Sharon, 78, suffered a massive stroke resulting in a coma in early January.
He was transferred from Hadassah Medical Center in Jerusalem to Chaim Sheba Medical Center, a long-term care facility near Tel Aviv in late May.
Doctors now report a worsening in the functioning of his kidney and a change in brain tissue, the hospital spokesman said. Sharon is also accumulating more fluids in his body, the doctors reported.
More tests are being performed to determine a course of treatment, the spokesman said.
When Sharon was moved to Chaim Sheba Medical Center, Dr. Zeev Rotstein, head of the center, told reporters, “We are expecting a difficult treatment because in his condition complications are expected. We will treat him as best we can. It is not a short-term treatment. We are talking about long-term treatment.”
Sharon, nicknamed “The Bulldozer” for his stamina during meetings and long working hours, is a former army general and larger-than-life personality in Israel. He was first elected prime minister in 2001 and re-elected in 2003.
Before he suffered his massive stroke in January, Sharon broke from the Likud Party that he helped found to start the Kadima Party. Many members of Likud frowned on Sharon’s decision to withdraw Israeli troops and settlers from Gaza and parts of the West Bank.
Three months after his stroke, Sharon was declared permanently incapacitated by the Israeli Cabinet, formally ending his premiership.
Acting Prime Minister Ehud Olmert took over the post officially when a new government was formed.
Sharon is twice widowed and has two sons.