Four-time overall alpine World Cup champion Lindsey Vonn was in hospital in Colorado Tuesday, suffering from "severe intestinal pain", her spokesman said.
Lewis Kay said Vonn has had the condition for about two weeks and that they are now waiting for test results.
Vonn cancelled a promotional event in Vail, Colorado on Friday because she did not feel well.
She also skipped a World Cup slalom in Finland at the weekend, preferring to prepare for the giant slalom and slalom set for Aspen, Colorado, on November 24-25.
Vonn, who has won four of the past five women's downhill season crowns, had hoped to compete against men at Lake Louise, Alberta, on November 24.
However, that request was turned down by the International Ski Federation.
Had she been permitted to compete against the men, Vonn would have missed the two women's races in Aspen that take place the same weekend.
Last year Vonn posted 14 victories to finish atop the World Cup points standings with 1,980 and reclaim the overall crown. Maria Hoefl-Riesch was 578 points back in second place.
Vonn's next races are in Aspen, followed by the women's events in Lake Louise.