Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of hospital operator Tenet Healthcare (NYSE: THC) needed a trip to the emergency room today as they dove as much as 12% in intraday trading after the company lowered its full-year guidance.

So what: Most companies aren't shy about telling investors when they're raising guidance, but most prefer to find better ways to communicate lowered guidance. For Tenet, the company said that it "refined" its full-year guidance and now expects EBITDA to be at the lower end of its $1.175 billion to $1.275 billion range. Management also said that third quarter EBITDA will likely be flat with last year.

The blame for the lowered view was placed on the admission mix at the hospitals. Though admissions have been up, the mix has skewed heavily towards the lower-reimbursing Medicaid patients. At the same time, the company saw less business from Medicare patients that it said was partially (but not fully) offset by commercially-insured patients.

Now what: If we take the stock's trading multiples as any sign, investors don't think much of Tenet right now. And maybe that shouldn't be too surprising -- the company has a very hefty debt load and there are question marks galore in the healthcare industry. But with pessimism thick in the air, perhaps now is a good time to take a closer look at the stock.

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