Chronic kidney disease (CKD) manifests with gradual loss of kidney function over months to years. In early stages of CKD, patients might have very few signs or symptoms. In many cases patients do not realise the presence of CKD until an advanced stage.
Introduction: Functions of the kidneys
The kidneys perform many vital functions:
- They filter about 200 litres of blood daily to produce around 2 litres of urine. In the process, they remove waste and excess fluid.
- They secrete hormones that regulate blood pressure (i.e. aldosterone), and production of red blood cells (i.e. erythropoietin).
- They balance the levels of electrolytes (salts and minerals e.g. calcium, phosphorus, sodium, potassium) circulating in the blood for bodily processes e.g. maintaining bone health.
Prevalence of CKD
A recent 2020 study in Asia shows that more than 360 million people, 8% of Asian population, have CKD. A substantial number of them present with advanced forms of the disease. Countries in Eastern Asia were estimated to have more than 13% greater prevalence of CKD compared to other subregions in Asia. The greatest number of adults living with CKD were in China (150.2 million) and India (139.4 million), collectively forming 79% of the total number of adults with CKD in the region.
Symptoms of CKD
CKD symptoms are a result of the kidneys’ inability to perform aforementioned functions. Many of the symptoms are non-specific and can be present in other diseases as well. Some of the symptoms may manifest only in the later stages of CKD.
Accumulation of toxins and impurities in blood due to reduced clearance by kidneys may cause:
- Nausea/vomiting and loss of appetite
- Decreased mental sharpness
- Dry, itchy skin
As diseased kidneys do not stimulate adequate production of red blood cells, anaemia may develop and cause fatigue or weakness.
Without proper regulation of levels of electrolytes, salts and minerals by kidneys, imbalances may cause:
- Muscle cramps
- Bone and joint pain
- Irregular heart rhythm
Accumulation of salt and fluid may cause:
- Reduction in urine output
- Swelling of feet and ankles
- Shortness of breath, if fluid builds up in the lungs
- Chest pain, if fluid builds up around the lining of the heart
- High blood pressure that is difficult to control
4 Main Causes of CKD
Chronic high blood pressure will put extra force on blood vessel walls and eventually result in irreversible damage (stiffening, narrowing or weakening). Damaged arteries are unable to deliver sufficient blood to kidney tissue for proper functioning; damaged blood vessels within the glomeruli (filtering units of the kidneys) also affects filtration capacity.
Reduction in blood supply to kidneys will trigger hormones to bring about more reabsorption of sodium and water by kidneys, contributing to further increase in blood pressure. Therein the vicious cycle of uncontrolled high blood pressure and kidney damage continues in a negative spiral.
Diabetes is a condition when our blood sugar level is higher than normal. The sugar can cause narrowing and obstruction especially in the blood vessels within the glomeruli.
Furthermore, nerve damage from diabetes may cause pooling of urine in bladder and risk of infection to the kidneys as well as bacteria grows well in urine with high levels of sugar.
Glomerulonephritis is inflammation of the glomeruli, commonly caused by bacteria infection that results in acute kidney disease. However if the infection is not cleared in a timely manner, permanent damage may result.
Polycystic kidney disease (PKD)
Polycystic kidney disease cause numerous fluid-filled cyst growth in the kidneys. When the cysts accumulate in size and number, it can result in loss of kidney function. PKD is mainly an inherited condition classified as a genetic disorder.
Figure 1. Healthy-vs.-Polycystic-kidney
Other causes include:
- Toxicity from drugs, e.g. overuse of NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen, naproxen.
- Long-term obstruction of urinary tract due to conditions like enlarged prostate, or kidney stones
- Recurrent kidney infection
- Autoimmune conditions e.g. Systemic Lupus Erythematosus (SLE), where the body’s immune system attacks healthy kidney tissue
Diagnosis of CKD
Multiple tests may be ordered to reach a conclusive diagnosis.
- Blood tests to determine levels of waste products in blood e.g. creatinine
- Your doctor uses your creatinine level, plus age, weight, gender to calculate how many millilitres (ml) of waste your kidneys should be able to filter in a minute.
- This calculation is known as estimated Glomerular Filtration Rate (eGFR).
- A GFR<60ml/min may indicate kidney disease.
- Urine tests – test for blood, glucose, protein
- Albumin is a protein found in blood. A healthy kidney does not let albumin pass into the urine.
- Urine albumin-to-creatinine ratio (UACR) measures and compares the amount of albumin with the amount of creatinine in your urine sample. It estimates how much albumin would pass into your urine over 24 hours. A urine albumin result of > 30 mg/g may be a sign of kidney disease
- Ultrasound/MRI scan to visualise kidneys and check for blockages
- Kidney biopsy – a small sample of kidney tissue is removed using a needle and the cells examined under a microscope for signs of damage
Treatment of CKD
- Treat underlying conditions such as high blood pressure, diabetes.
- Two types of blood pressure medications, ACE inhibitors and ARBs, may slow progression of kidney disease, even in people who without high blood pressure. The names of these medications end in –pril or –sartan.
- Diuretics, sometimes called water pills, e.g. frusemide, may be prescribed to pass out excess fluid.
- Erythropoietin injections, sometimes with added iron supplementation, may be prescribed to help produce more red blood cells to relieve fatigue and weakness associated with anaemia from CKD.
- Calcium and vitamin D supplements can help prevent weak bones and lower your risk of fracture associated with CKD.
- Phosphate binders may be prescribed to lower the amount of phosphate in your blood (as diseased kidneys are unable to clear it) and protect your blood vessels from damage by calcium deposits (calcification).
For end-stage kidney disease patients, dialysis artificially removes waste products and extra fluid from the blood when kidneys can no longer do this.
A kidney transplant involves surgically placing a healthy kidney from deceased or living donors into your body. After a transplant, you will need to take medications for the rest of your life to keep your body from rejecting the new organ.
Prevention of CKD
Certain lifestyle modifications may help prevent CKD or its progression.
- Quit smoking: Smoking contributes to high blood pressure, cardiovascular disease, and kidney damage.
- Engage in frequent exercise, ≥150 minutes a week, or 30 minutes 5 times/week
- Eat a healthy diet
- Restrict sodium intake
- Use spices and herbs in place of salt to season food
- Avoid convenience/processed foods e.g. frozen dinners, canned soups which are high in sodium
- Read food labels when buying packaged foods. A Daily Value of ≥20% means the food is high in sodium and should be avoided.
- Restrict high-potassium foods e.g. bananas, oranges, certain salt substitutes as diseased kidneys allow potassium to build up which may cause heart problems
- Limit the amount of protein you eat.
- When your body uses protein, it produces waste for your kidneys to remove. Eating more protein than needed may make your kidneys work harder.
- Talk with a dietitian to estimate how many grams of protein you need daily and work out a suitable meal plan. High-protein foods include meat, dairy products and beans. Low-protein foods include vegetables, fruits, breads and cereals.
- Restrict sodium intake
- Lose weight if you are obese as obesity contributes to both high blood pressure and diabetes, which can drive further kidney damage.
- Avoid overuse of NSAIDs. These can damage your kidneys and lead to acute kidney injury, especially in those with kidney disease, diabetes, and high blood pressure.
CKD can progress to kidney failure if left untreated, necessitating dialysis or a kidney transplant to maintain life. If you have risk factors for CKD, get tested for kidney disease and protect your kidneys by making healthy lifestyle choices, and managing health conditions that cause kidney damage.