Of all the things that could sideline the great Ron Jeremy -- STDs, jealous suitcase pimps, too much sex -- we were sad to hear that it was an aneurysm near his heart.

The 59-year-old porn legend was hospitalized in critical condition after driving himself to Cedars-Sinai Medical Center last night, TMZ reports.

According to the site ...

... his condition worsened after he was admitted and he was taken to intensive care: Jeremy was expected to undergo surgery today.

Besides appearing in thousands of adult videos, Jeremy has been an active voice in the industry and lobbied (unsuccessfully) against a mandatory condom law for porn in L.A. county:

[@dennisjromero / djromero@laweekly.com / @LAWeeklyNews]