Acquired Cystic Kidney Disease 

Renal cystic disease is a term that represents a wide spectrum of diseases that may be hereditary, developmental, or acquired; these diseases share the feature of renal cysts. These cysts can occur in the cortex, the corticomedullary junction, and/or the medulla depending on the underlying disease process. Acquired cysts can be simple or part of acquired cystic kidney disease (ACKD), also called acquired renal cystic disease (ARCD). Acquired renal cystic disease is characterized by the development of numerous fluid-filled cysts in the kidneys in individuals who have no history of hereditary cystic disease. Acquired renal cystic disease is a bilateral condition. It can antedate the clinical recognition of end-stage renal failure. In the early stages, acquired renal cystic disease does not produce symptoms and is usually discovered inadvertently in the course of abdominal imaging procedures.

Acquired renal cystic disease was thought to be a consequence of hemodialysis. Studies have shown that, although the association of dialysis and acquired renal cystic disease is indisputable, it is the uremic state that promotes the development of acquired renal cystic disease. Dialysis prolongs the patient's survival to allow more time for acquired renal cystic disease to occur.

The exact mechanism is not known. The postulates are as follows:

• Tubule block: The development of cysts is due to tubular abnormalities; tubular obstruction due to oxalate crystals, fibrosis, or micropolyps; and tubular fluid accumulation due to glomerular filtrate and tubular fluid excretion.
• Compensatory growth: The profound loss of renal tissue in end-stage kidney disease promotes tubular cell hypertrophy and hyperplasia. Hypertrophy and hyperplasia, together with transepithelial secretion of fluid by the tubular epithelium, result in the development of cysts. Many factors may influence the process, but most important among them are growth factors and activation of oncogenes.
• Ischemia: Kidney atrophy is a recognized consequence of ischemia that may be caused either by primary renal arterial occlusion or by the secondary arterial occlusions that develop after dialysis is begun. Parenchymal acidosis may result from chronic progressive occlusion and, if sustained just short of causing cell death, might result in renal cyst formation.

Frequency

United States

The rates of occurrence of acquired renal cystic disease are 7-22% in the predialysis population, 44% within 3 years after beginning dialysis, 79% more than 3 years after beginning dialysis, and 90% longer than 10 years after beginning dialysis. The rate of progression appears to slow after 10-15 years of dialysis.

Mortality/Morbidity

Acquired renal cystic disease gives rise to many significant complications, the most serious of which is the development of renal cell neoplasms, ranging from adenoma to metastatic renal cell carcinoma. The incidence of renal cell carcinoma is 0.18% per year in patients with acquired renal cystic disease compared to 0.005% in the general population.

Race

Acquired renal cystic disease is relatively more common in blacks. Blacks account for 53% of cases of acquired renal cystic disease; however, in the United States, only 25% of patients on dialysis are black.

Sex

Acquired renal cystic disease occurs more frequently in men than in women.

Acquired renal cystic disease-associated renal cell carcinoma is found predominantly in men; the male-to-female ratio is 7:1 compared with 2:1 in the general population.

Age

Acquired renal cystic disease occurs with equal frequency in children and adults.

Renal cell carcinoma occurs approximately 20 years earlier in people with acquired renal cystic disease than in the general population.

In children, acquired renal cystic disease-associated renal cell carcinoma is rare.