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. Medullary white pyramid sign is a pitfall sometimes seen on non-contrast CT KUBs.
On IVP, pyelogram may give a characteristic bouquet of flowers appearance 3.
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.
- 1. Eisenberg RL, Pfister RC. Medullary sponge kidney associated with congenital hemihypertrophy (asymmetry). A case report and survey of the literature. Am J Roentgenol Radium Ther Nucl Med. 1972;116 (4): 773-7. Am J Roentgenol Radium Ther Nucl Med (abstract) - Pubmed citation
- 2. Fulcher AS, Turner MA, Sanyal AJ. Case 38: Caroli disease and renal tubular ectasia. Radiology. 2001;220 (3): 720-3. doi:10.1148/radiol.2203000825 - Pubmed citation
- 3. Rommel D, Pirson Y. Medullary sponge kidney--part of a congenital syndrome. Nephrol. Dial. Transplant. 2001;16 (3): 634-6. doi:10.1093/ndt/16.3.634 - Pubmed citation
- 4. Joffe SA, Servaes S, Okon S et-al. Multi-detector row CT urography in the evaluation of hematuria. Radiographics. 23 (6): 1441-55. doi:10.1148/rg.236035085 - Pubmed citation