Medullary sponge kidney

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Medullary sponge kidney (MSK) is is a sporadic condition where the medullary and papillary portions of the collecting ducts are dysplastic, and dilated and in most cases develop medullary nephrocalcinosis. 

Epidemiology

The incidence of medullary sponge kidney is estimated at ≈1:5000.

Clinical presentation

Most patients with medullary sponge kidney remain asymptomatic throughout life, with the diagnosis only made incidentally when the renal tract is imaged for other reasons. 

Alternatively, patients may present with a complication (accounting for ~10% of patients), including:

Pathology

Medullary sponge kidney represents a developmental defect affecting the formation of collecting tubules and results in cystic dilatation of medullary and papillary portions of collecting ducts.   

Associations

Radiographic features

Medullary nephrocalcinosis occurs in the majority of cases (≈80%). It may be unilateral or bilateral, and affect a single or multiple pyramids. 

Plain radiograph / CT

Clusters of pyramidal medullary calcification are characteristic. Delayed post contrast CT may demonstrate a "paint brush" appearance to the renal medullary regions 4. Medullary white pyramid sign is a pitfall sometimes seen on non contrast-contrast CT KUBs.

Fluoroscopy

On IVP, pyelogram may give a characteristic bouquet of flowers appearance 3.

Ultrasound

Ultrasound of the kidneys of patients with medullary sponge kidneys typically demonstrates echogenic medullary pyramids. This appearance is found whether or not medullary nephrocalcinosis is also present. 

Differential diagnosis

The differential diagnosis is essentially that of medullary nephrocalcinosis and other causes of multiple medullary cysts as well as medullary white pyramid sign:

  • -<p><strong>Medullary sponge kidney (MSK)</strong> is a sporadic condition where the medullary and papillary portions of the collecting ducts are dysplastic, and dilated and in most cases develop <a href="/articles/medullary-nephrocalcinosis">medullary nephrocalcinosis</a>. </p><h4>Epidemiology</h4><p>The incidence of medullary sponge kidney is estimated at ≈1:5000.</p><h4>Clinical presentation</h4><p>Most patients with medullary sponge kidney remain asymptomatic throughout life, with the diagnosis only made incidentally when the renal tract is imaged for other reasons. </p><p>Alternatively, patients may present with a complication (accounting for ~10% of patients), including:</p><ul>
  • -<li><a href="/articles/urinary-tract-infection">urinary tract infection (UTI)</a></li>
  • +<p><strong>Medullary sponge kidney</strong> is a sporadic condition where the medullary and papillary portions of the collecting ducts are dysplastic, and dilated and in most cases develop <a href="/articles/medullary-nephrocalcinosis">medullary nephrocalcinosis</a>. </p><h4>Epidemiology</h4><p>The incidence of medullary sponge kidney is estimated at ≈1:5000.</p><h4>Clinical presentation</h4><p>Most patients with medullary sponge kidney remain asymptomatic throughout life, with the diagnosis only made incidentally when the renal tract is imaged for other reasons. </p><p>Alternatively, patients may present with a complication (accounting for ~10% of patients), including:</p><ul>
  • +<li><a href="/articles/urinary-tract-infection">urinary tract infection</a></li>
  • -<a href="/articles/urolithiasis">urolithiasis</a> / <a href="/articles/urolithiasis">ureteric calculi</a>
  • +<a href="/articles/urolithiasis">urolithiasis</a>/<a href="/articles/urolithiasis">ureteric calculi</a>
  • -</ul><h4>Radiographic features</h4><p><a href="/articles/nephrocalcinosis">Medullary nephrocalcinosis</a> occurs in the majority of cases (≈80%). It may be unilateral or bilateral, and affect a single or multiple pyramids. </p><h5>Plain radiograph / CT</h5><p>Clusters of pyramidal medullary calcification are characteristic. Delayed post contrast CT may demonstrate a "paint brush" appearance to the renal medullary regions <sup>4</sup>. Medullary <a href="/articles/white-pyramid-sign-1">white</a><a href="/articles/white-pyramid-sign-1"> pyramid </a><a href="/articles/white-pyramid-sign-1"> sign</a> is a pitfall sometimes seen on non contrast CT KUBs.</p><h5>Fluoroscopy</h5><p>On IVP, pyelogram may give a characteristic <a href="/articles/bouquet-of-flowers-appearance">bouquet of flowers appearance</a> <sup>3</sup>.</p><h5>Ultrasound</h5><p>Ultrasound of the kidneys of patients with medullary sponge kidneys typically demonstrates echogenic medullary pyramids. This appearance is found whether or not medullary nephrocalcinosis is also present. </p><h4>Differential diagnosis</h4><p>The differential diagnosis is essentially that of <a href="/articles/medullary-nephrocalcinosis">medullary nephrocalcinosis</a> and other causes of multiple medullary cysts as well as medullary <a href="/articles/white-pyramid-sign-1">white</a><a href="/articles/white-pyramid-sign-1"> pyramid </a><a href="/articles/white-pyramid-sign-1"> sign</a>:</p><ul>
  • +</ul><h4>Radiographic features</h4><p><a href="/articles/nephrocalcinosis">Medullary nephrocalcinosis</a> occurs in the majority of cases (≈80%). It may be unilateral or bilateral, and affect a single or multiple pyramids. </p><h5>Plain radiograph / CT</h5><p>Clusters of pyramidal medullary calcification are characteristic. Delayed post contrast CT may demonstrate a "paint brush" appearance to the renal medullary regions <sup>4</sup>. Medullary <a href="/articles/white-pyramid-sign-1">white</a><a href="/articles/white-pyramid-sign-1"> pyramid </a><a href="/articles/white-pyramid-sign-1"> sign</a> is a pitfall sometimes seen on non-contrast CT KUBs.</p><h5>Fluoroscopy</h5><p>On IVP, pyelogram may give a characteristic <a href="/articles/bouquet-of-flowers-appearance">bouquet of flowers appearance</a> <sup>3</sup>.</p><h5>Ultrasound</h5><p>Ultrasound of the kidneys of patients with medullary sponge kidneys typically demonstrates echogenic medullary pyramids. This appearance is found whether or not medullary nephrocalcinosis is also present. </p><h4>Differential diagnosis</h4><p>The differential diagnosis is essentially that of <a href="/articles/medullary-nephrocalcinosis">medullary nephrocalcinosis</a> and other causes of multiple medullary cysts as well as medullary <a href="/articles/white-pyramid-sign-1">white</a><a href="/articles/white-pyramid-sign-1"> pyramid </a><a href="/articles/white-pyramid-sign-1"> sign</a>:</p><ul>
  • -<a href="/articles/peroneus-brevis-1">renal tubular acidosis</a> (type 1)</li>
  • -<li><a href="/articles/peroneus-brevis-1">hypervitaminosis D</a></li>
  • +<a href="/articles/renal-tubular-acidosis">renal tubular acidosis</a> (type 1)</li>
  • +<li><a href="/articles/hypervitaminosis-d">hypervitaminosis D</a></li>

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