She also was not taking prescribed medication while in jail, Los Angeles County Sheriff Lee Baca said.

The stainless steel lavatory in the hotel heiress' 12-foot-by-8-foot cell was in plain view of a large window in the door, which guards could look through 24 hours a day.

"She was absolutely terrified that one of the guards or staffers would get her with the cell-phone cam and it would wind up on the Internet," a Hilton insider said yesterday.

"She didn't eat or drink a single thing for three days because she didn't want to use the toilet. She was in real danger."

Jail medical officials became concerned that severe dehydration and a buildup of waste and toxins in Hilton's body could cause a complete collapse and "even kill her," the source said.

Judge Michael Sauer didn't buy the medical excuse, sending Hilton back to jail on Friday to serve the remainder of her 45-day sentence. She could serve just over two weeks with time off for good behavior.