Chronic kidney disease

Chronic kidney disease, also known as chronic renal failure, is a condition affecting the kidneys' ability to filter and remove unwanted waste and excess fluid from the bloodstream. The function of the kidneys is reduced over time, which can lead to a build-up of fluid and waste, particularly urea, and cause serious and potentially fatal health complications.

During the early stages of kidney disease symptoms may not occur, so the condition may only be discovered when the function of kidneys has become very low. Kidney disease can be caused by multiple underlying medical conditions including hypertension or diabetes. Treatment is aimed at slowing the progress of kidney damage and treating the underlying cause. It can lead to end-stage kidney disease, which is fatal if left untreated. End-stage kidney disease must be managed using a form of artificial filtering called dialysis, or in some circumstances with kidney transplantation.

Anatomy of the kidneys. 

Causes

Chronic kidney disease can be caused by conditions that affect the ability of the kidneys to properly remove waste by-products and excess fluid from the bloodstream. This can be related to blood pressure, or to the flow of blood to the kidneys and conditions that affect the health of nephrons, the main filtering units of the kidney. Nephrons are comprised of glomeruli (filters) and tubules (collecting tubes). Some of the conditions that can affect the kidneys and result in chronic kidney disease include:

• High blood pressure (hypertension);
• Type 1 diabetes;
• Type 2 diabetes;
• Glomerulonephritis, or the inflammation of the glomeruli, the filtering unit within the nephron;
• Interstitial nephritis, or the inflammation of the tissue around the tubules, the collecting tubes within the nephron;
• Polycystic kidney disease, a genetic disorder characterised by clusters of cysts that grow within the kidneys;
• Blocking of the urinary tract which can occur from kidney stones, an enlarged prostate gland or some cancers, resulting in urine build-up and backflow into the kidneys;
• Recurrent pyelonephritis (repeated kidney infections);
• Atherosclerosis - the narrowing of arteries supplying blood to the kidneys caused by fatty deposits on the inner walls, and;
• Drugs and medications (e.g., gentamicin and vancomycin) can also affect the filtering ability of the kidneys over time.

Signs and symptoms

Chronic kidney disease is a condition that gradually becomes worse over time. The signs and symptoms associated with the condition may not become apparent until irreversible damage to the kidneys has occurred; this is because your kidneys are highly adaptable and can compensate for the condition. Some signs and symptoms can include:

• Generally feeling unwell;
• Tiredness and lethargy;
• Changes in urine (colour, blood or pus);
• Loss of appetite;
• Nausea and vomiting;
• Muscle twitches or cramps, and;
• Dry and itchy skin.

Methods for diagnosis

The primary function of your kidneys is to filter the waste products from the blood so that they can be passed from your body through your urine. There are various tests used to diagnose how well your kidneys are functioning. This can involve analysing the levels of different components in blood and urine, imaging tests and tissue sample tests.

Glomerular filtration rate

Glomerular filtration rate (GFR) is a measure of how well your kidneys are removing waste products from your blood stream. Creatinine is a waste product released by your muscles and is the basis for calculating GFR. GFR is used to stage the severity of the condition and is measured in the unit mL/min/1.73m.

The most common way of measuring GFR is an estimated glomerular filtration rate (eGFR). A routine blood test is performed to check the level of creatinine in your blood. A formula is then used, incorporating age, ethnicity, size and gender, to give the eGFR.

GFR can be more accurately measured by collecting all the urine you produce over a 2 hour period. The amount of creatinine in the urine is then measured and used to calculate the GFR. GFR can be used to stage kidney function as follows:

Urinalysis

Urinalysis (urine analysis) can be used to check for kidney damage or other abnormalities. A urine test can identify the type and level of protein which can indicate kidney damage. The presence of red blood cells in the urine is an indication of bleeding in the urinary system. The presence of white blood cells in the urine is an indication of an infection.

Kidney imaging

Ultrasound imaging and computerised tomography (CT) scans can be used to visualise the kidneys. These tests can be used to view the size of the kidneys and indicate whether abnormalities such as cysts, kidney stones or tumours are present.

Kidney biopsy

A kidney biopsy involves taking a very small tissue sample from the kidney and examining it under a microscope. This test is performed using a local anaesthetic and the insertion of a long thin needle to remove a kidney tissue sample. The sample is then examined in the laboratory by a pathologist. A biopsy is performed to identify the presence, type and extent of kidney damage.

Other tests may be performed to help identify the cause of the kidney disease, such as blood pressure tests to check for hypertension and blood tests for diabetes.

Types of treatment

The treatment of chronic kidney disease is aimed at slowing the progress of kidney damage and treating the underlying cause to reduce signs and symptoms. This will often require regular reviews to monitor if treatments are working and to check the condition is not worsening. The success of treatment depends on how much damage has already occurred and what the underlying cause is. In cases where kidney function is severely reduced, dialysis or a kidney transplant may be required.

A healthy lifestyle

Making changes to become healthy can help treat underlying conditions and help to prevent kidney disease from getting worse. This can include having a healthy diet to help reduce cholesterol and blood sugar and one that is low in protein, sodium and potassium. Avoiding toxins including cigarettes, alcohol and caffeine is also important. Exercise is also a great way to stay healthy.

Hypertension

Hypertension, or high blood pressure, is both a cause and a complication of kidney disease. It is therefore important to bring blood pressure down to a healthy level. Adopting a healthy lifestyle can help to reduce blood pressure and medications such as angiotensin converting enzyme (ACE) inhibitors can also be prescribed by your doctor.

Diabetes

If you have both chronic kidney disease and diabetes, it is important to maintain healthy blood glucose levels. This is important, as high levels of glucose in the blood can affect the filtering ability of the kidneys.

Anaemia

Anaemia, or the deficiency in the number or quality of red blood cells, can occur in people with chronic kidney disease. This occurs because kidneys that are not working properly produce a lower amount of erythropoietin, a hormone controlling the level of red blood cell formation. Anaemia can cause fatigue and other complications. This can be treated with erythropoietin replacement medication to help promote the production of red blood cells.

Dialysis

Dialysis is used as a treatment if you have Stage V or end-stage kidney disease. In this late stage of chronic kidney disease, dialysis is required to artificially filter the waste from your blood. This can be performed in two ways:

Haemodialysis

This technique uses an artificial kidney machine that is able to take blood from your body and pump it through a machine to filter it - the way your kidneys normally would. The blood is returned to the body at the same rate that it is taken in a continuous loop process. The treatment can sometimes be performed at home using the dialysis unit. Each treatment takes about 4-6 hours and is usually required three times a week.

Haemodialysis procedure. 

Peritoneal dialysis

Peritoneal dialysis is performed by infusing a special cleansing fluid into the abdomen through an indwelling catheter. The clean fluid enters the peritoneal cavity and the body can filter waste products into the fluid. The used fluid is then drained. The number of exchanges that are required can vary from person to person. The treatment can be performed at home in two ways, using continuous ambulatory peritoneal dialysis (CAPD) which takes about 30 minutes and is repeated about four times daily, or by automated peritoneal dialysis (APD), which can do the fluid exchange while you sleep.

Kidney transplant

Kidney transplantation is a possible treatment option that can allow a more active life, free from dialysis. This involves transplanting a healthy kidney from a deceased or living donor into your body. This comes with the complication of 'rejection' as the new kidney will appear as foreign to your body. To overcome this, anti-rejection medication is needed for the rest of your life.

Potential complications

Over time as kidney disease progresses, complications can include:

• Anaemia;
• High blood pressure;
• Heart disease;
• Oedema - swelling of the legs, feet or ankles;
• Bone disease due to the lack of vitamin D and calcium uptake, and;
• Nausea and vomiting.

The most significant complication of end-stage kidney disease is where the condition has progressed so far that the kidneys can no longer function to support life - this means that dialysis or a kidney transplant is required to take over kidney function. Untreated end-stage kidney disease results in excessive urea in the blood (uraemia) and causes fatigue, loss of appetite, muscle wasting, tremors and shallow respiration. Uraemia can lead to coma and death if left untreated.

Prognosis

Chronic kidney disease is a condition that progresses gradually over time to cause irreparable damage to the kidneys. The aim of treatment is to prevent the condition from progressing further by treating any underlying causative conditions and managing symptoms. It is best to diagnose and treat the condition as soon as possible.

Prevention

To help prevent chronic kidney disease, it is best to live a healthy lifestyle. This can be done by:

• Eating a diet high in fruit and vegetables;
• Maintaining healthy cholesterol levels;
• Maintaining a healthy weight;
• Exercising regularly;
• Drinking water instead of sugary drinks;
• Avoiding illicit drugs;
• Limiting alcohol intake, and;
• Quitting smoking.

It is also important to monitor and treat any underlying conditions (such as diabetes or hypertension) and be aware of any family history.