Medullary Sponge Kidney

Excerpt

Medullary sponge kidney is a benign congenital abnormality that was first described in 1939 by Lendarduzzi. Anatomically it is characterized by cystic dilatation of the renal medullary collecting ducts. These numerous small cysts range in diameter from 1 to 8 millimeters and give the kidney, when cut, the appearance of a sponge, thus the name.

Medullary sponge kidney is usually bilateral but can affect only one kidney. The condition is bilateral in 70% of cases, and it is a relatively rare disorder with a prevalence of about 1/5,000 population. It is usually asymptomatic but can present with hematuria, urinary tract infections (UTIs), or renal stone formation. The age of presentation is usually 20 to 30 years old.

Distinguishing medullary sponge kidney from medullary nephrocalcinosis is important. Medullary sponge kidney is one of several common causes of medullary nephrocalcinosis. Medullary nephrocalcinosis is defined as the deposition of calcium salts in the medulla of the kidney. Other causes of medullary nephrocalcinosis include hyperparathyroidism, renal tubular acidosis type I, hypervitaminosis D, milk-alkali syndrome, and sarcoidosis.