Table 5 Outcomes explored by the reviewed studies

Death occurring during a pre-defined time period (1, 7, 30, 60, 90 or 180 days, 1, 2, 3 or 5 years)

Continuous length of stay (from admission to discharge)

Readmission for any cause during a pre-defined time period (2 weeks, 30 days, 6 weeks, 90 days, or 1, 2, or 3 years)

Costs billed by the hospital, excluding physicians’ fees

Severity of the complication: Clavien-Dindo grade III or higher

At least one complication within a specific time period (in-hospital stay, 30 or 90 days, 75th percentile of the length of stay) or the complication rate

successful surgery: positive surgical margins (circumferential), number of resected lymph nodes, complete resection or not, restorative surgery performed or not.

Being in the intensive care unit (ICU) for longer than a specific time (1 or 2 days) or requiring organ support (mechanical ventilation or dialysis)

Patient safety indicators

Failure-to-rescue rates: death after a major complication within a pre-defined period of time (30 days, 90-days, in-hospital)

Continuous post-surgical length of stay (from surgery to discharge)

Readmission for a specific cause (aseptic revision, rescue surgery as a full procedure after a partial one, implant revision)

Sum of all costs except the cost of initial surgery (considered to be similar across all centres)

Abscess, haemorrhage, or anastomotic leakage

Major complications, defined as the need for surgical intervention or organ supply within a specific time period (in-hospital, 14 days)

Recurrence of cancer: local recurrence, distant metastases, and vital status

Routine discharge versus nonroutine discharge (i.e. to rehabilitation, home, or a care home)

Surgical reconstruction rate

Ratio between observed and expected (O/E) deaths

Continuous length of uninterrupted institutional care

A composite of readmission to an acute care hospital for any cause and all-cause death within a specific time period

Excess costs, defined as those above a defined cut-off (median, 75th percentile, etc.)

Surgical site bleeding, need for transfusion, or transfusion volume

Kidney failure or urinary tract infection

Risk ratios for positive margins

Time to surgery/transplantation or the door-to-balloon time

Proportion of pneumectomies

Risk-adjusted mortality: the O/E ratio multiplied by the overall mortality rate for the cohort

Prolonged length of stay: longer than a cut-off (insurance period, median value, 75th percentile, 90th percentile, etc.)

Risk-adjusted readmission rate, the O/E ratio multiplied by the overall readmission rate for the cohort

Cost per day of treatment: the total cost divided by the length of stay

Perforation or laceration (bowel, oesophageal, ureteral, rectum, bladder, nerve, etc.)

One of the eight emergency general surgery complications

Time to recurrence or progression-free survival time

Duration of treatment with antibiotics

Amputation-free survival

Hospital-standardized mortality ratio

Unplanned readmission to the same hospital

Cost-per-episode of surgery, adjusted for wage index

Surgical site infection, wound infection

Sepsis, septicaemia, shock, or prosthesis or implant infection

Travel time or distance to hospital

Sphincter preservation

Disease-related death (cancer, surgery, or sepsis related)

Readmission rate for each subspecialty or diagnosis

Cost-per-episode of surgery, adjusted for inflation

Major amputation (lower limb, organ)

Pulmonary embolism, deep venous thrombosis

Number of hours requiring organ support

Survival of thumb replantation

Time-to-death, as the time interval between surgery and death

Reoperation during the initial hospital stay

Neurological or cerebrovascular complications

Duration of surgery

Post-discharge mortality

Need for a permanent pacemaker

Duration of anaesthesia

In-hospital mortality

Respiratory failure or arrest

Cardiac arrest or myocardial infarction