The burden of surgically disease in low and middle-income countries (LMICs) is growing. Specific programmes have aimed to raise the profile of safe surgery and anaesthesia on the global health agenda. The Lancet Commission on Global Surgery have outlined six core indicators for the assessment of global surgical systems, including the postoperative mortality rate (POMR). Although mortality is the most extreme outcome of surgery, it only affects 1-4% of all patients. For major gastrointestinal surgery, efforts to quantify POMR alone neglect the associated morbidity, which is likely to affect a far greater proportion of patients \[1\]. More relevant markers of postoperative outcome are needed for the majority of patients, who will survive surgery.

Surgical site infection (SSI) is the most common complication following major gastrointestinal surgery, affecting between 25-40% of patients after midline laparotomy in high-income settings, and affects both adults and children. The effects of SSI can be life threatening. They are related to one-third of postoperative deaths and accounts for 8% of all deaths caused by a nosocomial infection. Furthermore, SSIs cause pain and discomfort, increasing the time taken to return home thus further amplifying the patient's potential nosocomial infection risk. This has an important economic impact. In the UK, hospital length of stay is doubled, with an attributable cost of £30 million per year.

The 2014 prospective, observational cohort study (GlobalSurg-1) included 10,475 patients from 58 countries. It showed that the incidence of SSI more than doubled from high (7.4%), to middle (14.4%), to low (20.0%) income countries. This persisted after multivariable risk adjustment for patient and hospital confounders (middle income: odds ratio 1.96 \[1.63-2.32\] and low income: 2.06 \[1.67-2.57\]). In the most contaminated and dirty operations, one in three patients from LMICs suffered an SSI. Dirty surgery doubled in low-income countries (29.7% versus 16.6% in high-income settings), which was in turn associated with doubling of SSI (34.5% low-income versus 15.4% high-income). However, SSI was assessed as a secondary outcome measure as part of that study, lacking validity and requiring external validation.

Antibiotic resistant organisms are now prevalent worldwide and a focus of interest for policy leaders and global health advocates. Some hospitals have no information on the rate of antibiotic resistant SSIs. For those patients who contract infections caused by resistant organisms, they are posed with a higher risk of mortality, morbidity and require more healthcare resources. Currently no data exists to describe the international epidemiology of SSIs, their causative organisms and drug-resistance. Therefore, investigating the diagnosis and treatment of SSIs is an urgent global health priority.

The primary aim of this study is to determine SSI rates across low, middle and high Human Development Index (HDI) countries. The secondary aims include describing organisms causing SSI rates, use of microbiologic tests, and rate of antibiotic resistant SSI. The impact of the method of 30-day follow-up on these outcomes will also be analysed. Other aims include describing the burden of surgical disease using 30-day mortality rates, perforated appendicitis rates and laparoscopic cholecystectomy rates.