How Kidney disease silently damages the body before symptoms appear

Many people may be living with damaged kidneys without knowing it, as chronic kidney disease can develop silently for years before symptoms such as swollen feet, persistent fatigue and difficulty breathing begin to appear. Dr Zebunissa Bagha says diabetes and high blood pressure are the leading causes, warning that patients may only discover the condition after their kidney function has already declined considerably.

Dr Bagha, a General Practitioner and Chief of Medical Services at Myer Kidney Health and Speciality Hospital, explained that chronic kidney disease is a progressive condition in which the kidneys gradually lose their ability to filter waste products and excess fluids from the blood.

Speaking on Radio Generation on Thursday, she said the condition is characterised by a decline in kidney function lasting at least three months, distinguishing it from acute kidney injury, which develops over a shorter period.

"To say that we're dealing with chronic kidney disease means we have an acute version of the same, right? So acute is obviously over a shorter period of time, and chronic is over a longer period of time. In most medical contexts, when we say chronic, it's mostly like three months or more," Dr Bagha explained.

She identified diabetes and high blood pressure as the biggest contributors to kidney disease worldwide, noting that both conditions can gradually damage the organs and interfere with their ability to filter blood.

"The biggest drivers that cause kidney issues all over are actually diabetes and high blood pressure. I think those are the biggest drivers, and this cuts across the world," she said.

Other causes include polycystic kidney disease, prostate enlargement in men and certain cancers in women.

Polycystic kidney disease is an inherited condition in which multiple fluid-filled cysts develop in the kidneys. As the cysts increase, they alter the structure of the organs and interfere with their ability to function normally.

"Remember, if you change the structure of the kidney, you are essentially inhibiting its ability to function well," Dr Bagha explained.

In men, an enlarged prostate can block the normal flow of urine, causing pressure to build up and potentially damaging the kidneys. In women, certain cancers, including cervical cancer, can also cause obstructions that interfere with normal kidney function.

The doctor explained that the kidneys perform several essential functions beyond producing urine. The two fist-sized organs, located towards the back of the abdomen on either side of the spine, each weigh approximately 150 grams.

Their primary role is to remove waste products and excess fluids from the blood before eliminating them through urine. They also help regulate blood pressure, maintain electrolyte levels such as sodium and potassium, control calcium and phosphate levels, and support the activation of vitamin D.

Additionally, the kidneys produce erythropoietin, a hormone that stimulates the production of red blood cells.

Dr Bagha said each kidney contains millions of tiny filtering units known as nephrons, which separate waste products from essential substances that the body needs to retain.

Each kidney can have approximately 1.5 million nephrons, with their number largely determined before birth. However, once these filtering units are damaged, they cannot regenerate.

"The thing about them is that once they're damaged, they don't grow back. So when you have an acute injury to the kidney, say malaria or dehydration, because it is acute, you go to the hospital in time, it can affect the kidneys.

"But because you go to the hospital in time, it's caught early. You'll be able to repair whatever is there, but you'll not be able to regenerate," she explained.

The kidneys can initially compensate for damaged filtering units by increasing the workload of those that remain functional. This allows patients to continue with their normal activities even as kidney damage progresses, making the condition difficult to detect in its early stages.

However, as more nephrons become damaged, the remaining filtering units eventually struggle to meet the body's needs.

Dr Bagha noted that patients may lose a considerable amount of kidney function before experiencing any noticeable changes in their health.

"By the time you're getting symptoms, most of the time, especially with kidney disease, it's a little later in the stages."

As the condition advances, patients may develop persistent fatigue, swelling of the feet and difficulty breathing due to fluid accumulating in the lungs. Some may also experience ascites, a condition in which fluid builds up in the abdomen.

Another possible complication is anaemia, which occurs when the body does not have enough red blood cells. Since damaged kidneys may produce insufficient amounts of erythropoietin, patients can develop low red blood cell levels, resulting in symptoms such as dizziness and fatigue.

The accumulation of waste products, particularly urea, can also affect other organs, including the brain and heart.

"When urea is now high, it can affect the brain as well. So you can have confusion, and it can affect the heart. All this from just the kidney. It literally affects the entire body," she said.

Given that symptoms may only appear after considerable damage has occurred, Dr Bagha advised people to seek medical assessment rather than waiting for obvious physical signs.

She explained that a general practitioner is often the first point of contact for patients seeking to establish whether their kidneys are functioning properly.

Among the tests doctors may recommend is urinalysis, which examines urine for abnormalities such as protein, glucose, blood and signs of infection.

Another important investigation is the urea, electrolytes and creatinine test, commonly known as UECs. It measures waste products in the blood and checks electrolyte levels, including sodium, potassium and chloride.

Elevated levels of urea and creatinine may indicate that the kidneys are not effectively removing waste products from the blood.

Doctors may also request a urine albumin-to-creatinine ratio (UACR), which measures the amount of albumin, a type of protein, leaking into the urine.

Dr Bagha compared the kidney's filtering system to a sieve that separates waste products from substances the body needs to retain.

"Think of the kidney as a sieve that filters waste products while retaining essential substances in the blood. When the filtering units become damaged, proteins that should remain in the blood begin leaking into the urine," Dr Bagha explained.

Another important investigation is the estimated glomerular filtration rate (eGFR), which measures kidney function and helps doctors determine the stage of the disease.

Chronic kidney disease is classified into five stages, with stages one and two representing the earlier stages, while stage five indicates kidney failure.

An eGFR below 60 millilitres per minute per 1.73 square metres, when persistent for at least three months, is one of the criteria used to diagnose the condition. At stage five, an eGFR below 15 indicates severely reduced kidney function and may require kidney replacement treatment.

Although damaged kidney tissue cannot regenerate, Dr Bagha explained that early diagnosis and treatment can help slow the progression of the disease and prevent further deterioration.

Treatment in the early stages mainly focuses on controlling the underlying conditions responsible for kidney damage, particularly diabetes and high blood pressure.

Patients may require medication, regular medical monitoring and lifestyle adjustments to preserve the kidney function that remains.

However, when kidney function declines considerably, patients may need dialysis or a kidney transplant.

Dialysis is a treatment that performs some of the functions of healthy kidneys by removing waste products and excess fluids from the blood. The two main forms are haemodialysis and peritoneal dialysis.

Haemodialysis involves connecting a patient to a machine that draws blood from the body, filters it and returns the cleaned blood.

Access to the bloodstream is established through a catheter or an arteriovenous fistula, which connects an artery to a vein. The machine then removes accumulated waste and excess water that the damaged kidneys can no longer eliminate.

"Dialysis essentially works like a kidney for you outside your body. It's a machine. So basically, it works like the kidney for you because your kidney can't do what it's supposed to do. The machine mimics the kidney," she said.

Dialysis sessions generally last approximately four hours, although patients spend additional time undergoing preparation and disconnection.

Depending on their medical needs, some patients require two sessions a week, while others may need three.

However, dialysis does not cure kidney disease. Instead, it replaces some of the functions of healthy kidneys and can be used as long-term treatment or to support patients awaiting a transplant.

A kidney transplant involves replacing a failed kidney with a healthy one from a donor.

Dr Bagha also noted that people can live healthy lives with one functioning kidney, although they must undergo medical assessment and continue monitoring their kidney health.

She emphasised that early detection remains essential in managing chronic kidney disease because treatment is aimed at preserving the kidney function that remains rather than restoring filtering units that have already been permanently damaged.