Medullary Sponge Kidney

Key Features

• A relatively common and benign disorder

• Present at birth and not usually diagnosed until the fourth or fifth decade

• Caused by autosomal dominant mutations in the MCKD1 or MCKD2 genes on chromosomes 1 and 16, respectively

• Kidneys have a marked irregular enlargement of the medullary and interpapillary collecting ducts

Clinical Findings

• May presents with gross or microscopic hematuria, recurrent urinary tract infections, or nephrolithiasis

• Common abnormalities are a decreased urinary concentrating ability and nephrocalcinosis

• Less common is incomplete type I distal renal tubular acidosis

Diagnosis

• CT shows

  • Cystic dilatation of the distal collecting tubules with a striated appearance

  • Calcifications in the renal collecting system

Treatment

• No known therapy

• Adequate fluid intake (2 L/day) helps prevent stone formation

• If hypercalciuria is present, thiazide diuretics are recommended because they decrease calcium excretion

• Alkali therapy is recommended if renal tubular acidosis is present