What is medullary sponge kidney?
Medullary sponge kidney (MSK) is a birth defect of the tubules—tiny tubes inside the kidneys. In a normal kidney, urine flows through these tubules as it is being formed. In MSK, tiny sacs called cysts form in the medulla—the inner part of the kidney—creating a sponge-like appearance. The cysts keep urine from flowing freely through the tubules. MSK is present at birth but most cases do not appear to be inherited. Problems caused by MSK include hematuria, or blood in urine; kidney stones; and urinary tract infections (UTIs). But these problems do not usually appear until the ages of 30 to 40. MSK affects about 1 person per 5,000 to 20,000 people in the United States.1 Researchers have reported that up to 20 percent of people who form kidney stones have MSK.2 MSK rarely leads to more serious problems, such as total kidney failure. 1Glassberg KI. Renal dysgenesis and cystic disease of the kidney. In: Walsh PC, Retik AB, Vaughan ED, Wein AJ, eds. Campbell’s Urology. Vol. 3. 8th ed. Philad
