Medullary Sponge Kidney: Current Perspectives

Abstract

Medullary Sponge Kidney (MSK) disease is a rare congenital malformation of the distal nephron where cystic dilatation is appreciable in the collecting ducts and renal papillae. Most cases of the malformation are thought to arise from a malfunction within neurotrophic factor and tyrosine kinase interactions. Presentation and prognosis are usually indolent; however, they include urinary tract infections (UTI), nephrolithiasis and nephrocalcinosis, distal renal tubular acidosis (dRTA) and hypocitraturia. With an insidious and asymptomatic onset, MSK is a difficult renal manifestation to both diagnose and treat. Difficulty diagnosing MSK today arises from clinical settings deviating from the usage of contrast methods when assessing the urogenital tract. Many healthcare standards for kidney disorders center diagnosis around imaging techniques rather than contrast methods. This ultimately leads to a decrease in the total number of confirmed cases of MSK. Though intra-venous urogram (IVU) remains as the current gold standard to diagnose MSK, other methods such as endoscopy and Multi-detector computed tomography (MDCT) are being put into place. Endoscopic examination and renal biopsy may allow definitive diagnosis; however, such invasive methods may be considered excessive. Moving forward, differential diagnoses for MSK can be made more precisely when patients present with other renal manifestations, especially in groups at risk. These groups include patients between the age of 20 and 30, patients with other renal malformations, high sodium diet patients, hyperparathyroid patients, and patients with family history of MSK. Basic treatment is aimed at controlling stone formation by stabilizing urinary pH. Treatment for patients, especially those prone to forming stones, includes the application of potassium citrate compounds, prophylactic water and diet control, surgical intervention or lithotripsy for removal of symptomatic kidney stones.

Keywords: medullary sponge kidney; nephrocalcinosis; nephron; renal stones.

Figure 1

Intravenous pyelogram showing brush-like striations (arrow) within dilated contrast-filled medullary tubules. Note: Reprinted from Perm J. 18(2), Imam TH, Taur AS, Patail H, image diagnosis: medullary sponge kidney. e130-e131, doi:10.7812/TPP/13-145, copyright(2014), with permission from The Permanente Press. Available from: www.thepermanentejournal.org.

Figure 2

Computerized tomography urogram (post-contrast) coronal view demonstrating dilated medullary contrast-filled tubules and medullary calcifications (arrow). Note: Reprinted from Perm J. 18(2), Imam TH, Taur AS, Patail H, image diagnosis: medullary sponge kidney. e130-e131, doi:10.7812/TPP/13-145, copyright(2014), with permission from The Permanente Press. Available from: www.thepermanentejournal.org.