"Turns out a ruptured ovarian cyst really hurts and morphine makes me cry," Beckinsale wrote in the caption of two pictures posted on her official Instagram account. "So thankful to everyone who looked after me #wobbly."
According to the Mayo Clinic's site, ovarian cysts "are fluid-filled sacs or pockets in an ovary or on its surface."
While they can be generally harmless, once ruptured they can cause some serious symptoms.
The "Underworld" star received some support from fellow celebs including Rose McGowan, David Spade, Sarah Silverman and Courtney Love who left comments on her page.
Beckinsale also responded to a person who made mention of the fact that the 45-year-old actress felt the need to selfie her experience.
"It's actually not a selfie," Beckinsale wrote. "My mum took it. In fact I would not have posted it if we had not noticed someone in a car taking a photo of me leaving the hospital in a wheelchair."
She went on to explain "I have Instagram largely to have my own honest narrative and not have to always be ambushed by stories that come out that are invented, I'd prefer to say what happened than endure speculation and so I chose to share."
"I agree, it's not a normal impulse," Beckinsale wrote. "But it's not normal to be photographed in vulnerable situations by people you don't know either. (If you were interested in knowing the provenance of this, which, you probably are not.)."
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