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$Title{Medullary Sponge Kidney}
$Subject{Medullary Sponge Kidney Sponge Kidney Tubular Ectasia }
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Copyright (C) 1986, 1989, 1990 National Organization for Rare Disorders, Inc.

223:
Medullary Sponge Kidney

** IMPORTANT **
It is possible the main title of the article (Medullary Sponge Kidney) is
not the name you expected.  Please check the SYNONYMS listing to find the
alternate names and disorder subdivisions covered by this article.

Synonyms

     Sponge Kidney
     Tubular Ectasia

General Discussion

** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only.  It should not be used for diagnostic or treatment
purposes.  If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section of this report.


Medullary Sponge Kidney is a hereditary congenital defect characterized
by dilation of the terminal collecting ducts in the kidneys.  Often small
calcium oxalate stones (calculi) appear in these ducts.  This condition may
affect one or both kidneys.

Symptoms

One or both kidneys may be affected in Medullary Sponge Kidney.  Some of the
papillary collecting ducts in the kidneys are dilated.  This disorder is
commonly associated with blood in the urine (hematuria) which can be
recurrent.

Infections of the urinary tract often are the first sign of an underlying
abnormality.  Kidney stones (nephrolithiasis) with renal colic, loin pain,
and the excretion of small stones is one of the more prominent features of
Medullary Sponge Kidney.  The stones form in the dilated portions of the
collecting ducts.  They may consist of calcium oxalate, calcium phosphate and
other types of calcium salts.  The disease seldom progresses to end stage
renal failure, although reduced glomurular filtration rates have been
observed.

The most common functional abnormalities include the inability of the
kidney to concentrate the salts that are excreted as urine, and acidity of
the body tissues (systemic acidosis) secondary to renal tubular acidosis.
Kidney stones (nephrolithiasis) are a common clinical problem for patients
with this disorder; it has been observed that 13% of patients who develop
kidney stones have Medullary Sponge Kidney.

Causes

Medullary Sponge Kidney is an autosomal dominant hereditary disorder.  (Human
traits including the classic genetic diseases, are the product of the
interaction of two genes for that condition, one received from the father and
one from the mother.  In dominant disorders, a single copy of the disease
gene (received from either the mother or father) will be expressed
"dominating" the normal gene and resulting in appearance of the disease.  The
risk of transmitting the disorder from affected parent to offspring is 50%
for each pregnancy regardless of the sex of the resulting child.)

A possible relationship between hyperparathyroidism and Medullary Sponge
Kidney has been suggested.

Affected Population

Medullary Sponge Kidney is more common in males than in females.

Therapies:  Standard

Patients with Medullary Sponge Kidney should take sufficient fluids in order
to excrete about 2 liters of urine each day.  Patients with too much calcium
in the urine (hypercalciuria) may benefit from long-term therapy with
thiazide diuretics as well as a high fluid intake.  For patients with calcium
urolithiasis and normal calcium excretion, oral phosphate therapy may be
useful.  A low calcium diet may prevent stone formation and thereby reduce
obstruction complications.  Patients should visit a physician at least yearly
for routine urinalysis.

Therapies:  Investigational

Calcium Acetate is a new orphan drug being used in the treatment of
hyperphosphatemia in end stage renal disease (ESRD).  It is manufactured by
Pharmedic Co., 130 Exmoor Ct., Deerfield, IL  60015.

This disease entry is based upon medical information available through
January 1990.  Since NORD's resources are limited, it is not possible to keep
every entry in the Rare Disease Database completely current and accurate.
Please check with the agencies listed in the Resources section for the most
current information about this disorder.

Resources

For more information on Medullary Sponge Kidney, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     (203) 746-6518

     National Kidney and Urologic Diseases Information Clearinghouse
     Box NKUDIC
     Bethesda, MD  20892
     (301) 468-6345

     The National Kidney Foundation
     30 East 33rd St.
     New York, NY  10016
     (212) 889-2210
     (800) 622-9010

     American Kidney Fund
     6110 Executive Blvd., Suite 1010
     Rockville, MD  20852
     (301) 881-3052
     (800) 638-8299
     (800) 492-8361 (MD)


For information on genetics and genetic counseling referrals, please
contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     (914) 428-7100

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     (301) 652-5553

References

THE MERCK MANUAL 15th ed:  R. Berkow, et al:  eds; Merck, Sharp & Dohme
Research Laboratories, 1987.  P. 1631.

CECIL TEXTBOOK OF MEDICINE, 18th ed.:  James B. Wyngaarden, and Lloyd H.
Smith, Jr., Eds.:  W. B. Saunders Co., 1988.  Pp. 645-8.