''ER'' and ''Chicago Hope'''s revolving doors

In the crowded halls of ER and Chicago Hope, there isn't room for all the doctors to be on call — which makes the dramas perfect for recurring guest characters. You may have noticed that ER's delightfully prickly Dr. Kerry Weaver (Laura Innes), who vanished after the Dec. 14 episode, has just resurfaced. (The doctor was last seen with a mystery man from Africa; the actress had committed to a stint on CBS' new sitcom The Louie Show.) But what about other notable hospital visitors? After some examination, EW offers these medical charts of disappearing acts, with prognoses for their characters' recovery.

Actor: Michael Ironside.
Role: Dr. William ''Wild Willie'' Swift, ER chief of staff.
Last original episode: May 18; Swift had no official departure, since Ironside left during summer hiatus.
Why he really left: To replace Roy Scheider on the now-canceled seaQuest 2032.
Injury to show: 5 (on a scale of 1 to 10); the chief added some quirkiness, but so does Dr. Weaver.
Prospects for returning: ''Now that seaQuest isn't on, it could very well happen,'' says ER coexecutive producer Carol Flint.
Where you can find him: In the NBC adaptation of Robin Cook's novel Terminal (Feb. 12).

Actor: Kathleen Wilhoite.
Role: Dr. Susan Lewis' troubled single-mom sister, Chloe.
Last episode: Oct. 5; Chloe left Big Susie in a parking lot holding Little Susie, on her way to sell junk at flea markets.
Why she really left: Wilhoite took time off to have her own baby, James, who was born in mid-October.
Injury to show: 7; wacky Chloe is a good foil for her somber sis.
Prospects for returning: Chloe will be back for at least one episode.

Actor: E.G. Marshall.
Role: Hope's Dr. Arthur Thurmond.
Last episode: Jan. 2, 1995; Thurmond left to recuperate from heart surgery.
Why he really left: He had a limited-episode deal.
Injury to show: 3, although Hope may have lost the Murder, She Wrote audience.
Prospects for returning: None to date.
Where you can find him: As John Mitchell in Oliver Stone's Nixon.

Actor: Ming-Na Wen.
Role: Med student Deb Chen.
Last episode: April 6; Chen dropped out after injuring a patient with a procedure she wasn't trained to do.
Why she really left: ''It was always understood that her story had a time deadline,'' says Flint.
Injury to show: 6; Chen's rivalry with Carter was a hoot.
Prospects for returning: Doesn't look good.
Where you can find her: As Trudy on NBC's The Single Guy.

Actor: Peter MacNicol.
Role: Alan Birch, Hope's lawyer.
Last episode: Nov. 13; Birch was gunned down by gang toughs.
Why he really left: ''Because [creator] David E. Kelley [wasn't as involved],'' says the actor's spokesman. ''Kelley was why he joined.''
Loss to show: 10; Hope lost its most complex, touching character.
Prospects for returning: It could happen. ''We started talking right away about how to get him back,'' says exec producer John Tinker. ''It's possible, but not probable.''
Where you can find him: NBC's upcoming movie Abducted: A Father's Love.