Close
New

Medscape is available in 5 Language Editions – Choose your Edition here.

 

Medullary Sponge Kidney

  • Author: Amit K Ghosh, MD, DM, FACP, MBA; Chief Editor: Vecihi Batuman, MD, FACP, FASN  more...
 
Updated: Mar 06, 2014
 

Background

Medullary sponge kidney is a benign congenital disorder characterized by dilatation of collecting tubules in 1 or more renal papillae, affecting 1 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 (see the image below). (See Presentation and Epidemiology.)[1, 2]

IVU-like, volume-rendered (VR) computed tomography IVU-like, volume-rendered (VR) computed tomography (CT) scan 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.

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.

Complications associated with medullary sponge kidney include the following (see Presentation, Workup, Treatmen t, and Medication):

  • Renal stones
  • Hematuria
  • Distal renal tubular acidosis (RTA; type 1 RTA)
  • Renal insufficiency (rarely)
Next

Pathophysiology and Etiology

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.

The disease is bilateral in 70% of cases, and unilateral involvement of only 1 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 1-7mm 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 with columnar or cuboidal epithelium and rarely by transitional epithelium, which is caused by the effects of calculi. Closed cysts are lined with atrophic epithelium. The rest of the kidney usually is normal, unless pyelonephritis or renal obstruction complicates the course of the disease.

Etiology

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 resulting from tubular obstruction due to calcium oxalate calculi secondary to infantile hypercalciuria.

In most patients with medullary sponge kidney, no family history of the condition is known, although there is a rare, familial, autosomal dominant form of the disease. A rare, autosomal recessive form is associated with Caroli disease.

Previous
Next

Epidemiology

Occurrence in the 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 addition, medullary sponge kidney has been identified in 12-20% of patients who form calcium stones.[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.

Sex- and age-related demographics

Women are affected by medullary sponge kidney more frequently than are men. In addition, while the overall incidence of calcium stones is 15-20% in medullary sponge kidney, the incidence is even higher in women, reaching 20-30%. In patients with nephrolithiasis, a higher relative prevalence of medullary sponge kidney occurs in female patients than in males.

Medullary sponge kidney is commonly diagnosed during the second or third decade of life. The mean age of patients diagnosed is approximately 27 years.

Previous
Next

Prognosis

Medullary sponge kidney is usually a benign disorder without any serious morbidity or mortality. However, renal insufficiency may occur in as many as 10% of patients with the disorder.

Occasionally, patients can have recurrent nephrolithiasis, which can lead to significant morbidity. Very rarely, patients may develop renal failure as a result of repeated pyelonephritis or urinary tract obstruction.

In approximately 10% of patients with medullary sponge kidney, major morbidity is caused by repeatedly passing renal stones and by 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 with 0.66 stones per year in other people who form calcium stones.

Some physicians may encounter patients with medullary sponge kidney who claim severe, chronic renal pain without any manifestation of infection, stones, or obstruction. The source of this pain is unclear. These patients may be treated best by physicians comfortable with chronic pain management.

A grading system has been devised that could identify patients with medullary sponge kidney who are at an increased risk for complications based on intravenous urographic findings.[4]

Previous
Next

Patient Education

Patients should receive educational materials, including handouts, informing them of the importance of maintaining volume expansion in order to maintain a daily urinary output in excess of 2L. Handouts should indicate that medullary sponge kidney is a benign disorder and requires no specific therapy.

Patients should also be informed of the possibility of a genetic role in their condition if other members of their families have a history of renal stones. For patient education information, see Blood in the Urine.

Previous
 
 
Contributor Information and Disclosures
Author

Amit K Ghosh, MD, DM, FACP, MBA Professor of Medicine, Mayo Medical School; Consultant in General Internal Medicine, Mayo Clinic

Amit K Ghosh, MD, DM, FACP, MBA is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine, American Society of Nephrology, Minnesota Medical Association, Society of General Internal Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Karthik Ghosh, MD Consultant, Associate Professor of Medicine, Department of Internal Medicine, Mayo Medical School

Karthik Ghosh, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine

Disclosure: Nothing to disclose.

Chief Editor

Vecihi Batuman, MD, FACP, FASN Huberwald Professor of Medicine, Section of Nephrology-Hypertension, Tulane University School of Medicine; Chief, Renal Section, Southeast Louisiana Veterans Health Care System

Vecihi Batuman, MD, FACP, FASN is a member of the following medical societies: American College of Physicians, American Society of Hypertension, American Society of Nephrology, International Society of Nephrology

Disclosure: Nothing to disclose.

Acknowledgements

Eleanor Lederer, MD Professor of Medicine, Chief, Nephrology Division, Director, Nephrology Training Program, Director, Metabolic Stone Clinic, Kidney Disease Program, University of Louisville School of Medicine; Consulting Staff, Louisville Veterans Affairs Hospital

Eleanor Lederer, MD is a member of the following medical societies: American Association for the Advancement of Science, American Federation for Medical Research, American Society for Biochemistry and Molecular Biology, American Society for Bone and Mineral Research, American Society of Nephrology, American Society of Transplantation, International Society of Nephrology, Kentucky Medical Association, National Kidney Foundation, and Phi Beta Kappa

Disclosure: Dept of Veterans Affairs Grant/research funds Research

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

References
  1. Fick GM, Gabow PA. Hereditary and acquired cystic disease of the kidney. Kidney Int. 1994 Oct. 46(4):951-64. [Medline].

  2. 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. 2006 Feb. 69(4):663-70. [Medline].

  3. 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. 2001 Jun. 37(6):1140-3. [Medline].

  4. 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].

  5. Levine E, Hartman DS, Meilstrup JW, et al. Current concepts and controversies in imaging of renal cystic diseases. Urol Clin North Am. 1997 Aug. 24(3):523-43. [Medline].

  6. Palubinskas AJ. Renal pyramid structure opacification in excretory urography and its relation to medullary sponge kidney. Radiology. 1963 Dec. 81:963-70. [Medline].

  7. Higashihara E, Nutahara K, Tago K, et al. Medullary sponge kidney and renal acidification defect. Kidney Int. 1984 Feb. 25(2):453-9. [Medline].

  8. Fabris A, Lupo A, Bernich P, et al. Long-term treatment with potassium citrate and renal stones in medullary sponge kidney. Clin J Am Soc Nephrol. 2010 Sep. 5(9):1663-8. [Medline].

  9. 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. 2003 Mar. 61(3):528-32. [Medline].

  10. McPhail EF, Gettman MT, Patterson DE, Rangel LJ, Krambeck AE. Nephrolithiasis in Medullary Sponge Kidney: Evaluation of Clinical and Metabolic Features. Urology. 2011 Oct 17. [Medline].

 
Previous
Next
 
IVU-like, volume-rendered (VR) computed tomography (CT) scan 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.
Unenhanced coronal, volume-rendered (VR) computed tomography (CT) scan of the kidneys demonstrates 2 small calculi in the midportion 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 scans. Image courtesy of Dr. Terri J. Vrtiska, Consultant, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
Table 1. Clinical Features of Medullary Sponge Kidney and Etiologic Correlation
Frequency Clinical Findings Etiology
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)



*Asymptomatic
Table 2. Radiologic Appearance in Medullary Sponge Kidney
Radiologic Test Appearance
Plain radiograph Normal or enlarged kidney



Medullary nephrocalcinosis indicated by isolated, single or multiple precaliceal concretions or clusters of grapelike calcifications



Excretory urogram* Papillary blush



Faint pyramidal striation



Papillary streaking or brushlike appearance



Precaliceal tubular dilatation filled with contrast



Papillary blush and multiple precaliceal dilatation



Bouquet of flowers



CT scan Papillary calcification



Hyperdense papilla



Ectasia of precaliceal tubules



*Findings limited to medullary pyramids
Previous
Next
 
 
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.