Short-term survival and mortality rates in a retrospective study of colic in 1588 Danish horses

Background: Outcomes of colic treatment are of great interest to clinicians, horse owners and insurers. One commonly used criterion of success is the overall short-term survival rate. This is used as to compare treatments and to measure quality of veterinary care, but may be biased by demographic or social factors such as attitudes towards animal suffering and euthanasia. The aims of this study were to 1) describe and analyse characteristics in horses with signs of colic referred to the University Hospital for Large Animals (UHLA), University of Copenhagen, Denmark over a 10-year period and 2) to compare these rates with those published in other comparable studies. Results: The overall survival rate for colic horses over the 10-year study period was 68% (confidence intervals (CI): 66-71%; 1087/1588). In the medical group, 1093 horses, short-term survival was 87% (CI: 85-89%). Thirty one % of referred horses were given diagnoses requiring surgical intervention (CI: 29-33%). In this group 32% of the horses were euthanized before surgery (CI: 28-36%; 159/495). Of the surgical cases 27% (CI: 23-31%) were euthanized or died during surgery. Of the horses that recovered from surgery 25% died or were euthanized (CI: 19-32%; 48/189), while 75% survived to discharge (CI: 68-81%). Conclusions: The short term survival rates of Danish horses with colic were similar or lower to those reported from other countries. Apart from variability of veterinary care, attitudes towards euthanasia vary among the countries, which may bias the outcomes. This study indicates that qualitative interview studies on owners' attitudes towards animal suffering and euthanasia need to be conducted. Our opinion is that survival rates are not valid as sole indicators of quality of care in colic treatment due to selection bias. If the survival rates are to be compared between hospitals, techniques or surgeons, prospective studies including mutually agreed-on disease severity scores and a predefined set of reasons for euthanasia are needed.