- Types & Causes
What are the kidneys? Where are they located?
The kidneys play key roles in body function, not only by filtering the blood and getting rid of waste products, but also by balancing the electrolyte levels in the body, controlling blood pressure, and stimulating the production of red blood cells.
The kidneys are located in the abdomen toward the back, normally one on each side of the spine. They get their blood supply through the renal arteries directly from the aorta and send blood back to the heart via the renal veins to the vena cava. (The term "renal" is derived from the Latin name for kidney.)
What do the kidneys do?
When blood flows to the kidney, sensors within specialized kidney cells regulate how much water to excrete as urine, along with what concentration of electrolytes. For example, if a person is dehydrated from exercise or an illness, the kidneys will hold onto as much water as possible and the urine becomes very concentrated. When adequate water is present in the body, the urine is much more dilute, and the urine becomes clear. This system is controlled by renin, a hormone produced in the kidney that is part of the fluid and blood pressure regulation systems of the body.
Kidneys are also the source of erythropoietin in the body, a hormone that stimulates the bone marrow to make red blood cells. Special cells in the kidney monitor the oxygen concentration in the blood. If oxygen levels fall, erythropoietin levels rise and the body starts to manufacture more red blood cells.
Urine that is made by each kidney flows through the ureter, a tube that connects the kidney to the bladder. Urine is stored within the bladder, and when urination occurs, the bladder empties urine through a tube called the urethra.
What are the types and causes of kidney failure?
Acute kidney failure (AKF)
In acute kidney failure, the kidneys lose their function suddenly, typically within a few hours or days, but the condition is often temporary.
Chronic kidney failure (CKF)
In the case of chronic kidney failure, damage to the kidneys occurs over years and kidney function worsens, eventually leading to permanent kidney failure.
Since most people have two kidneys, both kidneys must be damaged for complete kidney failure to occur. Fortunately, if only one kidney fails or is diseased it can be removed, and the remaining kidney may continue to have normal kidney (renal) function. If both patients' kidneys are injured or diseased, a donor kidney(s) may be transplanted.
The list of causes of kidney failure is often categorized based on where the injury has occurred.
Prerenal causes (pre=before + renal=kidney) causes are due to decreased blood supply to the kidney. Examples of prerenal causes of kidney failure include:
- Hypovolemia (low blood volume) due to blood loss
- Dehydration from loss of body fluid (for example, vomiting, diarrhea, sweating, fever)
- Poor intake of fluids
- Medication, for example, diuretics ("water pills") may cause excessive water loss
- Abnormal blood flow to and from the kidney due to obstruction of the renal artery or vein.
What causes acute kidney failure?
Renal causes of acute kidney failure (damage directly to the kidney itself) include:
Medications: Some medications are toxic to the kidney including:
- Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (Advil, Motrin, and others), and naproxen (Aleve, Naprosyn)
- Antibiotics like aminoglycosides gentamicin (Garamycin), tobramycin
- lithium (Eskalith, Lithobid)
- Iodine-containing medications such as those injected for radiology dye studies
Rhabdomyolysis: In rhabdomyolysis, there is significant muscle breakdown in the body, and the damaged muscle fibers clog the filtering system of the kidneys. Massive muscle injury may occur because of trauma, crush injuries, and burns. Some medications used to treat high cholesterol may cause rhabdomyolysis.
Acute glomerulonephritis or inflammation of the glomeruli, the filtering system of the kidneys. Many diseases can cause this inflammation including:
- Systemic lupus erythematosus
- Wegener's granulomatosis
- Goodpasture syndrome.
Hemolytic uremic syndrome: This condition results from the abnormal destruction of red blood cells. It most often occurs in children after certain infections, but also may be caused by medications, pregnancy, or can occur for unknown reasons.
Post-renal kidney failure causes
Post-renal causes of kidney failure (post=after + renal= kidney) are due to factors that affect the outflow of the urine:
- Obstruction of the bladder or the ureters can cause back pressure because the kidneys continue to produce urine, but the obstruction acts like a dam, and urine backs up into the kidneys. When the pressure increases high enough, the kidneys are damaged and shut down.
- Prostatic hypertrophy or prostate cancer may block the urethra and prevent the bladder from emptying.
- Tumors in the abdomen that surround and obstruct the ureters.
- Kidney stones. Usually, kidney stones affect only one kidney and do not cause kidney failure. However, if there is only one kidney present, a kidney stone may cause the remaining kidney to fail.
What are the causes of chronic kidney failure?
Chronic renal failure develops over months and years. The most common causes of chronic renal failure are related to the following:
Less common causes of chronic renal failure include:
- Polycystic kidney disease
- Reflux nephropathy (damage caused by urine backflow from the bladder into the ureters and kidney)
- Nephrotic syndrome
- Alport's disease
- Interstitial nephritis
- Kidney stones
- Prostate disease
What are the symptoms of kidney failure?
Initially, kidney failure may not produce any symptoms (asymptomatic). As kidney function decreases, the symptoms are related to the inability to regulate water and electrolyte balances, clear waste products from the body, and promote red blood cell production.
If unrecognized or untreated, the following symptoms of kidney failure may develop into life-threatening circumstances:
- Shortness of breath
- Generalized swelling (edema)
- Generalized weakness due to anemia
- Loss of appetite
- Congestive heart failure
- Metabolic acidosis
- High blood potassium (hyperkalemia)
- Fatal heart rhythm disturbances (arrhythmias) including ventricular tachycardia and ventricular fibrillation
- Rising urea levels in the blood (uremia) may lead to brain encephalopathy, pericarditis (inflammation of the heart lining), or low calcium blood levels (hypocalcemia)
Does kidney failure cause pain?
Normal functioning kidneys filter amyloid (a protein) from the bloodstream. In kidney failure amyloid proteins in the blood rise, and can separate and clump together forming amyloid deposits into a variety of tissues and organs, including joints and tendons. This can result in symptoms of the following:
- Joint stiffness
Underlying chronic disease pain
- Pain is often a consequence of the underlying chronic disease that led to kidney failure, for example:
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What procedures and tests diagnose kidney failure?
Often, a patient is seen for another medical condition and the diagnosis of kidney failure is a consequence of the patient's disease or injury. In patients with chronic kidney disease due to diabetes, high blood pressure, or another related medical condition his or her medical care team most likely monitors kidney function as part of his or her routine long-term medical care plan.
- Diagnosis of kidney failure can be confirmed by blood tests such as:
- GFR; which measures the buildup of waste products in the blood
- Urine tests may be ordered to measure the amount of protein, detect the presence of abnormal cells, or measure the concentration of electrolytes.
- Other tests are used to diagnose the type of kidney failure such as:
- Abdominal ultrasound
- Kidney biopsy
Understanding the 5 stages of kidney failure
The five stages of kidney failure range from very mild damage (stage I) to complete kidney failure (stage V). Stages are based on declining kidney function and glomerular filtration rate (GFR) measurements, which is the rate at which kidneys filter waste from the body.
GFR is calculated based on a blood test that estimates the amount of creatinine (waste product) in the blood. A higher GFR indicates a healthy kidney, whereas a lower GFR indicates a suboptimal kidney function. A normal GFR is about 90 to 120 mL/min/1.73 m2.
Symptoms and complications increase as the stages progress.
Stage I (normal or minimal loss of kidney function)
Kidney damage is very mild with GFR 90 mL/min/1.73 m2 or above (normal values). No symptoms are present, but there might be indications of kidney damage in tests, such as the presence of protein in the urine or physical changes in kidneys on a sonogram.
Stage II (mild or moderately reduced kidney function)
Mild kidney damage with GFR between 60 and 89 mL/min/1.73 m2. The filtration rate is slightly subpar. No symptoms are present, but certain indications may be more obvious, such as protein in the urine or physical damage to the kidneys.
Stage III (moderate to severe loss of kidney function)
Kidneys do not work as efficiently as they should, and GFR is between 30 and 59 mL/min/1.73 m2. Symptoms may become apparent at this stage and may include fatigue, swelling in hands and feet, back pain, frequent or infrequent urination, and high blood pressure.
Stage III kidney disease is divided into IIIA and IIIB.
- Stage IIIA (early) refers to GFR between 45 and 59 mL/min/1.73 m2.
- Stage IIIB (late) refers to GFR between 30 and 44 mL/min/1.73 m2.
Stage IV (severely reduced kidney function)
Kidneys are severely damaged with GFR between 15 and 29 mL/min/1.73 m2. This is the last stage before complete kidney failure. Symptoms such as fatigue, swelling, and back pain, may worsen and cause health complications such as anemia, high blood pressure, and bone disease.
Stage V (kidney failure or end-stage renal disease or ESRD)
Kidneys are close to or in complete failure with GFR less than 15 mL/min/1.73 m2. Symptoms of kidney failure become evident and include loss of appetite, vomiting and nausea, muscle cramps, swelling in hands and feet, back pain, urinating more or less than normal, trouble sleeping, breathing trouble, and itchy skin. Patients with kidney failure will need dialysis or a kidney transplant to survive.
What is the treatment for kidney failure?
Prevention is always the goal of kidney failure.
- Chronic diseases such as hypertension (high blood pressure) and diabetes are devastating because of the damage that they can do to kidneys and other organs.
- Lifelong diligence is important in keeping blood sugar and blood pressure within normal limits.
- Specific treatments depend upon the underlying diseases.
Once kidney failure is present, the goal is to prevent further deterioration of renal function. If ignored, the kidneys will progress to complete failure, but if underlying illnesses are addressed and treated aggressively, kidney function can be preserved, though not always improved.
What medications treat kidney failure?
Different classes of medications may be used to help control some of the issues associated with kidney failure including:
- Phosphorus-lowering medications, for example, calcium carbonate (Caltrate), calcitriol (Rocaltrol), and sevelamer (Renagel)
- Red blood cell production stimulation, for example, erythropoietin, darbepoetin (Aranesp)
- Red blood cell production (iron supplements)
- Blood pressure medications
Once the kidneys fail, the treatment options are limited to dialysis or kidney replacement by transplantation.
Is there a diet for kidney failure? What foods should be avoided?
Diet is an important consideration for those with impaired kidney function. Consultation with dietitians may be helpful to understand what foods may or may not be appropriate.
In this state of impaired kidney function, the kidneys cannot easily remove excess water, salt, or potassium from the blood, so foods high in potassium salt substitutes may need to be consumed in limited quantities. Examples of potassium-rich foods include:
- Sweet potatoes
Phosphorus is a forgotten chemical that is associated with calcium metabolism and may be elevated in the body in kidney failure. Too much phosphorus can leech calcium from the bones and cause osteoporosis and fractures. Examples of foods and beverages high in phosphorus include:
- Dark cola drinks
- Canned iced teas
- Organ meats
- Baked beans
- Black beans
- Kidney beans
- Bran cereals
- Whole grain products
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What are dialysis and hemodialysis?
Dialysis cleanses the body of waste products by body by use of filter systems. There are two types of dialysis:
- Peritoneal dialysis
Hemodialysis uses a machine filter called a dialyzer or artificial kidney to remove excess water and salt, balance the other electrolytes in the body, and remove waste products of metabolism. Blood is removed from the body and flows through tubing into the machine, where it passes next to a filter membrane. A specialized chemical solution (dialysate) flows on the other side of the membrane. The dialysate is formulated to draw impurities from the blood through the filter membrane. Blood and dialysate are never touched in the artificial kidney machine.
For this type of dialysis, access to the blood vessels needs to be surgically created so that large amounts of blood can flow into the machine and back to the body. Surgeons can build a fistula, a connection between a large artery and vein in the body, usually in the arm, that allows a large amount of blood to flow into the vein. This makes the vein swell or dilate, and its walls become thicker so that it can tolerate repeated needle sticks to attach tubing from the body to the machine. Since it takes many weeks or months for a fistula to mature enough to be used, significant planning is required if hemodialysis is to be considered as an option.
If kidney failure happens acutely and there is no time to build a fistula, special catheters may be inserted into the larger blood vessels of the arm, leg, or chest. These catheters may be left in place for weeks. In some diseases, the need for dialysis will be temporary, but if the expectation is that dialysis will continue for a prolonged period, these catheters act as a bridge until a fistula can be planned, placed, and matured.
Dialysis treatments normally occur three times a week and last a few hours at a time. Most commonly, patients travel to an outpatient center to have dialysis, but home dialysis therapy is becoming an option for some.
Outpatient dialysis is available on some cruise ships. They are equipped with dialysis machines with trained healthcare professionals ready to care for those with kidney failure while traveling.
What is peritoneal dialysis?
Peritoneal dialysis uses the lining of the abdominal cavity as the dialysis filter to rid the body of waste and to balance electrolyte levels. A catheter is placed in the abdominal cavity through the abdominal wall by a surgeon, and it is expected to remain in place for the long term. The dialysis solution is then dripped in through the catheter and left in the abdominal cavity for a few hours after which, it is drained out. During that time, waste products leech from the blood flowing through the lining of the abdomen (peritoneum) and attach themselves to the fluid that has been instilled by the catheters. Often, patients instill the dialysate fluid before bedtime and drain it in the morning.
There are benefits and complications for each type of dialysis. Not every patient can choose which type he or she would prefer. The treatment decision depends on the patient's illness and their past medical history along with other issues. Usually, the nephrologist (kidney specialist) will have a long discussion with the patient and family to decide what will be the best option available.
Dialysis is lifesaving. Without it, patients whose kidneys no longer function would die relatively quickly due to electrolyte abnormalities and the buildup of toxins in the bloodstream. Patients may live many years with dialysis but other underlying and associated illnesses often are the cause of death.
Is a kidney transplant an option?
If kidney failure occurs and is non-reversible, kidney transplantation is an alternative option to dialysis. If the patient is an appropriate candidate, the healthcare professional and nephrologist will contact an organ transplant center to arrange an evaluation to see whether the patient is suitable for this treatment. If so, the search for a donor begins. Sometimes, family members have compatible tissue types and, if they are willing, may donate a kidney. Otherwise, the patient will be placed on the organ transplant list that is maintained by the United Network of Organ Sharing.
Not all hospitals are capable of performing kidney transplants. The patient may have to travel to undergo their operation. The most successful programs are those that do many transplants every year.
While kidney transplants have become routine, they still carry some risks. The patient will need to take anti-rejection medications that reduce the ability of the immune system to fight infection. The body can try to reject the kidney or the transplanted kidney may fail to work. As with any operation, there is a risk of bleeding and infection.
Kidney transplants may provide a better quality of life than dialysis. After one year, 95% of transplanted kidneys are still functioning and after five years, the number is 80%. It seems that the longer a patient is on dialysis, the shorter the life of the transplanted kidney.
If the transplanted kidney fails, the alternative is another kidney transplant or a return to dialysis.
What is the prognosis and life expectancy for kidney failure?
The outlook for kidney failure depends upon the underlying condition that caused it. Kidney function may return to normal, especially if it is due to an acute obstruction and that obstruction is relieved. Other causes of decreased kidney function leading to kidney failure are due to underlying disease and occur slowly over time.
Prevention is the best chance to maintain kidney function, and controlling high blood pressure and diabetes over a lifetime can decrease the potential for progressive kidney damage. Chronic kidney failure may be managed to help monitor electrolyte and waste product levels in the bloodstream. Major abnormalities can be life-threatening, and treatment options may be limited to dialysis or transplant.
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Workeneh, BT, MD. "Acute Kidney Injury." Medscape..
Medscape Medical Reference
National Kidney Foundation https://www.kidney.org/atoz/content/understanding-your-lab-values
American Kidney Fund. Kidney Failure (ESRD) Causes, Symptoms, & Treatments. https://www.kidneyfund.org/kidney-disease/kidney-failure/
Arora P. Chronic Kidney Disease (CKD). Medscape. https://emedicine.medscape.com/article/238798-overview
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