Acquired cystic kidney disease is a form of kidney disease where cysts develop in patients who have had chronic kidney disease for a number of years, or patients who have reached end-stage kidney disease - the stage at which kidneys are permanently unable to work. The disease is not genetic.
Discovery of the disease
The condition was first recognised to be associated with long-term kidney dialysis in the 1970s. Prior to this, the structural states of patients’ kidneys once they reached end-stage kidney disease were not routinely examined in any detail, so there was no awareness of the disease.
However, scientists Dunnill, Millard and Oliver described the disease in 1977. They monitored 30 patients with long-term dialysis patients who had no traces of renal cystic diseases at the beginning of the study. Subsequently, 14 of these people went on to develop renal cysts. Since this initial study, the condition has further been confirmed by additional research.
When a kidney is functioning properly, it will filter out waste products from the body. However, with failing kidneys, this becomes increasingly difficult task, thus dialysis is used to help patients whose organs are deteriorating. Alternatively, the patient may be lucky enough to receive a kidney transplant from a donor, albeit donors are not readily available.
What happens during dialysis
During the dialysis process, the patient is connected to a dialysis machine which helps to filter out the waste on their behalf. The machine controls the flow of the blood from the patient and cleanses the blood with a substance called dialysate.
The chances of acquired cystic kidney disease occurring during dialysis increase the longer the person has to use the process. However, it is not believed that dialysis causes the condition. The disease’s development is just seen as a by-product of unnaturally prolonging the function of the kidneys.
Morphology and symptoms
In acquired cystic kidney disease, the kidneys are normal in size or smaller in comparison to polycystic kidney disease where they can grow to three or four times their size. For the patient to be classed as having the condition, they need to have at least five kidney cysts. The cysts are usually 0.5 cm in diameter.
The cysts produced by acquired cystic kidney disease tend to develop in certain key places in the kidney. They are most often found in the renal cortex, which is the outer section of the kidney. This is an extension of the cortical tissue and contains the nephrons that filter the blood. They can also extend down to the renal medulla, the area where most of the filtering of the blood occurs.
With chronic kidney disease, the patient will experience a number of symptoms including tiredness, nausea and swollen ankles. However, with acquired chronic kidney disease, the patient tends not to experience any obvious signs or symptoms. Problems can occur when the cysts burst.
Epidemiology and concomitant kidney diseases
Approximately 7 – 22% of chronic kidney disease patients start to develop acquired kidney disease before they begin with their dialysis treatment. This figure increases in individuals who have been undergoing dialysis for a few years. Furthermore, the figure rises to 60% after dialysis for 2 to 4 years. When patients have had dialysis for 8 years, about 90% of them have acquired cystic kidney disease.
Acquired cystic kidney disease can occur in conjunction with all forms of chronic kidney disease. The forms it is most commonly observed with are:
- Glomerulonephritis – damage occurs to the small filters in the kidneys
- Tubulointerstitial nephritis – the spaces between the kidney tubules become inflamed
- Nephrosclerosis – the blood vessels in the kidneys harden
- Diabetes mellitus – kidney disease represents a complication of this condition