Medullary Sponge Kidney

In medullary sponge kidney, the collecting ducts the renal pyramids dilate, and cavities, clefts, and cysts, form in the medulla. Medullary sponge kidney may affect only a single pyramid in one kidney or all pyramids in both kidneys. An affected kidney may be normal in size, but it's usually somewhat enlarged and spongy.

Because this disorder is usually asymptomatic and benign, it's commonly overlooked until the patient reaches adulthood. Although found in both sexes and in all age-groups, it's usually diagnosed in adolescents and adults ages 30 to 50. The prognosis usually is good.

This disorder is unrelated to medullary polycystic disease, a hereditary disorder. These conditions are similar only in the presence and location of the cysts.

Causes

Nephrocalcinosis may be caused by a number of conditions:

• Excess excretion of calcium by the kidney
• Renal tubular acidosis
• Medullary sponge kidney
• Hypercalcemia (high calcium levels in the blood)
• Renal cortical necrosis
• Tuberculosis

Fragments of calcium oxalate or calcium phosphate may break free from the kidney and provide nuclei for formation of stones ( nephrolithiasis ). This may result in obstructive uropathy , possibly leading to eventual kidney failure if the obstructing stones are not passed in the urine or removed. Nephrocalcinosis may therefore be discovered when symptoms of renal insufficiency / renal failure , obstructive uropathy, or urinary tract stones develop.

Signs and Symptoms

• Increased urine volume or urine output, decreased
• Urinary hesitancy
• Dribbling of urinary incontinence
• Decrease in the force of the urinary stream, stream small and weak
• Increased urinary frequency or urgency
• A need to urinate at night ( nocturia )
• Painful urination
• Feeling of incomplete emptying of the bladder
• Blood in the urine
• Nausea , vomiting
• Generalized swelling , fluid retention
• Decrease in sensation , especially the hands or feet
• Changes in mental status
  • drowsy , lethargic , hard to arouse
  • delirium or confusion
  • coma

Diagnostic tests

Excretory urography - usually the key to diagnosis­ typically reveals a characteristic flowerlike appearance of the pyramidal cavities when they fill with contrast material. It also may show renal calculi.

Urinalysis is normal unless complications develop, such as an increased white blood cell count and casts with infection, and an increased red blood cell count with hematuria. It may show hypercalciuria or a slight reduction in concentrating ability.

Diagnosis must distinguish medullary sponge kidney from renal tuberculosis, renal tubular acidosis, and healed papillary necrosis. If infection is suspected, calculi should be evaluated.

Treatment

Treatment is focused on preventing or treating complications caused by calculi and infection. Specific measures include increasing fluid intake and monitoring renal function and urine output. If new symptoms develop, the patient needs immediate evaluation.

Because medullary sponge kidney is benign, surgery is seldom necessary except to remove calculi during acute obstruction. Only serious, uncontrollable infection or hemorrhage necessitates nephrectomy.

Prevention

Diligent monitoring for infection at regular intervals and at the first symptom will give the best long-term results. By drinking extra liquids, most stones can be prevented. The most common kind of stones, calcium stones, can be deterred by regularly taking a medication that encourages urine production (thiazide diuretic).