I know there have been lots of questions and as you know I hate to answer many of them, so this should answer all of your questions.
Normal Kidneys and Their Function
The kidneys are a pair of bean-shaped organs that lie on either side of the spine in the lower middle of the back. Each kidney weighs about ¼ pound and contains approximately one million filtering units called nephrons. Each nephron is made of a glomerulus and a tubule. The glomerulus is a miniature filtering or sieving device while the tubule is a tiny tube like structure attached to the glomerulus.The kidneys are connected to the urinary bladder by tubes called ureters. Urine is stored in the urinary bladder until the bladder is emptied by urinating. The bladder is connected to the outside of the body by another tube like structure called the urethra.
The main function of the kidneys is to remove waste products and excess water from the blood. The kidneys process about 200 liters of blood every day and produce about two liters of urine. The waste products are generated from normal metabolic processes including the breakdown of active tissues, ingested foods, and other substances. The kidneys allow consumption of a variety of foods, drugs, vitamins and supplements, additives, and excess fluids without worry that toxic by-products will build up to harmful levels. The kidney also plays a major role in regulating levels of various minerals such as calcium, sodium, and potassium in the blood.
- As the first step in filtration, blood is delivered into the glomeruli by microscopic leaky blood vessels called capillaries. Here, blood is filtered of waste products and fluid while red blood cells, proteins, and large molecules are retained in the capillaries. In addition to wastes, some useful substances are also filtered out. The filtrate collects in a sac called Bowman's capsule.
- The tubules are the next step in the filtration process. The tubules are lined with highly functional cells which process the filtrate, reabsorbing water and chemicals useful to the body while secreting some additional waste products into the tubule.
- Active form of vitamin D (calcitriol or 1,25 dihydroxy-vitamin D), which regulates absorption of calcium and phosphorus from foods, promoting formation of strong bone.
- Erythropoietin (EPO), which stimulates the bone marrow to produce red blood cells.
- Renin, which regulates blood volume and blood pressure.
Chronic kidney disease occurs when one suffers from gradual and usually permanent loss of kidney function over time. This happens gradually, usually months to years. Chronic kidney disease is divided into five stages of increasing severity (see Table 1 below). The term "renal" refers to the kidney, so another name for kidney failure is "renal failure." Mild kidney disease is often called renal insufficiency.
With loss of kidney function, there is an accumulation of water; waste; and toxic substances, in the body, that are normally excreted by the kidney. Loss of kidney function also causes other problems such as anemia, high blood pressure, acidosis (excessive acidity of body fluids), disorders of cholesterol and fatty acids, and bone disease.
Stage 5 chronic kidney disease is also referred to as kidney failure, end-stage kidney disease, or end-stage renal disease, wherein there is total or near-total loss of kidney function. There is dangerous accumulation of water, waste, and toxic substances, and most individuals in this stage of kidney disease need dialysis or transplantation to stay alive.
Unlike chronic kidney disease, acute kidney failure develops rapidly, over days or weeks.
- Acute kidney failure usually develops in response to a disorder that directly affects the kidney, its blood supply, or urine flow from it.
- Acute kidney failure is often reversible, with complete recovery of kidney function.
- Some patients are left with residual damage and can have a progressive decline in kidney function in the future.
- Others may develop irreversible kidney failure after an acute injury and remain dialysis-dependent.
| Stage | Description | GFR* mL/min/1.73m2 |
| 1 | Slight kidney damage with normal or increased filtration | More than 90 |
| 2 | Mild decrease in kidney function | 60-89 |
| 3 | Moderate decrease in kidney function | 30-59 |
| 4 | Severe decrease in kidney function | 15-29 |
| 5 | Kidney failure | Less than 15 (or dialysis) |
Chronic Kidney Disease Causes
Although chronic kidney disease sometimes results from primary diseases of the kidneys themselves, the major causes are diabetes and high blood pressure.- Type 1 and type 2 diabetes mellitus cause a condition calleddiabetic nephropathy, which is the leading cause of kidney disease in the United States.
- High blood pressure (hypertension), if not controlled, can damage the kidneys over time.
- Glomerulonephritis is the inflammation and damage of the filtration system of the kidneys, which can cause kidney failure. Postinfectious conditions and lupus are among the many causes of glomerulonephritis.
- Polycystic kidney disease is an example of a hereditary cause of chronic kidney disease wherein both kidneys have multiple cysts.
- Use of analgesics such as acetaminophen (Tylenol) and ibuprofen (Motrin, Advil) regularly over long durations of time can cause analgesic nephropathy, another cause of kidney disease. Certain other medications can also damage the kidneys.
- Clogging and hardening of the arteries (atherosclerosis) leading to the kidneys causes a condition called ischemic nephropathy, which is another cause of progressive kidney damage.
- Obstruction of the flow of urine by stones, an enlarged prostate, strictures (narrowings), or cancers may also cause kidney disease.
- Other causes of chronic kidney disease include HIV infection, sickle cell disease, heroin abuse, amyloidosis, kidney stones, chronic kidney infections, and certain cancers.
- Diabetes mellitus type 1 or 2
- High blood pressure
- High cholesterol
- Heart disease
- Liver disease
- Amyloidosis
- Sickle cell disease
- Systemic Lupus erythematosus
- Vascular diseases such as arteritis, vasculitis, or fibromuscular dysplasia
- Vesicoureteral reflux (a urinary tract problem in which urine travels the wrong way back toward the kidney)
- Require regular use of anti-inflammatory medications
- A family history of kidney disease
How Common is Chronic Kidney Disease?
- Chronic kidney disease is a growing health problem in the United States. A report by the Centers for Disease Control (CDC) determined that 16.8% of all adults above the age of 20 years have chronic kidney disease. Thus, one in six individuals has kidney disease. By disease stage, the prevalence is as follows:
- stage 1, 3.1%;
- stage 2, 4.1%;
- stage 3, 7.6%;
- stage 4; and
- stage 5, 0.5%.
- stage 1, 3.1%;
- There are over 500,000 persons on dialysis or who have received kidney transplants.
- The prevalence of chronic kidney disease has increased by 16% from the previous decade. The increasing incidence of diabetes mellitus, hypertension (high blood pressure), obesity, and an aging population have contributed to this increase in kidney disease.
- Chronic kidney disease is more prevalent among individuals above 60 years of age (39.4%).
- Kidney disease is more common among Hispanic, African American, Asian or Pacific Islander, and Native American people.
Chronic Kidney Disease Symptoms
The kidneys are remarkable in their ability to compensate for problems in their function. That is why chronic kidney disease may progress without symptoms for a long time until only very minimal kidney function is left.Because the kidneys perform so many functions for the body, kidney disease can affect the body in a large number of different ways. Symptoms vary greatly. Several different body systems may be affected. Notably, most patients have no decrease in urine output even with very advanced chronic kidney disease.
Effects and symptoms of chronic kidney disease include;
- need to urinate frequently, especially at night (nocturia);
- swelling of the legs and puffiness around the eyes (fluid retention);
- high blood pressure;
- fatigue and weakness (from anemia or accumulation of waste products in the body);
- loss of appetite, nausea and vomiting;
- itching, easy bruising, and pale skin (from anemia);
- shortness of breath from fluid accumulation in the lungs;
- headaches, numbness in the feet or hands (peripheral neuropathy), disturbed sleep, altered mental status (encephalopathy from the accumulation of waste products or uremic poisons), andrestless legs syndrome;
- chest pain due to pericarditis (inflammation around the heart);
- bleeding (due to poor blood clotting);
- bone pain and fractures; and
- decreased sexual interest anderectile dysfunction.
When to Seek Medical Care
Several signs and symptoms may suggest complications of chronic kidney disease. Call your health care practitioner if you notice any of the following symptoms:- Change in energy level or strength
- Increased water retention (puffiness or swelling) in the legs, around the eyes, or in other parts of the body
- Shortness of breath or change from normal breathing
- Nausea or vomiting
- Lightheadedness
- Severe bone or joint pain
- Easy bruising
- Itching
See your health care practitioner as recommended for monitoring and treatment of chronic conditions such as diabetes, high blood pressure, and high cholesterol.
The following signs and symptoms represent the possibility of a severe complication of chronic kidney disease and warrant a visit to the nearest hospital emergency department.
- Change in level of consciousness - extreme sleepiness or difficult to awaken
- Fainting
- Chest pain
- Difficulty breathing
- Severe nausea and vomiting
- Severe bleeding (from any source)
- Severe weakness
Chronic Kidney Disease Diagnosis
Chronic kidney disease usually causes no symptoms in its early stages. Only lab tests can detect any developing problems. Anyone at increased risk for chronic kidney disease should be routinely tested for development of this disease.- Urine, blood, and imaging tests (X-rays) are used to detect kidney disease, as well as to follow its progress.
- All of these tests have limitations. They are often used together to develop a picture of the nature and extent of the kidney disease.
- In general, this testing can be performed on an outpatient basis.
Urinalysis: Analysis of the urine affords enormous insight into the function of the kidneys. The first step in urinalysis is doing a dipstick test. The dipstick has reagents that check the urine for the presence of various normal and abnormal constituents including protein. Then, the urine is examined under a microscope to look for red and white blood cells, and the presence of casts and crystals (solids).
Only minimal quantities of albumin (protein) are present in urine normally. A positive result on a dipstick test for protein is abnormal. More sensitive than a dipstick test for protein is a laboratory estimation of the urine albumin (protein) and creatinine in the urine. The ratio of albumin (protein) and creatinine in the urine provides a good estimate of albumin (protein) excretion per day.
Twenty-four hour urine tests: This test requires you to collect all of your urine for 24 consecutive hours. The urine may be analyzed for protein and waste products (urea nitrogen, and creatinine). The presence of protein in the urine indicates kidney damage. The amount of creatinine and urea excreted in the urine can be used to calculate the level of kidney function and the glomerular filtration rate (GFR).
Glomerular filtration rate (GFR): The GFR is a standard means of expressing overall kidney function. As kidney disease progresses, GFR falls. The normal GFR is about 100-140 mL/min in men and 85-115 mL/min in women. It decreases in most people with age. The GFR may be calculated from the amount of waste products in the 24-hour urine or by using special markers administered intravenously. An estimation of the GFR (eGFR) can be calculated from the patient's routine blood tests. Patients are divided into five stages of chronic kidney disease based on their GFR (see Table 1 above).
Blood Tests
Creatinine and urea (BUN) in the blood: Blood urea nitrogen and serum creatinine are the most commonly used blood tests to screen for, and monitor renal disease. Creatinine is a product of normal muscle breakdown. Urea is the waste product of breakdown of protein. The level of these substances rises in the blood as kidney function worsens.
Estimated GFR (eGFR): The laboratory or your physician may calculate an estimated GFR using the information from your blood work. It is important to be aware of your estimated GFR and stage of chronic kidney disease. Your physician uses your stage of kidney disease to recommend additional testing and suggestions on management.
Electrolyte levels and acid-base balance: Kidney dysfunction causes imbalances in electrolytes, especially potassium, phosphorus, and calcium. High potassium (hyperkalemia) is a particular concern. The acid-base balance of the blood is usually disrupted as well.
Decreased production of the active form of vitamin D can cause low levels of calcium in the blood. Inability to excrete phosphorus by failing kidneys causes its levels in the blood to rise. Testicular or ovarian hormone levels may also be abnormal.
Blood cell counts: Because kidney disease disrupts blood cell production and shortens the survival of red cells, the red blood cell count and hemoglobin may be low (anemia). Some patients may also have iron deficiency due to blood loss in their gastrointestinal system. Other nutritional deficiencies may also impair the production of red cells.
Other tests
Ultrasound:Ultrasound is often used in the diagnosis of kidney disease. An ultrasound is a noninvasive type of imaging test. In general, kidneys are shrunken in size in chronic kidney disease, although they may be normal or even large in size in cases caused by adult polycystic kidney disease, diabetic nephropathy, and amyloidosis. Ultrasound may also be used to diagnose the presence of urinary obstruction, kidney stones and also to assess the blood flow into the kidneys.
Biopsy: A sample of the kidney tissue (biopsy) is sometimes required in cases in which the cause of the kidney disease is unclear. Usually, a biopsy can be collected with local anesthesia by introducing a needle through the skin into the kidney. This is usually done as an outpatient procedure, though some institutions may require an overnight hospital stay.
Chronic Kidney Disease Treatment
Self-Care at Home
Chronic kidney disease is a disease that must be managed in close consultation with your health care practitioner. Self-treatment is not appropriate.- There are, however, several important dietary rules you can follow to help slow the progression of your kidney disease and decrease the likelihood of complications.
- This is a complex process and must be individualized, generally with the help of your health care practitioner and a registered dietitian.
- Protein restriction: Decreasing protein intake may slow the progression of chronic kidney disease. A dietitian can help you determine the appropriate amount of protein for you.
- Salt restriction: Limit to 4-6 grams a day to avoid fluid retention and help control high blood pressure.
- Fluid intake: Excessive water intake does not help prevent kidney disease. In fact, your doctor may recommend restriction of water intake.
- Potassium restriction: This is necessary in advanced kidney disease because the kidneys are unable to remove potassium. High levels of potassium can cause abnormal heart rhythms. Examples of foods high in potassium include bananas, oranges, nuts, and potatoes.
- Phosphorus restriction: Decreasing phosphorus intake is recommended to protect bones. Eggs, beans, cola drinks, and dairy products are examples of foods high in phosphorus.
- carefully follow prescribed regimens to control your blood pressure and/or diabetes;
- stop smoking; and
- lose excess weight.
- Certain analgesics: Aspirin; nonsteroidal antiinflammatory drugs (NSAIDs, such as ibuprofen [Motrin, for example])
- Fleets or phosphosoda enemas because of their high content of phosphorus
- Laxatives and antacids containing magnesium and aluminum such asmagnesium hydroxide (Milk of Magnesia) and famotidine (Mylanta)
- Ulcer medication H2-receptor antagonists: cimetidine (Tagamet), ranitidine (Zantac), (decreased dosage with kidney disease)
- Decongestants such as pseudoephedrine (Sudafed) especially if you have high blood pressure
- Alka Seltzer, since this contains large amounts of salt
- Herbal medications
Medical Treatment
There is no cure for chronic kidney disease. The four goals of therapy are to:- slow the progression of disease;
- treat underlying causes and contributing factors;
- treat complications of disease; and
- replace lost kidney function.
- Control of blood glucose: Maintaining good control of diabetes is critical. People with diabetes who do not control their blood glucose have a much higher risk of all complications of diabetes, including chronic kidney disease.
- Control of high blood pressure: This also slows progression of chronic kidney disease. It is recommended to keep your blood pressure below 130/80 mm Hg if you have kidney disease. It is often useful to monitor blood pressure at home. Blood pressure medications known as angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARB) have special benefit in protecting the kidneys.
- Diet: Diet control is essential to slowing progression of chronic kidney disease and should be done in close consultation with your health care practitioner and a dietitian. For some general guidelines, see the Self-Care at Home section of this article.
- Fluid retention can be treated with any of a number of diuretic medications, which remove excess water from the body. However, these drugs are not suitable for all patients.
- Anemia can be treated with erythropoiesis stimulating agents such as erythropoietin ordarbepoetin (Aranesp, Aranesp Albumin Free, Aranesp SureClick). Erythropoiesis stimulating agents are a group of drugs that replace the deficiency of erythropoietin, which is normally produced by healthy kidneys. Often, patients treated with such drugs require iron supplements by mouth or sometimes even intravenously.
- Bone disease develops in kidney disease due to an inability to excrete phosphorus and a failure to form activated Vitamin D. In such circumstances, your physician may prescribe drugs binding phosphorus in the gut, and may prescribe active forms of vitamin D.
- Acidosis may develop with kidney disease. The acidosis may cause breakdown of proteins, inflammation, and bone disease. If the acidosis is significant, your doctor may use drugs such as sodium bicarbonate (baking soda) to correct the problem.
Renal Replacement Therapies
In end-stage kidney disease, kidney functions can be replaced only by dialysis or by kidney transplantation. The planning for dialysis and transplantation is usually started in Stage 4 of chronic kidney disease. Most patients are candidates for both hemodialysis and peritoneal dialysis (see below). There are few differences in outcomes between the two procedures. Your physician or an educator will discuss the appropriate options with you and help you make a decision that will match your personal and medical needs. It is best to choose your modality of dialysis after understanding both procedures and matching them to your lifestyle, daily activities, schedule, distance from the dialysis unit, support system, and personal preference.Your doctor will consider multiple factors when recommending the appropriate point to start dialysis, including your laboratory work and your actual or estimated glomerular filtration rate, nutritional status, fluid volume status, the presence of symptoms compatible with advanced kidney failure, and risk of future complications. Dialysis is usually started before individuals are very symptomatic or at risk for life-threatening complications.
Dialysis
There are two types of dialysis 1) hemodialysis (in-center or home) and 2) peritoneal dialysis. Before dialysis can be initiated, a dialysis access has to be created.Dialysis Access
A vascular access is required for hemodialysis so that blood can be moved though the dialysis filter at rapid speeds to allow clearing of the wastes, toxins, and excess fluid. There are three different types of vascular accesses: arteriovenous fistula (AVF), arteriovenous graft, and central venous catheters.
- Arteriovenous fistula (AVF): The preferred access for hemodialysis is an AVF, wherein an artery is directly joined to a vein. The vein takes two to four months to enlarge and mature before it can be used for dialysis. Once matured, two needles are placed into the vein for dialysis. One needle is used to draw blood and run through the dialysis machine. The second needle is to return the cleansed blood. AVFs are less likely to get infected or develop clots than any other types of dialysis access.
- Arteriovenous graft: An arteriovenous graft is placed in those who have small veins or in whom a fistula has failed to develop. The graft is made of artificial material and the dialysis needles are inserted into the graft directly.
- Central venous catheter: A catheter may be either temporary or permanent. These catheters are either placed in the neck or the groin into a large blood vessel. While these catheters provide an immediate access for dialysis, they are prone to infection and may also cause blood vessels to clot or narrow.
Hemodialysis
Hemodialysis involves circulation of blood through a filter or dialyzer on a dialysis machine.- The dialyzer has two fluid compartments and is configured with bundles of hollow fiber capillary tubes.
- Blood in the first compartment is pumped along one side of a semipermeable membrane, while dialysate (the fluid that is used to cleanse the blood) is pumped along the other side, in a separate compartment, in the opposite direction.
- Concentration gradients of substances between blood and dialysate lead to desired changes in the blood composition, such as a reduction in waste products (urea nitrogen and creatinine); a correction of acid levels; and equilibration of various mineral levels.
- Excess water is also removed.
- The blood is then returned to the body.
Some centers may offer the option of nocturnal (night-time) hemodialysis wherein the therapy is delivered while you sleep. Long nocturnal dialysis offers patients a better survival and an improvement in their quality of life.
Home hemodialysis is possible in some situations. A care partner is needed to assist you with the dialysis treatments. A family member or close friend are the usual options, though occasionally people may hire a professional to assist with dialysis. Home hemodialysis may be performed as traditional three times a week treatments, long nocturnal (overnight) hemodialysis, or short daily hemodialysis. Daily hemodialysis and long nocturnal hemodialysis offer advantages in quality of life and better control of high blood pressure, anemia, and bone disease.
Peritoneal dialysis
Peritoneal dialysis utilizes the lining membrane (peritoneum) of the abdomen as a filter to clean blood and remove excess fluid. Peritoneal dialysis may be performed manually (continuous ambulatory peritoneal dialysis) or by using a machine to perform the dialysis at night (automated peritoneal dialysis).
- About 2 to 3 liters of dialysis fluid are infused into the abdominal cavity through the access catheter. This fluid contains substances that pull wastes and excess water out of neighboring tissues.
- The fluid is allowed to dwell for two to several hours before being drained, taking the unwanted wastes and water with it.
- The fluid typically needs to be exchanged four to five times a day.
- Peritoneal dialysis offers much more freedom compared to hemodialysis since patients do not need to come to a dialysis center for their treatment. You can carry out many of your usual activities while undergoing this treatment. This may be the preferable therapy for children.
Kidney Transplantation
Kidney transplantation offers the best outcomes and the best quality of life. Successful kidney transplants occur every day in the United States. Transplanted kidneys may come from living related donors, living unrelated donors, or people who have died of other causes (cadaveric donors). In people with type I diabetes, a combined kidney-pancreas transplant is often a better option.However, not everyone is a candidate for a kidney transplant. People need to undergo extensive testing to ensure their suitability for transplantation. Also, there is a shortage of organs for transplantation, requiring waiting times of months to years before getting a transplant.
A person who needs a kidney transplant undergoes several tests to identify characteristics of his or her immune system. The recipient can accept only a kidney that comes from a donor who matches certain of his or her immunologic characteristics. The more similar the donor is in these characteristics, the greater the chance of long-term success of the transplant. Transplants from a living related donor generally have the best results.
Transplant surgery is a major procedure and generally requires four to seven days in the hospital. All transplant recipients require lifelong immunosuppressant medications to prevent their bodies from rejecting the new kidney. Immunosuppressant medications require careful monitoring of blood levels and increase the risk of infection as well as some types of cancer.
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