Medullary sponge kidney

Medullary sponge kidney 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

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

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:

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

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 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. 

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

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Article Information

rID: 1653
System: Urogenital
Section: Pathology
Tag: kidney
Synonyms or Alternate Spellings:
  • Medullary sponge kidney (MSK)
  • Medullary sponge kidneys (MSK)
  • Medullary sponge kidneys

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Cases and Figures

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    Case 4 : with Caroli disease
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