Chronic Kidney Disease Causes

What is chronic kidney disease?

Chronic kidney disease (CKD) is a condition in which the kidneys are unable to function correctly over a long period of time.

We have two kidneys in our body, each of which is about the size of a fist and is located beneath your ribcage on either side of the spine. Kidneys are vital for the filtration of blood; they remove toxins and filter out excess water and small molecules (glucose and ions). Our bodies are able to function well with just one working kidney.

Each kidney is made up of roughly a million nephrons. They filter the blood and reabsorb electrolytes, water, and glucose in the correct concentrations and pH, as well as removing toxins and excessive small molecules.

The part that filters the blood is known as the glomerulus: made up of lots of small blood vessels. The other part of the nephron is a tubule which is responsible for reabsorption.¹

Symptoms

CKD tends to not exhibit any symptoms until its late stages. The body is usually able to survive with a significant reduction in kidney function, meaning that for the majority of individuals, diagnosis only occurs in the later stages of CKD.

Early diagnosis is much less common and tends to occur as a result of routine tests for other conditions: blood or urine tests may indicate a potential problem for further investigation. 

If the above does not occur, a range of symptoms may develop. This stage is kidney failure or end-stage renal disease:

• Weight loss
• Loss of appetite
• Oedema in ankles, feet or hands (water retention)
• Shortness of breath
• Tiredness
• Blood in urine
• Polyuria 
• Nocturia
• Insomnia
• Itchy skin
• Muscle cramps
• Nausea
• Headaches
• Erectile dysfunction in males

Following end-stage renal failure, treatment options tend to be limited to renal dialysis or kidney transplant.²

Acute vs. chronic kidney disease

Acute kidney injury (AKI) is the sudden onset of kidney dysfunction. The common causes of AKI include metastatic cancer, urinary tract obstructions, and pre-renal disease. Unlike CKD, AKI is usually reversible, which is achieved by treating the cause.

The symptoms of AKI tend to vary from CKD, although many individuals are also asymptomatic.³

In comparison, CKD develops slowly over a long time and as a result of prolonged, untreated damage. The causes of CKD also involve irreversible damage to the kidneys, meaning that CKD can’t be treated. Instead, treatment involves relieving the symptoms and preventing the progression of CKD. The options for this are lifestyle changes and medication to control conditions that may make the kidneys worse. With respect to the improper functioning of the kidneys, the options are dialysis or transplant.⁴

Causes of chronic kidney disease

The causes of chronic kidney disease are usually long-term conditions that haven’t been well controlled and therefore put a strain on the kidneys, causing damage to nephrons.

Diabetes

• Approximately 33% of individuals with diabetes have CKD,
• Both type 1 and type 2 can cause CKD.⁵

Individuals with diabetes tend to have excessive glucose in their blood. As the blood flows through the glomerulus, excessive glucose causes damage to the tiny blood vessels over time. The damage means that blood isn’t properly filtered before entering the tubule. This causes improper functioning of the kidneys, and over time causes diabetic nephropathy, leading to CKD. 

High blood pressure

• High blood pressure is the second leading cause of CKD in the US.
• Approximately 20% of adults in the US with high blood pressure may have CKD.⁶

Also known as hypertension, high blood pressure is the increased force of blood flowing through the blood vessels around the body. High blood pressure can cause CKD if the hypertension is unmanaged for a long period of time. This is because, during hypertension, blood vessels can become narrowed or constricted which in turn damages the vessels around the body including the kidneys. If arteries near the kidneys become damaged, they are unable to provide a good blood supply to the kidney tissue.

The glomerulus can become damaged with hypertension, causing improper filtering of the blood.⁷ 

High cholesterol

Having high cholesterol can result in the deposition of excess fatty deposits in the blood vessels. The build-up of fat in the vessels can cause a decreased blood flow to the kidneys, causing improper functioning. Similar to the above causes, over a prolonged period of time, this can cause significant damage to the kidneys.^8,9

Severe kidney damage

Although an unlikely complication, severe kidney damage can result in CKD if left untreated for prolonged periods of time. The severe damage tends to be a result of acute infections, such as pyelonephritis, or immune dysfunction conditions, such as AIDS.

Pyelonephritis 

Kidney infections occur as a result of bladder infections, typically cystitis. The bad bacteria, usually E. coli, enters through the urethra and travels up front there to the bladder. Bladder infections normally clear up themselves, but occasionally the bad bacteria can go up the urinary tract to the kidneys.

Once it reaches the kidneys, it’s known as acute pyelonephritis. When treated in time with antibiotics, the kidney infection tends to clear up without significant damage. However, when it isn’t, permanent kidney damage can happen.¹⁰ 

long-term and permanent kidney damage is known as chronic pyelonephritis - this rare complication can result in CKD. 

Although extremely rare, complications of CKD due to chronic sepsis can lead to sepsis: the bacteria in the kidneys can enter the bloodstream during the filtering process and spread throughout the body.¹¹ 

Immune dysfunction

Infections and conditions that affect the immune system (e.g. HIV) increase the risk of CKD.¹² Using the example of HIV: the virus can cause CKD by infecting the cells in the kidneys, causing improper functioning of nephrons within the kidneys.¹³ 

Summary

Chronic kidney disease (CKD) is an irreversible condition in which the kidneys become damaged and are unable to function correctly. This condition tends to not exhibit any symptoms until it has progressed significantly. During its later stages, symptoms may include weight loss, oedema, and loss of appetite. 

In comparison to CKD, acute chronic injury is sudden onset and reversible.

The causes of CKD are usually long-term conditions that are not well managed, causing improper functioning in the kidneys. Examples include diabetes, hypertension, and severe kidney damage.