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.
- Ehlers-Danlos syndrome 3
- congenital hemihypertrophy / Beckwith-Wiedemann syndrome (rare) 1
- Caroli disease 2
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 paintbrush appearance to the renal medullary regions 4. The medullary white pyramid sign is a pitfall sometimes seen on non-contrast CT KUBs.
On IVP, the pyelogram may give a characteristic bouquet of flowers appearance 3 or paintbrush appearance.
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.
History and etymology
In 1931, Lenarduzzi described the medullary sponge kidney for the first time.
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