National Kidney and Urologic Diseases
Information Clearinghouse (NKUDIC)

A service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH)

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The Kidney Diseases Dictionary: R - W


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renal (REE-nuhl):

of or relating to the kidneys. A renal disease is a disease of the kidneys. Renal failure means the kidneys are damaged.

renal agenesis (REE-nuhl) (ay-JENuh-siss):

the absence or severe malformation of one or both kidneys.

renal artery stenosis (REE-nuhl) (AR-tur-ee) (steh-NOH-siss):

narrowing of the artery that supplies blood to the kidney, often resulting in hypertension and kidney damage.

renal cell carcinoma (REE-nuhl) (sel) (KAR-sih-NOH-muh):

a type of kidney cancer.

renal cysts (REE-nuhl) (sists):

abnormal fluid-filled sacs in the kidney that range in size from microscopic to much larger. Many simple cysts are harmless, while other types can seriously damage the kidneys.

renal osteodystrophy (REE-nuhl) (OSS-tee-oh-DISS-troh-fee):

weak bones caused by chronic kidney disease-mineral and bone disorder. Renal osteodystrophy is a common problem for people on dialysis who have high phosphate levels or insufficient vitamin D supplementation.

renal pelvis (REE-nuhl) (PEL-viss):

the basin into which the urine formed by the kidneys is excreted before it travels to the ureters and bladder.

renal tubular acidosis (REE-nuhl) (TOO-byoo-lur) (ASS-ih-DOHsiss):

a defect in the kidneys that hinders their normal excretion of acids. Failure to excrete acids can lead to weak bones, kidney stones, and poor growth in children.

renal vein thrombosis (REE-nuhl) (vayn) (throm-BOH-siss):

blood clots in the vessel that carries blood away from one of the kidneys. This condition can occur in people with nephrotic syndrome.

renin (REE-nin):

a hormone made by the kidneys that helps regulate the volume of fluid in the body and blood pressure.


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semipermeable membrane (SEM-ee-PUR-mee-uh-buhl) (MEM-brayn):

a thin sheet, or layer, of tissue that lines a body cavity or separates two parts of the body. A semipermeable membrane can act as a filter, allowing some particles to pass from one part of the body to another while keeping other particles in place. In hemodialysis, the artificial membrane in a dialyzer acts as the semipermeable membrane filtering waste products from the blood. In peritoneal dialysis, the peritoneum acts as the semipermeable membrane.

Drawing of a section of a semipermeable membrane that could be used in a dialyzer. The section looks something like a sponge. The area above the membrane is labeled “Blood compartment.” The area below the membrane is labeled “Dialysis solution compartment.” Labels explain that waste products move from the blood compartment to the dialysis solution compartment through holes in the membrane. Other labels explain that blood cells bounce off the membrane and remain in the blood compartment. The membrane is labeled “Semipermeable membrane” because it allows wastes, but not blood cells, to permeate into the dialysis solution compartment.
Semipermeable membrane

struvite stone (STROO-vyt) (stohn):

a type of kidney stone caused by infection.


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a vibration or buzz that can be felt in an arteriovenous fistula, an indication that blood is flowing through the fistula.

transplant (TRANZ-plant):

placement of a healthy organ into the body to take over the work of a damaged organ. A kidney transplant may come from a living donor, often a relative, or from someone who has just died.

tubule (TOO-byool):

one of millions of tiny structures within the kidneys that collect urine from the glomeruli.


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see urine albumin-to-creatinine ratio.

ultrasound (UHL-truh-sound):

a technique that bounces safe, painless sound waves off organs to create an image of their structure.

urea (yoo-REE-uh):

a waste product found in the blood that results from the normal breakdown of protein in the liver. Urea is normally removed from the blood by the kidneys and then excreted in the urine. Urea accumulates in the body of people with kidney failure.

urea reduction ratio (URR) (yoo-REE-uh) (ree-DUHKshuhn) (RAY-shee-oh):

a blood test that compares the amount of blood urea nitrogen before and after dialysis to measure the effectiveness of the dialysis dose.

uremia (yoo-REE-mee-uh):

the illness associated with the buildup of urea in the blood because the kidneys are damaged. Symptoms include nausea, vomiting, loss of appetite, weakness, and mental confusion.

ureteroscope (yoo-REE-tur-ohskohp):

a tool for examining the bladder and ureters and for removing kidney stones through the urethra. The procedure is called ureteroscopy.

ureters (YOOR-uh-turz):

tubes that carry urine from the kidneys to the bladder.

urethra (yoo-REE-thruh):

the tube that carries urine from the bladder to the outside of the body.

uric acid stone (YOOR-ik) (ASS-id) (stohn):

a kidney stone that may result from a diet high in animal protein. When the body breaks down this protein, uric acid levels rise and can form stones.

urinalysis (YOOR-ih-NAL-ih-siss):

a test of a urine sample that can reveal many problems of the urinary tract and other body systems. The sample may be observed for color, cloudiness, and concentration; signs of drug use; chemical composition, including glucose; the presence of protein, blood cells, or germs; or other signs of disease.

urinary tract (YOOR-ih-NAIR-ee) (trakt):

the system that takes wastes from the blood and carries them out of the body in the form of urine. The urinary tract includes the kidneys, renal pelvises, ureters, bladder, and urethra.

urinary tract infection (UTI) (YOOR-ih-NAIR-ee) (trakt) (in-FEK-shuhn):

an illness caused by harmful bacteria growing in the urinary tract.

urinate (YOOR-ih-nayt):

to release urine from the bladder to the outside of the body.

urine (YOOR-in):

liquid waste product filtered from the blood by the kidneys, stored in the bladder, and expelled from the body through the urethra by the act of voiding or urinating. See urinate and void.

urine albumin-to-creatinine ratio (UACR) (YOOR-in) (al-BYOOmin) (too) (kree-AT-ih-neen)(RAY-shee-oh):

a measurement that compares the amount of albumin with the amount of creatinine in a urine sample. A patient has chronic kidney disease if the UACR is over 30 milligrams (mg) of albumin for each gram (g) of creatinine (30 mg/g).

urolithiasis (YOOR-oh-lih-THY-uh-siss):

the condition of having stones in the urinary tract.


see urea reduction ratio.


see urinary tract infection.


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vascular access (VASS-kyoo-lur) (AK-sess):

a general term to describe where blood is removed from and returned to the body during hemodialysis. A vascular access may be an arteriovenous fistula, an arteriovenous graft, or a catheter. See hemodialysis under dialysis.

vasculitis (VAS-kyoo-LY-tiss):

inflammation of the blood vessel walls. This swelling can cause rash and disease in multiple organs of the body, including the kidneys.

vasopressin (VAY-soh-PRESS-in):

see antidiuretic hormone.

vein (vayn):

a blood vessel that carries blood to the heart.

vesicoureteral reflux (VESS-ih-kohyoo-REE-tur-uhl) (REE-fluhks):

an abnormal condition in which urine backs up into the ureters, and occasionally into the kidneys, raising the risk of infection.


to urinate; to empty the bladder.


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Wegener's granulomatosis (VUHG-uh-nurz) (GRANyoo-loh-muh-TOH-siss):

an autoimmune disease that damages the blood vessels and causes disease in the lungs, upper respiratory tract, and kidneys.

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Page last updated September 9, 2011


The National Kidney and Urologic Diseases Information Clearinghouse is a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

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