There is no consistent pattern as to the cause or prognosis of renal cysts. Although usually associated with children, renal cysts can strike at any age. They can be caused by malignancies, genetic transmission or developmental problems in utero. In many instances such as polycystic kidney disease, kidneys can become so riddled with cysts that transplant or dialysis is necessary. This outcome is far from universal, as many adults do not become symptomatic until midlife.
Malignancy
A 2010 article appearing in "Current Opinions in Urology" reports that five to seven percent of all renal tumors occur due to cystic renal cell carcinoma. This article recommends kidney biopsy as the best way to distinguish malignant from non-malignant cysts. In the event the tumor is malignant, prompt removal via laparoscopy is often recommended.
Joubert Syndrome
Joubert syndrome is a genetic disease that produces mild to moderate retardation and various physical abnormalities such as malformed fingers and toes and poor muscular control. A 2010 paper published by the journal "Arquivos de Neuro-Psiquiatria" reports that some children with Joubert syndrome also suffer from cystic kidney disease.
Renal Dysplasia
Renal dysplasia is the leading cause of pediatric renal failure. Thanks to a developmental error, at least some of the collecting ducts in the kidneys are disconnected from the glomeruli. Since the urine that forms has nowhere to go, it remains backed up in the glomeruli, where it produces cysts.
Renal dysplasia can affect one or both kidneys and can be mild or severe. In many instances, serious problems do not develop until the child is an adolescent, at which time transplant or dialysis are very favorable outcomes.
PKD
Polycystic kidney disease is described as being autosomal recessive PKD or autosomal dominant PKD. Autosomal dominant is the more common variant. It is caused by a dominant gene. According to the National Institute of Diabetes, Digestive and Kidney Disease, "symptoms usually develop between the ages of 30 and 40."
The recessive variety is more severe as it is often associated with lung and liver problems. This can be diagnosed prenatally using ultrasound. Children with the recessive variant who survive their first months often do very well, although transplant or dialysis are often needed.
