Medullary Sponge Kidney is a rare disorder characterized by the formation of cystic malformations in the collecting ducts and the tubular structures within the kidneys (tubules) that collect urine. One or both kidneys may be affected. The initial symptoms of this disorder may include blood in the urine (hematuria), calcium stone formation in the kidneys (nephrolithiasis) or infection. The exact cause of Medullary Sponge Kidney is not known.
The first symptoms of Medullary Sponge Kidney typically blood in the urine, stone formation or signs of a urinary infection such as excessive urination (polyuria) and/or burning and pain while urinating. In some affected individuals, calcium stones may form in the kidneys (nephrolithiasis). These stones can cause low back pain in the area of the kidneys (renal colic) and pain in the lower back and lower abdomen. A prominent feature of Medullary Sponge Kidney is the excretion of small stones with the urinary flow. The passage of these stones can be profoundly painful. In a small number of cases, repeated urinary infections and damage to the kidneys may occur if stones become sufficiently large enough to block the flow of urine to the bladder (renal obstruction).
The most common complication of Medullary Sponge Kidney involves the loss of the kidneys’ capacity to concentrate waste products in the urine (filtration). This is due to the abnormal widening (dilatation) of the collecting tubes deep within the kidneys. Impaired filtration by the kidneys can result in the excessive accumulation of acidic waste products in the blood and body fluids (metabolic acidosis). Rare complications of Medullary Sponge Kidney may include severe damage to the kidneys (i.e., renal tubular acidosis) and kidney failure (i.e., end-stage renal disease).
The exact cause of Medullary Sponge Kidney is not known and most cases occur sporadically for no apparent reason. Some cases are thought to run in families (familial) and may be inherited as an autosomal dominant genetic trait. However, this inheritance pattern has not been proven. Some studies have suggested there may be a a possible relationship between overactivity of the parathyroid gland (Hyperparathyroidism) and Medullary Sponge Kidney.
Medullary Sponge Kidney is a rare disorder that affects slightly more women than men. It is thought to occur in 1 in 1,000 to 5,000 people in the United States. Although the symptoms of Medullary Sponge Kidney may begin at any age, they usually develop during adolescence or in adults between the ages of 30 and 50 years. Approximately 13 percent of all people who develop kidney stones are eventually diagnosed with Medullary Sponge Kidney. Medullary Sponge Kidney may also develop in people with Beckwith-Wiedemann Syndrome. (For more information on Beckwith-Wiedemann Syndrome, see the related disorders section of this report.)
The diagnosis of Medullary Sponge Kidney Disease may be confirmed by a thorough clinical evaluation and specialized X-ray studies (i.e., intravenous urography) that reveal the presence of abnormal widening (dilatation) or stretching of collecting ducts, cyst formations or kidney stones. CT scan (computerized tomography) is another imaging study that is effective in revealing calcifications that may later form kidney stones. In some affected individuals, urinary filtration rates (glomerular) may be measured and found to be reduced.
The kidney stones associated with Medullary Sponge Kidney are composed of calcium oxalate, calcium phosphate, and other calcium salts (urolithiasis). If normal levels of calcium are excreted, affected individuals may be given oral phosphate therapy. Individuals with Medullary Sponge Kidney should take sufficient fluids in order to excrete about 2 liters of urine each day. Those people with Medullary Sponge Kidney who have too much calcium in their urine (hypercalciuria) may benefit from long-term therapy with thiazide diuretics as well as a high fluid intake.
In some people with Medullary Sponge Kidney, a low calcium diet may help t. prevent the formation of kidney stones and thereby reduce the complications of urinary obstruction. Patients should be evaluated at least on a yearly basis, including routine urinalysis and urine cultures. Many patients with Medullary Sponge Kidney have recurrent urinary tract infections and may require antibiotic drugs to help prevent future infections (prophylaxis).
Stones in the collecting system may be treated with electromagnetic shock waves (extracorporeal shock wave lithotripsy [ESWL]). During this procedure, the patient is placed in a large tub of water and shock waves (high energy) are delivered by a special machine (ellipsoid reflector) directly to the area of the kidney stones. The stones are broken into small pieces and excreted with the urine. It has not been determined if ESWL is beneficial in treating stones in the kidney tubules.
Genetic counseling may be of benefit for people with Medullary Sponge Kidney if the disease appears in other family members. In rare cases of kidney failure, renal dialysis may be required. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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The orphan drug calcium acetate is being investigated for the treatment of excessive levels of phosphate in the blood (hyperphosphatemia) associated with end-stage renal disease (ESRD), which can occur as a rare complication in some people with Medullary Sponge Kidney. More studies are needed to determine the long-term safety and effectiveness of this drug for the treatment of renal disease. For more information on this drug, contact the manufacturer:
Braintree Laboratories, Inc.
P.O. Box 361
60 Columbian St.
Braintree, MA 02184
Another orphan drug, calcium carbonate, is also being investigated for the treatment of hyperphosphatemia associated with end-stage renal disease (ESRD). More studies are needed to determine the long-term safety and effectiveness of this drug for the treatment of renal disease that can occur in association with Medullary Sponge Kidney. For more information, contact the manufacturer:
4094 Glencoe Ave.
Marine del Ray, CA 90292
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Nakada SY, Erturk E, Monaghan J, et al. Role of extracorporeal shock-wave lithotripsy in treatment of urolithiasis in patients with medullary sponge kidney. Urology. 1993;41:331-333.
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