Cavanagh, who plays eccentric Julie Carp on the ITV1 soap, was struck down with severe stomach pains ahead of the on-location shoot and had to take time off work, The Mirror claims.
It is thought that Coronation Street chiefs quickly recruited a stand-in for Cavanagh, who was filmed from behind in all of her scenes. Plans to give Julie lines at the ceremony had to be scrapped.
A Coronation Street source told the newspaper: "Viewers won't know it's not Katy because the stand-in looked identical from behind - her hair was styled in the same way.
"She is a very popular member of the cast and people are wishing her a speedy return."
Brooke Vincent, Sacha Parkinson and other Coronation Street stars were spotted filming Sophie and Sian's wedding in Hale, Cheshire last week.
However, reports suggest that the big day does not go according to plan - leading up to Sian's departure from Weatherfield.
> Coronation Street Julie should marry Brian, says Katy Cavanagh
> Coronation Street films dramatic Sophie, Sian wedding scenes
> Coronation Street Sophie, Sian wedding twist revealed?
> Read more Coronation Street spoilers and news
Browse through on-location pictures from Sophie and Sian's wedding day in the gallery below: