Liver Transplantation Research from India During the Last 25 Years: 1998–2022

Abstract

Background and aims

Liver transplant surgery has been performed in India for the last 25 years. We aimed to analyse the trends, characteristics, and key elements in the field of liver transplantation research from India.

Methods

On April 23, 2023, we conducted a search of the Scopus database for the literature on liver transplantation research, using a well-defined search strategy. MS Excel and VOS viewer software programs were used to examine the articles for organisation, author, journal, keywords, and high-cited literature.

Results

This analysis examined a total of 556 papers, which constituted only a 1.55% share of the global output. These papers involved 442 organizations, 1575 authors, and 147 journals. External funding was received in 4.13% and 23.56% were involved in international collaboration. Three Delhi-NCR organizations, namely the Medanta–The Medicity (n = 63), Institute of Liver & Biliary Sciences (n = 60), and Indraprastha Apollo Hospital (n = 48) led in publication productivity. M. Rela (n = 90) and A.S. Soin (n = 63) were the leading authors in publication productivity, while S. Sudhindran and P. Bhangui were the most impactful authors. Liver Transplantation (n = 96) and Journal of Clinical & Experimental Hepatology (n = 65) published the maximum number of these papers, whereas, Annals of Surgery and Journal of Hepatology led in the citation impact per paper. The most significant keywords were “Liver Transplantation” (n = 484), and “Living Donor” (n = 254). Only 1.80% (n = 10) of the papers were highly cited papers that received 50 to 142 citations and they together registered 69.9 citations per paper.

Conclusion

Although the number of publications on liver transplantation from India started growing recently, it forms only 1.55% of the global report. There is an unmet need to increase government-supported research and multicenter collaborative studies at national and international levels for high-quality patient care.

Graphical abstract

Highlights

• •A total of 556 papers on liver transplantation research from India constitutes a 1.55 % share of the global output.
• •This is the first comprehensive bibliometric analysis of India's liver transplant research over the last 25 years.
• •Delhi-NCR authors and institutions were the leaders in this area of research.
• •There has been a continuous rise in publications, with the maximum surge seen in the last decade.

The first liver transplantation (LT) was performed in 1963 by Thomas Starzl¹ It was over three decades later in 1998 that the first successful deceased donor liver transplant (DDLT) and a living donor LT (LDLT) were performed in India.^2,3 Currently, more than 3000 LT are being performed in India annually, in 90–100 active LT centres.⁴ According to the Global Observatory on Donation and Transplantation (https://www.transplant-observatory.org/summary/), in 2022, the total LT done in India was 3920; out of which the majority of 3174 were LDLT (80.96 %). Southeast Asia (unlike the Western world) is characterised by a dramatic diversity in social, economic, and cultural factors. In addition to the religious and cultural beliefs, limited universal healthcare access and lack of strong legislation in others have been identified as the stumbling blocks in the promotion of DDLT.^5,6 These factors may be the main contributory factors for the LDLT being the predominant form of LT in India.⁷

The Indian Liver Transplant Registry (ILTR; www.iltr.org) is now established and accruing prospective data from August 2019. Although there is no law or directive yet making it compulsory for all centres to contribute data to the ILTR, the Liver Transplant Society of India (LTSI) is trying its best to encourage every active centre to do so. The National Organ and Tissue Transplant Organization is a regulatory body deemed to function as an apex centre for all Indian activities of coordination and networking for the procurement and distribution of Organs and Tissues in the country.

Following the first successful LT in 1998, the next decade witnessed a very slow growth in LT in India, although data on outcome is lacking.⁸ Up until 2004, 131 LTs were performed, but by 2007 the number only rose to 318,⁹ although the Transplantation of Human Organs Act, which authorised deceased donation in India, was passed in 1994. The last decade has seen an interesting and specific pattern of growth in LT in India. Northern India, especially Delhi, was the seat of growth of LDLT from 2001,¹⁰ and southern India, especially Chennai and Hyderabad, played a key role in establishing DDLT in the country.^11,12

In 1990, LT as the only effective treatment for end-stage liver disease was being performed in most of the Western world and Southeast Asia. The operative success rate then was 86% and the 5-year survival was 70%. At the same time, more than 200,000 people die in India every year from liver failure without receiving LT.³ In 2022, India has performed the third largest number of all organ transplants in the world, after the USA and China, which have increased from 4990 (in 2013) to 12,746 (in 2019), and to over 15,000 (in 2022) ((https://www.transplant-observatory.org/summary/). Peer-reviewed publication is a powerful tool to bring attention to the authors, institution, and the country. Although the term “publish or perish” may have become a harsh reality in superseding the real-world clinical work, there is no doubt that honest publication of results is crucial to the growth of medical science and advancement of patient care.

The present study aimed to examine India's publications on “Liver Transplantation” research during the last 25 years, as covered in the Scopus database during 1998–2022, focussing on.

• i)Analysing the characteristics and trends of India's literature, and its distribution by document and source types
• ii)Studying the funded and international collaborative research, identifying the leading collaborative countries and major funded sources
• iii)Examining the leading organizations, authors and journals (iv) to present the distribution of publication output by broad subject areas and by significant keywords
• iv)Identifying the leading journals
• v)Describing the characteristics of highly cited papers.

METHODS

Publications related to “Liver Transplantation” research globally and from India were identified from the Scopus database using a well-developed search strategy, involving keywords “liver” and “hepatic” and “transplantation” in “Title” and source title “SRCTITLE” tags and restricting the search to “AFFILCOUNTRY” and period tags covering the literature from 1998 to 2022. The search yielded 35,915 global papers and 556 Indian papers on LT research. Further, by using analytical provisions as listed in the Scopus database, the search string was restricted by “subject area tag”, “source title tag”, and “affiliation tag” as a means to download publications data by subject, collaborating countries, journal wise, and organisation wise. The citation data was collected from the date of publication till 23rd April, 2023. The final results of the literature search were exported in plain text format to form source files for further analysis. Excel and VOS viewer software were used for further analysis and bibliometric data visualization.

The following search strategy and keywords were used to retrieve the publications for this review:

TITLE ((“liver” OR “hepatic”) AND “transplantation”) OR SRCTITLE ((“liver” OR “hepatic”) AND “transplantation”) AND PUBYEAR > 1997 AND PUBYEAR < 2023 AND PUBYEAR > 1997 AND PUBYEAR < 2023.

We defined the most productive authors as those who contributed more than the average productivity of all the authors. The most impactful organizations were those which registered citation per paper (CPP) more than the average CPP of all the organizations. India's author and institution were included in this study when one of the authors or institutions in the publication was from India.

RESULTS

Overview

India's research on LT resulted in 556 papers, which constitute a 1.55% share of global output during 1998–2022. India's research output has shown a systematic increase since 2002. It increased from one paper in 2002 to 73 in 2022, with maximum output (83) reported in 2021. It registered an annual average growth rate of 51.24% during 2002–2022. India's 556 papers received 4722 citations, averaging 8.49 CPP. 23.74% (n = 32) of the papers were involved in international collaboration (IC) and 4.13% (n = 23) received external funding support. These funded papers together received 313 citations, averaging 13.61 CPP. The leading funding agencies supporting research in this field along with their output were: Health Resources & Services Administration (n = 5), Indian Council of Medical Research (ICMR), New Delhi, National Institute of Diabetes and Digestive & Kidney Diseases, National Institute of Alcohol Abuse & Alcoholism, National Institute of Health (n = 2) and 22 other agencies with one paper each.

Of the 556 papers, only 131 (23.56%) were involved in IC and they together received 1630 citations, averaging 12.44 CPP. Among 131 international collaborative papers (ICP), the major contribution came from U.K (n = 59), followed by the USA (n = 53), Canada (n = 16), Hong Kong and Italy (n = 15 each), Japan (n = 14), South Korea (n = 13), France (n = 12), Spain (n = 11), and Turkey (n = 9). Of the total 556 documents, 332 (59.71%) were published as research articles, 97 (17.45%) as letters, 66 (11.87%) as reviews, 22 (3.96%) as book chapters, 19 (3.42%) as editorials, 10 (1.8%) as notes, 8 (1.44%) as conference papers and 2 (0.36%) as short surveys. Of the 556 LT papers, adults (251 papers and 45.14% share) constituted the largest population group, followed by middle-aged (135 papers and 24.28% share), children & adolescents (123 papers and 22.12% share), and aged (41 papers and 7.37% share). In terms of citation impact measured by CPP, the aged group registered the highest impact (21.22 CPP), followed by middle-aged (13.29 CPP), adults (11.08 CPP), and children & adolescents (22.12 CPP).

Trend of Publications From INDIA and Globally

The global publications on “Liver Transplantation” research consisted of 35,915 papers during 1998–2022 and showed a systematic increase from 954 in 1998 to 1916 in 2022, witnessing an average annual growth rate of 3.28% (Supplementary Table 1). The maximum number of publications (2103) was reported in 2021. The trend of publications on LT from India has shown a progressive increase in the last 25 years, with a substantial increase every 5 years, with the maximum surge happening in the last decade (Figure 1).

Figure 1.

Trend of Indian publications on Liver Transplantation, showing a significant growth per 5-year period between 1998 and 2022.

Among top 20 contributing countries, the maximum global share (27.40%) was contributed by USA, followed by China (10.74%), Japan (9.56%), Germany (7.27%), Italy, U.K., Spain and France (from 4.78% to 6.43%), South Korea, Canada, Brazil and Turkey (from 2.08% to 3.98%), and other 8 countries contributing from 1.05% to 1.95%) (Table 1).

Table 1.

Top 20 Countries Contributing to Global Liver Transplantation Research.

S. No.	Country name	TP	%TP	S. No.	Country name	TP	%TP
1	USA	9842	27.40	13	Belgium	701	1.95
2	China	3859	10.74	14	Netherlands	697	1.94
3	Japan	3434	9.56	15	Taiwan	674	1.88
4	Germany	2610	7.27	16	Switzerland	560	1.56
5	Italy	2308	6.43	17	India	556	1.55
6	U.K.	2208	6.15	18	Australia	517	1.44
7	Spain	2015	5.61	19	Poland	472	1.31
8	France	1715	4.78	20	Hong Kong	377	1.05
9	South Korea	1430	3.98		Global Total	35,915
10	Canada	1014	2.82
11	Brazil	827	2.30
12	Turkey	746	2.08

(TP = Total Papers).

Profile of Leading Organizations

The study encompassed 442 organizations actively involved in Indian LT research, contributing to a total of 556 publications. Among these organizations, 297 made a single contribution, while 115 organizations contributed 2 to 5 papers. Additionally, 18 organizations made 6–10 contributions, 11 organizations made 11–50 contributions, and one institute significantly contributed 60 papers.

Individually, the top 30 organizations contributed 3 to 60 papers (Supplementary Table 2). They together published 428 papers which received 4802 citations, accounting for 76.98% and more than 100.0% share in India's LT total papers and citations. Among the top 30 organizations, the top 9 organizations are mentioned in Figure 2, with the number of publications of LT. The publication productivity of these 9 organizations was more than the average publication productivity of all the 30 organizations.

Figure 2.

The most productive Indian organizations contributing to liver transplant research (Institute of Liver & Biliary Sciences: ILBS; Medanta—The Medicity: MTM; Indraprastha Apollo Hospital: IAH; The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research: BIHER; Amrita Institute of Medical Sciences: AIMS; Sir Ganga Ram Hospital: SGH; Postgraduate Institute of Medical Education & Research: PGIMER).

Table 2 lists the top 7 most productive and 7 most impactful organizations.

Table 2.

Profile of the Top 7 Most Productive and 7 Most Impactful Organizations.

S. No.	Name of the organization	TP	TC	CPP	RCI	ICP	%ICP	TLS
Most productive organizations
1	Medanta—The Medicity, Gurgaon	63	856	13.59	1.6	15	23.81	202
2	Institute of Liver & Biliary Sciences (ILBS), New Delhi	60	404	6.73	0.79	10	16.67	92
3	Indraprastha Apollo Hospital	48	343	7.15	0.84	4	8.33	55
4	The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai	36	126	3.5	0.41	8	22.22	91
5	Global Hospitals & Health City, Chennai	33	312	9.45	1.11	19	57.58	49
6	Amrita Institute of Medical Sciences (AIMS), Kochi	31	317	10.23	1.2	2	6.45	34
7	Sir Ganga Ram Hospital, New Delhi	29	203	7	0.82	3	10.34	14
Most impactful organizations
1	Owaisi Hospital, Hyderabad	3	154	51.33	6.05	0	0	11
2	Centre for Liver Research & Diagnostics, Hyderabad	7	343	49	5.77	0	0	15
3	Centre for Cellular & Molecular Biology (CCMB), Hyderabad	5	233	46.6	5.49	0	0	13
4	Deccan College of Medical Sciences, Hyderabad	8	362	45.25	5.33	0	0	19
5	Christian Medical College (CMC), Vellore	4	174	43.5	5.12	3	75	26
6	Sri Ramchandra Institute of Higher Education & Research, Chennai	5	163	32.6	3.84	1	20	27
7	National Foundation for Liver Research, Chennai	9	173	19.22	2.26	3	33.33	7

TP = Total papers; TC = Total citations; CPP = Citations per paper; RCI = Relative citation index; ICP = International collaborative papers; TLS = Total link strength.

The top 11 impactful organizations (as per CPP and RCI) were Owaisi Hospital, Hyderabad (51.33 and 6.05), Centre for Liver Research & Diagnostics, Hyderabad (49.0 and 5.77), Centre for Cellular & Molecular Biology, Hyderabad (46.6 and 5.49), Deccan College of Medical Sciences, Hyderabad (45.25 and 5.33), Christian Medical College, Vellore (43.5 and 5.12), Sri Ramchandra Institute of Higher Education & Research, Chennai (32.6 and 3.84), National Foundation for Liver Research (19.22 and 2.26), Manonmaniam Sundaranar University (16.0 and 1.88), University of Kerala (16.0 and 1.88), Army Hospital Research & Referral, New Delhi (12.57 and 1.48) and Medanta—The Medicity, Gurgaon (12.45 and 1.47). The ICP share of all 30 organizations varied from 0.0 % to 75.0 %, with an average of 19.41 %.

The total link strength (TLS) of top 30 organizations varied from 3 to 212, with maximum collaborative linkages (n = 212) depicted by Medanta—The Medicity, Gurgaon, followed by the Institute of Liver & Biliary Sciences, New Delhi (n = 92), The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai (n = 89), Postgraduate Institute of Medical Education & Research, Chandigarh (n = 83), Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow (n = 61), Indraprastha Apollo Hospital (n = 55) and Asian Institute of Gastroenterology, Hyderabad (n = 53).

Network analysis revealed a network of 28 interconnected Indian institutions out of the top 30 engaged in LT research (Figure 3). Each institution was represented as a node, with node size proportional to the number of publications contributed. Thicker lines connecting nodes indicated a higher degree of collaboration, resulting in a total of 94 links and link strength of 269. The network was further categorised into nine distinct clusters. The red cluster encompassed prominent organizations like PGIMER, Chandigarh; AIIMS, New Delhi; BHU, Varanasi, and the University of Delhi. These organizations exhibited varying levels of productivity in terms of documents, citations, CPP, and TLS. The green cluster institutions demonstrated a collaborative network with a TLS of 8, the lavender cluster institutions had a TLS of 23, the blue cluster institutions amounted to a TLS of 93, and the yellow cluster institutions had a TLS of 94.

Figure 3.

The top Indian organizations' collaborative network map.

Profile of Organizations Working in Adult and Children Liver Transplantation

The top 10 organizations individually contributing to adult LT research in India varied from 34 to 40. They together published 181 papers which received 1919 citations, accounting for 72.11% and 64.25% share in India's adult LT total papers and citations. The top 10 organizations individually contributing to children and adolescent LT research in India varied from 43 to 18. They together published 92 papers which received 660 citations, accounting for 24.8% and 54.19% share in India's children and adolescents' LT total papers and citations. Table 3 lists the top 10 organizations working in the area of adults and children and adolescents.

Table 3.

Bibliometric Profile of Top 10 Organizations Working in Adult and Children Liver Transplantation Research.

Adults					Children and adolescents
S. No.	Name of the organization	TP	TC	CPP	S. No.	Name of the organization	TP	TC	CPP
1	Institute of Liver & Biliary Sciences, New Delhi	40	319	7.98	1	Indraprastha Apollo Hospitals, New Delhi	18	128	7.11
2	Medanta, Gurgaon	37	512	13.84	2	Gleneagles Global Health City, Chennai	15	46	3.07
3	Amrita Institute of Medical Sciences, Kochi	26	209	8.04	3	Bharat Institute of Higher Education & Research, Chennai	13	59	4.54
4	Indraprastha Apollo Hospitals, New Delhi	18	159	8.83	4	Medanta, Gurgaon	11	107	9.73
5	Bharat Institute of Higher Education & Research, Chennai	18	87	4.83	5	Institute of Liver & Biliary Sciences, New Delhi	9	59	6.56
6	Sir Ganga Ram Hospital, New Delhi	13	110	8.46	6	Sir Ganga Ram Hospital, New Delhi	7	58	8.29
7	Global Hospitals & Health City, Chennai	13	158	12.15	7	Amrita Institute of Medical Sciences, Kochi	6	52	8.67
8	National Foundation for Liver Research	4	100	25.00	8	Global Hospitals & Health City, Chennai	5	54	10.80
9	PGIMER, Chandigarh	8	184	20.25	9	National Foundation for Liver Research, Chennai	4	82	20.50
10	Fortis Healthcare Ltd., Multi city locations	4	81	20.25	10	Jaslok Hospital & Research Center, Mumbai	4	15	3.75
	Total of the top 10 organizations	181	1919	10.60		Total of the top 10 organizations	92	660	7.17
	India's total	251	2987	11.90		India's total	123	1218	9.90
	Share of top 10 organizations in India's total LT research	72.11	64.25			Share of top 10 organizations in India's total LT research	74.80	54.19

(TP = Total papers; TC = Total citations; CPP = Citations per paper).

Profile of Top 30 Authors

A total of 1575 authors participated in 556 papers. Individually, the top 30 authors contributed 12 to 90 papers (Supplementary Table 3). They together published 797 papers which received 7505 citations, accounting for more than 100.0% share in India's LT total papers and citations. Among the top 30 authors, the top 11 included M. Rela (n = 90), A.S. Soin (n = 63), M.S. Reddy (n = 50), S. Saigal (n = 47), P. Bhangui (n = 46), N.S. Choudhary, and N. Saraf (n = 42 each), A. Rammohan (n = 37), S. Gupta (n = 35), V. Pamecha (n = 33) and A. Rastogi (n = 30) individually contributed more than the average publication productivity (n = 26.57) of all 30 authors. Also, the top 15 including S. Sudhindran (17.93 and 2.11), P. Bhangui (13.72 and 1.62), A. Rastogi (13.17 and 1.55), R. Mohanka (13.0 and 1.53), N. Goyal (12.69 and 1.49), S. Goja (11.5 and 1.35) S. Saigal (10.91 and 1.29), N. Saraf (10.76 and 1.27), V. Vohra (10.64 and 1.25), S.K. Yadav (10.38 and 1.22), D. Gautam (10.36 and 1.22), A.S. Soin (10.17 and 1.2), V. Vij (9.94 and 1.17), N.S. Choudhary (9.62 and 1.13), and M.S. Reddy (9.5 and 1.12) registered more than the average CPP & RCI (9.42 and 1.11) of all 30 authors. The international collaborative papers (ICP) share of all 30 authors varied from 0.0% to 44.44%, with an average of 17.94%.

The total link strength (TLS) of top 30 authors varied from 32 to 486, with maximum collaborative linkages (n = 486) depicted by A.S. Soin, followed by P. Bhangui (n = 452), S. Saigal (n = 417), M. Rela (n = 398), M.S. Reddy (n = 340), N. Saraf (n = 335), A. Rastogi (n = 319), N.S. Choudhary(n = 307), V. Pamecha (n = 250), A. Rammohan (n = 224), and S. Sudhindran (n = 217). The one-to-one author collaboration linkages varied from 1 to 46, with maximum collaborative linkages (46) depicted by author pair “M. Rela and M.S. Reddy”, followed by authors pairs such as “S. Saigal and N. Saraf”(n = 40)” A.S. Soin and S. Saigal”(n = 39), “S. Saigal and N.S. Choudhary”, “N. Saraf and N.S. Choudhary”, and “A.S. Soin and N. Saraf” (n = 38 each), “A.S. Soin and N.S. Choudhary”(n = 37), “M. Rela and A. Rammohan”(n = 34), “A.S. Soin and P. Bhangui” (n = 27)), “A.S. Soin and A. Rastogi” (n = 26), “N. Saraf and A. Rastogi”(n = 24), and “N. Saigal and P. Bhangui” (n = 22).

Profile of Authors Working in Adult and Children Liver Transplantation

The publications of the top 10 authors individually contributing to adult LT research in India varied from 18 to 38. They together published 288 papers which received 3253 citations, accounting for more than 100% share each in India's adult liver transplantation total papers and citations. Table 4 lists the top 10 authors working in the area of adults.

Table 4.

Bibliometric Profile of Top 10 Authors Working in Adult Liver Transplantation Research.

S. No.	Name	Affiliation	TP	TC	CPP
1	M. Rela	The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai	38	347	9.13
2	P. Bhangui	Medanta, Gurgaon	34	561	16.50
3	S. Saigal	Medanta, Gurgaon	32	356	11.13
4	A.S. Soin	Medanta, Gurgaon	32	337	10.53
5	N. Saraf	Medanta, Gurgaon	31	353	11.39
6	V. Pamecha	Institute of Liver & Biliary Sciences, New Delhi	28	202	7.21
7	N.S. Choudhary	Medanta, Gurgaon	27	295	10.93
8	A. Rastogi	Medanta, Gurgaon	27	331	12.26
9	M.S. Reddy	The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai	21	245	11.67
10	S. Goja	Medanta, Gurgaon	18	226	12.56
		Total of the top 10 authors	288	3253	11.30
		India's total	251	2780	11.08
		Share of top 10 authors in India's total LT publications

(TP = Total papers; TC = Total citations; CPP = Citations per paper).

The top 10 organizations individually contributing to children and adolescent LT research in India varied from 7 to 37 (Table 5). They together published 140 papers which received 1060 citations, accounting for more than 100.0% and 87.03% share in India's children and adolescents LT total papers and citations.

Table 5.

Bibliometric Profile of Top 10 Authors Working in Children & Adolescent Liver Transplantation Research.

S. No.	Name	Affiliation	TP	TC	CPP
1	M. Rela	The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai	37	275	7.43
2	M.S. Reddy	Gleneagles Global Hospitals, Chennai	23	210	9.13
3	A. Rammohan	Global Hospital & Health City, Chennai	14	54	3.86
4	S. Gupta	Indraprastha Apollo Hospital, New Delhi	13	80	6.15
5	A. Sibal	Indraprastha Apollo Hospital, New Delhi	11	64	5.82
6	P. Bhangui	Medanta, Gurgaon	9	93	10.33
7	N. Shanmugam	Global Hospital & Health City, New Delhi	9	53	5.89
8	A.S. Soin	Medanta-The Medicity, Gurgaon	9	89	9.89
9	G. Narasimhan	Global Hospital & Health City, New Delhi	8	80	10.00
10	I. Kaliamoorthy	The Institute of Liver Disease and Transplantation, Dr Rela Institute and Medical Centre, Bharath Institute of Higher Education and Research, Chennai	7	62	8.86
		Total of the top 10 authors	140	1060	7.57
		India's total	123	1218	9.90
		Share of top 10 authors in India's total LT publications		87.03

(TP = Total papers; TC = Total citations; CPP = Citations per paper).

Profile of the Top 30 Journals

Among 556 papers, 532 appeared in journals, 20 in books, 3 in book series and 1 as conference proceedings. A total of 532 research papers on liver transplantation were published across 147 journals, indicating a wide distribution of papers among reporting journals (Supplementary Table 4). The distribution pattern reveals that 86 journals published one paper each, while 30 journals published two papers each. Additionally, seven journals published three papers each, five journals published four papers each, and three journals published five papers each. Among the top 30 journals, a cumulative total of 406 papers were published, with individual journal publication counts ranging from 3 to 96 papers. Among these journals, “Liver Transplantation” emerges as the most productive, publishing 96 documents and receiving a substantial citation count of 1262. Notably, it exhibits a high CPP ratio of 13.146, indicating the significant impact of each paper in terms of citations. Another influential journal is “Hepatology International,” which published 11 documents and received 146 citations, resulting in a commendable CPP ratio of 13.273. Similarly, “Transplantation Proceedings” stands out with 11 published documents and 205 citations, yielding a high CPP ratio of 18.636. These findings suggest the considerable impact and frequency of citations for papers published in these journals.

Profile of the Top 10 Journals Publishing Indian Research on Liver Transplantation in Adults and Children

The top 10 journals individually contributing to adult LT research in India varied from 4 to 57. They together published 156, accounting for a 62.15% share of India's adult LT total papers. Table 5 lists the top 10 journals working in the area of adults. The top 10 journals individually contributing to children and adolescent LT research in India varied from 3 to 18. They together published 93 papers, accounting for 75.61% share of India's children and adolescents LT total papers (Table 6).

Table 6.

Profile of Top 10 Most Productive Journals (Engaged in Adult and Children & Adolescent Liver Transplantation).

Adults			Children & adolescents
S. No.	Name	Total Publications	S. No	Name	Total Publications
1	Liver Transplantation	57	1	Pediatric Transplantation	18
2	Journal of Clinical & Experimental Hepatology	39	2	Liver Transplantation	17
3	Indian Journal of Gastroenterology	16	3	Indian Pediatrics	14
4	Indian Journal of Anaesthesia	13	4	Indian Journal of Anaesthesia	9
5	Clinical Transplantation	6	5	Indian Journal of Gastroenterology	9
6	Indian Journal of Transplantation	6	6	Journal of Clinical & Experimental Hepatology	9
7	Transplantation Proceedings	6	7	Transplantation	6
8	Transplantation	5	8	Indian Journal of Pediatrics	4
9	Hepatology International	4	9	Transplantation Proceedings	4
10	Journal of Anaesthesiology Clinical Pharmacology	4	10	Hepatology International	3
	Total of top 10 journals	156	–	Total of top 10 journals	93
	India's total	251	–	India's total	123
	Share of top 10 journals in India's total	62.15	–	Share of top 10 journals in India's total	75.61

Significant Keywords

Keywords play a significant role in research papers as they provide essential information about the subject. Systematic analysis of keywords in specific research fields can facilitate a clear understanding of the field's developmental trends and research differences. Keyword co-occurrence analysis is a commonly used method to analyse the strength of relationships between different keywords in a large number of documents. By analysing the co-occurrence relationships of keywords, one can understand the internal composition relationship and structure of a specific academic domain and reveal its research frontiers. Consequently, keyword co-occurrence analysis has become a standard research method in Scientometric research.

In the context of LT, a total of 4263 keywords were identified in all the 556 collected papers. However, to understand the relationships among the documents, a selection criterion was established, wherein only those keywords appearing at least 18 times were recognised by the VOSviewer software. As a result, 59 qualified keywords were identified, leading to the formation of a co-occurrence network consisting of 1538 links and total link strength of 11,241, as displayed in Supplementary Figure 1 and Supplementary Table 5. Each node in Supplementary Figure 1 represents a keyword, and the size of the node corresponds to the number of occurrences of the keyword, while the link between the two nodes indicates the relationship between them.

The analysis of the co-occurrence network reveals that the research theme of liver transplantation has formed four distinct clusters, with significant correlations between keywords in each cluster. Based on the current state of Liver Transplantation research, the four clusters can be characterised as follows.

The red cluster, centred on immunosuppressive treatment, was primarily concerned with the management of graft rejection and its associated complications. The green cluster, centred around LT, highlighted the surgical aspects of the procedure, including living donors and organ transplantation. The blue cluster, focused on liver disease and cirrhosis, emphasised the importance of diagnosing and managing end-stage liver disease. Finally, the yellow cluster, centred around liver cell carcinoma and chronic liver disease, dealt with the pathophysiology and management of these conditions.

High-cited Papers

Only 10 (1.80%) out of 556 papers published on LT research in India received 50 to 142 citations and they were assumed as high-cited papers (HCPs). These 10 HCPs together received 669 citations, averaging 69.9 CPP. The details of these 10 HCPs are provided in Table 7.

Table 7.

List of Top 10 High-Cited Papers.

S. No.	Name of authors	Title	Source	No. of citations received
1	Khan AA, Shaik MV, Parveen N et al.	Human fetal liver-derived stem cell transplantation as a supportive modality in the management of end-stage decompensated liver cirrhosis (Original Article)	Cell Transplantation, 2010, 19(4), pp. 409–418.	142
2	Shukla A, Vadeyar H, Rela M, Shah S.	Liver Transplantation: East versus West (Review)	Journal of Clinical and Experimental Hepatology, 2013, 3 (3), pp. 243–253	82
3	Bhangui P, Allard MA, Vibert E et al.	Salvage versus primary liver transplantation for early hepatocellular carcinoma: Do both strategies yield similar outcomes? (Original Article)	Annals of Surgery, 2016, 264 (1), pp. 155–163	80
4	Choudhary NS, Saigal S, Bansal RK et al..	Acute and Chronic Rejection After Liver Transplantation: What A Clinician Needs to Know (Review)	Journal of Clinical and Experimental Hepatology, 2017, 7 (4), pp. 358–366.	71
5	Saigal S, Gupta S Sudhindran S et al.	Liver transplantation and COVID-19 (Coronavirus) infection: guidelines of the Liver Transplant Society of India (LTSI) (Original Article)	Hepatology International, 2020, 14 (4), pp. 429–431	60
6	Mehta N, Bhangui P, Yao FY et al.	Liver Transplantation for Hepatocellular Carcinoma. Working Group Report from the ILTS Transplant Oncology Consensus Conference (Review)	Transplantation, 2020, pp. 1136–1142	59
7	Rammohan A, Reddy MS, Farouk M et al.	Pembrolizumab for metastatic hepatocellular carcinoma following live donor liver transplantation: The silver bullet? (Note).	Hepatology, 2018, 67 (3), pp. 1166–1168.	52
8	Khan AA, Parveen N, Mahaboob VS et al.	Treatment of Crigler-Najjar Syndrome Type 1 by Hepatic Progenitor Cell Transplantation: A Simple Procedure for Management of Hyperbilirubinemia (Original Article)	Transplantation Proceedings, 2008, 40 (4), pp. 1148–1150.	52
9	Devarbhavi H, Abraham S, Kamath PS.	Significance of nodular regenerative hyperplasia occurring de novo following liver transplantation (Original Article)	Liver Transplantation, 2007, 13 (11), pp. 1552–1556.	51
10	Wadhawan M, Gupta S, Goyal N. et al.	Living-related liver transplantation for hepatitis B-related liver disease without hepatitis B immune globulin prophylaxis (Original Article)	Liver Transplantation, 2013, 19 (9), pp. 1030–1035.	50

DISCUSSION

Liver transplantation (LT)-related research at the global and national level has rarely been studied from a bibliometric perspective. The present study, therefore, makes the first comprehensive bibliometric analysis of India's LT research during the last 25 years (between 1988 and 2022). Only a few bibliometric studies have been undertaken in the past on global and regional transplantation research,^{13, 14, 15, 16, 17, 18, 19, 20, 21} focussing on scientific publications from mainland China, Japan, South Korea, and Taiwan between 2006 and 2015 and citation analysis of the top 100 most cited papers in transplantation. In LT, bibliometric studies were made on the assessment of global clinical LT research (covering the literature from January 1981 and May 2021), Chinese and Turkey LT research, global research on anaesthesia for LT and global research on paediatric LT research. In our study, we identified 556 peer-reviewed publications on India's LT research in the Scopus database. These papers received 4722 citations, averaging 8.49 CPP; 10 papers (1.80%) received 50 or more citations and were termed as HCPs.

Although liver problems are plenty in India, and a large number of patients require LT, the research output on LT from India is only 1.55% of the global output, which needs to be strengthened in future. India has witnessed an increasing trend of deceased donor liver transplants in southern India, but major regional imbalances exist. In addition, LT is mainly done in the hospitals of the private sector and with live donor transplants. The LT is a costly procedure and lack of these facilities in most public hospitals it is not affordable to most needy patients. Moreover, the lack of a national registry and reporting outcomes is concerning. The future of LT in India should be more accountable, equitable, and accessible to the majority of patients.²² Our findings confirm that the majority of the institutions publishing on LT in India are located in metropolitan and big cities, and more such centres need to be established across India to deal with the large pool of cases requiring LT. In addition, the regulations regarding cadaveric transplantation must be liberalised to make an easier to use DDLT. The National Liver Allocation Policy consensus document was formed to address all aspects of DDLT, including minimum listing criteria, listing for acute liver failure, wait-list management, a system of prioritisation based on clinical urgency for adults and children, guidelines for allocation of paediatric organs and allocation priorities for liver grafts recovered from public sector hospitals.²³

The LT surgery has been reported as highly successful by Indian authors, both in adults and children. The LT in India has grown exponentially in the last decade, with 135 centres now performing between 1500 and 2000 transplants a year, 10% of which are pediatric, with a >90% survival rate. More complex cases are now being taken up for LT and the financial constraints are being addressed through crowdfunding and increasing philanthropic efforts.²⁴ Bhangui et al. reported satisfactory outcomes of LDLT in recipients with lower ejection fraction [EF] (of <50 %), with 1-year, and 5-year survival rates of 75%, and 66%, respectively.²⁵ The COVID-19 pandemic also affected LT badly. Gupta et al.,²⁶ observed that there was an increased risk of infection to the transplant recipients; and a significant risk of mortality in cases waiting for LT.

The LRLT has been successful at many centres in India, which confirms that this model is reliable, replicable, and affordable. No significant donor complications are reported in paediatric LT.²⁷ Mittal et al.²⁸ described their successful experience of paediatric living donor LT for auto immune liver diseases (AILD) in 244 children over 10 years. The complications, graft, and patient survival rates were quite acceptable.

Non-alcoholic steatohepatitis (NASH) is now considered the leading indication for LT in India, which has surpassed viral hepatitis in recent years. Moreover, Jothimani et al.²⁹ found that the LT for non-alcoholic steatohepatitis (NASH) had lower 5-year survival compared with viral hepatitis (75.9% vs 87.4%; P = 0.03). Vaishya et al.³⁰ noticed a rising trend of publications on NAFLD from the Indian subcontinent during 2001–2022. However, there is inadequate regional research collaboration among these countries.

We observed that about a quarter of the Indian publications were involved in IC, which together received 12.44 CPP (higher than the average 8.49 CPP), hence, it is obvious that the international collaboration at institutional and scholars' level with potentially important countries should be explored. It would help improve research output impact and quality. It was noticed that a more active IC started from 2015 onwards when ICP increased from 7 in 2015 to 25 in 2022. Only 4.13% of India's publications on LT research received external funding support and it is suggested that more funding sources be made available, at national and international levels, for the researchers to increase the scholarly output. Furthermore, the Indian government should give priority to this area in the national plans, which is likely to lead to more improvement in research output impact and quality, and thereby help improve the management strategies for needy patients. It is important to realise that the research done in high-income countries (HIC) cannot be translated directly to the patients of low-middle-income countries (LMIC), who may have very different problems and financial constraints related to the treatment.

We concur that health research has high value to society, as it can provide valuable information about disease trends and risk factors, outcomes of treatment or public health interventions, etc. It is crucial to record and assess the experience of a treatment modality (like LT), to develop guidelines for the best practices, and to provide high-quality patient care.³¹

The pace of India's research is expected to increase in LT. We found that the distribution of research by Indian organizations and authors is uneven, and hence collaboration and research communication between organizations and authors must be substantially enhanced.

Limitations of the Study

The articles included in this study are not related to LT surgery alone, but may also include various ancillary fields related to the LT publications e.g., anaesthesia, hepatology, pathology, radiology and basic science research. Since we are unable to separate these, we consider it as a weakness of the methodology. We also acknowledge that the age group categorisation into children, adolescents, middle-aged, adults, and elderly is based on the Scopus data, which does not exactly define their age profile. Sometimes, the authors use variable affiliations of their institutions in different papers, and hence the Scopus data reflects these as separate institutions.

This study is the first comprehensive bibliometric analysis of India's liver transplant research over the last 25 years. Delhi-NCR (National Capital Region) authors and institutions were the leaders in this area of research. There has been a continuous rise in publications, with the maximum surge seen in the last decade. This study provides insight into its current and past research status and hopes to guide scholars to understand research frontiers and directions in liver transplantation-related research.

Credit Authorship Contribution Statement

RV: Conceptualisation, Literature search, Data analysis, Manuscript writing, editing, and final approval; BMG: Data extraction and analysis, Literature search, Manuscript writing, editing, and final approval; MKK: Data extraction and analysis, Literature search, Manuscript writing, editing, and final approval; AS: Conceptualization, Manuscript writing, editing, and final approval; NG: Conceptualization, Manuscript writing, editing, and final approval.

Conflicts of interest

All authors have none to declare.

Acknowledgement

We are grateful to Dr. Madhan Jeyaraman, Assistant Professor of Orthopaedics, Sri Lalithambigai Medical College and Hospital, Chennai for his help in making the Graphical Abstract of our paper.

Funding

No funding was received for this research.

Data availability

Raw data are available with the corresponding author in case of any need.

Ethical approval

Not required.

Use of AI technology

None.

Appendix A. Supplementary data

The following is the supplementary data to this article: