Pathophysiology of Kidney Failure

by JI KEON LOOI

Acute Kidney Failure
http://www.mayoclinic.com/health/kidney-failure/DS00280
Acute kidney failure is the sudden loss of your kidneys' ability to perform their main function — eliminate excess fluid and waste material from your blood. When your kidneys lose their filtering ability, dangerous levels of fluid and waste accumulate in your body.
Acute kidney failure is most common in people who are already hospitalized, particularly people who need intensive care. Acute kidney failure tends to occur after complicated surgery, after a severe injury or when blood flow to your kidneys is disrupted.
Loss of kidney function may also develop gradually over time, with few signs or symptoms in the early stages. In this case, it's referred to as chronic kidney failure. High blood pressure and diabetes are the most common causes of chronic kidney failure.
Acute kidney failure can be serious and generally requires intensive treatment. Unlike the chronic form, however, acute kidney failure is reversible and if you're otherwise in good health you should recover normal kidney function within a few weeks. If acute kidney failure occurs in the context of severe chronic illness — a heart attack, stroke, overwhelming infection or multiorgan failure — the outcome is often worse.
Prerenal
Prerenal problems are among the most common causes of acute kidney failure. Examples of problems that may leave your kidneys with an insufficient blood supply to function properly include:
§ Extremely low blood pressure. Severe bleeding, infection in the bloodstream (sepsis), dehydration or shock can all lead to a drastic drop in blood pressure that prevents an adequate amount of blood from reaching your kidneys. These conditions tend to occur after a traumatic injury or as a risk of major surgery.
§ Poor heart function. If your heart isn't functioning at full capacity, such as during a heart attack or with congestive heart failure, the result can be reduced blood flow to your kidneys.
§ Low blood volume. Severe dehydration — which can be brought on by prolonged vomiting or diarrhea, heatstroke or major burns — results in excessive loss of fluid, diminishing the volume of blood in your body and the amount available to your kidneys.
RenalConditions that may affect the structure and function of the kidney itself, potentially leading to acute kidney failure, include:
§ Disorders that reduce blood supply in your kidneys. Any number of disorders can lead to decreased blood supply in your kidneys, which can lead to organ damage and acute kidney failure. One example is atheroembolic kidney disease.
Atheroembolic kidney disease can occur when masses of cholesterol and cellular debris (plaques) accumulate in arteries and harden in a process called atherosclerosis. If a plaque is injured or disturbed — cardiac catheterization, a procedure used to conduct diagnostic tests and treatments on the heart, is a common cause — pieces of it may break off into your bloodstream and move throughout your body. These moving pieces are called emboli. When these emboli move to your kidneys, the cholesterol emboli accumulate in small blood vessels (arterioles). Within the arterioles, these emboli can produce severe inflammation, leading to decreased blood supply and acute kidney failure.

Other causes of reduced blood supply include a blood disorder called idiopathic thrombocytopenic purpura, development of blood clots in kidney vessels, a reaction to a blood transfusion, or a sudden onset of severe high blood pressure (malignant hypertension).
§ Hemolytic uremic syndrome. This condition, which is associated with certain strains of Escherichia coli (E. coli) bacteria, is a leading cause of acute kidney failure in infants and young children. The bacterium causes inflammation of the intestine. It also produces a toxin that causes damage and swelling in the lining of blood vessels, especially the small blood vessels (glomerular capillaries) in the kidneys. As red blood cells travel through the damaged blood vessels, they're often broken apart (hemolysis). This complex condition may result in acute kidney failure.
§ Inflammation in the kidneys. Acute kidney failure may result from sudden inflammation of the spaces between the glomeruli and the tubules (acute interstitial nephritis) and inflammation of the glomeruli (acute glomerulonephritis). Acute interstitial nephritis is usually associated with an allergic reaction to a drug. Examples include certain antibiotics — especially streptomycin or gentamicin — and common pain medications, such as aspirin and ibuprofen (Advil, Motrin, others). Antibiotics pose a greater risk of acute kidney failure for people who already have liver or kidney disease or who use diuretics or other drugs that affect your kidneys.
Acute glomerulonephritis may be associated with immune diseases, such as lupus or IgA nephropathy (Berger's disease). It may also follow an infection in another part of your body, such as strep throat, infection of a heart valve (endocarditis), typhoid fever, syphilis and malaria. Viruses that cause AIDS, mononucleosis, mumps, measles or hepatitis also may trigger glomerulonephritis.
§ Toxic injury. Because the main purpose of your kidneys is to filter toxins from your body, your kidneys are particularly vulnerable to toxic injury. Exposure to toxic substances — such as excessive amounts of alcohol, cocaine, heavy metals, solvents and fuels — can induce acute kidney failure. Certain drugs also have the potential to injure the tubules in your kidneys, including chemotherapy drugs and contrast dyes used in medical tests, such as arteriography. Contrast dyes are a common cause of acute renal failure, especially in people with diabetic kidney disease or multiple myeloma, a type of cancer.
PostrenalPostrenal causes of acute kidney failure are generally related to obstruction of the flow of urine out of your kidneys on the way out of your body. This may occur at the level of the tubes that lead from your kidneys to your bladder (ureters), or at the bladder level (urethral obstruction).
§ Ureter obstruction. Kidney stones in both ureters (or in a single ureter if only one kidney is functioning) or tumors pushing in on the ureters can cause obstruction at this level.
§ Bladder obstruction. In the bladder, the most common cause of obstruction in men is an enlarged prostate, which causes obstruction at the bladder outlet. Other obstructive bladder causes, in both men and women, include a bladder stone, blood clot, tumor or a nerve disorder that prevents the bladder from contracting properly
Chronic Renal Failure
slowly progressive loss of renal function over a period of months or years and defined as an abnormally low glomerular filtration rate, which is usually determined indirectly by the creatinine level in blood serum.
§ Diabetes. Diabetes mellitus is a leading cause of chronic kidney failure in the United States. Chronic kidney failure is related to both type 1 and type 2 diabetes.
§ High blood pressure (hypertension). Untreated or inadequately treated high blood pressure is another common cause of chronic kidney failure in the United States. The added force of elevated blood pressure exerted on the glomeruli can cause damage and scarring. When this happens, the nephrons containing the damaged glomeruli eventually lose their ability to filter waste from your blood.
§ Obstructive nephropathy. This occurs when urine outflow is blocked over time by an enlarged prostate, kidney stones or tumors, or by vesicoureteral reflux, a condition that results from urine backing up into your kidneys from your bladder. The backflow pressure in your kidneys reduces their function.
§ Kidney diseases. These include clusters of cysts in the kidneys (polycystic kidney disease), kidney infection (pyelonephritis) and inflammation of the glomeruli (glomerulonephritis), a condition that causes your kidneys to leak protein into your urine and damages nephrons.
§ Kidney (renal) artery stenosis. This is a narrowing or blockage of the kidney artery before it enters your kidney. In older adults, blockages often result when fatty deposits accumulate under the lining of the artery walls (atherosclerosis). Kidney artery stenosis can also affect young women in the form of a condition known as fibromuscular dysplasia, which causes the walls of the arteries to become thicker. Both conditions are often associated with high blood pressure.
§ Toxins. Ongoing exposure to fuels and solvents, such as carbon tetrachloride, and lead — in lead-based paint, lead pipes, soldering materials, jewelry and even alcohol distilled in old car radiators — can lead to chronic kidney failure.

http://www.mayoclinic.com/health/kidney-failure/DS00682/DSECTION=1
http://en.wikipedia.org/wiki/Chronic_renal_failure