If a horse has colic and doesn't get treatment, the colic can cause serious health problems, such as impaction colic or rupture of the intestines. These problems can lead to death in some cases.
If you think your horse might have colic, it's important to get veterinary care as soon as possible. If colic is caught early, a veterinarian may be able to treat the horse without surgery, only with colic medicine such as phenylbutazone. However, if colic is more severe, surgery may be necessary.
So, colic can be fatal if not treated. It's important to watch your horse for any signs of colic and to get veterinary care as soon as possible if you think your horse might be sick.