Kidney Failure: What is it?

What is kidney failure?

Kidney failure is defined as a loss of the kidneys ability to correctly filter waste and toxic substances from your blood. In fact, to diagnose you with kidney failure, your kidneys must be functioning at less than 15% of normal, or they must have a decreased glomerular filtrate as we will explain later. Many people use the terms kidney failure and kidney disease as synonyms. But, in fact, kidney failure can be considered as one type of acute kidney disease or the end-stage of the chronic kidney disease.

kidney failure

Types and cause of Kidney Failure?

Regarding the installation time and resolution, it can be classified in acute and chronic kidney failure. The acute type is installed in a few days (usually two) and it is solved before 3 months, although some experts consider 3 weeks. On the contrary, the chronic type lasts more than 3 months and does not usually resolve but progresses over time.

Regarding the cause, it can be classified into acute prerenal kidney failure, acute intrinsic kidney failure, chronic intrinsic kidney failure, and chronic post-renal kidney failure. The acute prerenal type is caused by insufficient blood flow to the kidneys because if the kidneys do not receive blood, they cannot filter the waste and toxins from it. For example, a blood clot in the renal arteries, a heart attack, excessive blood loss, dehydration, a severe burn, sepsis (a severe infection), among others. Once the cause of the decreased blood flow is determined, it can be treated and the kidneys return to function properly.

The acute intrinsic failure is the result of a direct injury of the kidneys, like a direct trauma, a physical impact or an accident. However, anything that can cause damage to the kidneys can be a cause of acute intrinsic failure. For example, toxin overload (like heavy metals), excessive use of drugs and alcohol, chemotherapy drugs, contrasts used in some image tests and certain antibiotics and ischemia. The ischemia is a deficit of oxygen supply to the renal tissue, which can be caused by severe bleeding, shock, renal blood vessel obstruction by a clot and glomerulonephritis. If this condition is maintained over time, the acute pre-renal failure can evolve to chronic pre-renal kidney failure, so the kidneys’ tissues die, shrink and lose their ability to function.

The chronic intrinsic failure is caused by a long-term damage to the kidneys due to intrinsic kidney disease like polycystic kidney disease and nephrotic syndrome. However, in most cases, the cause of chronic kidney failure is not a problem of the kidney itself but other systemic disease that somehow has damaged your kidneys over time. In fact, Diabetes Mellitus is the most common cause of kidney failure, and high blood pressure (medically called hypertension) is the second one.

There are other systemic diseases that can cause kidney failure. For example, multiple myeloma, hemolytic uremic syndrome, autoimmune diseases like lupus, scleroderma, vasculitis and IgA nephropathy.

Finally, the chronic post-renal kidney failure is caused by a long-term blockage of the urinary tract that prevents urination, which increases the pressure in the kidneys and eventually leads to kidney damage. For example, kidney stones, blood clots within the urinary tract, enlarged prostate and kidney, colon, cervical, prostate and bladder cancer.

What are the Symptoms of Kidney Failure?

As kidneys have very important functions in our body, their failure can cause a wide range of symptoms such as urinating more or less than normal, face, hands, abdomen and legs swelling (edema), foamy urine (due to the presence of albumin protein in the urine), feeling tired, nausea, vomiting, loss of appetite, itching, back pain, trouble breathing and sleeping, muscles cramps and confusion (being able to cause coma in the most severe cases).

All those symptoms derive from the kidneys inability to eliminate the waste from the blood (like urea and excess potassium) and recover the nutrients, proteins (mainly albumin protein) and minerals necessary for the proper functioning of our body.

Likewise, in kidney failure there is an inability to maintain the water balance in our body, which causes blood volume overload expressed as high blood pressure. Some complications like anemia and bone disease can also appear due to the inability to produce the hormones normally produced by the kidneys.

5 stages of Kidney failure

The chronic kidney disease can be classified into 5 stages according to the degree of kidney damage. The stage 1 refers to a mild kidney damage and the stage 5 refers to a complete kidney failure. To determine the level of kidney function and, in consequence, the stage of kidney disease, the eGFR is used. The eGFR is a blood test that measures how well are your kidneys filtering the toxins and waste from your blood.

Stage 1

Mild kidney damage and eGFR greater than 90. In this stage the kidneys are working relatively well, but you might have proteins in your urine or physical damage in the kidneys.

Stage 2

It always involves a kidney damage and an eGFR between 60 and 89. You do not usually have symptoms at this stage.

Stage 3

This stage means that kidneys are moderately damaged. The eGFR is between 30 and 59. It is separated into two stages; Stage 3a between 45 and 59 and stage 3b between 30 and 44. At this stage you might have some symptoms of kidney disease.

Stage 4

At this stage kidneys are moderately or severely damaged, so they don’t work as they should. The eGFR is between 15 and 30. Most people in this stage have moderate to severe symptoms and may start to develop complications. In some cases, the nephrologist can recommend to start dialysis at this stage.

Stage 5

This is the worse stage of kidney disease, and it means that your kidneys are getting very close to failure or have completely failed, so it is also called total kidney failure. The eGFR is less than 15 and it is already necessary to resort to dialysis if it had not been started in stage 4.

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Author: Dr.Aurelysmar GrimandecollantesDr.Aurelysmar is 29 years old MD and medical writer. Medical degree from the Universidad Centroccidental "Lisandro Alvarado", Venezuela, 2014. Diploma in Occupational Health and Safety, Venezuela, 2015. Course: Specialized Health Training for Physicians, Spain, 2017.