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.

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:

• urinary tract infection
• hematuria
• urolithiasis/ureteric calculi

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

• Ehlers-Danlos syndrome 
• congenital hemihypertrophy / Beckwith-Wiedemann syndrome (rare) 
• Caroli disease 

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 paintbrush appearance to the renal medullary regions . The medullary white pyramid sign is a pitfall sometimes seen on non-contrast CT KUBs.

Fluoroscopy

On IVP, the pyelogram may give a characteristic bouquet of flowers appearance or paintbrush appearance.

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:

• medullary calcifications
  • hyperparathyroidism
  • renal tubular acidosis (type 1)
  • hypervitaminosis D
  • milk-alkali syndrome
  • other pathological hypercalcemic or hypercalciuric states
• medullary cysts
  • medullary cystic disease (nephronophthisis)
• renal tubular ectasia
  • a less pronounced, incidental variant

Siehe auch:

• primärer Hyperparathyreoidismus
• medulläre Nephrokalzinose
• Nierenverkalkungen
• Nephronophthise

und weiter:

• genitourinary curriculum
• Nierentuberkulose
• Randall-Plaques
• paintbrush appearance
• echogenic renal pyramids
• caroli disease with medullary sponge kidney and nephrocalcinosis
• Caroli's disease associated with medullary sponge kidney
• bouquet of flowers appearance