eMedicine Specialties > Pediatrics: General Medicine > Nephrology

Medullary Sponge Kidney

Howard Trachtman, MD, Program Director, Pediatrics Research, Schneider Children's Hospital, Department of Pediatrics, Division of Nephrology, Professor, Albert Einstein College of Medicine

Updated: Nov 4, 2009

Introduction

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 medullary sponge kidney may result from disruption of the ureteric bud/metanephric-blastema interface that is critical in normal kidney development.¹

Medullary sponge kidney 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.

Unenhanced coronal volume-rendered (VR) CT image of the kidneys demonstrates 2 small calculi in the mid portion of the right kidney and 2 small calculi in the lower pole of the left kidney (arrowheads). A large low-density lesion in the lower pole of the right kidney and a small low-density lesion in the upper pole of the left kidney (short arrows) were shown to represent benign simple renal cysts on the contrast enhanced CT images. Image courtesy of Dr. Terri J. Vrtiska, Consultant, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.

CT image of both kidneys demonstrates brushlike densities throughout multiple papillae of both kidneys consistent with renal tubular ectasia. Correlation of the stone disease with the ectatic tubules is diagnostic of medullary sponge kidney. Image courtesy of Dr. Terri J. Vrtiska, Consultant, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.

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.

The association of medullary sponge kidney with different malformation conditions suggests that it belongs to the developmental disorders that result from disruption of the ureteric bud-metanephric blastema interface. This is based on the occasional presence of remnant embryonal tissue in the affected papillae. 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. Although the cause of medullary sponge kidney is unknown, family occurrence suggests a genetic component. 

Medullary sponge kidney has been linked to defects in tubular function, including acidification and concentration. Two patients with medullary sponge kidney in association with distal renal tubular acidosis, late sensorineural hearing loss, and a mutation in the proton pump genes ATP6V1B1 and ATP6V0A4 were described.²

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 as many as 12.5% of cases of BWS, if congenital hemihypertrophy is part of the clinical picture. Finally, medullary sponge kidney was recently described in a 10-year-old boy with Rabson-Mendenhall syndrome (ie, severe insulin resistance, hyperinsulinemia, postprandial hyperglycemia, growth retardation, and dysmorphic features).³

Frequency

United States

The prevalence rate is 1 case per 5,000-20,000 population. Medullary sponge kidney 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 medullary sponge kidney is similar to that found in the United States.

Mortality/Morbidity

Morbidity or mortality is not directly related to medullary sponge kidney. In the absence of hematuria, urinary tract infection (UTI), or renal calculi, medullary sponge kidney 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 medullary sponge kidney . The lifetime risk of renal stones may be as high as 60% in adults with medullary sponge kidney. The prevalence of medullary sponge kidney is higher (8.5%) in adults with renal stones compared with the control population (1.5%). 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 medullary sponge kidney and was thought to cause the disease and trigger stone formation. However, the urinary findings and clinical features of medullary sponge kidney 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 medullary sponge kidney has not been established. The only genetic pattern observed in select pedigrees is an autosomal dominant type of transmission. Medullary sponge kidney 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

History

• Patients with medullary sponge kidney (MSK) are usually asymptomatic.
• Patients may develop microhematuria or signs and symptoms of gross hematuria, renal stone development, or urinary tract infection (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 is noted. Children with medullary sponge kidney and hemihypertrophy may have an incomplete form of Beckwith-Wiedemann syndrome (BWS). Moreover, because of the high risk of malignancies in patients with BWS, these patients should be periodically screened for malignancies, including abdominal tumors.
• Urinalysis findings may show hematuria, low-grade proteinuria, and mild acidification and concentrating defects.

Causes

The cause of medullary sponge kidney is unknown.

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

Differential Diagnoses

Polycystic Kidney Disease

Other Problems to Be Considered

Calyceal diverticulum
Papillary necrosis
Other causes of nephrocalcinosis

Workup

Laboratory Studies

In patients with medullary sponge kidney (MSK) and hemihypertrophy, serial screening should be performed to exclude malignancies, including abdominal tumors. The following studies are also indicated:

• Urinalysis
  • Assessment of urinary calcium excretion
  • Urine culture
• A 24-hour urine collection for calcium, magnesium, and citrate: Patients with medullary sponge kidney may have high excretion of lithogenic molecules or low excretion of urinary inhibitors of stone formation.

Imaging Studies

• Intravenous pyelography reveals 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 medullary sponge kidney may be unilateral or may affect only a few papillae. Declining use of intravenous pyelography as an imaging technique may result in underdiagnosis of medullary sponge kidney cases.
• Renal ultrasonography and CT scanning are unnecessary except to distinguish medullary sponge kidney 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

Medical Care

No specific treatment for medullary sponge kidney (MSK) 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 urinary tract infections (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.

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 medullary sponge kidney is a nonprogressive condition with small medullary cysts, restriction of physical activity is unnecessary.

Medication

No medications are warranted for routine care of medullary sponge kidney (MSK). Use antibiotics in accordance with standard prescription practices to treat urinary tract infections (UTIs). See Urinary Tract Infection. Consider thiazide diuretics in patients with hypercalciuric urolithiasis.

Diuretics

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

Hydrochlorothiazide (Esidrix, HydroDIURIL, Microzide)

Decreases hypercalciuria and reduces risk of urolithiasis by promoting calcium reabsorption in distal convoluted tubule.

Dosing

Adult

50-100 mg/d PO

Pediatric

1-2 mg/kg/d PO

Interactions

Thiazides may decrease effects of anticoagulants, antigout agents, and sulfonylureas; thiazides may increase toxicity of allopurinol, anesthetics, antineoplastics, calcium salts, loop diuretics, lithium, diazoxide, digitalis, amphotericin B, and nondepolarizing muscle relaxants

Contraindications

Documented hypersensitivity; anuria or renal decompensation

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in patients with renal disease, hepatic disease, gout, diabetes mellitus, or erythematosus

Follow-up

Further Inpatient Care

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

Further Outpatient Care

• Periodic screening for hematuria, bacteriuria, and kidney stones

Inpatient & Outpatient Medications

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

Complications

• Gross hematuria
• Renal stones
• UTIs

Prognosis

• Medullary sponge kidney 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

Medicolegal Pitfalls

• Overtreatment of patients with medullary sponge kidney (MSK) is a pitfall.
• Failure to discriminate medullary sponge kidney, 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 medullary sponge kidney.

Multimedia

Media file 1: Unenhanced coronal volume-rendered (VR) CT image of the kidneys demonstrates 2 small calculi in the mid portion of the right kidney and 2 small calculi in the lower pole of the left kidney (arrowheads). A large low-density lesion in the lower pole of the right kidney and a small low-density lesion in the upper pole of the left kidney (short arrows) were shown to represent benign simple renal cysts on the contrast enhanced CT images. Image courtesy of Dr. Terri J. Vrtiska, Consultant, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.

Media file 2: CT image of both kidneys demonstrates brushlike densities throughout multiple papillae of both kidneys consistent with renal tubular ectasia. Correlation of the stone disease with the ectatic tubules is diagnostic of medullary sponge kidney. Image courtesy of Dr. Terri J. Vrtiska, Consultant, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.

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. Carboni I, Andreucci E, Caruso MR, et al. Medullary sponge kidney associated with primary distal renal tubular acidosis and mutations of the H+-ATPase genes. Nephrol Dial Transplant. Sep 2009;24(9):2734-8. [Medline].

3. Harris AM, Hall B, Kriss VM, Fowlkes JL, Kiessling SG. Rabson-Mendenhall syndrome: medullary sponge kidney, a new component. Pediatr Nephrol. Dec 2007;22(12):2141-4. [Medline].

4. 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].

5. Avner ED. Medullary sponge kidney. In: Greenber A, Cheung AK, Coffman TM, et al, eds. NKF Primer on Kidney Disease. 1997.

6. 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].

7. Patriquin HB, O'Regan S. Medullary sponge kidney in childhood. AJR Am J Roentgenol. Aug 1985;145(2):315-9. [Medline].

8. [Guideline] Tiselius HG, Alken P, Buck C, Gallucci M, Knoll T, Sarica K, Turk C. Guidelines on urolithiasis. Arnhem, The Netherlands: European Association of Urology (EAU); 2008 Mar. [Full Text].

Keywords

medullary sponge kidney, MSK, medullary cysts, renal cyst, Beckwith-Wiedemann syndrome, BWS, hemihypertrophy, Caroli disease, Ehlers-Danlos syndrome, Marfan syndrome, Marfan's syndrome, pyloric stenosis, kidney stones, treatment, diagnosis

Contributor Information and Disclosures

Author

Howard Trachtman, MD, Program Director, Pediatrics Research, Schneider Children's Hospital, Department of Pediatrics, Division of Nephrology, Professor, Albert Einstein College of Medicine
Howard Trachtman, MD is a member of the following medical societies: American Society of Hypertension, American Society of Nephrology, American Society of Pediatric Nephrology, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Medical Editor

Uri S Alon, MD, Director of Research and Education, Department of Pediatrics, Division of Pediatric Nephrology, Children's Mercy Hospital of Kansas City; Professor, University of Missouri at Kansas City
Uri S Alon, MD is a member of the following medical societies: American Federation for Medical Research
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Frederick J Kaskel, MD, PhD, Director of the Division and Training Program in Pediatric Nephrology, Vice Chair, Department of Pediatrics, Montefiore Medical Center and Albert Einstein School of Medicine
Frederick J Kaskel, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American Pediatric Society, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, American Society of Transplantation, Eastern Society for Pediatric Research, Federation of American Societies for Experimental Biology, International Society of Nephrology, National Kidney Foundation, New York Academy of Sciences, Renal Physicians Association, Sigma Xi, and Society for Pediatric Research
Disclosure: Nothing to disclose.

CME Editor

Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine
Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine
Disclosure: Baxter Honoraria Consulting

Chief Editor

Craig B Langman, MD, The Isaac A Abt, MD, Professor of Kidney Diseases, Feinberg School of Medicine, Northwestern University; Division Head of Kidney Diseases, Children's Memorial Hospital, Chicago
Craig B Langman, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Nephrology, and International Society of Nephrology
Disclosure: Amgen Grant/research funds None; Altus Pharmaceuticals Grant/research funds None; Genzyme Grant/research funds None; Merck Grant/research funds None; NIH Grant/research funds None

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