{'fraction_non_alphanumeric': 0.03377085042384468, 'fraction_numerical': 0.027344818156959255, 'mean_word_length': 4.956840390879479, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Farewell from the CKJ Editor-in-Chief: key kidney topics from 2014 to 2021

ABSTRACT The year 2021 was the last full year of Alberto Ortiz’s editorship at Clinical Kidney Journal (CKJ). On May 2022, Maria José Soler will start her term as the Editor-in-Chief. Over these years, CKJ obtained its first journal impact factor and has consolidated its position among the top journals in the field, consistently ranking among the top 25% (first quartile) journals in Urology and Nephrology. The 2020 journal impact factor rose to 4.45, becoming the top open access journal in Nephrology and the ninth ranked Nephrology journal overall. We now review the recent history of the journal and the most highly cited topics which include the epidemiology of kidney disease, chronic kidney disease topics, such as the assessment and treatment of chronic kidney disease, onconephrology, cardionephrology, glomerular disease, transplantation and coronavirus disease 2019 (COVID-19).

Ortiz has been the Editor-in-Chief (EiC), a term that will end in May 2022 when Maria José Soler will become the first female CKJ EiC [1,2]. As the last full year as EiC ends, it is worth reflecting on the path so far and on the most impactful topics published in CKJ.

THE FIRST JOURNAL IMPACT FACTOR
The single event that has most influenced the trajectory of the journal during Alberto Ortiz's editorship was the journal's first impact factor (JIF) in 2019 [3]. Overnight, the number of submissions doubled and the quality increased, forcing the editorial board to make painful rejection decisions. Triaging became necessary and the acceptance rate for original manuscripts dropped to 10-15%. As of January 2021, the number of issues increased from 6 to 12 a year, to accelerate the speed of publication of new science.
From the first JIF, CKJ has been part of the select group of journals ranked among the top 25% (first quartile, Q1) of Urology and Nephrology journals. Moreover, as the JIF progressively increased to over 3.0 and, most recently, to over 4.0, CKJ slowly climbed the ranks of Q1 journals. As of the summer of 2021, the 2020 JIF was 4.452 and Clarivate ranked CKJ as the top open access Nephrology journal and the ninth Nephrology journal overall (Table 1). It was also the sixth ranked Nephrology journal among journals that publish mainly original research. FIGURE 1: Key milestones in the history of CKJ. Source for journal ranking: reference number [3].

MOST IMPACTFUL NEPHROLOGY TOPICS IN CKJ OVER THE YEARS
It is worth reflecting on the items that drew the most citations over the years, the ones that most impacted other scientists and, potentially, clinical practice. The most cited manuscripts are presented in Table 2 and summarized per topic in Figure 2 [4-37]. Older items have had more time to build awareness and be cited and thus may be overrepresented. This issue is only partially addressed by the column depicting average citations per year, as there will be a lag time from publication to first notice by readers and to citation in the readers' manuscript, and this will be followed by a lag time from manuscript submission to publication. Thus, citations shown in Table 2 will more accurately reflect the impact of older items than of newer items, whose full impact will be realized in the next few years. To visualize newer items, Table 3 shows the top publications ranked according to average yearly citations and Table 4 the top five cited manuscripts from each year . While only one manuscript from 2019 or later is among the manuscripts with most overall citations ( Table 2), 45% of manuscripts with the most annualized citations were from 2019 to 2021, illustrating the increased quality and visibility of CKJ contents (Table 3).
Overall, the most cited manuscripts had chronic kidney disease (CKD) as topic, either non-dialysis or dialysis CKD (Figure 2), followed by onconephrology, cardionephrology, glomerular disease and transplantation. In line with a recent bibliographical analysis, acute kidney injury (AKI) was remarkably underrepresented, except for the coronavirus disease 2019 (COVID-19) context in more recent years [61]. Tables 3 and 4 provide a greater granularity as well as the emergence of topics that have become more relevant in recent years (Table 5). Thus, assessment of CKD by either improving glomerular filtration rate (GFR) assessment by using iohexol to measure GFR or novel methods for assessment of kidney injury, such as the urinary peptidomics biomarker CKD273, were highly cited topics [7,11]. Regarding onconephrology, the nephrotoxicity of novel anticancer agents also attracted the attention of readers [12,31,34]. More recently, novel therapeutic approaches for CKD or its complications, such as sodium-glucose transport protein 2 (SGLT2) inhibitors or hypoxia-inducible factor (HIF) stabilizers, were also topics of interest [5,39], as well as several manuscripts dealing with the interaction between COVID-19 and kidney disease [38,40,44,47,56,57,59]. COVID-19-related highly cited manuscripts dealt with characterization of AKI in patients with severe COVID-19 and kidney replacement therapy in this context, COVID-19 in CKD and the key role that collective transport to and from hemodialysis units played in the spread of the disease among hemodialysis patients [38,40,44,47]. Finally, topics at the top of the global agenda, such as the impact of air pollution on health and, specifically, on kidney disease have also been highly cited [41]. A special mention should be devoted to the concept of CKD hotspots, first formulated in CKJ as consisting of countries, regions, communities or ethnicities with higher-than-average incidence of

CKJ AND THE ERA REGISTRY
CKJ publishes the summary of the ERA Registry Annual Report. This is one of the most cited items in the journal and was not included in the above analyses. It represents the longest running multinational registry that is searchable as a publication in PubMed. In recent years, Registry Reports have consistently ranked among the top 10 cited items per year, often on the top spot. Furthermore, their citation record has increased over the years [62][63][64][65][66][67][68][69]. The most cited Registry Report was the 2015      2014 Onconephrology (nephrotoxicity of anticancer agents) and cardiovascular disease (anticoagulation) report published in 2018 [69]. That year, World Kidney Day was devoted to women and kidney disease, and the ERA Registry was a solid source of information on the epidemiology, treatment and outcomes of kidney replacement therapy in men and women [70,71].

THE PERSONS WHO MADE IT POSSIBLE
High-quality journals do not just happen. We should be grateful to the authors who considered CKJ to disseminate their expertise and research as well as the reviewers who devoted their time to constructively criticize and improve the quality of the manuscripts (Supplementary data, Tables S1-S8). Finally, a hardworking and expert editorial board liaised with reviewers and integrated their concerns to select the highest quality manuscripts that would be most informative and useful to our readership (Supplementary data, Table S9). A big thank you to all of you and good luck to our new Editor-in-Chief!

SUPPLEMENTARY DATA
Supplementary data are available at ckj online.