AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Medullary sponge kidney (MSK) is likely the result of an abnormality in renal development, as evidenced by the occasional presence of embryonal tissue in the affected papillae. Recent findings suggest that MSK may result from disruption of the ureteric bud/metanephric-blastema interface that is critical in normal kidney development.¹

MSK is characterized by ectasia and cystic formation in the medullary collecting duct. This characterization contrasts with autosomal recessive polycystic kidney disease and with autosomal dominant polycystic kidney disease, in which cysts predominantly develop along the cortical collecting tubule or the entire nephron, respectively. Medullary cysts give the kidney the gross anatomic appearance of a sponge. In the absence of hematuria, renal calculi, or infection, the disease is an asymptomatic nonprogressive condition.

Pathophysiology

The kidney is the primary organ affected. Ectasia and cystic malformation are present along the intrapyramidal or intrapapillary portion of the medullary collecting duct. Cysts may be heterogeneous in size within one kidney and between the 2 kidneys, ranging in size from 1-3 mm. Cysts may communicate and often contain spherical concretions composed of apatite.

Although the cause of medullary sponge kidney is unknown, family occurrence suggests a genetic component. Pathological studies suggest that medullary sponge kidney is due to an obstruction of the fetal-collecting duct or to a structural defect caused by hypercalciuria. The presence of embryonal remnant tissue in some cases links the condition to a congenital developmental defect in this nephron segment.

Medullary sponge kidney may be part of other syndromes and conditions such as Beckwith-Wiedemann syndrome (BWS), hemihypertrophy, Caroli disease, Ehlers-Danlos syndrome, Marfan syndrome, and pyloric stenosis. Medullary sponge kidney may occur in up to 12.5% of cases of BWS, if congenital hemihypertrophy is part of the clinical picture.

Frequency

United States

The prevalence rate is 1 case per 5,000-20,000 population. MSK may be detected in 0.5-1% of asymptomatic individuals who undergo renal imaging studies for assorted clinical indications.

International

Evidence indicates that worldwide incidence of MSK is similar to that found in the United States.

Mortality/Morbidity

Morbidity or mortality is not directly related to MSK. In the absence of hematuria, urinary tract infection (UTI), or renal calculi, MSK is usually a nonprogressive asymptomatic condition.

• Under normal conditions, patients may have a mild urinary-concentrating defect or low-grade proteinuria.
• Patients have a higher risk for developing calcium oxalate/apatite or struvite renal calculi. Factors that may contribute to the susceptibility to recurrent calcium urolithiasis include: (1) urine stasis, (2) incomplete renal tubular acidosis (RTA) with a mild defect in urinary acidification and increased urine pH levels, (3) hypocitric aciduria, and (4) hypercalciuria. Patients are usually aged 20-50 years at presentation, although the condition may occur in children younger than 5 years. As many as 20% of adults with kidney stones may have MSK; the corresponding figure in children is unknown. Among patients with kidney stones, hypercalciuria may occur in 40-50%, and recurrent gross hematuria may occur in 10-20%.
• Hyperparathyroidism is frequently associated with MSK and was thought to cause the disease and trigger stone formation. However, the urinary findings and clinical features of MSK usually precede the detection of hyperparathyroidism.  
• Although no evidence indicates that risk of UTIs is higher in patients with medullary sponge kidney, as many as 5% of males and 35% of females have a UTI. These patients do not have an increased frequency of concomitant structural anomalies (eg, vesicoureteral reflux) to account for the occurrence of UTI.

Race

No epidemiologic data indicate that incidence varies among racial or ethnic subgroups.

Sex

No evidence indicates that the frequency differs between the sexes. Fewer than 5% of cases are familial, and a clear genetic basis for MSK has not been established. The only genetic pattern observed in select pedigrees is an autosomal dominant type of transmission. MSK appears to be somewhat more severe in women; the incidence of renal calculi and UTIs in women is higher than in men.

Age

Symptoms occur primarily in adults aged 20-50 years; however, infants as young as 2 years and adolescents have shown clinical symptoms.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Patients are usually asymptomatic.
• Patients may develop microhematuria or signs and symptoms of gross hematuria, renal stone development, or UTI.

Physical

• Although physical examination findings are usually normal, as many as 25% of patients have hemihypertrophy, and 10% of patients with hemihypertrophy may have medullary sponge kidney, although no explanation for this association exists. Children with medullary sponge kidney (MSK) and hemihypertrophy may have an incomplete form of BWS. Moreover, because of the high risk of malignancies in patients with BWS, these patients should be screened periodically for malignancies, including abdominal tumors.
• Urinalysis findings may show hematuria, low-grade proteinuria, and mild acidification and concentrating defects.

Causes

The cause of MSK is unknown.

• No cases link MSK to a drug or environmental exposure.
• Cases occasionally occur in a familial pattern consistent with autosomal dominant transmission. In these circumstances, MSK may be associated with unilateral renal agenesis or other renal or genitourinary tract abnormalities.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Calyceal diverticulum
Papillary necrosis
Other causes of nephrocalcinosis

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Urinalysis
• • Assessment of urinary calcium excretion
  • Urine culture
• In patients with medullary sponge kidney (MSK) and hemihypertrophy, serial screening should be performed to exclude malignancies, including abdominal tumors.

Imaging Studies

• Intravenous pyelography demonstrates radial, linear striations in the papillae or cystic collections of contrast material in ectatic collecting ducts. The result is a characteristic blushlike pattern to the papillae, the so-called "bouquet of flowers" or "paintbrush" appearance. Typical cases involve all renal papillae but MSK may be unilateral or may affect only a few papillae. Declining use of intravenous pyelography as an imaging technique may result in underdiagnosis of MSK cases.
• Renal ultrasonography and CT scanning are unnecessary except to distinguish MSK from papillary necrosis or autosomal dominant polycystic kidney disease.
• The role of MRI is unknown.

Other Tests

• Appropriate workup is needed if MSK appears to be associated with another condition, such as hemihypertrophy or pyloric stenosis, or is part of a syndrome, such as Marfan or Ehlers-Danlos. This testing should be performed to exclude the presence of a malignancy.

Procedures

• No additional, specific, diagnostic procedures are warranted for diagnostic evaluation.

Histologic Findings

• Neither renal biopsy nor nephrectomy is routinely performed.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

No specific treatment is warranted.

• If hypercalciuria-associated kidney stone disease is present, use of thiazide diuretics or other measures to reduce the hypercalciuria may be justified.
• Renal stones are managed in the same way as in individuals without medullary sponge kidney.
• Treat UTIs with standard courses of antibiotics. Prophylactic antibiotics may help patients with medullary sponge kidney and recurrent UTIs.
• In patients with hemihypertrophy, serial screening should be performed to exclude a malignancy.

Surgical Care

Surgery is not needed for most patients with medullary sponge kidney (MSK).

Diet

Although decreased dietary calcium intake may decrease urinary calcium excretion, concern has been expressed that it might also result in skeletal undermineralization. Decreased sodium intake and increased potassium intake may improve urinary calcium excretion by themselves and are recommended in patients taking thiazide diuretics.

Activity

Because MSK is a nonprogressive condition with small medullary cysts, restriction of physical activity is unnecessary.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

No medications are warranted for routine care. Use antibiotics in accordance with standard prescription practices to treat UTIs (see Urinary Tract Infection). Consider thiazide diuretics in patients with hypercalciuric urolithiasis.

Drug Category: Diuretics

Thiazide diuretics may be prescribed to patients who have medullary sponge kidney and hypercalciuria, with or without urolithiasis.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Further inpatient care is needed only for patients with renal stones or severe UTI.
• Serial screening for malignancies is required in patients with medullary sponge kidney (MSK) and hemihypertrophy.

Further Outpatient Care

• Periodic screening for hematuria, bacteriuria, and kidney stones

In/Out Patient Meds

• Medications are needed only for patients with UTIs or kidney stones.

Complications

• Gross hematuria
• Renal stones
• UTIs

Prognosis

• MSK is a nonprogressive disease and has no adverse impact on renal or patient survival.

Patient Education

• Inform the patient of possible complications.
• For excellent patient education resources, visit eMedicine's Kidneys and Urinary System Center. Also, see eMedicine's patient education article Blood in the Urine.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Overtreatment of patients with medullary sponge kidney (MSK) is a pitfall.
• Failure to discriminate MSK, a nonprogressive disease, from forms of cystic kidney disease that have a worse prognosis is a pitfall. Autosomal recessive polycystic kidney disease is the disease most commonly mistaken for MSK.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. 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].
2. Abeshouse BS, Abeshouse GA. Sponge kidney: a review of the litrature and a report of five cases. J Urol. Aug 1960;84:252-67. [Medline].
3. Avner ED. Medullary sponge kidney. In: Greenber A, Cheung AK, Coffman TM, et al, eds. NKF Primer on Kidney Disease. 1997.
4. Osther PJ, Mathiasen H, Hansen AB, et al. Urinary acidification and urinary excretion of calcium and citrate in women with bilateral medullary sponge kidney. Urol Int. 1994;52(3):126-30. [Medline].
5. Patriquin HB, O'Regan S. Medullary sponge kidney in childhood. AJR Am J Roentgenol. Aug 1985;145(2):315-9. [Medline].

Article Last Updated: Dec 11, 2007