Katherine Heigl Taking Temporary Leave From Grey's Anatomy

Katherine Heigl will be taking a five-episode leave of absence from Grey's Anatomy.

According to reports, the reason is to film romantic comedy Life as We Know It.

The controversial star has cited her busy schedule and worked around Grey's Anatomy before, but never for an extended period of time like this. Heigl’s absence will reportedly be explained somehow on screen, although it is not yet clear how it will be broached.

Heigl’s temporary exit - which starts this month, and is a little surprising in light of recent remarks she made about the show and the 17-hour work days she puts in, will almost certainly be overlapping with co-star Ellen Pompeo’s maternity leave.

That means Grey’s Anatomy without Izzie and Meredith at the same time.

Grey’s Anatomy executive producer Shonda Rhimes has hinted that the sixth season will be a transitional one for the medical drama, with one of the most beloved original cast members (T.R. Knight) having already departed this past offseason.

Guess she wasn't kidding.

What prompts Izzie to leave Seattle Grace?

The reason for Heigl's upcoming leave of absence?

According to inside sources, Season 6 of Grey's Anatomy is defined by the merger of Seattle Grace and its rival, Mercy West. Seattle Grace is about to double in size.

That means a bunch of new doctors coming in paving the way for shake-ups in the season(s) of Grey's Anatomy to come. One of those shakeups? Izzie gets fired.

Yes, fired. Izzie gets laid off in the big merger.

This allows Heigl to vanish for a number of episodes, and for Pompeo's maternity leave (though producers say Meredith will be in "as many episodes as possible").

Reportedly, the show wants to think long-term (like ER long term, 10-years plus) and feels the merger/shake-up will provide more characters and plot flexibility.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.