Guide for authors

Cirugía Española is the official publication of the Asociación Española de Cirujanos (Spanish Association of Surgeons), which is an association comprised of the majority of Spanish surgeons from different surgical sub-specialties. The Journal is the best platform for presenting technical and conceptual advances made in Spanish surgery. Furthermore, its pages have been giving an increasing amount of attention to the biological and clinical aspects of surgical pathologies, thereby transcending surgery alone, which was formerly the main focal point of this area of medicine. An English edition of the Journal has also been published since 2008.Cirugía Española is included in prominent online databases, including Science Citation Index, Medline/Pubmed and SCOPUS.

Any article submitted to this journal must follow the guidelines outlined in the "Ethics and Policies" section of this author’s guide. It is essential to consult it before submitting manuscripts.

For any article type of this journal, except Letters to the Editor, the three headings: Ethical Considerations, Funding, and Conflicts of Interest, should be included on the first page.

Ethical Considerations:
If the work involves the use of human subjects, the author must ensure that the described work has been carried out in accordance with the World Medical Association's Declaration of Helsinki for experiments involving human beings; and in accordance with uniform requirements for manuscripts submitted to biomedical journals. Authors should include a statement confirming that informed consent was obtained from human subjects and that all ethical procedures were followed. The rights to privacy of human subjects must always be respected. Approval from the Institutional Review Board (IRB) or the relevant ethics committee should be indicated in this section.

Funding:
Authors are requested to identify who provided financial support for the research and/or preparation of the article and to briefly describe the role of the sponsor(s), if applicable, in the study design, data collection, analysis, interpretation, manuscript drafting, and decision to submit the article for publication. If the funding source(s) had no such involvement, this should be stated.

Conflicts of Interest:
All authors must disclose any financial or personal relationships with other individuals or organizations that could influence their work, even if they are not directly related to the current manuscript.

Possible conflicts of interest include employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, other funding, travel grants, and participation in courses and conferences as paid experts. If none of these conditions apply, the statement should read: "Conflicts of Interest: None."

For any of the article types, the content of the accepted manuscripts including text, images, tables, etc. will be susceptible of being used in the journal social media channels with the aim of providing greater visibility to the article.

Editorials: Without exception, editing will be the responsibility of the Editorial Committee on a current topic, which may or may not refer to an article that is published in the same volume number of Cirugía Española. They normally are between 800 and 1000 words with a maximum of 15 bibliographical references. A single author is preferred.

Original Articles: Description of clinical studies, experiments, or techniques that contribute to broadening understanding of surgery. The original articles must follow the format of Introduction, Methods, Results, and Discussion. The maximum length of the text will be 2,500 words and up to 6 images or tables will be allowed. The inclusion of a structured abstract is required, in Spanish and English, with a length no greater than 250 words. After the abstract, 3 to 8 keywords will be included. The maximum number of authors will be 8. In the case of manuscripts with more than 8 authors, the reason must be justified in the letter of presentation to the Editorial Committee.

The investigators who develop a randomised prospective trial must consult the latest version of the CONSORT criteria (see more details later).

A Graphical abstract is mandatory in this section, please see more details below.

Systematic Reviews: Cirugía Española will give priority to systematic reviews and Meta-analysis. The maximum length of the text will be 3,500 words and up to 6 figures or tables will be allowed. The inclusion of an unstructured abstract is required, in Spanish and English, with a length no greater than 150 words. After the abstract, 3 to 8 key-words will be included.

The authors must adhere to the recommendations laid out by PRISMA (http://www.prisma-statement. org).

A Graphical abstract is mandatory in this section, please see more details below.

Special Articles: This section will include articles related to General and Digestive Tract Surgery that, because of their characteristics, cannot be considered for the Original Articles or Review sections. The maximum length of the text will be 3,500 words and up to 6 figures or tables will be allowed. The inclusion of an unstructured abstract is required, in Spanish and English, with a length no greater than 150 words. After the abstract, 3 to 8 keywords will be included.

Case reports are not allowed in this section.

Innovation in surgical technique: This type of manuscript can describe a new surgical technique or original modifications or new indications of a technique already known. The manuscript must have a summary in Spanish of no more than 150 words, unstructured and translated into English. The manuscript should be divided into the following sections: introduction, surgical technique (indications and technical details), discussion (relevant aspects, justification, advantages and disadvantages in the context of other techniques and published studies that are the antecedent of the proposed technique) and bibliography. In the surgical technique section it is worth mentioning the number of patients in whom the technique has been performed as well as its indications.
The number of words in the text (excluding summary and bibliography) should not exceed 1,500. The maximum number of authors is 4. It is very convenient that the article is illustrated with quality images, diagrams, drawings or original frames that detail the technical aspects. Once the manuscript has been accepted, the Editorial Committee will invite an expert to comment on the proposed technique and its relevance.

Scientific Letters: In this section the Cirugía Española Editorial Committee will evaluate case series studies of patients in which new aspects are described or relevant assessments are added on the mechanisms of the disease, its diagnosis or treatment. Only those unique clinical cases that provide a very outstanding exceptionality will be admitted for evaluation. The maximum length will be 850 words and the test will not be structured into sections. Two images or tables will be accepted. The bibliography should be no longer than 10 references. Scientific articles will not be accompanied by an abstract. The maximum number of authors will be 5.

Letters to the Editor: Letters with objections or comments related to articles published recently in the Journal and, in some cases, on relevant articles published in other journals, will evaluated. This correspondence must contain interesting ideas and commentar-ies that will always be supported by data and bibliographic references. All of the letters will be reviewed by the Editorial Committee and, if they are accepted, will be published in the Journal. Whenever possible, the letter will be published simultaneously with the response from the author of the article mentioned. The maximum length will be 450 words. The maximum number of authors will be 4.

Image of the Month and Videos: Included in this category are medical or surgical images that have educational value. The maximum length of the text will be 100 words. The resolution of the image must be at least 600 dots per inch (dpi) in TIFF or JPEG format. The diagnosis of the case must be indicated at the end of the text and differentiated from it. The maximum number of authors will be 4. In the case of the videos, the authors will send a short text of a maximum of 100 words. The duration of the video will not exceed 4 minutes, see detailed instructions later. For the videos, two files will be sent, one with audio in Spanish and the other with audio in English.

Surgical Perspectives

These articles will address in a practical way any relevant and current topic related to health or medicine in general and that are of specific interest to the profession of surgery. Topics in these articles may include surgical quality or safety, surgical reimbursement, surgical education, or other issues facing the profession. Like all articles published in the journal, these articles will be peer-reviewed.

Articles should not have more than 3 authors. Maximum length: up to 1200 words of text, or 1000 words of text with 1 table or small figure, and no more than 10 references.

Study Protocolos

These manuscripts will describe in detail a research project or study protocol to be developed prospectively. It is recommended that the study is officially registered, including in the manuscript the registration number and date of registration. The study should not have exceeded the 50% of the recruitment of cases over the calculated sample size.
The maximum word length should be 3000 words and the number of authors should not exceed 8. If it is essential to exceed 8 authors, the contribution of each of them should be justified.
Study protocols will have a maximum of 4 figures and tables.
The title should be presented both in Spanish and English. The abstract will have a maximum of 250 words (including registration number) and should be accompanied by key words defining the study (3 to 8). The protocol should include an introduction, main and secondary hypothesis, methods and design (where the statistical methods and sample size should be justified, clearly specifying inclusion and exclusion criteria for the study), discussion and bibliography with a maximum of 15 references.

You can send your manuscript at https://www.editorialmanager.com/ciresp/default.aspx, where you can also register your persistent digital identifier as author ORCID (https://orcid.org).

This journal has no page charges.

This journal is published in Spanish and in English language.

You can use this list to carry out a final check of your submission before you send it to the journal for review. Please check the relevant section in this Guide for Authors for more details.
Ensure that the following items are present:
One author has been designated as the corresponding author with contact details:

• E-mail address
• Full postal address

All necessary files have been uploaded:
Manuscript:

• Include keywords
• All figures (include relevant captions)
• All tables (including titles, description, footnotes)
• Ensure all figure and table citations in the text match the files provided
• Indicate clearly if color should be used for any figures in print

Graphical Abstracts / Highlights files (where applicable)
Supplemental files (where applicable)
Further considerations

• Manuscript has been 'spell checked' and 'grammar checked'
• All references mentioned in the Reference List are cited in the text, and vice versa

Permission has been obtained for use of copyrighted material from other sources (including the Internet)

• A competing interests statement is provided, even if the authors have no competing interests to declare
• Journal policies detailed in this guide have been reviewed
• Referee suggestions and contact details provided, based on journal requirements

For further information, visit our Support Center.

Please see our information pages on Ethics in publishing and Ethical guidelines for journal publication.

If the work involves the use of human subjects, the author should ensure that the work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans. The manuscript should be in line with the Recommendations for the Conduct, Reporting, Editing and Publication of Scholarly Work in Medical Journals and aim for the inclusion of representative human populations (sex, age and ethnicity) as per those recommendations. The terms sex and gender should be used correctly.

Authors should include a statement in the manuscript that informed consent was obtained for experimentation with human subjects. The privacy rights of human subjects must always be observed.

All animal experiments should comply with the ARRIVE guidelines and should be carried out in accordance with the U.K. Animals (Scientific Procedures) Act, 1986 and associated guidelines, EU Directive 2010/63/EU for animal experiments, or the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978) and the authors should clearly indicate in the manuscript that such guidelines have been followed. The sex of animals must be indicated, and where appropriate, the influence (or association) of sex on the results of the study.

Studies on patients or volunteers require ethics committee approval and informed consent, which should be documented in the paper. Appropriate consents, permissions and releases must be obtained where an author wishes to include case details or other personal information or images of patients and any other individuals in an Elsevier publication. Written consents must be retained by the author but copies should not be provided to the journal. Only if specifically requested by the journal in exceptional circumstances (for example if a legal issue arises) the author must provide copies of the consents or evidence that such consents have been obtained. For more information, please review the Elsevier Policy on the Use of Images or Personal Information of Patients or other Individuals. Unless you have written permission from the patient (or, where applicable, the next of kin), the personal details of any patient included in any part of the article and in any supplementary materials (including all illustrations and videos) must be removed before submission.

All authors must disclose any financial and personal relationships with other people or organizations that could inappropriately influence (bias) their work. Examples of potential conflicts of interest include employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding. If there are no conflicts of interest then please state this: 'Conflicts of interest: none'. More information.

The below guidance only refers to the writing process, and not to the use of AI tools to analyse and draw insights from data as part of the research process.

Where authors use generative artificial intelligence (AI) and AI-assisted technologies in the writing process, authors should only use these technologies to improve readability and language. Applying the technology should be done with human oversight and control, and authors should carefully review and edit the result, as AI can generate authoritative-sounding output that can be incorrect, incomplete or biased. AI and AI-assisted technologies should not be listed as an author or co-author, or be cited as an author. Authorship implies responsibilities and tasks that can only be attributed to and performed by humans, as outlined in Elsevier’s AI policy for authors.

Authors should disclose in their manuscript the use of AI and AI-assisted technologies in the writing process by following the instructions below. A statement will appear in the published work. Please note that authors are ultimately responsible and accountable for the contents of the work.

Disclosure instructions
Authors must disclose the use of generative AI and AI-assisted technologies in the writing process by adding a statement at the end of their manuscript in the core manuscript file, before the References list. The statement should be placed in a new section entitled ‘Declaration of Generative AI and AI-assisted technologies in the writing process’.

Statement: During the preparation of this work the author(s) used [NAME TOOL / SERVICE] in order to [REASON]. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.

This declaration does not apply to the use of basic tools for checking grammar, spelling, references etc. If there is nothing to disclose, there is no need to add a statement.

Submission of an article implies that the work described has not been published previously (except in the form of an abstract or as part of a published lecture or academic thesis, see 'Multiple, redundant or concurrent publication' section of our ethics policy for more information), that it is not under consideration for publication elsewhere, that its publication is approved by all authors and tacitly or explicitly by the responsible authorities where the work was carried out, and that, if accepted, it will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder. To verify originality, your article may be checked by the originality detection service Crossref Similarity Check.

Please note that preprints can be shared anywhere at any time, in line with Elsevier's sharing policy. Sharing your preprints e.g. on a preprint server will not count as prior publication (see 'Multiple, redundant or concurrent publication' for more information).

Reporting guidance
For research involving or pertaining to humans, animals or eukaryotic cells, investigators should integrate sex and gender-based analyses (SGBA) into their research design according to funder/sponsor requirements and best practices within a field. Authors should address the sex and/or gender dimensions of their research in their article. In cases where they cannot, they should discuss this as a limitation to their research's generalizability. Importantly, authors should explicitly state what definitions of sex and/or gender they are applying to enhance the precision, rigor and reproducibility of their research and to avoid ambiguity or conflation of terms and the constructs to which they refer (see Definitions section below). Authors can refer to the SSex and Gender Equity in Research (SAGER) guidelines and the S SAGER guidelines checklist. These offer systematic approaches to the use and editorial review of sex and gender information in study design, data analysis, outcome reporting and research interpretation - however, please note there is no single, universally agreed-upon set of guidelines for defining sex and gender.

Definitions
Sex generally refers to a set of biological attributes that are associated with physical and physiological features (e.g., chromosomal genotype, hormonal levels, internal and external anatomy). A binary sex categorization (male/female) is usually designated at birth ("sex assigned at birth"), most often based solely on the visible external anatomy of a newborn. Gender generally refers to socially constructed roles, behaviors, and identities of women, men and gender-diverse people that occur in a historical and cultural context and may vary across societies and over time. Gender influences how people view themselves and each other, how they behave and interact and how power is distributed in society. Sex and gender are often incorrectly portrayed as binary (female/male or woman/man) and unchanging whereas these constructs actually exist along a spectrum and include additional sex categorizations and gender identities such as people who are intersex/have differences of sex development (DSD) or identify as non-binary. Moreover, the terms "sex" and "gender" can be ambiguous—thus it is important for authors to define the manner in which they are used. In addition to this definition guidance and the SAGER guidelines, the Sresources on this page offer further insight around sex and gender in research studies.

All authors should have made substantial contributions to all of the following: (1) the conception and design of the study, or acquisition of data, or analysis and interpretation of data, (2) drafting the article or revising it critically for important intellectual content, (3) final approval of the version to be submitted.

Authors are expected to consider carefully the list and order of authors before submitting their manuscript and provide the definitive list of authors at the time of the original submission. Any addition, deletion or rearrangement of author names in the authorship list should be made only before the manuscript has been accepted and only if approved by the journal Editor. To request such a change, the Editor must receive the following from the corresponding author: (a) the reason for the change in author list and (b) written confirmation (e-mail, letter) from all authors that they agree with the addition, removal or rearrangement. In the case of addition or removal of authors, this includes confirmation from the author being added or removed.
Only in exceptional circumstances will the Editor consider the addition, deletion or rearrangement of authors after the manuscript has been accepted. While the Editor considers the request, publication of the manuscript will be suspended. If the manuscript has already been published in an online issue, any requests approved by the Editor will result in a corrigendum.

Randomized controlled trials should be presented according to the CONSORT guidelines. At manuscript submission, authors must provide the CONSORT checklist accompanied by a flow diagram that illustrates the progress of patients through the trial, including recruitment, enrollment, randomization, withdrawal and completion, and a detailed description of the randomization procedure. The CONSORT checklist and template flow diagram are available online.

This journal uses the Elsevier Article Transfer Service to find the best home for your manuscript. This means that if an editor feels your manuscript is more suitable for an alternative journal, you might be asked to consider transferring the manuscript to such a journal. The recommendation might be provided by a Journal Editor, a dedicated Scientific Managing Editor, a tool assisted recommendation, or a combination. If you agree, your manuscript will be transferred, though you will have the opportunity to make changes to the manuscript before the submission is complete. Please note that your manuscript will be independently reviewed by the new journal. More information.

Upon acceptance of an article, authors will be asked to complete a 'Journal Publishing Agreement' (see more information on this). An e-mail will be sent to the corresponding author confirming receipt of the manuscript together with a 'Journal Publishing Agreement' form or a link to the online version of this agreement.

Subscribers may reproduce tables of contents or prepare lists of articles including abstracts for internal circulation within their institutions. Permission of the Publisher is required for resale or distribution outside the institution and for all other derivative works, including compilations and translations. If excerpts from other copyrighted works are included, the author(s) must obtain written permission from the copyright owners and credit the source(s) in the article. Elsevier has preprinted forms for use by authors in these cases.

For open access articles: Upon acceptance of an article, authors will be asked to complete an 'License Agreement' (more information). Permitted third party reuse of open access articles is determined by the author's choice of user license.

Author rights
As an author you (or your employer or institution) have certain rights to reuse your work. More information.

Find out how you can share your research published in Elsevier journals.

You are requested to identify who provided financial support for the conduct of the research and/or preparation of the article and to briefly describe the role of the sponsor(s), if any, in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. If the funding source(s) had no such involvement then this should be stated.

This journal offers authors a choice in publishing their research:

Subscription
• Articles are made available to subscribers as well as developing countries and patient groups through our universal access programs.
• No open access publication fee payable by authors.

The Author is entitled to post the accepted manuscript in their institution's repository and make this public after an embargo period (known as green Open Access). The published journal article cannot be shared publicly, for example on ResearchGate or Academia.edu, to ensure the sustainability of peer-reviewed research in journal publications. The embargo period for this journal can be found below.

Gold open access
• Articles are freely available to both subscribers and the wider public with permitted reuse.
• A gold open access publication fee is payable by authors or on their behalf, e.g. by their research funder or institution.

Regardless of how you choose to publish your article, the journal will apply the same peer review criteria and acceptance standards.

For gold open access articles, permitted third party (re)use is defined by the following Creative Commons user licenses:

Researcher Academy is a free e-learning platform designed to support early and mid-career researchers throughout their research journey. The "Learn" environment at Researcher Academy offers several interactive modules, webinars, downloadable guides and resources to guide you through the process of writing for research and going through peer review. Feel free to use these free resources to improve your submission and navigate the publication process with ease.

Please write your text in good English (American or British usage is accepted, but not a mixture of these). Authors who feel their English language manuscript may require editing to eliminate possible grammatical or spelling errors and to conform to correct scientific English may wish to use the English Language Editing service available from Elsevier's Author Services.

This journal uses double-anonymized review, which means the identities of the authors are concealed from the reviewers, and vice versa. More information is available on our website. To facilitate this, please include the following separately:
Title page (with author details): This should include the title, authors' names affiliations, acknowledgements and any Declaration of Interest statement, and a complete address for the corresponding author including an e-mail address.
Anonymized manuscript (no author details): The main body of the paper (including the references, figures, tables and any acknowledgements) should not include any identifying information, such as the authors' names or affiliations.

It is important that the file be saved in the native format of the word processor used. The text should be in single-column format. Keep the layout of the text as simple as possible. Most formatting codes will be removed and replaced on processing the article. In particular, do not use the word processor's options to justify text or to hyphenate words. However, do use bold face, italics, subscripts, superscripts etc. When preparing tables, if you are using a table grid, use only one grid for each individual table and not a grid for each row. If no grid is used, use tabs, not spaces, to align columns. The electronic text should be prepared in a way very similar to that of conventional manuscripts (see also the Guide to Publishing with Elsevier). Note that source files of figures, tables and text graphics will be required whether or not you embed your figures in the text. See also the section on Electronic artwork.
To avoid unnecessary errors you are strongly advised to use the 'spell-check' and 'grammar-check' functions of your word processor.

Divide your article into clearly defined sections. Each subsection is given a brief heading. Each heading should appear on its own separate line. Subsections should be used as much as possible when cross-referencing text: refer to the subsection by heading as opposed to simply 'the text'.

It will be concise and directly related to the work. It should contain the purpose of the work and summarise the logical basis for carrying it out. Only the most relevant references should be made and no aspect of the subject being addressed or data or conclusions about the work being published will be reviewed.

The first paragraph of the Materials and Methods section must indicate the type of design (experimental, clinical, retrospective, prospective, observational, clinical trial, controlled or not, etc) and the study´s setting (multisite or not, type of centre, etc). For more information on the different types of designs and the information that must be included in the Materials and Methods section, authors are advised to consult the section “Style Manual for Expressing Results of Specific Types of Scientific Works in Cirugía Española” on this guide. 

The methods and procedures used will be identified in sufficient detail in order to allow the other investigators to reproduce the study. In the clinical trials, the method for randomisation will be identified. Also, the method used to calculate the sample size must be indicated, specifying the primary variable of the study and the estimations made for its calculation. In the statistical analysis, the methodology used must be explained. For more detailed information on this important section, authors are advised to consult the information found in the section “Expressing Results of Statistical Tests in Cirugía Española.” 

When the experiments are presented in humans, the pro-cedures that were followed must be in compliance with the ethical norms of the Committee responsible for human experimentation (institutional or regional) and with the prin-ciples of the 1975 Declaration of Helsinki, revised in 1983 and available at http://www.wma.net/e/policy/b3.htm. A photocopy of the corresponding Ethics Committee shall be provided. When animal experiments are performed, it will indicate if the European Union rules on animal research were followed.

Observations made with the Methods used will be conveyed, not interpreted. These data will be presented in a logical sequence and may be expressed in detail in the text or in the form of tables and images, but not repetitively in the text and in the tables or images.

The author or authors will attempt to offer their own opinions on the subject without repeating in detail the data provided in the Introduction or Results. The following are highlighted here: a) the significance and practical application of the results; b) considerations of the possible inconsistencies in the methodology and the reasons why the results may be valid; c) the relationship between similar publications and comparison among the areas of agree-ment and disagreement; and d) the indications and directives for future investigations, explaining new hypotheses when they are justified, clearly labelling them as such. Emphasis should be placed on the new and important aspects of the study and the conclusions that are reached.

• Title. Concise and informative. Titles are often used in information-retrieval systems. Avoid abbreviations and formulae where possible.
• Author names and affiliations. Please clearly indicate the given name(s) and family name(s) of each author and check that all names are accurately spelled. You can add your name between parentheses in your own script behind the English transliteration.  Present the authors' affiliation addresses (where the actual work was done) below the names. Indicate all affiliations with a lower-case superscript letter immediately after the author's name and in front of the appropriate address. Provide the full postal address of each affiliation, including the country name and, if available, the e-mail address of each author.
• Corresponding author. Clearly indicate who will handle correspondence at all stages of refereeing and publication, also post-publication. This responsibility includes answering any future queries about Methodology and Materials. Ensure that the e-mail address is given and that contact details are kept up to date by the corresponding author.
• Present/permanent address. If an author has moved since the work described in the article was done, or was visiting at the time, a 'Present address' (or 'Permanent address') may be indicated as a footnote to that author's name. The address at which the author actually did the work must be retained as the main, affiliation address. Superscript Arabic numerals are used for such footnotes.

A structured abstract, by means of appropriate headings, should provide the context or background for the research and should state its purpose, basic procedures (selection of study subjects or laboratory animals, observational and analytical methods), main findings (giving specific effect sizes and their statistical significance, if possible), and principal conclusions. It should emphasize new and important aspects of the study or observations.

This is one of the most important sections in the manuscript because through this section, the basic information about the study is obtained in the bibliographic indexes. In Cirugía Española, it must have a maximum length of 250 words and it must be structured into 4 parts: Introduction, which indicates the objectives of the study; Methods, which describes the patient series, the laboratory and other methods used, and the nature of the study (randomised, retrospective, experimental, etc); Results, which will include the fundamental data with numerical values and their statis-tical significance; and Conclusions, where the main resolutions of the study are indicated succinctly. 

In Reviews and Special Articles, the abstract does not have to be structured but should be equally informative on its content. The use of abbreviations will be avoided. In all cases, the authors must also include the English version of the abstract. 

Following the abstract, the authors must specify and identify 3 to 8 keywords that will help identifying the article when it is indexed in the databases. Terminology from “Medical Subject Headings” (MeSH Terms) from Index Medicus must be used, which can be consulted and downloaded at http://www.nlm.nih.gov/mesh/, as well as its translation to Spanish. If adequate terms are not found in MeSH due to recent introduction, the terms in common use can be used.

A graphical abstract is mandatory for original articles, systematic reviews and special articles. The graphical abstract should summarize the contents of the article in a concise, pictorial form designed to capture the attention of a wide readership. Graphical abstracts should be submitted as a separate file in the online submission system. Image size: Please provide an image with a minimum of 531 × 1328 pixels (h × w) or proportionally more. The image should be readable at a size of 5 × 13 cm using a regular screen resolution of 96 dpi. Preferred file types: TIFF, EPS, PDF or MS Office files. You can view Example Graphical Abstracts on our information site. In this link you can access examples and resources of the journal for the preparation of graphical abstracts: https://bit.ly/2w7eEiU. Authors can make use of Elsevier's Illustration and Enhancement service to ensure the best presentation of their images and in accordance with all technical requirements: Illustration Service.

List funding sources in this standard way to facilitate compliance to funder's requirements:

Funding: This work was supported by the National Institutes of Health [grant numbers xxxx, yyyy]; the Bill & Melinda Gates Foundation, Seattle, WA [grant number zzzz]; and the United States Institutes of Peace [grant number aaaa].

It is not necessary to include detailed descriptions on the program or type of grants and awards. When funding is from a block grant or other resources available to a university, college, or other research institution, submit the name of the institute or organization that provided the funding.

If no funding has been provided for the research, please include the following sentence:

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Whilst it is accepted that authors sometimes need to manipulate images for clarity, manipulation for purposes of deception or fraud will be seen as scientific ethical abuse and will be dealt with accordingly. For graphical images, this journal is applying the following policy: no specific feature within an image may be enhanced, obscured, moved, removed, or introduced. Adjustments of brightness, contrast, or color balance are acceptable if and as long as they do not obscure or eliminate any information present in the original. Nonlinear adjustments (e.g. changes to gamma settings) must be disclosed in the figure legend.

General points
• Make sure you use uniform lettering and sizing of your original artwork.
• Embed the used fonts if the application provides that option.
• Aim to use the following fonts in your illustrations: Arial, Courier, Times New Roman, Symbol, or use fonts that look similar.
• Number the illustrations according to their sequence in the text.
• Use a logical naming convention for your artwork files.
• Provide captions to illustrations separately.
• Size the illustrations close to the desired dimensions of the published version.
• Submit each illustration as a separate file.
• Ensure that color images are accessible to all, including those with impaired color vision.

A detailed guide on electronic artwork is available.
You are urged to visit this site; some excerpts from the detailed information are given here.

Formats
If your electronic artwork is created in a Microsoft Office application (Word, PowerPoint, Excel) then please supply 'as is' in the native document format.
Regardless of the application used other than Microsoft Office, when your electronic artwork is finalized, please 'Save as' or convert the images to one of the following formats (note the resolution requirements for line drawings, halftones, and line/halftone combinations given below):
EPS (or PDF): Vector drawings, embed all used fonts.
TIFF (or JPEG): Color or grayscale photographs (halftones), keep to a minimum of 300 dpi.
TIFF (or JPEG): Bitmapped (pure black & white pixels) line drawings, keep to a minimum of 1000 dpi.
TIFF (or JPEG): Combinations bitmapped line/half-tone (color or grayscale), keep to a minimum of 500 dpi.
Please do not:
• Supply files that are optimized for screen use (e.g., GIF, BMP, PICT, WPG); these typically have a low number of pixels and limited set of colors;
• Supply files that are too low in resolution;
• Submit graphics that are disproportionately large for the content.

Please make sure that artwork files are in an acceptable format (TIFF (or JPEG), EPS (or PDF) or MS Office files) and with the correct resolution. If, together with your accepted article, you submit usable color figures then Elsevier will ensure, at no additional charge, that these figures will appear in color online (e.g., ScienceDirect and other sites). Further information on the preparation of electronic artwork.

Ensure that each illustration has a caption. Supply captions separately, not attached to the figure. A caption should comprise a brief title (not on the figure itself) and a description of the illustration. Keep text in the illustrations themselves to a minimum but explain all symbols and abbreviations used.

Please submit tables as editable text and not as images. Tables can be placed either next to the relevant text in the article, or on separate page(s) at the end. Number tables consecutively in accordance with their appearance in the text and place any table notes below the table body. Be sparing in the use of tables and ensure that the data presented in them do not duplicate results described elsewhere in the article. Please avoid using vertical rules and shading in table cells.

Please ensure that every reference cited in the text is also present in the reference list (and vice versa). Any references cited in the abstract must be given in full. Unpublished results and personal communications are not recommended in the reference list, but may be mentioned in the text. If these references are included in the reference list they should follow the standard reference style of the journal and should include a substitution of the publication date with either 'Unpublished results' or 'Personal communication'. Citation of a reference as 'in press' implies that the item has been accepted for publication.

Increased discoverability of research and high quality peer review are ensured by online links to the sources cited. In order to allow us to create links to abstracting and indexing services, such as Scopus, CrossRef and PubMed, please ensure that data provided in the references are correct. Please note that incorrect surnames, journal/book titles, publication year and pagination may prevent link creation. When copying references, please be careful as they may already contain errors. Use of the DOI is highly encouraged.

A DOI is guaranteed never to change, so you can use it as a permanent link to any electronic article. An example of a citation using DOI for an article not yet in an issue is: VanDecar J.C., Russo R.M., James D.E., Ambeh W.B., Franke M. (2003). Aseismic continuation of the Lesser Antilles slab beneath northeastern Venezuela. Journal of Geophysical Research, https://doi.org/10.1029/2001JB000884. Please note the format of such citations should be in the same style as all other references in the paper.

As a minimum, the full URL should be given and the date when the reference was last accessed. Any further information, if known (DOI, author names, dates, reference to a source publication, etc.), should also be given. Web references can be listed separately (e.g., after the reference list) under a different heading if desired, or can be included in the reference list.

This journal encourages you to cite underlying or relevant datasets in your manuscript by citing them in your text and including a data reference in your Reference List. Data references should include the following elements: author name(s), dataset title, data repository, version (where available), year, and global persistent identifier. Add [dataset] immediately before the reference so we can properly identify it as a data reference. This identifier will not appear in your published article.

Where a preprint has subsequently become available as a peer-reviewed publication, the formal publication should be used as the reference. If there are preprints that are central to your work or that cover crucial developments in the topic, but are not yet formally published, these may be referenced. Preprints should be clearly marked as such, for example by including the word preprint, or the name of the preprint server, as part of the reference. The preprint DOI should also be provided.

Please ensure that the words 'this issue' are added to any references in the list (and any citations in the text) to other articles in the same Special Issue.

Most Elsevier journals have their reference template available in many of the most popular reference management software products. These include all products that support Citation Style Language styles, such as Mendeley. Using citation plug-ins from these products, authors only need to select the appropriate journal template when preparing their article, after which citations and bibliographies will be automatically formatted in the journal's style. If no template is yet available for this journal, please follow the format of the sample references and citations as shown in this Guide. If you use reference management software, please ensure that you remove all field codes before submitting the electronic manuscript. More information on how to remove field codes from different reference management software.

Text: Indicate references by superscript numbers in the text. The actual authors can be referred to, but the reference number(s) must always be given.
List: Number the references in the list in the order in which they appear in the text.
Examples:
Reference to a journal publication:
1. Van der Geer J, Hanraads JAJ, Lupton RA. The art of writing a scientific article. J Sci Commun 2010;163:51–9. https://doi.org/10.1016/j.Sc.2010.00372.
Reference to a journal publication with an article number:
2. Van der Geer J, Hanraads JAJ, Lupton RA. The art of writing a scientific article. Heliyon. 2018;19:e00205. doi:10.1016/j.heliyon.2018.e00205.
Reference to a book:
3. Strunk Jr W, White EB. The elements of style. 4th ed. New York: Longman; 2000.
Reference to a chapter in an edited book:
4. Mettam GR, Adams LB. How to prepare an electronic version of your article. In: Jones BS, Smith RZ, editors. Introduction to the electronic age, New York: E-Publishing Inc; 2009, p. 281–304.
Reference to a website:
5. Cancer Research UK. Cancer statistics reports for the UK, http://www.cancerresearchuk.org/aboutcancer/statistics/cancerstatsreport/; 2003 [accessed 13 March 2003].
Reference to a dataset:
[dataset] 6. Oguro M, Imahiro S, Saito S, Nakashizuka T. Mortality data for Japanese oak wilt disease and surrounding forest compositions, Mendeley Data, v1; 2015. https://doi.org/10.17632/xwj98nb39r.1.
Note shortened form for last page number. e.g., 51–9, and that for more than 6 authors the first 6 should be listed followed by 'et al.' For further details you are referred to 'Uniform Requirements for Manuscripts submitted to Biomedical Journals' (J Am Med Assoc 1997;277:927–34)(see also Samples of Formatted References).

Journal names should be abbreviated according to the List of Title Word Abbreviations.

Elsevier accepts video material and animation sequences to support and enhance your scientific research. Authors who have video or animation files that they wish to submit with their article are strongly encouraged to include links to these within the body of the article. This can be done in the same way as a figure or table by referring to the video or animation content and noting in the body text where it should be placed. All submitted files should be properly labeled so that they directly relate to the video file's content. In order to ensure that your video or animation material is directly usable, please provide the file in one of our recommended file formats with a preferred maximum size of 150 MB per file, 1 GB in total. Video and animation files supplied will be published online in the electronic version of your article in Elsevier Web products, including ScienceDirect. Please supply 'stills' with your files: you can choose any frame from the video or animation or make a separate image. These will be used instead of standard icons and will personalize the link to your video data. For more detailed instructions please visit our video instruction pages. Note: since video and animation cannot be embedded in the print version of the journal, please provide text for both the electronic and the print version for the portions of the article that refer to this content.

Supplementary material such as applications, images and sound clips, can be published with your article to enhance it. Submitted supplementary items are published exactly as they are received (Excel or PowerPoint files will appear as such online). Please submit your material together with the article and supply a concise, descriptive caption for each supplementary file. If you wish to make changes to supplementary material during any stage of the process, please make sure to provide an updated file. Do not annotate any corrections on a previous version. Please switch off the 'Track Changes' option in Microsoft Office files as these will appear in the published version.

Elsevier encourages and supports authors to share raw data sets underpinning their research publication where appropriate and enables interlinking of articles and data. More information on depositing, sharing and using research data.

This journal encourages and enables you to share data that supports your research publication where appropriate, and enables you to interlink the data with your published articles.  Research data refers to the results of observations or experimentation that validate research findings. To facilitate reproducibility and data reuse, this journal also encourages you to share your software, code, models, algorithms, protocols, methods and other useful materials related to the project.

Below are a number of ways in which you can associate data with your article or make a statement about the availability of your data when submitting your manuscript. If you are sharing data in one of these ways, you are encouraged to cite the data in your manuscript and reference list. Please refer to the "References" section for more information about data citation. For more information on depositing, sharing and using research data and other relevant research materials, visit the research data page.

Abbreviations and Symbols

Only standard abbreviations will be used, avoiding their use in the title and the abstract. When an abbreviation is used for the first time, it will be preceded by the complete term to which it corresponds, except when dealing with common units of measure. The abbreviations and symbols must be standard and adhere to the international system of units, except for blood pressure which must be indicated in mm Hg. Abuse of abbreviations should be avoided, limiting them to expressions that are repeated more than three times in the text and always indicating their meaning the first time they appear. 

Whenever possible, the official generic drug names should be indicated. If the brand name of a drug is used, capital letters will be used as in proper nouns and their registration will be specified with the symbols ® or ™ as appropriate.

Numerals 

Spanish language notation must be used for figures with decimal numbers. Therefore, a comma is used to separate units of the decimal portion of numbers and a period is used to separate units of thousands and millions. Self restraint is recommended in the use of decimals in the text as well as in tables and figures. Therefore, the use of non significant decimals should be avoided by rounding the figure to the closest value. As a general rule, figures that are expressed as a measure of dispersion (standard deviation or standard error of the mean) must have half as many decimals as the arithmetic mean to which they refer. 

Incorrect: (age 16.68 ± 3/12 years) Correct: (age 16.7 [3] years)

The inclusion of results with P=.000 (transcribed directly from the result obtained from the statistical calculation program) must be specifically avoided and substituted with P P

Percentages

Certain consensus exists in scientific editing on the use of percentages:

• If the number is less than 25, percentages are not used.
• If the total number is between 25 and 100, percentages must be expressed without decimals (7%, and not 7.2%).
• If the total number is between 100 and 100 000, a deci-mal may be added (7.2%, and not 7.23%).
• Only if the number exceeds 100 000 can two decimal places be used (7.23%).
• The original data must always be included: Complications appeared in 209 (7.2%) of 2901 patients. Note that the percentage is included between parenthe-ses in order to emphasise the original data. Therefore, it should not be expressed in the following manner: 7.2% (209).
• The original data should never be presented with a slash. Therefore, the following construction should not be used: 209/2901 (7.2%).

Guidelines for expressing the results of Statistical Tests  

• Normal or nearly symmetrical distribution variable must be described as the median (standard deviation). For variables that are clearly not normal or that contain extreme or atypical values, it is better to describe them as the median and the range (minimum and maximum value). When the median and its standard deviation are expressed, the figures that are shown in that standard deviation must have half the number of decimals as the arithmetic median that they refer to: 

Correct: (age 16.7 [3] years) 

Incorrect: [age 16.68 [3.12] years)

Frequencies (number of observations) and percentages are used for the qualitative variables.  

• When hypothesis testing is used, and if the study was designed for decision-making, the level of statistical significance and/or the level of reliability of the confidence intervals must be reported. This will not be required if the study is explanatory about the existing relationship between the variables. The usual P value is .05; for confidence intervals, it will be 95%. Any value other than these must be justified.
• As in the other case, the P values must consist of three decimals, rounded the last one (for example, P=.238.) Only in the event that it is less than a thousandth should it be expressed as PP<.05, P>.05, P=NS, or similar expressions will be avoided.
• When the effects of 2 variables are compared, the confidence intervals must accompany the value for the estimated difference between them, making it incorrect to, for example, assign a value to the median of variable A with its confidence interval together with the median of variable B with its confidence interval.
• Currently, the ICMJE (International Committee of Medical Journal Editors) highly recommends the use of the confidence intervals in place of the P values or at least always accompanying them in order to complement the primary result of the study or the most significant secondary results. In no case they are used accompanying the intermediate or marginal results.
• The calculation of the sample size and the method used must be detailed in all prospective studies. To do this, it is essential to describe the primary variable of the result and the reasoning or bibliographical source on which the estimation of the expected differences is based. These differences must be, in principle, close to the minimums that may be important from a clinical or practical point of view.
• The statistical test used to calculate the P values and the confidence intervals must be specified as well as the statistical program and its version number that was used. The statistical tests used are specified both in the Materials and Methods section as well as in the tables and figures.
• If uncommon statistical tests are used, it will be necessary to explain the idea behind the need for these in the Materials and Methods section. It is also necessary to include a bibliographical source that makes it possible to obtain additional useful knowledge.
• Certain hypothesis comparison tests, known as parametric equations, can only be applied if the variables follow a normal distribution (such as the Student t test). This restriction, which is sometimes insurmountable, has led some specialists to recommend systematic use of non-parametric tests. The Mann-Whitney test for quantitative variables is one of them. Cirugía Española will not put any restrictions on authors who decide to follow this directive. However, when parametric tests are used to compare hypotheses (such as the Student t test) that require a normal distribution, there should be specific mention of how normality of the variable has been verified (such as with a Kolmogorov-Smirnov test, for example). If this normality cannot be verified, the use of non-parametric tests to compare the hypothesis is preferred (Mann-Whitney or Wilcoxon instead of the Student t test, for example).
• With regard to multivariate tests, their most common use is directed towards controlling the effects of confusion between several predicting variables when faced with a variable that is representative of the result that is being analysed. The requirements for reporting the result of the analysis consist of creating an abstract table with the following information for each predictive variable: coefficient Beta, standard Beta error, p, Odds ratio (95% confidence interval).

*The odds ratio belongs to the logistical regression. In the Cox regression, it is used as a hazard ratio. In the Poisson regression, it is used as a relative ratio. 

On other occasions, the multivariate analysis will be directed towards creating a prognostic model where the be-ta coefficient may be used for the creation of a point scale. In this situation, it is necessary to include the model´s constant in the table and, conversely, it requires a series of confirmations of the functionality of that model which must specify in the manuscript: 

• The internal calibration of the model (goodness of fit), which is generally performed by using the Hosmer-Leme show test
• The ability to discriminate between opposite results, which is generally performed using the calculation of the area under the ROC curve

One set of page proofs (as PDF files) will be sent by e-mail to the corresponding author (if we do not have an e-mail address then paper proofs will be sent by post) or a link will be provided in the e-mail so that authors can download the files themselves. To ensure a fast publication process of the article, we kindly ask authors to provide us with their proof corrections within two days. Elsevier now provides authors with PDF proofs which can be annotated; for this you will need to download the free Adobe Reader, version 9 (or higher). Instructions on how to annotate PDF files will accompany the proofs (also given online). The exact system requirements are given at the Adobe site.
If you do not wish to use the PDF annotations function, you may list the corrections (including replies to the Query Form) and return them to Elsevier in an e-mail. Please list your corrections quoting line number. If, for any reason, this is not possible, then mark the corrections and any other comments (including replies to the Query Form) on a printout of your proof and scan the pages and return via e-mail. Please use this proof only for checking the typesetting, editing, completeness and correctness of the text, tables and figures. Significant changes to the article as accepted for publication will only be considered at this stage with permission from the Editor. We will do everything possible to get your article published quickly and accurately. It is important to ensure that all corrections are sent back to us in one communication: please check carefully before replying, as inclusion of any subsequent corrections cannot be guaranteed. Proofreading is solely your responsibility.

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