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Educating yourself is one of the most important strategies when managing chronic kidney disease. Understanding your doctor, your nutritionist or dietician and your care team will make managing your disease easier, and ensure that you are in sync with your care strategy. There are three essential terms to understand and monitor if you have chronic kidney disease. They are explained in detail below.

Blood Urea Nitrogen (BUN)

Your doctor will conduct several blood tests to determine the level of your chronic kidney disease CKD. When you have stage 3 kidney disease, your doctor looks at white and red blood cells, your BUN and creatinine, and other enzymes that indicate overall kidney function.  Your blood urea nitrogen (BUN) level is critical. When your body metabolizes protein, it produces urea. The kidneys filter the urea from the blood into the urine.

Your doctor will run a test that measures the amount of nitrogen from urea–a BUN test. Healthy kidneys work by removing urea from the blood and preventing BUN from rising excessively. A high level of BUN is one of the symptoms indicating that the kidneys are not functioning well.  Your kidney doctor, called a nephrologist, may recommend consuming less protein. He or she will also monitor other health conditions you may have and certain medications you may take.


Creatinine is a waste product of muscle activity that is filtered out of the blood by the kidneys and passed into the urine. If the amount of creatinine in the urine decreases, while the amount in the blood increases, this may signify that your kidneys are damaged and aren’t functioning well.

BUN to creatinine ratio – Your nephrologist or doctor will use this to determine if your kidneys are functioning correctly.

Estimated Glomerular Filtration Rate eGFR

Your eGFR tells your doctor how much kidney function you have based on how well your kidneys filter waste and extra fluid out of your blood. An eGFR test is usually conducted early in the diagnosis process.  As chronic kidney disease progresses, your eGFR number decreases.   You have approximately a million glomeruli of tiny filters inside the kidneys that filter out waste. Your eGFR indicates your chronic kidney disease stage. Starting with healthy kidney function, early stages of kidney disease, mid-stage with moderate kidney damage, later and end-stage kidney failure.  The following chart defines specific stages and eGFR stages.



Estimated Glomerular Filtration Rate (eGFR)

Stage 1

Kidney damage (some protein in the urine) with normal GFR

Greater than 90

Stage 2

Kidney damage with mild decrease in GFR

60 to 89

Stage 3

Moderate decrease in kidney function

30 to 59

Stage 4

Severe kidney damage

15 to 29

Stage 5

Kidneys are close to failing or have already failed

Less than 15

We recommend asking questions! Be sure you rely on your medical team to help you fully understand any term they use.  But, in an effort to provide baseline information, we’ve compiled a glossary of terms relating to Chronic Kidney Disease (CKD):

Glossary of Terms Relating to Chronic Kidney Disease (CKD)

Acute kidney injury (AKI) or Acute renal failure (ARF)
: An abrupt reduction in kidney function with elevation of blood urea nitrogen (BUN) and plasma creatinine, often caused by an accident or illness.

Acute tubular necrosis (ATN): This is the most common cause of ARF. It can be caused by ischemia (blood vessel obstruction) post surgery, sepsis, obstetric complications or severe burns.

Anemia: A condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body’s tissues. Having anemia, also referred to as low hemoglobin, can make you feel tired and weak.

Analgesic nephropathy: A kidney disease caused from high consumption of analgesic (pain-relieving) medications.

Azotemia: A biochemical abnormality, defined as elevation, or buildup of, nitrogenous products (BUN-usually ranging 7 to 21 mg/dL), creatinine in the blood, and other secondary waste products within the body.

Bacteriuria: The presence of bacteria in the urine.

Bladder: The urinary bladder, or simply bladder, is a hollow muscular organ in humans and other vertebrates that stores urine from the kidneys before disposal.

Blood typing: A procedure performed to determine the compatibility between an organ donor and an organ recipient’s red blood cells.

Calculi: Also known as renal stones or kidney stones, a calculus (plural calculi), often called a stone, is a concretion of material, usually mineral salts, that forms in a kidney or duct of the body.

Catheter: A hollow tube used to transport fluids to or from the body.

Chronic glomerulonephritis: A group of kidney diseases characterized by long-term inflammation and scarring of the glomeruli (microscopic structures in the kidney that filter blood and produce urine). This form of kidney disease usually develops slowly (over years) and may not produce symptoms at the outset. The diseases can lead to chronic renal failure.

Colic: Acute, abdominal pain.

Complete proteins: Foods, such as meat, fish and eggs, which contain all of the protein-building materials, the essential amino acids that a body needs but cannot produce on its own.

Continuous ambulatory peritoneal dialysis (CAPD): A form of continuous peritoneal dialysis (a way to remove waste products from your blood when your kidneys can’t adequately do the job any longer). This procedure filters the blood in a different way than does the more common blood-filtering procedure called hemodialysis. in which dialysis fluid is exchanged at regular intervals throughout the day.

Continuous cycling peritoneal dialysis (CCPD): A form of continuous dialysis in which the peritoneal cavity is continuously filled with dialysis fluid by a dialysis machine.

Cystitis: An inflammation of the bladder.

Detrusor muscle: A basket weave of smooth muscle fibers that form the urinary bladder

Diabetes mellitus: A disease of the pancreas in which production of insulin is decreased (commonly called diabetes) or insufficient for the body’s needs, resulting in unhealthy levels of glucose in the blood.

Dialyzer: The part of a kidney dialysis machine which acts like an artifical kidney to filter and remove waste and fluid from the blood.

Dialysis fluid: A special fluid used in dialysis into which wastes are passed.

Dialysis: A treatment for kidney failure which removes wastes and water from the blood; a process by which small molecules pass from one fluid where they are in high concentration to another fluid where the concentration is lower, through a porous membrane.

Diuretic: Any agent that enhances the flow of urine.

Dyselectrolytemia: An imbalance of electrolytes, certain ionized salts (i.e. calcium, magnesium, potassium, and sodium) in the blood.

End-stage kidney disease (ESKD): The stage in kidney disease when treatment, such as dialysis or transplantation, becomes necessary. ” End-stage” refers to the end of kidney function.

End-stage kidney failure (ESKF): Irreversible total kidney failure.

End-stage renal disease (ESRD): See end-stage kidney disease.

Erythropoietin (EPO): A hormone made by the kidneys that signals the bone marrow to produce red blood cells.

Extracorporeal shockwave lithotripsy (ESWL): Ultrasound waves are used to break up stones in the kidney, ureter and bladder into smaller pieces that can be eliminated from the body in the urine.

Fistula: a surgically created passage used for providing access to the bloodstream during hemodialysis; it is created by connecting an artery and a vein in the arm, creating a larger, stronger vein for access during regular hemodialysis.

Glomerular capillaries: The glomerular capillaries are the barrier to the distribution of large plasma proteins into the urine. Large proteins such as albumin and IgM are impeded by the capillaries whereas smaller proteins pass through the filtration barrier into the tubular fluid.

Glomerulonephritis (GN): A condition in which the glomeruli, the tiny filters in the kidneys are damaged; often referred to as nephritis.

Hematuria: The presence of blood in your urine. The two types of hematuria are: gross hematuria—when you can see the blood in your urine; and microscopic hematuria—when you cannot see the blood in your urine, yet it is seen under a microscope.

Hemodialysis: A procedure where a dialysis machine and a special filter called an artificial kidney, or a dialyzer, are used to clean your blood. To get your blood into the dialyzer, the doctor needs to make an access, or entrance, into your blood vessels. This is done with minor surgery (to create a fistula), usually in your arm.

Hemoglobin (Hb): A protein found in the red blood cells that carries oxygen from the lungs to the body’s tissues and returns carbon dioxide from the tissues back to the lungs.

Hemorheology: The study of the blood flow properties of the cellular and plasma components, erythrocytes, of the blood and the blood vessels.

Heparin: A substance added to blood during dialysis to prevent it from clotting in the dialyzer.

Hypertension: High blood pressure. May be either the cause of, or the result of, kidney disease.

Hypoproteinemia: Very low levels of the amount of protein in the blood.

Incomplete proteins: Foods, such as fruits, vegetables and cereals, which do not contain all of the protein-building essential amino acids that your body needs.

Insulin: A hormone produced by the pancreas that regulates the level of glucose (sugar) in the blood.

Intermittent peritoneal dialysis (IPD): A form of peritoneal dialysis in which exchanges are done hourly for two or three days each week.

Internal urethral sphincter: A ring of smooth muscle at the junction of the urethra and the bladder.

Juxtaglomerular apparatus: The juxtaglomerular apparatus is a structure in the kidney that regulates the function of each nephron, the functional units of the kidney.

Kidneys: Organs in your body that play a central role in regulating water concentration, inorganic ion composition, acid-base balance, and the fluid volume of the blood volume. Kidneys balance solute and water transport, enable excretion of metabolic wastes, conserve nutrients and regulate acids and bases. The kidney also has an endocrine function by secreting the hormones renin, erythropoietin and 1,25-dihydroxyvitamin D for the regulation of blood pressure, red blood cell production and calcium metabolism.

Kilojoules: The metric measure of the energy value of food (also called calories or KCals).

Kt/V: The quotient of this fraction is used to quantify the adequacy of dialysis: K is the rate at which blood passes through the dialyzer, t is the amount of time of the session, and V is the volume of water your body contains.

Micturition: Urination

Neoplasm: Any new and abnormal growth, in particular new growth of tissue in which the growth is uncontrolled and progressive.

Nephritis: A condition in which the glomeruli, the tiny filters in the kidneys are damaged; often referred to as nephritis (see also glomerulonephritis).

Nephrolithiasis: (also known as calculi, nephrolithiasis, renal stones or kidney stones) masses of crystals and protein and are common causes of urinary tract obstruction in adults.

Nephrology: The branch of medicine that deals with the kidneys.

Nephron: Each kidney contains approximately 1 million subunits called nephrons. Each nephron contains a renal corpuscle and a tubule.  Ultimately, the fluid remaining at the end of each nephron exits the kidneys as urine.

Nephropathy: The deterioration of kidney function.

Nephrosis: The Degeneration of the renal tubular epithelium.

Nephrotic syndrome: The excretion of large amounts of protein in the urine per day.

Neurogenic bladder: A condition in which problems with the nervous system affect the bladder and urination.

Oliguria: Diminished production of urine.

Organ: A structurally distinct part of the body that usually performs a particular function. Usually made up of several types of tissue in a very organized structure, e.g. kidney, heart, lungs, liver.

Osteomalacia: Inadequate or delayed mineralization of the bone matrix in mature compact and spongy bone, referred to as a softening of the bones.

Peritoneal cavity: Abdominal cavity that contains the stomach, spleen, liver, part of the duodenum, jejunum, ileum, transverse, and sigmoid colon; lined by the peritoneum or peritoneal membrane.

Peritoneal dialysis: A treatment for kidney failure in which dialysis fluid is introduced into the peritoneal cavity to remove wastes and water from the blood

Peritoneum: The thin membrane that encloses the peritoneal cavity and surrounds the abdominal organs.

Peritonitis: Inflammation of the peritoneum.

Phosphate binder: A  medication that binds with phosphates in the intestine to reduce the absorption of phosphorus causing some of the phosphate to be excreted.

Phosphate: A mineral in your body fluids that is regulated by the kidneys. At normal levels, it keeps bones and other parts strong and healthy. At high levels, it causes itching and painful joints.

Plasma creatinine (PCr) concentration: A blood test which is directly related to GFR. When the GFR decreases, PCr increases.

Podocytes: Specialized cells located in the glomerular epithelium. These are octopus-like structures with many extensions in which fluid filters through ultimately forming urine.

Polycystic kidney disease (PKD): An inherited kidney disease that produces fluid-filled cysts in the kidneys that produce chronic renal failure over many years.

Potassium:  A mineral and an electrolyte, in your body fluids that is regulated by the kidneys. At normal levels, helps nerves, muscles and other cells work well. At high levels, may result in cardiac arrest or arrhythmias.

Purpura: A disease characterized by purple or livid spots on the skin or mucous membranes caused by blood being forced out of the blood vessels and into the surrounding tissue. Henoch-Schönlein purpura nephritis is a rare chronic kidney disease.

Pyuria: A urinary condition that is characterized by an elevated number of white blood cells in the urine. Doctors define a high number as at least 10 white blood cells per cubic millimeter (mm3) of centrifuged urine. Pyuria can cause the urine to look cloudy or as if it contains pus.

Pyelonephritis: A type of urinary tract infection that begins in the urethra or bladder and travels to the kidneys causing a kidney infection.

Reflux nephropathy: Kidney disease caused by the backflow of urine from the bladder up the ureters (duct by which urine passes from the kidney to the bladder) into the kidney tissue.

Renal arteries: Arteries that branch from the abdominal aorta and supply blood to the kidneys.

Renal cortex: The area of the kidney that contains all the glomeruli and portions of the tubules.

Renal failure: The complete loss of kidney function.

Renal insufficiency: A decline in renal function to about 25% of normal or a GFR of 25-30 ml/min.

Renal pelvis: A hollow structure which is an extension of the upper end of the ureter.

Renal stones (also known as calculi, nephrolithiasis): Masses of crystals and protein and are common causes of urinary tract obstruction in adults.

Renin: The enzyme which is produced, secreted, and stored by the kidneys, that is part of a physiological system that regulates blood pressure.

Renin-angiotensin system: A critical regulator of blood volume and systemic vascular resistance.

Septicemia: The presence and persistence of pathogenic microorganisms or their toxins in the blood which affects your body as a whole (i.e. a systemic disease).

Sodium: An electrolyte and a mineral in the body fluids regulated by the kidneys that affects the level of water retained in your body tissues.

Staghorn calculi: Large kidney stones which grow in the pelvis and extend into the renal calyces, the chambers of the kidney through which urine passes, to form branching stones.

Steroid: A family of medications which reduce inflammation that are used to fight rejection of a transplanted kidney.

Subclavian vein: A large blood vessel located underneath the collarbone sometimes used to provide access for dialysis.

Tissue typing: procedure to determine the degree of compatibility between lymphocytes (type of white blood cell) of a donor organ and a recipient.

Transplant: To transfer a kidney from one person to another.

Ultrafiltration: The process of removing excess fluid from a patient during dialysis, after kidneys can no longer do that.

Uremia: A syndrome of renal failure which includes elevated blood urea and creatinine levels accompanied by fatigue, anorexia, nausea and vomiting.

Urea: Waste product from the breakdown of protein and the major constituent of urine along with water.

Ureterorenoscopy (URS): A visual inspection of the interior of the ureter and kidney by means of a fiberoptic endoscope.

Ureter: A tubular structure that transports urine from the kidney to the bladder.

Urethra: A tubular structure that transports the urine from the bladder to the outside of the body.

Urinalysis: A test to measure the presence of protein, blood and other substances in the urine.

Urology: The branch of medicine dealing with the urinary system.



National Kidney Foundation

National Institute of Diabetes and Digestive and Kidney Diseases

Medical News Today

Hopkins Medicine Nephrology

Cleveland Clinic

Mayo Clinic