eMedicine Specialties > Nephrology > Hereditary Kidney Disorders
Medullary Sponge Kidney
Updated: Dec 15, 2008
Introduction
Background
Medullary sponge kidney (MSK) is a benign congenital disorder characterized by dilatation of collecting tubules in one or more renal papillae, affecting one or both kidneys. Medullary sponge kidney is usually a benign condition, and patients can remain asymptomatic. Despite being a congenital disorder, medullary sponge kidney usually is not diagnosed until the second or third decade of life or later.1,2
Among the most frequent complications are renal stone disease and urinary tract infection (UTI), but progression to renal failure is very rare. The diagnosis is usually made using excretory urography, which demonstrates the presence of radial striations in the renal papillae due to collection of contrast in dilated and cystic collecting tubules.
The name medullary sponge kidney is misleading because the affected kidney does not resemble a sponge. The names tubular ectasia and cystic dilatation of the collecting ducts have been suggested as alternatives; however, medullary sponge kidney is the most commonly used name for this disorder.Pathophysiology
The most important abnormality in medullary sponge kidney is the spherical, oval, or irregular dilatation of the medullary and papillary portions of the collective ducts. The underlying abnormality responsible for this developmental anomaly is unknown. Despite a few cases where an autosomal dominant pattern of inheritance might be suggested, in most cases no family history of medullary sponge kidney is available.
The disease is bilateral in 70% of cases, and unilateral involvement of only one pyramid is uncommon. The dilated duct often communicates proximally with the collecting duct of normal size and shows a constriction of normal diameter at the point of communication with the calyx.1
These cysts usually measure 1-7 mm and contain clear, jellylike material and, frequently, small calculi. The kidney may appear to be slightly enlarged when several papillae are involved.
Microscopically, communicating cysts are lined by columnar or cuboidal epithelium and rarely by transitional epithelium, which is caused by the effects of calculi. Closed cysts are lined by atrophic epithelium. The rest of the kidney usually is normal, unless pyelonephritis or renal obstruction complicates the course of the disease.
Frequency
United States
The exact prevalence of medullary sponge kidney is unknown. The frequency of medullary sponge kidney in the general population has been estimated to be 1 case per 5000 population, and the prevalence may be as much as 1 case per 1000 population in urology clinics. In patients who form calcium stones, medullary sponge kidney has been identified in 12-20% of them.3
Approximately 0.5% of patients undergoing intravenous urography are estimated to have medullary sponge kidney, while another 1% have papillary blush. No autopsy series have examined the prevalence of medullary sponge kidney specifically.
In patients with nephrolithiasis, up to 20% may have mild degrees of medullary sponge kidney.
A familial form of medullary sponge kidney has also been reported, which is consistent with an autosomal dominant pattern of inheritance.
Mortality/Morbidity
The clinical course of medullary sponge kidney is usually benign. Very rarely, patients may develop renal failure as a result of repeated pyelonephritis or urinary tract obstruction.
- Major morbidity observed in approximately 10% of patients with medullary sponge kidney is due to repeatedly passing renal stones and recurrent UTI. Complete obstruction of the kidney by renal stones is rare.
- Surgery is rarely required to remove the stones because they are usually very small and pass spontaneously.
- A patient with medullary sponge kidney is estimated to pass 1.23 stones per year compared to 0.66 stones per year in other people who form calcium stones.
Sex
- Women are affected more frequently than men. The incidence of calcium stones is 15-20% in medullary sponge kidney. In women, the incidence is even higher, at 20-30%.
- A higher relative prevalence of medullary sponge kidney occurs in female patients compared to male patients with nephrolithiasis.
Age
- This condition is commonly diagnosed during the second or third decade of life.
- The mean age of patients diagnosed is approximately 27 years.
Clinical
History
- Patients with medullary sponge kidney often are asymptomatic. Not infrequently, the diagnosis is made during radiological investigations, including abdominal radiograph and excretory pyelography, performed for other clinical situations.4,5 Table 1 depicts the common clinical symptoms of medullary sponge kidney.
- Hematuria is frequent, and gross hematuria may be present in 10-20% of cases. Gross hematuria usually results from pelvic obstruction due to stones; however, microscopic hematuria may be present with or without UTI.
- UTI is common in medullary sponge kidney, both with and without nephrolithiasis. Sterile pyuria also is common. Patients with medullary sponge kidney have more UTIs than other patients with nephrolithiasis, and the incidence of urinary infection is higher in women than in men.
- Recurrent nephrolithiasis is a major complication of medullary sponge kidney. The most common presenting symptom of this complication is renal colic, often accompanied by hematuria. Renal stones also result in UTI, urinary obstruction, and nephrocalcinosis. The stones in medullary sponge kidney are usually composed of calcium phosphate (apatite) and calcium oxalate.
- Medullary sponge kidney can occur in conjunction with other congenital abnormalities (see Congenital conditions associated with medullary sponge kidney, below).
- As many as 10% of patients with hemihypertrophy can have medullary sponge kidney, and as many as 25% of patients with medullary sponge kidney have hemihypertrophy.
- When associated with medullary sponge kidney, Beckwith-Wiedemann syndrome (high birth weight, macroglossia, omphalocele, visceromegaly, mental retardation, cysts in adrenal cortex, enlarged kidneys, medullary sponge kidney, and hemihypertrophy) has a high tumor rate, especially Wilms tumor, adrenal gland cancer, and hepatoblastoma.
Table 1. Clinical Features of Medullary Sponge Kidney and Pathophysiological Correlation
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Table
| Frequency | Clinical Findings | Pathophysiology |
| Common* | Nephrolithiasis (calcium oxalate, calcium apatite) | Hypercalciuria Increased oxalate concentration Tubular acidification defects Hypocitraturia |
| Hematuria (gross 10-20%, microscopic) | Acute pelvic obstruction UTI, renal stones, or absence of both | |
| UTI | Sterile pyuria common even in absence of stones Presence of renal stones | |
| Rare | Chronic kidney disease | Repeated urinary obstruction Repeated pyelonephritis due to urease-producing organisms (Proteus) |
| Frequency | Clinical Findings | Pathophysiology |
| Common* | Nephrolithiasis (calcium oxalate, calcium apatite) | Hypercalciuria Increased oxalate concentration Tubular acidification defects Hypocitraturia |
| Hematuria (gross 10-20%, microscopic) | Acute pelvic obstruction UTI, renal stones, or absence of both | |
| UTI | Sterile pyuria common even in absence of stones Presence of renal stones | |
| Rare | Chronic kidney disease | Repeated urinary obstruction Repeated pyelonephritis due to urease-producing organisms (Proteus) |
- Congenital conditions associated with medullary sponge kidney
- Anodontia
- Autosomal dominant polycystic kidney
- Beckwith-Wiedemann syndrome
- Caroli syndrome
- Congenital hemihypertrophy
- Congenital pyloric stenosis
- Distal renal tubular acidosis
- Ehlers-Danlos syndrome
- Horseshoe kidney
- Marfan syndrome
- Parathyroid adenomas
- Renal artery stenosis
- Ureteral duplication
Physical
- No physical findings are usually present except for hematuria.
- Renal colic may occur.
- Costovertebral angle tenderness occurs in cases of pyelonephritis or ureteral obstruction by a calculus.
- Hemihypertrophy is present in 25% of cases.
- Other signs of associated congenital disorders may be present (see Congenital conditions associated with medullary sponge kidney, above).
Causes
- Most cases of medullary sponge kidney are sporadic.
- Theories suggest that dilatation of a collecting duct may occur, caused by occlusion by uric acid during fetal life or caused by tubular obstruction due to calcium oxalate calculi secondary to infantile hypercalciuria.
- A rare autosomal dominant form is inherited in familial cases of medullary sponge kidney.
- A rare autosomal recessive form is associated with Caroli disease.
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| References |
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References
Fick GM, Gabow PA. Hereditary and acquired cystic disease of the kidney. Kidney Int. Oct 1994;46(4):951-64. [Medline].
Gambaro G, Feltrin GP, Lupo A, et al. Medullary sponge kidney (Lenarduzzi-Cacchi-Ricci disease): a Padua Medical School discovery in the 1930s. Kidney Int. Feb 2006;69(4):663-70. [Medline].
Yagisawa T, Kobayashi C, Hayashi T, et al. Contributory metabolic factors in the development of nephrolithiasis in patients with medullary sponge kidney. Am J Kidney Dis. Jun 2001;37(6):1140-3. [Medline].
Levine E, Hartman DS, Meilstrup JW, et al. Current concepts and controversies in imaging of renal cystic diseases. Urol Clin North Am. Aug 1997;24(3):523-43. [Medline].
Palubinskas AJ. Renal pyramid structure opacification in excretory urography and its relation to medullary sponge kidney. Radiology. Dec 1963;81:963-70. [Medline].
Higashihara E, Nutahara K, Tago K, et al. Medullary sponge kidney and renal acidification defect. Kidney Int. Feb 1984;25(2):453-9. [Medline].
Lang EK, Macchia RJ, Thomas R, et al. Improved detection of renal pathologic features on multiphasic helical CT compared with IVU in patients presenting with microscopic hematuria. Urology. Mar 2003;61(3):528-32. [Medline].
Forster JA, Taylor J, Browning AJ, et al. A review of the natural progression of medullary sponge kidney and a novel grading system based on intravenous urography findings. Urol Int. 2007;78(3):264-9. [Medline].
Further Reading
Keywords
medullary sponge kidney, sponge kidney, MSK, cystic dilatation of renal pyramids, cystic disease of renal pyramids, cystic dilatation of renal collecting tubules, congenital cystic dilatation of renal collecting tubules, precalyceal canalicular ectasia, tubular ectasia, renal tubular ectasia, renal tubules, Cacchi-Ricci disease, Lenarduzzi-Cacchi-Ricci disease, collecting tubules, medullary pyramids, kidney disease, renal disease, urinary tract infection, UTI, renal stone disease
