Kidney Failure | Information and Doctor Search

Doctors refer to this condition as chronic kidney disease (CKD) or chronic kidney failure. This should be distinguished from the sudden loss of kidney function, which is known as acute kidney failure (AKF). Kidney insufficiency or kidney weakness leads to a range of complications and symptoms. Without treatment, these ultimately result in death when kidney function is completely lost.

People with end-stage renal insufficiency always require dialysis and can only improve their quality of life in the long term through a kidney transplant (kidney donation). But what exactly are the kidneys’ main functions? Can they do more than just produce urine?

Absolutely—the kidneys’ most important functions in the body:

• Excretion of waste products—often toxic—or medications
• Regulation of water balance
• Regulation of electrolyte balance (homeostasis)
• Regulation of acid-base balance
• Production of hormones (e.g., erythropoietin, renin)
• Participation in vitamin D metabolism
• Regulation of blood pressure

The kidneys serve as a vital filtration station within the human circulatory system. Blood is supplied to the kidneys via the renal artery. Inside the kidney, this artery branches into increasingly smaller blood vessels, which eventually form a capillary tuft. These smallest blood vessels, with the smallest diameter, are called glomeruli, which means “tuft” in Latin.

Each kidney has more than one million such glomeruli in its so-called renal cortex. The glomeruli, in turn, are surrounded by very fine urinary tubules. Blood is filtered from the vessels through the thin capillary wall of the glomeruli. It enters the tubules as what is known as primary urine. This process produces up to 180 liters of primary urine every day! However, only 1 to 1.5 liters are excreted daily. But what happens to the rest of the filtered primary urine?

The answer to this mystery is reabsorption. In the tubule structures connected to the glomeruli, final urine is formed from the primary urine through a series of steps. This final urine ultimately flows out of the body via the ureters, bladder, and urethra. The original 180 liters of primary urine are concentrated to approximately two liters of urine per day through the reabsorption of minerals and water.

If the kidneys are not functioning properly, it is not just urine production that is affected. Rather, the effects of renal insufficiency manifest in a variety of other organs. Edema can develop due to the body’s inability to excrete water. This most commonly occurs in the legs, the abdominal cavity, and the lungs.

In addition, people with chronic kidney failure often suffer from high blood pressure (hypertension). Atherosclerosis poses a particular risk for kidney failure. If the body’s blood vessels become increasingly narrowed by plaque buildup, this can also lead to high blood pressure. It can also cause damage to the fine renal capillaries in the glomeruli. Very often, atherosclerosis also leads to coronary heart disease. 

As renal insufficiency develops, the body can no longer adequately excrete waste products and toxins. As a result, it slowly poisons itself. In chronic kidney failure, this process eventually leads to damage to the brain, individual nerves, and muscle tissue.

In addition, the immune system is overwhelmed by the toxins and functions at a significantly reduced capacity. The concentration of substances excreted in the urine can be regulated by adjusting one’s diet. As a result, people with kidney failure are often much more susceptible to illness. Kidney insufficiency alone can lead to a lack of red blood cells, known as anemia.

Anemia is also typical in dialysis patients. These are patients who are already in a very advanced stage of renal insufficiency. Anemia develops because a diseased kidney produces less erythropoietin, a hormone that stimulates the production of red blood cells (erythrocytes).

Renal insufficiency indicates a slow loss of kidney function. The term “insufficiency” means that the kidneys are no longer performing their function adequately; in short, the kidneys are no longer functioning effectively. The term “chronic,” in turn, means that the destruction of kidney tissue continues to progress over the course of years.

The causes of chronic kidney failure include

• diabetes mellitus,
• kidney infections,
• high blood pressure (hypertension), and
• long-term misuse of painkillers.

Chronic kidney failure develops slowly and progresses through various stages, which allow doctors to classify patients.

Chronic kidney failure typically develops slowly through five stages, which are distinguished based on the severity of the disease. As the stage number increases, chronic kidney insufficiency becomes more advanced.

The classification of stages is not arbitrary but is based on a laboratory value measured in patients, known as the glomerular filtration rate (GFR). The GFR indicates how well the kidneys are able to excrete waste products and toxic substances.

If the excretion of these substances is no longer sufficient, waste products accumulate in the blood. Since these often act as toxins, they increasingly impair the functions of other organs in the body. But what exactly are waste products? Examples of waste products include:

• creatinine from muscle metabolism,
• urea, the end product of protein metabolism, and
• uric acid, which is an end product of cellular metabolism.

Chronic kidney insufficiency, or chronic kidney failure, essentially develops according to the following stages:
Compensated stage: When filtration capacity is first mildly impaired, the blood creatinine level remains normal at first.

• Compensated retention: The creatinine level in the blood rises slowly. However, the patient still does not experience any symptoms.
• Pre-terminal renal insufficiency: The creatinine level continues to rise. In addition, the first typical symptoms of renal insufficiency appear. These include nausea, vomiting, decreased energy, fatigue, loss of appetite, itching, difficulty concentrating, shortness of breath, paresthesia, and cramps.
• End-stage renal failure: Creatinine levels rise dramatically as a result of kidney failure. The blood becomes increasingly acidic because chemically acidic substances are no longer excreted by the kidneys. All typical symptoms of late-stage renal failure now appear. These include very shallow breathing (also known as Kussmaul breathing), dropping blood pressure, and possibly symptoms of shock. Without dialysis, the affected patient will inevitably die at this stage of the disease.

The normal GFR value for creatinine is between 95 and 110 ml per minute. A healthy kidney therefore clears at least 95 ml of blood of creatinine per minute, which can then be excreted in the urine. If this value is significantly lower, the creatinine level in the patient’s blood also rises.

Measuring the GFR is vitally important. It allows for the early diagnosis of kidney failure and the initiation of treatment or therapy. If only the creatinine level in the blood were measured, it would take much longer to detect that the kidneys were not functioning properly. Specifically, the five stages of kidney failure are defined as follows:

Stage 1: Blood values within the normal range

The GFR is still greater than 90 ml/min.
This value indicates that the kidneys are still functioning normally. Initially, blood levels of substances normally excreted in the urine are still within the normal range. In some cases, protein is already being excreted in the urine at the onset of kidney failure. In Stage 1, the goal is to determine why the kidneys are no longer functioning fully.

If the underlying cause of the disease is ultimately treated, further deterioration can still be prevented at this stage of kidney failure. The diagnosis of kidney failure at this early stage is often merely an incidental finding, as the patients do not yet exhibit any symptoms. 

Stage 2: First minor signs of kidney failure

The GFR ranges between 60 and 89 ml/min.
Even in Stage 2, kidney failure is not always easy to diagnose. A blood test can provide initial clues. The kidneys are still functioning adequately. However, a more detailed nephrological examination quickly reveals deficits in the GFR.

High blood pressure and diabetes are the two conditions that can regularly lead to kidney damage. Prompt treatment or management of these conditions is important to halt the progression of kidney insufficiency. Particular attention should also be paid to diet, especially in cases of diabetes.

Stage 3: Kidney damage is detectable

The GFR drops to 30 to 59 ml/min.
Kidney damage has progressed further, and elevated creatinine and urea levels are found in the blood. Symptoms of kidney failure begin to appear: Affected individuals suffer from high blood pressure (hypertension), reduced energy levels, and fatigue. These symptoms are usually still far too nonspecific to alert the patient to a kidney problem.

At this stage, the risk of cardiovascular disease is also significantly increased. Medications that are normally excreted by the kidneys must be administered at lower doses to avoid causing side effects. 

Stage 4: Progressive Kidney Failure

The GFR drops to 15 to 29 ml/min.
Kidney failure continues to progress, and at the same time, symptoms worsen: Patients suffer from loss of appetite, vomiting, nausea, nerve pain, itching, and often bone pain as well. The body excretes less salt and water. This leads to water retention in the tissues. Edema develops, for example, in the legs or face.

In Stage 4, the damage to the kidney cells is already very extensive. The entire body is affected by the inadequate excretion of waste products. However, the symptoms of kidney failure are not caused solely by the accumulation of toxins. Rather, impaired kidney function is accompanied by the loss of important hormones and minerals.

One cause of fatigue, for example, is a shortage of red blood cells. In addition to its role as a filtration system, the kidney produces hormones and signaling molecules. Erythropoietin (EPO), which has also often been used as a performance-enhancing drug in sports, stimulates the production of red blood cells. Without it, less vital oxygen reaches the body’s cells, causing their performance to decline.

By stage 3 at the latest, a nephrologist must be involved in the treatment. Kidney failure can be slowed through medication and changes in diet and fluid intake. Special attention should be paid to protein intake in the diet. However, as soon as medication is discontinued, or if infections affect these organs, kidney failure continues to progress. 

Stage 5: Dialysis Required

The GFR drops below 15 ml/min.

If kidney function eventually ceases completely, the nephrologist refers to this as end-stage renal failure. This corresponds to stage 5 renal failure. Prompt intervention is then absolutely necessary, as the body will otherwise rapidly become poisoned by its own waste products. Various methods are available to filter substances that must be excreted in the urine:

• Blood filtration (hemodialysis)
• Peritoneal dialysis
• Kidney transplant

In general, there are far too few donor kidneys available for the many dialysis patients. Long wait times for a life-saving kidney transplant are therefore unavoidable. Alternatively, a kidney transplant can be planned even before stage 5 if a living donor from within the family is a suitable candidate.

Despite dialysis being performed up to once a day, end-stage renal disease has an impact on the body. This can lead to yellowing of the skin or increased itching. Both are caused by the accumulation of urinary substances in the skin. In addition, there are other problems associated with end-stage renal failure, such as:

• severe restrictions on daily fluid intake
• Fluctuations in blood pressure
• muscle cramps
• Sensory disturbances or cardiac arrhythmias

This shows that even regular dialysis cannot completely replace kidney function. On the other hand, without dialysis, people with end-stage renal failure cannot survive under any circumstances.

People with chronic kidney failure have a significantly increased risk of stroke. In addition, they also have a poorer prognosis after a stroke compared to healthy individuals.

Overall, chronic kidney disease is about twice as common today as it was ten years ago. In industrialized nations, the prevalence of chronic kidney disease ranges between 10 and 20 percent. Among patients aged 70 and older, it reaches nearly 40 percent. This high prevalence also affects stroke rates. For example, the risk of stroke triples when the glomerular filtration rate (GFR) is less than 30 ml/min. In people requiring dialysis, it increases sixfold.

Even after surviving a stroke, people with chronic kidney disease fare worse: Two years later, on average, up to 15% of patients without kidney failure have died, but over 40% of those with chronic kidney disease have died. Among patients requiring hemodialysis, the mortality rate was as high as 60%.

Among stroke patients with end-stage renal insufficiency, up to three-quarters have died after two years. Among those not on dialysis, the figure is slightly more than half. In contrast, the two-year mortality rate for people with healthy kidneys is only about 30%. These findings are confirmed by a registry analysis of over 132,000 patients with atrial fibrillation (AF): This study showed that individuals with renal insufficiency had a significantly higher risk of thrombotic strokes, as well as of bleeding.