American Kidney Fund
Email Sign Up | Sign In | HelpLine | AKF Store

Blog | En Español | Partners | Newsroom | About Us | Contact Us
 text size Text Size OneText Size TwoText Size Three

The Kidney Disease Dictionary

Do you need to know the definition of a kidney disease term?  Simply click on the first letter of the word and we’ll provide the answer! 

A  B  C  D  E  F  G  H  I  K  L  M  N  O  P  R  S  T  U  V  W


ACE (Angiotensin-Converting Enzyme) Inhibitor:  A medicine used to treat high blood pressure.  ACE inhibitors keep the body from making the hormone angiotensin.  Often, ACE inhibitors are used to slow kidney damage.  See our page about high blood pressure for more information.

Acute:  Urgent.  An acute disease happens suddenly and lasts only a short time.  This is the opposite of chronic, or on-going.

Acute Renal Failure:  When the kidneys suddenly stop working.  This can be caused by many health problems.  In these cases, kidneys can sometimes recover from almost complete loss of function.

ATN (Acute Tubular Necrosis):  A severe type of acute renal failure.  It develops in people with severe infections or blood pressure that is too low.  Patients may need dialysis until kidney function improves.  Kidney function often improves if the cause of the disease is successfully treated.

Albumin:  A type of protein.  If too much albumin is found in the urine (called albuminuria), it may be an early sign of kidney disease.

Albuminuria:  More than normal amounts of a protein called albumin in the urine.  Albuminuria may be a sign of kidney disease or other health issues.

Allograft:  An organ or tissue transplant from one person to another.

Alport Syndrome:  An inherited condition that causes kidney disease.  It usually appears during childhood.  It is more serious in boys than in girls.  The condition can lead to end stage renal disease (ESRD), hearing and vision problems.  Symptoms may include chronic blood and protein in the urine.

Amyloidosis:  A condition in which certain types of protein build up in one or more organs.  This material cannot be broken down.  It interferes with the normal function of that organ.  In kidneys, amyloidosis can lead to proteinuria, nephrotic syndrome and end stage renal disease (ESRD).

Analgesic-Associated Kidney Disease:  Loss of kidney function from long-term use of analgesic (pain-relieving) medicines.  Analgesics that combine aspirin and acetaminophen are most dangerous to the kidneys. 

Anemia:  Not having enough red blood cells.  Healthy red blood cells carry oxygen to all parts of the body.  When there are not enough red blood cells, not enough oxygen reaches the body’s organs and tissues.  People with anemia may be tired and pale or may feel their heartbeat change.  Anemia is common in people with chronic kidney disease (CKD) or those on dialysis.  Also see erythropoietin.

ADH (Antidiuretic Hormone):  A natural chemical in the body that slows urine flow.  Some children who wet their beds regularly may not have enough antidiuretic hormone.

Anuria:  When the body stops making urine.

ARB (Angiotensin II Receptor Blocker/Inhibitor):  A medicine used to treat high blood pressure.  ARBs work by keeping the body from using the hormone angiotensin, which raises blood pressure.  Often, ARBs are used to help slow kidney damage.  See our page about high blood pressure for more information.

AV (Arteriovenous) Fistula:  Surgical connection of an artery and a vein, usually in the forearm.  This is created in patients who will need hemodialysis, so that the vein will grow thicker to allow for repeated needle sticks.  In most hemodialysis patients, this is the best option.

Autoimmune Disease:  Any disorder in which part of the body is attacked by its own immune system.  Examples include Goodpasture’s syndrome and lupus nephritis.

Return to top of page


Berger’s Disease:  See IgA Nephropathy.

Biopsy:  A medical procedure where a small piece of body tissue is removed and examined under a microscope.  For example, the tissue removed could be from a kidney or the bladder.

Bladder:  The balloon-shaped organ inside the pelvis that holds urine.

Blood Pressure:  The force that blood puts on arteries and veins as it flows through them.  A blood pressure reading should give both a systolic pressure and a diastolic pressure.  See our page about high blood pressure for more information.

BUN (Blood Urea Nitrogen):  A waste in the blood that comes from the breakdown of protein.  When the kidneys work normally, they filter blood to remove the urea.  As kidney function decreases, the BUN level increases.

Return to top of page


Calcium:  A mineral that the body needs for strong bones and teeth.  It can be found in dairy products (like milk, cheese or yogurt) and some vegetables, or it can be taken as a supplement. 

Calcium Stone:  The most common type of kidney stone.  See also calcium, oxalate and kidney stoneSee our page about kidney stones for more information.

Cholesterol:  A fatty, waxy substance.  This comes from some foods and is made in the body.  Cholesterol is needed to digest foods and make certain hormones.  Too much cholesterol can clog blood vessels.

Chronic:  Long-lasting.  Chronic diseases develop slowly. 

CKD (Chronic Kidney Disease):  Slow and progressive loss of kidney function over several years, often resulting in end stage renal disease (ESRD).  People with ESRD need dialysis or a transplant to take over the work of their failing kidneys.  Also called chronic renal failure.

Creatinine:  A waste from meat protein in the diet and muscle use.  Creatinine is removed from the blood by healthy kidneys, and leaves the body in urine.  When kidneys do not work correctly, creatinine levels in the blood increase.

Creatinine Clearance:  A test that measures how well the kidneys remove creatinine and other wastes from the blood.  Low creatinine clearance may mean kidney damage.

CT (Computerized Tomography) Scan:  A kind of moving X-ray that creates pictures of the kidneys.  Also called CAT (Computerized Axial Tomography) Scan.

Cyst:  An abnormal sac filled with gas, fluid or a more solid material.  Cysts may form in kidneys or in other parts of the body.  See also simple cyst.

Cystine:  An amino acid found in blood and urine.  Amino acids are building blocks of protein.  See also cystine stone and cystinuria.

Cystine Stone:  A rare type of kidney stone made of the amino acid cystine.  See our page about kidney stones for more information.

Cystinuria:  A condition where urine contains high levels of the amino acid cystine.  If cystine does not dissolve in the urine, it can build up and form kidney stones.

Cystitis:  Inflammation (irritation) of the bladder, causing pain and a burning feeling in the pelvis or urethra.

Cystoscope:  A tool for looking at the bladder in a procedure called cystoscopy.

Return to top of page


Diabetes Insipidus:  A condition where a person has frequent and heavy urination, excessive thirst, and an overall feeling of weakness.  This condition may be caused by a problem in the pituitary gland or kidney.  In diabetes insipidus, blood sugar levels are normal.  See also nephrogenic diabetes insipidus.

Diabetes Mellitus:  A condition when a person has high blood sugar.  This is from a lack of working insulin, a hormone used to turn glucose (sugar) into a form your body can use.  See our page about diabetes for more information

Dialysate:  A liquid used to clean waste from the blood in the two major kinds of dialysis.

Dialysis:  The process of cleaning wastes from the blood artificially.  This job is normally done by the kidneys.  If the kidneys fail, the blood must be cleaned artificially with special equipment.  The two major forms of dialysis are hemodialysis and peritoneal dialysis

Dialyzer:  A part of the hemodialysis machine.  The dialyzer has two sections that are separated by a membrane.  One section holds dialysate, and the other section holds the patient’s blood.

Diastolic Pressure:  The force that blood puts on arteries and veins when the heart is relaxed (between heartbeats).  This is the bottom number of a blood pressure reading.  See our page about high blood pressure for more information.

Diuretic:  A medicine or chemical that causes a person’s body to make more urine.  Also called a “water pill.”

Dominant Gene:  A gene that causes one trait to overpower others.  For example, brown hair comes from a dominant gene.  If a person inherits a brown hair gene from one parent and a blonde hair gene from another parent, his or her hair will be brown because that is the dominant gene.

Dwell Time:  In peritoneal dialysis, the amount of time that dialysate stays in the patient’s abdominal cavity during each exchange. 

Return to top of page


Edema:  Swelling caused by too much fluid in the body.  In kidney patients, this often occurs at the ankles, feet, hands and around the eyes.

Electrolytes:  Chemicals in the body that result from the breakdown of sodium, potassium, magnesium and chloride.  Healthy kidneys control the amount of electrolytes in the body.  When kidneys fail, electrolyte levels get out of balance.  This can cause serious health problems. 

Enzymes:  Special chemicals in the body that are made of proteins.  Enzymes help control important jobs in the body.

ESRD (End Stage Renal Disease):  Total chronic kidney failure.  When the kidneys fail, the body retains fluids and harmful wastes.  A person with ESRD needs dialysis or a kidney transplant to take over the work of the failed kidneys.  See our page about end stage renal disease for more information.

Erythropoietin:  A hormone made by the kidneys to help form red blood cells.  Lack of this hormone may lead to anemia

eGFR (estimated Glomerular Filtration Rate):  A measure of how well the kidneys are working.  An eGFR is based on a person's creatinine level, age, sex and race.  See our eGFR page for more information.

Exchange:  A cycle in peritoneal dialysis when dialysate fills the abdominal cavity, stays there for a certain dwell time and empties to prepare for another cycle.

ESWL (Extracorporeal Shockwave Lithotripsy):  A non-surgical procedure that uses shockwaves to break kidney stones into smaller pieces.  See our page about kidney stones for more information.

Return to top of page


Fistula:  See AV (arteriovenous) fistula.

Return to top of page


GFR (Glomerular Filtration Rate):  See eGFR (estimated Glomerular Filtration Rate).

Glomeruli:  Plural of glomerulus.

Glomerulonephritis:  Inflammation of the glomeruli.  Most often, it is caused by an autoimmune disease, but it can also be caused by infection.

Glomerulosclerosis:  Scarring of the glomeruli.  It may result from diabetes mellitus (called diabetic glomerulosclerosis) or from deposits in parts of the glomerulus (called focal segmental glomerulosclerosis).  The most common signs of glomerulosclerosis are proteinuria and kidney failure.

Glomerulus:  A tiny set of looping blood vessels in the nephron, the part of the kidney where blood is filtered.

Goodpasture’s Syndrome:  An uncommon autoimmune disease that usually results in bleeding from the lungs and coughing up blood.  It can also cause inflammation (irritation) of the kidneys, which may lead to kidney failure.

Return to top of page


Hematocrit:  A measure that tells how many red blood cells are present in a blood sample.  Low hematocrit suggests anemia or massive blood loss.

Hematuria:  Blood in the urine, which can be a sign of a kidney stone, glomerulonephritis or other kidney problem.  See our page about blood in your urine for more information.

Hemodialysis:  A way to clean wastes and extra fluid from the blood using a machine.  This helps to replace the work of the kidneys after they have failed.  Hemodialysis is the most common kind of dialysis.  See our page about hemodialysis for more information.

Hemoglobin A1C:  A blood test that looks at a person’s blood sugar levels for the past 2 to 3 months.  This is often used to track the blood sugar of people with diabetes mellitusSee our page on diabetes for more information.

HUS (Hemolytic Uremic Syndrome):  A disease that destroys red blood cells and the lining of blood vessels.  HUS is often caused by a bacteria called Escherichia coli (E. coli) in contaminated food.  People with HUS may get acute renal failure or lose the ability for blood to clot.

Hormone:  A natural chemical produced by a part of the body and released into the bloodstream.  Hormones trigger or regulate specific body functions.  The kidneys release some hormones, including erythropoietin and an active form of vitamin D that helps manage calcium for bones.

Hydronephrosis:  Swelling of the top of the ureter.  It is usually because something is blocking the urine from flowing into the bladder.

Hypercalciuria:  Too much calcium in the urine.

Hyperoxaluria:  Too much of a chemical called oxalate in the urine.  This can lead to kidney stones

Hypertension:  High blood pressure.  This can be caused by too much fluid in the blood vessels or by narrowing of the blood vessels.  Hypertension is the second leading cause of kidney failure.  It can also be caused by kidney disease.  See our page about high blood pressure for more information.

Return to top of page


IgA Nephropathy:  A kidney disorder caused by deposits of the protein immunoglobulin A (IgA) inside the glomeruli.  IgA protein damages the glomeruli, which may lead to blood and protein in the urine, swelling in the hands and feet or kidney failure.  Also called Berger’s Disease.

Immune system:  A series of defenses that the body uses to protect itself against viruses, bacteria and other “foreign” bodies.

Immunosuppressant:  A drug that prevents the body’s immune system from working as it normally would.  Immunosuppressants are given to transplant patients to prevent the new organ from being rejected and to patients with autoimmune diseases.

Insulin:  A hormone that turns the sugars we eat into energy.  Diabetes mellitus happens when insulin does not work right.

Interstitial Nephritis:  Inflammation (irritation) of the cells that are between the filtering units in the kidneys.  This can lead to either acute renal failure or end stage renal disease (ESRD).

IVP (Intravenous Pyelogram):  An x-ray of the urinary tract.  Dye is injected to make the kidneys, ureters, bladder and any blockages in the urinary tract visible on the image.

Return to top of page


Kidney Cancer:  Abnormal cells that grow out of control in one or both kidneys.  Over time, these cancer cells crowd out the healthy cells and damage the kidneys.  This causes the kidneys to fail and may spread to other parts of the body.

Kidneys:  Bean-shaped organs that filter wastes and extra fluid from the blood.  People usually have two, and they are located on either side of the spine, just under the ribcage.  The waste and fluid filtered by the kidneys is called urine and is delivered to the bladder through the ureters

Kidney Stone:  A small, hard crystal that forms from certain chemicals that build up on the surfaces of the kidney, renal pelvis or uretersSee our page about kidney stones for more information.

Kt/V:  A way to measure how well dialysis is working.  It looks at how well the dialyzer works, treatment time and total volume of urea in the body.  See also Urea Reduction Rate (URR).

Return to top of page


Lipid:  A kind of substance in the body.  This includes fat, cholesterol, triglycerides, steroids, hormones and other waxy chemicals.  Lipids are an important part of the body’s cells.  Having too much of some types of lipids can be dangerous.

Lithotripsy:  A way of breaking kidney stones into smaller pieces using shock waves or other meathods.  See also electrocorporeal shockwave lithotripsy (ESWL).

Lupus Nephritis:  Inflammation (irritation) of the kidneys, caused by an autoimmune disease called systemic lupus erythematosus (eh-rih-theh-mah-TOH-sis) or “SLE”.  Lupus nephritis can cause hematuria and proteinuria or progress to end-stage renal disease (ESRD).

Return to top of page


Membrane:  A thin layer of tissue that lines a body cavity or separates two body parts.  Membranes can act as filters, allowing some things to pass through while keeping others where they are.  The membrane in a dialyzer filters waste from the blood.

Membranoproliferative Glomerulonephritis:  A disease occurring primarily in children and young adults.  Over time, inflammation caused by the disease leads to scarring of the glomeruli.  This can cause proteinuria, hematuria or chronic kidney failure.

Minimal Change Disease:  The most common type of nephrotic syndrome in children.  Doctors usually treat patients with prednisone.  Children will often out-grow minimal change disease.  See our page about childhood nephrotic syndrome for more information.

MRI (Magnetic Resonance Imaging):  A way of using radio waves to create pictures of the kidneys.  This lets doctors view inside the organs and make a diagnosis without cutting the patient.

Return to top of page


Nephrectomy:  Surgical removal of a kidney.

Nephritis:  Inflammation of the kidney.  See also glomerulonephritis and pyelonephritis.

Nephrogenic Diabetes Insipidus:  Constant thirst and frequent urination because the kidneys cannot respond correctly to the antidiuretic hormone (ADH).  This may cause increased urination.  See also diabetes insipidus.

Nephrolithiasis:  Kidney stones.  See our page on kidney stones for more information.

Nephrologist:  A doctor who treats kidney problems and high blood pressure.

Nephron:  A tiny unit in the kidney that filters waste and extra fluid from the blood.  Each kidney contains about 1 million nephrons.

Nephrotic Syndrome:  A condition where too much protein is in the urine and too little protein is in the blood.  This causes swelling.  There are two types of nephrotic syndrome:  childhood and adult.  See our pages about nephrotic syndrome for more information.

Nuclear Scan:  A test of the kidneys’ structure, blood flow and function.  The doctor injects a slightly radioactive solution into an arm vein and uses x-rays to watch how it moves through the kidneys.

Return to top of page


Oxalate:  A chemical that combines with calcium to create the most common type of kidney stone (calcium oxalate stone).

Return to top of page


Percutaneous Nephrolithotomy:  Surgical removal of kidney stones through a small incision in the patient’s back.

Peritoneal Dialysis:  A process that uses dialysate and the membrane of the patient’s abdominal cavity to clean wastes and extra fluid from the blood. 

PKD (Polycystic Kidney Disease):  An inherited disorder that causes many grape-like clusters of fluid-filled cysts to form in both kidneys over time.  These cysts destroy working kidney tissue.  PKD may lead to chronic kidney disease (CKD) and end-stage renal disease (ESRD).  See our page about polycystic kidney disease for more information.

Prednisone:  A medicine often used to treat minimal change disease and other kidney conditions.  Prednisone is from a class of medicines called corticosteroids.  Talk to your doctor about the side effects that prednisone may cause.  See our pages on childhood and adult nephrotic syndrome for more information.

Proteinuria:  Abnormally high levels of protein in the urine.  This is often a sign that the kidneys are not working correctly.  See also albuminuria.

Pyelonephritis:  Irritation of the kidneys that is caused by an infection.  The infection may have been started by a germ that traveled through the urethra, bladder and ureters from outside the body.  See also nephritis.

Return to top of page


Recessive Gene:  A gene that can “hide” behind dominant genes.  For a recessive gene to show up, a person must inherit the gene from both parents.  People may have or “carry” recessive genes, but they may not show because they also have the dominant genes.

Renal:  Of the kidneys.  A renal disease is a kidney disease.  Renal failure means that the kidneys have stopped working.

Renal Agenesis:  Being born without one or both kidneys.

Renal Cell Carcinoma:  Cancer of the kidneys.  The most successful treatment is surgical removal of all or part of the kidney (nephrectomy). 

Renal Cysts:  Abnormal fluid-filled sacs in the kidney.  They may be microscopic or quite large.  Most simple cysts do not need treatment.  See also cysts and polycystic kidney disease (PKD).

Renal Osteodystrophy:  A condition where poorly working kidneys cause bones to be weak.  Renal osteodystrophy is common among dialysis patients who have high phosphate levels or low vitamin D intake.

Renal Pelvis:  A small cavity into which urine, formed by the kidneys, is sent before it travels through the ureters to the bladder.  Also called the renal basin.

Renal Tubular Acidosis:  A problem in the kidneys that keeps them from removing acids normally.  This can lead to weak bones, kidney stones and poor growth in children. 

Renal Tubule:  A part of the nephron that leads away from the glomerulus.  This is where the wastes and fluid filtered by the glomerulus become urine.

Renal Vein Thrombosis:  Blood clots in the vein that carries blood away from the kidney.  This can be a problem for people with nephrotic syndrome.

Renin:  An enzyme made by the kidneys to help control blood pressure and the amount of fluid in the body.  See our page about high blood pressure for more information.

Return to top of page


Simple Cyst:  An abnormal, fluid-filled sac.  These may form as the kidneys age, and they usually do not need treatment.

Struvite Stone:  A type of kidney stone caused by an infection.  See our page on kidney stones for more information.

Systolic Pressure:  The force that blood puts on arteries and veins when the heart contracts (beats).  This is the top number of a blood pressure reading.  See our page about high blood pressure for more information.

Return to top of page


Transplant:  Replacement of a diseased organ with a healthy one.  A kidney transplant may come from a living donor or someone who has just died.  See our page on transplant for more information.

Triglycerides:  A kind of fat in the body.  Triglycerides can come from foods and are made in the liver.  The body stores triglycerides to have energy for later.

Return to top of page


Ultrasound:  A way of using high pitched sound waves to get pictures of the kidneys.  It does not involve cutting.  This can be used to help find a problem or guide a biopsy.

Urea:  A natural chemical made by the liver and filtered out of the blood by the kidneys.

Ureters:  A long, thin tube that connects the renal pelvis of the kidneys to the bladder.  Urine made by the kidneys travels through the ureters to the bladder.

URR (Urea Reduction Ratio):  A measure of the amount of urea removed during a dialysis treatment.  The URR is often given as a percent (%). 

Urethra:  A thin tube from the bladder to outside the body.  Urine empties from the bladder through the urethra. 

Uric Acid Stone:  A type of kidney stone often caused by eating too much red meat.  See our page about kidney stones for more information.

Urinary Tract:  The organ system of the body that filters waste and extra fluid from the blood.  The urinary tract includes the kidneys, ureters, bladder and urethra.

Return to top of page


Vasculitis:  Inflammation (irritation) of blood vessel walls.  This can cause rash and disease in multiple organs, including the kidneys. 

Vesicoureteral Reflux:  A condition that causes urine to back up into the ureters, and sometimes the kidneys.  This raises the risk of infection and can eventually cause kidney damage.

Void:  To empty the bladder; urinate.

Return to top of page


Wegener’s Granulomatosis:  An autoimmune disease that damages blood vessels.  This can cause disease in the lungs, upper respiratory tract and kidneys.


Updated on 12/18/07.

GMS Login
Donate Now
Stay Connected

Check out our blog!

Putting Your Contributions to Work

GuideStar Gold Participation    CharityWatch Top-Rated CharityCharity Navigator Better Business Bureau LogoNational Health Council Standards of Excellence
Consumers Digest Top Charity
Consumers Digest
4-Star Charity (14th consecutive year)
Charity Navigator

Stay Connected With the American Kidney Fund:

American Kidney Fund on Facebook   American Kidney Fund on Twitter   American Kidney Fund on YouTube   American Kidney Fund on YouTube   American Kidney Fund on Instagram