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Internal Medicine

Medullary sponge kidney (MSK)

Congenital disorder of the kidneys characterized by cystic dilatation of the collecting tubules in one or both kidneys.

Congenital disorder of the kidneys characterized by cystic dilatation of the collecting tubules in one or both kidneys.

History:

The introduction of radiological contrast media and IV urography in clinical diagnostics in the 1930s enabled the discovery of several diseases, including the medullary sponge kidney (MSK). MSK is a renal malformation characterized by cystic anomalies of precalyceal ducts, which is frequently associated with nephrocalcinosis and renal stones. Although it was first recognized by G Lenarduzzi in 1939, its thorough description was the result of the ante litteram multidisciplinary cooperation between a radiologist (Lenarduzzi), a urologist (Cacchi), and a pathologist (Ricci), all at the Padua University Hospital. These authors ‘established’ the paradigm for its diagnosis that is still used today Lenarduzzi-Cacchi-Ricci disease

Clinical features

  • Hematuria
  • Renal colic
  • Fever
  • Dysuria

Complications:

  • Recurrent urinary tract infections (UTI)
  • Nephrolithiasis and nephrocalcinosis
  • Type I (distal) renal tubular acidosis (dRTA)
  • Hypocitraturia
  • Long-term bone loss (d/t persistent renal leak type hypercalciuria)

Diagnosis

24-hour urine test:

Recommended to help optimize the urinary chemistry in motivated patients with medullary sponge kidney who develop stones
  • Renal leak type hypercalciuria
  • Hypocitraturia

USG/X-ray

  • Kidneys with hyperdense papillae with clusters of small stones

IV urogram (IVU)

GOLD STANDARD
  • “Paintbrush-like” or “feathered” appearance of  irregular (ectatic) collecting ducts
    • At interface of papilla & calyx
  • Cystic collections of ectatic collecting ducts like “bunches of grapes” or “bouquet of flowers“
Intravenous pyelogram showing brush-like striations (arrow) within dilated contrast-filled medullary tubules. | Perm J. 18(2), Imam TH, Taur AS, Patail H, image diagnosis: medullary sponge kidney. e130-e131, doi:10.7812/TPP/13-145, copyright(2014), Available from: www.thepermanentejournal.org.7

CT-urogram:

CT urogram (post-contrast) coronal view demonstrating dilated medullary contrast-filled tubules and medullary calcifications (arrow). | Perm J. 18(2), Imam TH, Taur AS, Patail H, image diagnosis: medullary sponge kidney. e130-e131, doi:10.7812/TPP/13-145, copyright(2014), Available from: www.thepermanentejournal.org.7

Differential diagnosis:

Other causes of medullary nephrocalcinosis (deposition of calcium salts in medulla of kidney)
  • Hyperparathyroidism
  • Renal tubular acidosis type I
  • Hypervitaminosis D
  • Milk-alkali syndrome
  • Sarcoidosis

Management

Treatment consists of managing the complications of medullary sponge kidney.

UTI management:

  • Antibiotics
  • Meticulous personal hygiene practices

Calcium stone management:

Most of the stones in patients with medullary sponge kidney tend to be small and will usually pass spontaneously, but occasionally surgery, ureteroscopy, or lithotripsy may be needed.
  • High fluid intake (sufficient to generate 2000 mL/day urine)
  • Dietary changes: Low in sodium, normal in calcium, high in potassium, and low to normal in protein
  • Potassium citrate supplementation (minimize long-term bone loss)
  • Bicarbonate supplements (↑ bone calcium)

Type I (distal) RTA:

  • Alkali therapy (replenish HCO3–)
  • K3-citrate supplementation (correct hypokalemia)

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