COVIDCIR is an observational, multicenter, cohorts' study of patients undergoing emergency/urgent gastrointestinal surgery during the period of maximum impact of the COVID-19 pandemic in Spain (from March 1st to June 30th, 2020).

The study conforms to the stipulations of the Declaration of Helsinki. The protocol was approved by the local Institutional Review Board (Ethics and Clinical Investigation Committee) and a waiver for written informed consent was given. The level of protection of confidentiality, in terms of protection of personal data as required by Spanish Law (LOPD 3/2018), was also ensured.

A total of 30 surgical teams from different Spanish hospitals have been proposed as participants in this study, which has been coordinated by the Department of General and Digestive Surgery of Bellvitge University Hospital (L'Hospitalet del Llobregat, Barcelona, Spain). All hospitals participating are from Spain, with different surgical capabilities.

Patients operated on for emergency/urgent gastrointestinal surgery constitute the target population.

Inclusion criteria: 18 years, both genders, and operated on for urgent/emergency gastrointestinal pathology.

Exclusion criteria: patients who have undergone a scheduled surgical intervention or patients operated on by a service other than General and Digestive Surgery.

Three cohorts will be defined:

Cohort 1: Covid-19-positive (infected by SARS-CoV-2) patients who required emergency/urgent gastrointestinal surgery from March 1st to June 30th, 2020 Cohort 2: Covid-19-negative (not infected by SARS-CoV-2)patients who required emergency/urgent gastrointestinal surgery from March 1st to June 30th, 2020.

Cohort 3: Consecutive patients who required emergency/urgent gastrointestinal surgery from March 1st to June 30th, 2019 (control cohort of a "pre-pandemic" period, all patients Covid-19-negative).

Primary outcome is 30-day postoperative mortality. Secondary variables are 90-day mortality, postoperative complications, severa complications (graded as Clavien-Dindo score >= IIIA), and length of stay.

Main variables related to postoperative mortality and complications will be: Age, comorbidities, ASA score, type of surgical pathology, type of performed surgery, POSSUM score, P-POSSUM score, LUCENTUM score and specific analitic parameters for Covid-19 patients.

Baseline characteristics will be summarized using standard descriptive statistics, and a descriptive and exploratory comparative analysis between cohorts will be carried out.

The cumulative incidence of mortality (and its 95% confident interval) and the incidence of morbidity (and its 95% confident interval) at 30 and 90 days will be estimated by SARS-CoV-2 infection status (cohort 1) and in the control groups (cohorts 2 and 3).

To minimize the selection bias effect of potential confounders, propensity scores will be estimated using a multinomial model to estimate the probability that subjects were SARS-CoV-2-positive, SARS-CoV-2-negative. Then, subjects will be matched using the propensity score. After matching, to identify imbalance between groups, the standardized mean difference will be estimated and plotted. In the matched sample, the cumulative incidence of mortality (and its 95% confidence interval) and the incidence of morbidity (and its 95% confidence interval) at 30 and 90 days will be compared using a generalized linear model with a binomial distribution and a logarithm link function. Those variables that remain imbalance between groups after matching would be added to the model with an adjusting purpose.

A generalized linear model with a binomial distribution and a logarithm link function will be used to estimate relative risk as a measure to indentify prognostic factors associated with 30 and 90 days mortality and morbidity incidences. Five predictive scores of postoperative complications and/or mortality will be calculated: POSSUM-mortality, POSSUM-complications, P-POSSUM, LUCENTUM-logistic regression and LUCENTUM-CHAID. Their applicability on the complications and/or mortality prediction in COVID-19 pandemic will be assessed.