Elkington, 36, an Australian who attended the University of Houston and now lives in the American city, sought treatment late on Saturday night and remained in the hospital overnight, forcing him to pull out of the event.
Elkington was only five strokes behind the tournament leader Hal Sutton heading into yesterday's fourth and final round. Elkington picked up his 10th career win in March at the Doral Ryder Open and is 12th on the money list this year with $776,263 (pounds 482,000). His career victories also include a pair of Players Championships and the 1995 US PGA Championship.
He spent most of 1998 fighting health problems, including a bout of meningitis, but bounced back to win the Buick Challenge in October.
Sutton had birdied the last two holes to seize a two-stroke lead over Joey Sindelar heading into the final round. His hot finish gave him a three-under-par 69 for an 11-under 205 total.