<p>Medullary Sponge Kidney: Current Perspectives</p>

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.

Ultrasound to address medullary sponge kidney: a retrospective study

“…MSK was recognized as a distinct disease with the introduction of urography in clinical practice. However, this pathological entity seems to be disappearing, likely because urography has almost been abandoned in favor of abdominal CT, usually without administration of contrast medium, which lacks specific/pathognomonic signs of MSK [1,2,4,6,12]. In fact unenhanced abdominal CT has replaced IVU in the diagnostic work-up of acute renal colic from ureteral calculi because of a higher sensitivity and specificity [11].…”

“…Medullary sponge kidney (MSK) is a rare renal disease, characterized by ectasia and cystic dilatation of intrapapillary portions of medullary collecting ducts that give the renal medulla a "spongy" appearance at autopsy. Its prevalence in the general population is not exactly known, but is estimated to be about 1/5000 persons and, among patients with recurrent nephrolithiasis, it ranges from 12 to 20% [1][2][3][4][5][6][7]. MSK is typically associated with nephrocalcinosis and recurrent renal stones formation, distal renal tubular acidosis, hypocitraturia, hypercalcemia, renal concentration defects and defects of the proximal tubule, such as low molecular weight proteinuria and an altered Tm (transport maximum) for glucose, phosphate and para-aminohippuric acid [1,2,7].…”

“…In fact, neither ultrasonography, nor CT or magnetic resonance (MR) are thought to provide specific findings for the diagnosis of the disease [1,2,8]. Nevertheless, recognizing MSK is clinically important becauseeven if there is no specific therapy-these patients should receive prophylaxis against stone formation and urinary tract infections to avoid progression to renal failure [1,2,[5][6][7].…”

“…Intravenous urography (IVU) is still considered the gold standard for the diagnosis of MSK. This technique reveals pathognomonic images of collection of contrast medium in dilated papillary ducts, giving the appearance of a blush or linear striations in the mildest cases or of a bouquet of flowers in full-blown cases [ 1 – 4 , 6 , 8 – 10 ]. However, as in patients with nephrolithiasis urography is now less used in favor of computed tomography (CT), the chances to diagnose MSK are likely reduced [ 11 ].…”

Considerations for utilizing medullary sponge kidney allografts in pediatric patients

“…It normally affects the medulla, and cortical structures are almost always spared.Presentation is usually indolent and can include urinary tract infections (UTI), kidney stones, nephrocalcinosis, distal kidney tubular acidosis, and hypocitraturia. 8 Deciding whether to accept a living donor with MSK is a multifaceted task because of the potential challenge of managing pediatric recipients post-transplant given risk of UTI and recurrent nephrolithiasis with progression to chronic kidney disease. 6,9,10 Recently, it was reported that donors with history of MSK had lower kidney stone-related events after nephrectomy compared with non-donors with MSK.…”