Kidneys normally remove extra water and wastes from you blood. If they fail, blood levels of urea increase. Urea is toxic to the body and can affect all the major organs including the brain. Symptoms usually only appear when kidney function falls to less than 10 percent of normal. It precedes uremic coma and causes disorders of memory, thinking, speech, perception, emotions and other neurological manifestations.
When urea is removed from the blood too quickly during dialysis, a net movement of fluid into the brain seems to occur. This is quite rare and causes headache, double vision, nausea and vomiting. Tremors and seizures may follow.
Dialysis dementia is a progressive disease found in some patients on long-term haemodialysis. The cause of this disease is still controversial, but thought to be due to the deposition of aluminum in the brains of those patients. In order to avoid this complication the water used for dialysis is purified by a process called reverse osmosis. The intake of aluminum-containing phosphate binders is also limited.
Written by Dr K. Coetzee, reviewed by Dr R. Moosa, head of the Renal Unit, Tygerberg Academic Hospital.
Healthy toilet habits
National Kidney Foundation