A student who was left handcuffed and forgotten in a tiny holding cell for four days is suing US authorities for 20 million dollars.

After two days and desperate for food and water, Daniel Chong said he realised he had to stop wondering when he would be let out and start thinking about how to stay alive.

Entering what he called "survival mode," and already drinking his own urine, he tried to trigger an overhead fire sprinkler for some water, stacking clothes and a blanket and swinging his cuffed arms in an attempt to set it off.

Chong, 23, a student at the University of California, San Diego, had been picked up in a drug sweep but was never arrested or charged.

He spent four days forgotten in the windowless cell before Drug Enforcement Administration agents opened the door.

"I just couldn't believe that this was legal," Chong said. "I'm thinking 'no way.'"

After his release, he spent five days in hospital for dehydration, kidney failure, cramps and a perforated oesophagus. He had lost 15lbs (6.8 kilos).

His lawyers have filed the 20 million dollar claim against the Drug Enforcement Administration, saying his treatment constitutes torture under US and international law.

The top DEA agent in San Diego, William R Sherman, said he was "deeply troubled" by what happened to Chong.

Sherman said he has personally ordered an extensive review of his office's policies and procedures. The agency declined to say what those were.

Chong said no one has contacted him personally to apologise.

He was among nine people taken into custody when agents stormed the house he was staying in and netted 18,000 ecstasy pills, other drugs and weapons.

Chong was questioned then agents told him he was not a suspect and would be released shortly. He signed some paperwork, was put in handcuffs and sent back to the holding cell.

As the hours dragged into days, he said he kicked and screamed as loud as he could. At one point, he ripped a piece of his jacket off with his teeth and shoved it under the door, hoping someone would spot it and free him.

Chong said he ingested a white powder that he found in the cell. Agents later identified it as methamphetamine. Chong said he ingested it to survive.

The next day, hallucinations started, he said. They included Japanese animation characters who told him to dig into the walls to search for water, which he tried, tearing apart the wall's plastic lining.

People can die from dehydration in as little as three to seven days, said Dr Wally Ghurabi at UCLA Medical Centre in Santa Monica.

Ghurabi said Chong was wise to drink his own urine to stay hydrated.

As the days dragged on, Chong said he accepted that he would die. He considered taking his own life rather than withering away by dehydration.

"I thought 'wow, this was a terrible way to go,'" Chong said. "I just wanted to have a little bit of dignity."

He sat in the dark, his hallucinations deepening, his breath getting shorter and shorter, even the urine running out, and he screamed for the agents to at least let him have a quick death.

"That's when the lights turned on and the agents opened the door with very confused looks on their faces," Chong said. "They said, 'Who are you? Where'd you come from?'"