Medullary Sponge Kidney
Review literature: (Foster et al, 2007).
Definition of the Medullary Sponge Kidney
A medullary sponge kidney is a congenital malformation of the kidney with cystic enlargement and calcification of the collecting ducts.
- Symptomatic medullary sponge kidney: 1:5000 to 1:20000
- Asymptomatic medullary sponge kidney in urography: 1:200
Pathology of the Medullary Sponge Kidney
The distal collecting ducts are dilated and have cysts with a diameter of 1–8 mm. The cut surface of the renal medulla looks like a sponge. Calcifications (70% calcium phosphate and 30% calcium oxalate) develop within the cysts. In 75%, medullary sponge kidney is bilateral.
Signs and Symptoms of a Medullary Sponge Kidney
- A medullary sponge kidney is often asymptomatic (incidental finding in urography or computed tomography)
- Recurrent nephrolithiasis
- Recurrent urinary tract infections
- Symptoms of renal insufficiency (rare)
Diagnostic Work-Up of a Medullary Sponge Kidney
Ultrasound of the kidneys:
- Hyperechoic papillae
The contrast media fills the ectatic collecting ducts, the excretion is delayed: appearance suggestive of "bristles on a brush" [fig. medullary sponge kidney in urography]. With progression of the disease, calcifications are seen in the distal collecting ducts: appearance suggestive of a "bouquet of flowers".
Urography of a medullary sponge kidney: The contrast media fills the ectatic collecting ducts, the excretion is delayed: appearance suggestive of "bristles on a brush". With kind permission of Dr. G. Antes, Kempten.
Differential Diagnosis of Bilateral Renal Calcification:
- Medullary sponge kidney
- Vitamin D intoxication
- Multiple myeloma
- Urogenital tuberculosis
- Milk-alkali syndrome
Treatment of the Medullary Sponge Kidney
Treatment in medullary sponge kidney is only necessary in complications like nephrolithiasis, urinary tract infection or renal insufficiency.
Treatment of Nephrolithiasis:
Thiazide diuretics are suitable for the prevention of nephrolithiasis in nephrocalcinosis. Otherwise, the stone therapy does not differ to patients without medullary sponge kidney.
Treatment of Urinary Tract Infections:
Frequent urinary tract infections with coagulase-positive staphylococci should be treated even in non-significant number of bacteria according to the results of the urine culture.
Prognosis of Medullary Sponge Kidney
The risk of renal failure in medullary sponge kidney for symptomatic patients was reported to be 10% in previous studies. Due to improved minimally invasive stone therapy options, this figure should be lower nowadays.
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- Forster, J. A.; Taylor, J.; Browning, A. J. & Biyani, C. S.
- A review of the natural progression of medullary sponge kidney and a novel grading system based on intravenous urography findings.
Urol Int, 2007, 78, 264-269