A retrospective study evaluated 200 surgical colic cases. A gravity score (GS) based on four clinical parameters estimating intestinal obstruction (rectal palpation, borborygmi, abdominal distension, pain) and classified into three categories was established and tested to determine if it could evaluate prognosis. A shock score (SS) based on six parameters was also attributed to each case. The overall survival rate was 54 %. The statistical analysis showed a significant (P < 0.01) difference in the survival rate in the different categories of the GS, as well as in the categories of the SS. A multivariate logistic regression model showed that horses with GS 3 are 10.6 times more likely to die than those with GS 1. A model combining the two scores showed an odds ratio of 7.1 for GS 3 versus GS 1, and for SS 3 versus SS 1, the odds ratio was 7.2.