An intra-abdominal abscess is a potentially life-threatening condition where a pocket of infected fluid and pus is found inside the abdominal cavity of the horse. If an abscess ruptures it can cause fatal septic peritonitis.

Abdominal abscesses are most often caused by invasion with bacteria including Streptococcus spp., Corynebacterium spp., Clostridium spp., Bacteroides spp., and Escherichia coli. They are often brought on by a complication of a previous strangles infection.