The medical condition of Ariel Sharon further deteriorated Thursday, leaving the former prime minister in grave condition.

Sharon, 85, is hospitalized at Tel Hashomer hospital in Tel Aviv, and has been comatose since January 4, 2006 when he suffered a brain hemorrhage.

The former prime minister's health took a turn for the worse last week, when he suffered renal failure and could not undergo dialysis due to the dangers the procedure could present given his fragile physical state.

Sharon's condition was termed "grave" for the first time on Thursday, a more severe classification than the previous "critical" condition.

Despite reports of his heart rate and blood pressure stabilizing earlier this week, current forecasts are that the process of system failure is in an advanced state, and might soon lead to his death.

The accumulative effect of Sharon's renal failure may lead to fast deterioration, since the kidneys are involved in many of the bodily functions. Renal failure untreated by dialysis leads to an increase in waste and toxins, the most immediate and dangerous outcome of which is the inability to excrete potassium, which may lead to heart failure.

According to estimates, the further deterioration in Sharon's condition is due to the renal failure, not to the blood infection that was treated with antibiotics.  

Sharon has been comatose in the hospital for the past eight years. He has been getting medical care and receiving fluids through a feeding tube.

Last September, Sharon underwent abdominal surgery to correct a problem in his intravenous feeding system. The operation, which lasted an hour, was planned several months prior.

Prior to that, In January, neurological scans demonstrated significant brain activity in Sharon's brain. During the two-hour fMRI scan conducted, researchers tested Sharon's response to various stimuli: family pictures, a recording of his son's voice, and human touch.

They said they were surprised to discover significant activity in relevant parts of his brain in response to all tests.