Medullary Sponge Kidney - Renal Tubular Acidosis
Cacchi-Ricci Disease

General Considerations

• Developmental dilatation of the collecting tubules in the medullary pyramids of kidneys
• Usually in people 10-30 years old
• Pathogenesis is not known
• Multiple cysts connect the collecting tubule with the papillary ducts or calyces
  • The cysts may contain calcifications
  • Stones are usually calcium apatite and calcium oxalate or calcium apatite alone
  Clinical Findings
  • Most patients are asymptomatic
  • Complications of hematuria, infection or stone formation produce symptoms
  Imaging Findings
  • Usually bilateral
  • Plain radiographs may show numerous medullary calcifications
    • Discrete clusters of small calcifications in the regions of the renal pyramids is characteristic
  • A non-contrast and contrast-enhanced CT is now the study of choice
  • Cystic dilatation of the distal collecting tubules called bunch of grapes or bouquet of flowers
  • Striated appearance to distal tubules
  • Calyces can become cupped and distorted
  • Calcifications arrange around calyx
  • Calculi can cause ureteral obstruction and hydronephrosis
  Differential Diagnosis
  • Benign tubular ectasia
    • Paintbrush appearance of distal tubules
    • Tubules are not dilated
    • No calcifications
  • Other causes of nephrocalcinosis
  • See table below

  Causes of Medullary Nephrocalcinosis

  Hyperparathyroidism

  Renal tubular acidosis

  Medullary sponge kidney

  Multiple bony metastases

  Paget disease

  Sarcoid

  Hypervitaminosis D

  Milk-alkali syndrome

  Williams syndrome

  
  Treatment
  • Rarely needed
  • Drainage procedures if kidney because obstructed
  Complications
  • Infection
  • Stone formation
  • Hematuria
  • Rarely, progression to renal impairment
  • When associated with Beckwith-Wiedemann Syndrome, there is a high rate of Wilms tumors, hepatoblastomas and other tumors
  • Rarely, growth failure in children due to concomitant renal tubular acidosis
  Prognosis
  • Normal life expectancy



Medullary Sponge Kidneys with Calculi. The enhanced CT coronal reconstruction on the left demonstrates the typical ectatic distal ducts in the renal papillae (inset). The images of the right show numerous small bilateral renal calculi (white circles).
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eMedicine Medullary Sponge Kidney Khan, A; Chandramohan, M; MacDonald, S