My best mare got impaction colic in June. Vet went in rectally and could feel the very large blockage. He pumped her with Parafin Oil and something else I can't remember, stayed until 11pm at night then left me with instructions to check on her every 2 hours and to call him the second she goes "off" again.
She made it through the night and passed the impaction. I rang him that morning to thank him and tell him that she was okay. He admitted that he was awake most of the night, expecting a phone call to come and put her down. He didn't think she'd make it on her own but she did. So keep your fingers crossed!!!

She never showed any signs of colic when I called him; no rolling, kicking out or at her stomach, laying down, nothing. She was just "off". She wasn't herself and I know this horse better than I know myself. She usually runs around screaming at dinner time and she didn't. She just stood there and gave me a little whinny. I checked her for injuries then called then vet. Colic. Sometimes it's good to go with your gut instinct.