Complicated intra-ABdominal Infections (CABIs) are abdominal infections where there is an abscess inside the abdomen, or a hole (perforation) in an abdominal organ such that infected material e.g. faeces, leaks into the abdominal cavity. A recent review of CABIs after gut surgery found that they can occur in several ways. They can occur in different parts of the abdomen, can be different sizes, and may or may not be caused by a perforated bowel. Management includes, where possible, surgical drainage of an abscess or treatment of the damaged bowel. In addition, all patients are given antibiotic therapy. Despite the varied ways that CABIs occur, we currently tend to treat all CABIs with antibiotics in a similar way. CABIs are associated with significant morbidity and mortality. Despite a significant amount of disease there is little clinical evidence with which to base treatment on. One research study evaluated a short course of antibiotics (4 days) compared with a longer course (up to 10 days) in combination with surgical removal of infection. There was little difference in outcomes, but in both groups about 1 out of every 7 patients had a relapse. A recent review of patients with CABI in Leeds, not in a research study and where surgical removal infection is uncommon and antibiotic durations were short, showed that the risk of relapse was even higher (about 1 in every 3 patients). The antibiotic management of CABIs in the UK is variable and involves giving between 4 days to 28 days of antibiotics.