal values:
- Not diagnostic of CKD > 60
- CKD 15– 59
- Kidney failure < 15
Urine Albumin-to Creatinine Ratio (UACR)
- It is the referred measure for screening, assessing, and monitoring kidney damage.
- It may be the earliest sign of glomerular diseasesincluding diabetic kidney disease.
- Other common names include
- Urine albumin
- Albumin-to-creatinine ratio (ACR)
- Microalbumin/ creatinine ratio
- The result (mg/g) approximates milligrams of albumin excreted in 24 hours.
- Normal 0 – 29
- Albuminuria > 30
Treatment and medications
There’s no cure for CKD, but treatment can help relieve the symptoms and stop it getting worse.
Your treatment will depend on how severe your kidney disease is.
The main treatments are:
- Lifestyle changes to ensure you remain as healthy as possible
- Medication to control associated problems such as high blood pressure and high cholesterol
- Dialysis– treatment to replicate some of the kidney’s functions; this may be necessary in advanced CKD
- Kidney transplant– this may also be necessary in advanced CKD
Prevention of chronic kidney disease
Smoking increases your risk of cardiovascular disease, including heart attacks or strokes, which is associated with a higher risk of kidney disease.
- A balanced diet should include:
- Plenty of fruit and vegetables – aim for at least five portions a day
- Meals based on starchy foods – such as potatoes, bread, rice or pasta
- Some dairy or dairy alternatives
- Some beans or pulses, fish, eggs, meat and other sources of protein
- Low levels of saturated fat, salt and sugar
Cut down on alcohol
Drinking excessive amounts of alcohol can cause your blood pressure and cholesterol levels to rise to unhealthy levels.
- Men and women are advised not to regularly drink more than 14 units a week
- Spread your drinking over three days or more if you drink as much as 14 units a week
- Regular exercise should help lower your blood pressure and reduce your risk of developing kidney disease.
- At least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity such as cycling or fast walking every week is recommended.
Be careful with painkillers
- Kidney disease can be caused by taking too many non-steroidal anti-inflammatories (NSAIDs), such as aspirin and ibuprofen, or taking them for longer than recommended.