What are the kidneys?
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.)
The kidneys have the ability to monitor the amount of body fluid, the concentrations of electrolytes like sodium and potassium, and the acid-base balance of the body. They filter waste products of body metabolism, like urea from protein metabolism and uric acid from DNA breakdown. Two waste products in the blood usually are measured; 1) blood urea nitrogen (BUN), and 2) creatinine (Cr).
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 from 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 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
Kidney failure facts
- Kidneys are the organs that help filter waste products from the blood. They are also involved in regulating blood pressure, electrolyte balance, and red blood cell production in the body.
- Symptoms of kidney failure are due to the build-up of waste products in the body that may cause weakness, shortness of breath, lethargy, and confusion. Inability to remove potassium from the bloodstream may lead to abnormal heart rhythms and sudden death. Initially kidney failure may cause no symptoms.
- There are numerous causes of kidney failure, and treatment of the underlying disease may be the first step in correcting the kidney abnormality.
- Some causes of kidney failure are treatable and the kidney function may return to normal. Unfortunately, kidney failure may be progressive in other situations and may be irreversible.
- The diagnosis of kidney failure usually is made by blood tests measuring BUN, creatinine, and glomerular filtration rate (GFR).
- Treatment of the underlying cause of kidney failure may return kidney function to normal. Lifelong efforts to control blood pressure and diabetes may be the best way to prevent chronic kidney disease and its progression to kidney failure. As we age kidney function gradually decreases over time.
- If the kidneys fail completely, the only treatment options available may be dialysis or transplant.
Kidney failure can be divided into acute kidney failure and chronic kidney failure, and their causes are different.
What can cause patients to have acute kidney failure?
Acute kidney failure means patient’s kidney function toboggans in a short period, and its causes can be mainly divided into three categories.
A major cause of acute kidney failure is prerenal axotemia, which means the blood flow into kidney reduces, but renal parenchyma has not been damaged. Acute intrarenal failure is another category of acute kidney failure, and it is often caused by toxication and renal ischemia. The third acute kidney failure is acute postrenal failure, because patients have bilateral urine flow obstruction.
What are the causes of chronic kidney failure?
While chronic kidney failure is a progressive process, and it needs a long time for patients to have kidney failure and it also needs a long period for patients to lose their kidney function completely.
In fact, chronic kidney failure can also be caused by many factors, like genetic factors, autoimmune disorders, hypertension, diabetes, toxins, bacteria, infection, medicine, etc.
For example, PKD is a typical kidney disease that is caused by genetic factor. Lupus nephritis and purpura nephritis is caused by autoimmune disorder. Diabetic nephropathy and hypertensive nephropathy are the most common reasons of kidney disease.
The treatment of kidney failure. If your kidneys fail, you will need dialysis or kidney transplant to take over their job.
What are the signs and symptoms of kidney failure?
Initially, kidney failure may be 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)
How is kidney failure diagnosed?
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; the patient’s medical care team most likely monitors kidney function as part of the patient’s routine long-term medical care plan.
Diagnosis of kidney failure can be confirmed by blood tests such as BUN, creatinine, and GFR; that measure 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
Diet is an important consideration for those with impaired kidney function. Consultation with a dietician 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 meets
- Baked beans
- Black beans
- Kidney beans
- Soy beans
- Bran cereals
- Whole grain products
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 completely, the treatment options are limited to dialysis or kidney replacement by transplantation.
Dialysis and Hemodialysis
Dialysis cleanses the body of waste products in the body by use of filter systems. There are two types of dialysis; 1) hemodialysis, and 2) peritoneal dialysis.
Hemodialysis uses a machine filter called a dialyzer or artificial kidney to remove excess water and salt, to balance the other electrolytes in the body, and to 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 never touch 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 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 the 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 of time, 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 health care professionals ready to care for those with kidney failure while traveling.