Lavinia,
Dorsal displacement colics are often caused because of gas buildup. So technically, they are usually a gas colic that progresses to displacement. I believe that is what was meant by gas colic/dorsal displacement.  Juniper had to have surgery to correct a nephrosplenic ligament entrapment ( a displacement) caused by gas buildup from grazing on fresh clover.  The following explains this issue and it's treatment well.Gas colics and Displacements – Large Animal Surgery – Supplemental Notes (umn.edu)
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Dawn Wagstaff and Tipperary   

Saline, MI  2003

Tipperary Case History

Juniper Case history: https://ecir.groups.io/g/CaseHistory/files/Dawn%20and%20Juniper/Case%20history%20Juniper.pdf .