Footnotes

• Twitter Follow Alfredo Redondo Diéguez @Alfredo_Redondo

• Contributors AG and CDM planned and drafted the first manuscript. AG, IDK, ARD and GL took part in the selection and elaboration of images as well as in table preparation. IV, NP, RK, RDS and CDM revised the text and offered important feedback based on their practical experience in the field. ARD, CDM and RDS edited the final version. All the authors have contributed to and approved this final version.

• Competing interests None declared.

• Patient consent Obtained.

• Provenance and peer review Commissioned; externally peer reviewed.