Medullary 

Sponge Kidney 

National Kidney and Urologic Diseases Information Clearinghouse 

U.S. Department 

of Health and 

Human Services 

NATIONAL 

INSTITUTES 

OF HEALTH 

What is medullary sponge 

kidney? 

Medullary sponge kidney (MSK) is a birth 

defect of the tubules—tiny tubes inside the 

kidneys. In a normal kidney, urine fl ows 

through these tubules as it is being formed. 

In MSK, tiny sacs called cysts form in the 

medulla—the inner part of the kidney— 

creating a sponge-like appearance. The 

cysts keep urine from flowing freely through 

the tubules. 

MSK is present at birth but most cases 

do not appear to be inherited. Problems 

caused by MSK include hematuria, or 

blood in urine; kidney stones; and urinary 

tract infections (UTIs). But these problems do not usually appear until the ages 

of 30 to 40. MSK affects about 1 person 

per 5,000 to 20,000 people in the United 

States.1 Researchers have reported that 

up to 20 percent of people who form kidney 

stones have MSK.2 MSK rarely leads to 

more serious problems, such as total kidney 

failure. 

1Glassberg KI. Renal dysgenesis and cystic disease 

of the kidney. In: Walsh PC, Retik AB, Vaughan 

ED, Wein AJ, eds. Campbell’s Urology. Vol. 3. 

8th ed. Philadelphia: WB Saunders Company; 2002: 

1925–1994. 

2Grantham JJ, Nair V, Winklhoffer F. Cystic diseases 

of the kidney. In: Brenner BM, ed. Brenner & 

Rector’s The Kidney. Vol. 2. 6th ed. Philadelphia: WB 

Saunders Company; 2000: 1699–1730. 

What are the kidneys and 

what do they do? 

The kidneys are two bean-shaped organs, 

each about the size of a fist. They are 

located on either side of the spine, just 

below the rib cage. The kidneys fi lter 

wastes and extra fluid from the blood to 

produce urine. They also release hormones 

that help control blood pressure and that 

keep blood and bones healthy. 

Blood flows into the kidneys through two 

blood vessels called renal arteries. Inside 

the kidneys, the arteries branch off into 

smaller and smaller arteries. The smallest 

blood vessels intertwine with tubules that 

start to collect wastes and extra fl uid from 

Kidneys 

Bladder 

Ureters 

Kidney 

Ureter 

Urethra Bladder 

The kidneys remove wastes and extra fluid from the 

blood to form urine. Urine flows from the kidneys to 

the bladder through the ureters. 
2 Medullary Sponge Kidney

the blood. The point where the blood vessel and tubule intertwine is called a nephron. Each kidney contains about 1 million 

nephrons.

Urine leaves the nephron and drips through 

the tubules, which connect to increasingly 

larger tubules, and fi nally to the ureters, 

which are tubes that carry urine to the 

bladder.

In MSK, abnormal sacs called cysts form in 

the collecting tubes in the medulla of the 

kidneys. The cysts keep urine from fl owing freely through the kidneys. UTIs and 

kidney stones can develop because the urine 

fl ow is blocked.

Blood with 

wastes

Clean blood

Wastes (urine) 

to the bladder

Nephron

Tubule

Glomerulus

In the nephron (left), 

tiny blood vessels 

intertwine with urinecollecting tubes. Each 

kidney contains about 

1 million nephrons.

Cysts

In MSK, cysts form in 

the collecting tubes 

and keep urine from 

flowing freely through 

the kidneys.

What are the signs and 

symptoms of MSK?

For many people, MSK causes no symptoms. The fi rst sign that a person has MSK 

is usually a UTI or kidney stone. UTIs 

and kidney stones share many of the same 

symptoms:

• burning or painful urination

• pain in the back, lower abdomen, or 

groin

• cloudy, dark, or bloody urine

• foul-smelling urine

• fever and chills

• vomiting

People who experience these symptoms 

should see a doctor as soon as possible.
How is MSK diagnosed? 

A doctor may suspect MSK when a person 

has repeated UTIs or kidney stones. To confirm the diagnosis, the doctor may order an 

x ray called an intravenous pyelogram (IVP). 

In an IVP, dye is injected into a vein. The 

dye travels through the blood to the kidneys. 

As the dye is filtered into the urinary tract, 

it makes urine visible on the x ray and shows 

any blockage in the urinary tract. Cysts 

show up as clusters of light in an IVP. 

Cysts 

In an intravenous pyelogram of a medullary sponge 

kidney, cysts appear as clusters of light. 

How is MSK treated? 

No treatment can get rid of cysts in the 

affected kidneys. Once a doctor is sure 

that a person has MSK, treatment focuses 

on curing existing infection, removing any 

stones, and preventing future infection and 

stone formation. 

•	 UTIs. To treat UTIs, the doctor may 

prescribe a medicine called an antibiotic that kills bacteria. A person with 

MSK may need to continue taking a 

low-dose antibiotic to prevent recurrent 

infections. 

•	 Kidney stones. Stone removal may 

require a procedure called lithotripsy, 

which uses sound waves to break stones 

into sand-like particles. The particles 

can then pass easily through the urinary 

tract with the flow of urine. Another 

way to remove stones is to insert a thin 

tube called a ureteroscope through the 

urethra and bladder to catch the stone 

and retrieve it. A person with MSK 

may be able to prevent more stones 

from forming through diet changes 

or taking medicine. Increasing fl uid 

intake so the person makes more urine 

is also very important to reduce the risk 

of new stone formation. 

3 	 Medullary Sponge Kidney 
Points to Remember 

•	 Medullary sponge kidney (MSK) is a 

birth defect of the tubules inside the 

kidneys. 

•	 Problems caused by MSK include 

hematuria, kidney stones, and urinary 

tract infections (UTIs). 

•	 MSK problems do not usually appear 

until ages 30 to 40. 

•	 Many people with MSK have no 


symptoms.
 

•	 Diagnosis of MSK may require an x ray 

called an intravenous pyelogram (IVP). 

•	 No treatment can get rid of cysts in 


MSK.
 

•	 Treatment for MSK focuses on curing 

UTIs, removing kidney stones, and preventing recurrent infections and stones. 

Hope through Research 

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) 

conducts and supports research into many 

kinds of kidney disease. NIDDK-supported 

researchers are exploring the genetic and 

molecular mechanisms that control kidney 

development in a fetus. These studies will 

point the way to more effective treatments 

for MSK and other kidney defects that are 

present at birth. 

Participants in clinical trials can play a more 

active role in their own health care, gain 

access to new research treatments before 

they are widely available, and help others by 

contributing to medical research. For information about current studies, visit 

www.ClinicalTrials.gov. 

4 	 Medullary Sponge Kidney 
5 Medullary Sponge Kidney

For More Information

American Association of Kidney Patients

3505 East Frontage Road, Suite 315 

Tampa, FL 33607 

Phone: 1–800–749–2257 

Fax: 813–636–8122 

Email: info@aakp.org 

Internet: www.aakp.org 

American Kidney Fund 

6110 Executive Boulevard, Suite 1010 

Rockville, MD 20852 

Phone: 1–800–638–8299 

Fax: 301–881–0898 

Email: helpline@kidneyfund.org 

Internet: www.kidneyfund.org

Life Options Rehabilitation Resource Center

c/o Medical Education Institute, Inc. 

414 D’Onofrio Drive, Suite 200 

Madison, WI 53719 

Phone: 1–800–468–7777 

Email: lifeoptions@MEIresearch.org 

Internet: www.lifeoptions.org 

www.kidneyschool.org

National Kidney Foundation

30 East 33rd Street 

New York, NY 10016 

Phone: 1–800–622–9010 or 212–889–2210 

Fax: 212–689–9261 

Internet: www.kidney.org

You may also find additional information about this 

topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about medications. When prepared, this publication included 

the most current information available. For updates 

or for questions about any medications, contact 

the U.S. Food and Drug Administration toll-free at 

1–888–INFO–FDA (463–6332) or visit www.fda.gov. 

Consult your doctor for more information.
National Kidney and 

Urologic Diseases 

Information Clearinghouse 

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Bethesda, MD 20892–3580 

Phone: 1–800–891–5390 

TTY: 1–866–569–1162 

Fax: 703–738–4929 

Email: nkudic@info.niddk.nih.gov 

Internet: www.kidney.niddk.nih.gov 

The National Kidney and Urologic Diseases 

Information Clearinghouse (NKUDIC) is a 

service of the National Institute of Diabetes 

and Digestive and Kidney Diseases (NIDDK). 

The NIDDK is part of the National Institutes 

of Health of the U.S. Department of Health 

and Human Services. Established in 1987, the 

Clearinghouse provides information about 

diseases of the kidneys and urologic system to 

people with kidney and urologic disorders and 

to their families, health care professionals, and 

the public. The NKUDIC answers inquiries, 

develops and distributes publications, and 

works closely with professional and patient 

organizations and Government agencies to 

coordinate resources about kidney and urologic 

diseases. 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists and 

outside experts. This publication was reviewed 

by the following members of the American 

Society of Pediatric Nephrology Clinical Affairs 

Committee for their review of this fact sheet: 

Deepa Chand, M.D.; Maria Ferris, M.D.; 

Joseph Flynn, M.D., M.S.; Keith Lau, M.D.; 

Tej Mattoo, M.D.; Asha Mougdil, M.D.; and 

Robert Weiss, M.D. 

This publication is not copyrighted. The Clearinghouse 

encourages users of this fact sheet to duplicate and 

distribute as many copies as desired. 

This fact sheet is also available at 

www.kidney.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 08–6235 

July 2008