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Medullary Sponge Kidney Workup

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

Approach Considerations

The diagnosis of medullary sponge kidney is usually suspected in patients presenting with renal calculi, hematuria, or multiple urinary tract infections (UTIs). Prior clinical suspicion of medullary sponge kidney is important because it helps in ordering the most relevant radiologic tests.

Metabolic acidosis may occur secondary to renal tubular acidosis (RTA) (type 1 RTA or distal RTA) and is usually diagnosed during an acidification test as an inability to reduce the pH of urine to less than 5.3. Incomplete distal RTA is more common than frank type 1 RTA and, thus, may be missed on electrolyte testing because incomplete RTA does not show resting metabolic acidosis. However, incomplete distal RTA has been known to contribute to stone formation.[7]

A defective urinary concentrating ability is the inability to achieve maximal urine osmolality (ie, 900 mOsm/kg or greater) with water restriction. However, the defect in urinary concentrating ability is usually mild, and patients are asymptomatic.

Hypercalciuria may occur in 30-50% of cases. Patients with medullary sponge kidney nephrolithiasis who are hypercalciuric have a higher incidence of renal leak–type hypercalciuria than do patients with hypercalciuric calcium stones without medullary sponge kidney. A higher incidence of hypocitraturia occurs in medullary sponge kidney.

Pediatric patients

Children with medullary sponge kidney identified in childhood must be evaluated for other urologic abnormalities and must undergo surveillance for future urologic and abdominal tumors.

Patients with medullary sponge kidney and microscopic hematuria

In rare instances, this condition may be associated with nephrocalcinosis. However, other causes of microhematuria, such as bladder cancer, renal tumors, and benign prostatic hypertrophy, must be excluded and often require a urology referral.

Patients with medullary sponge kidney and gross hematuria

Bladder tumors and pelvic obstruction must be ruled out aggressively. Children with medullary sponge kidney and gross hematuria must be evaluated for Wilms tumor.

Stone risk factors

Fabris and colleagues indicated that patients with medullary sponge kidney should be screened using 24-hour urine collection to evaluate for stone risk factors (ie, hypocitraturia, hypercalciuria, hyperuricosuria, hyperoxaluria).[8]

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Symptomatic Patients With Medullary Sponge Kidney

These patients must be evaluated routinely using a renal function test, radiologic surveillance, and ultrasonography. Urinary pH of more than 5.3 in adults and more than 5.6 in children in the setting of non–anion gap metabolic acidosis can indicate the presence of distal RTA (type 1). However, urinary pH can also be alkaline in the presence of UTI because of urea-splitting organisms.

The diagnosis of distal RTA can be established simply by raising the plasma bicarbonate concentration toward the reference range (ie, 18-20 mEq/L) with an intravenous infusion of sodium bicarbonate at a rate of 0.5-1.0 mEq/kg/h. The fractional excretion of bicarbonate is less than 3%, and the urine pH remains relatively stable in type 1 disease. Raising the plasma bicarbonate concentration to 18-20 mEq/L has little effect on bicarbonate excretion in type 1 RTA because no defect in proximal reabsorptive capacity exists.

The presence of urinary infection with urea-splitting organisms can lead to struvite stones and subsequent renal insufficiency. This must be identified and promptly treated. Moreover, patients with medullary sponge kidney and other renal or congenital abnormalities must be evaluated for oncologic tumors.

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Imaging Studies

Urography

The diagnosis of medullary sponge kidney is usually confirmed by findings on excretory urography (see Table 2, below), which reveals radial, linear striations in the papillae. These striations, which are often referred to as "brushlike" patterns, result from the collection of contrast in dilated and cystic collecting tubules.[6] Cystic collections of contrast media in the ectatic collecting duct are referred to as "bunches of grapes" or "bouquets of flowers."

High-quality excretory urography with renal tomograms obtained before and after injection of contrast medium and then every 4 minutes during the next 20 minutes has been described as the most accurate method of identifying medullary sponge kidney. The diagnosis of medullary sponge kidney can be missed if the preparation is suboptimal.

CT scanning

Computed tomography (CT) scanning can reveal papillary calcification or hyperdense papillae, but it is usually is not as sensitive as excretory urography. CT scanning can also be used to help identify other renal abnormalities, such as associated cysts, horseshoe kidney, renal abscess, and papillary necrosis. Helical CT scanning has been demonstrated to improve the definition of the abnormalities in medullary sponge kidney. (See the images below and Table 2.)[9]

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.
Unenhanced coronal, volume-rendered (VR) computed 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.

Radiography and ultrasonography

Abdominal plain film may reveal nephrocalcinosis (see Table 2, below). Ultrasonography of the kidney in medullary sponge kidney may reveal calcification in the medullary region. In earlier cases of medullary sponge kidney without calcification, the papillae may appear bright on an ultrasonogram.

Table 2. Radiologic Appearance in Medullary Sponge Kidney (Open Table in a new window)

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
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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].

 
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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
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