Section 11. Kidney and Urinary Tract Disorders

Chapter 146. Tubular and Cystic Kidney Disorders

Topics: Introduction | Renal Tubular Acidosis | Renal Glucosuria | Nephrogenic Diabetes Insipidus | Cystinuria | Fanconi's Syndrome | Hypophosphatemic Rickets | Hartnup Disease | Bartter's Syndrome | Liddle's Syndrome | Polycystic Kidney Disease | Medullary Cystic Disease | Medullary Sponge Kidney | Alport's Syndrome | Nail-Patella Syndrome

Medullary Cystic Disease

Medullary cystic disease is a rare disorder in which fluid-filled sacs (cysts) develop deep within the kidneys, leading to kidney failure.

Medullary cystic disease either is hereditary or is caused by a non-genetic abnormality that occurs during development of the fetus. The disorder damages microscopic tubules within the kidneys. The damaged tubules are less able to concentrate urine and reabsorb sodium. Dehydration, a low level of sodium in the blood, and an elevated concentration of urea and creatinine in the blood may occur if sodium intake is not adequate.

Symptoms and Diagnosis

Symptoms usually begin before age 20, but symptoms vary greatly, and a few people do not have any symptoms until much later. A person starts to produce excessive amounts of urine as the kidneys' responsiveness to antidiuretic hormone diminishes. Retarded growth and evidence of bone disease are common in children. In many people, these problems develop slowly over several years, and the body compensates so well that the problems are not recognized until kidney failure is advanced.

Laboratory tests reveal poor kidney function. The level of sodium in the blood is often low. X-rays show that the kidneys are small. Ultrasonography may detect cysts deep within the kidneys, although the cysts may be too small to be detected. Computed tomography (CT) is the test that is most likely to detect cysts.

Prognosis and Treatment

The disease progresses slowly but relentlessly. A large daily intake of fluids and salt (sodium) is needed to compensate for the excessive excretion of sodium and the production of large volumes of dilute urine. When kidney failure occurs, dialysis or kidney transplantation is needed.