The top 100 cited articles in pediatric urology: a bibliometric analysis

Summary

Introduction:

In the last 120 years, the field of pediatric urology has seen an exponential growth. In this time, there has not been a comprehensive review of top cited articles within the field.

Objectives:

We aim to identify and categorize the top 100 most cited peer-reviewed articles in pediatric urology using citation analysis.

Study design:

We searched for articles in the Web of Science^™ Core Collection between 1900 and 2020 using terms specific to pediatric urology. We identified relevant pediatric urology articles and selected the top 100 most cited articles. We analysed trends over time for topics and categories and we evaluated the relatedness of these articles using citation analysis software.

Results:

The top 100 most cited articles in pediatric urology were published between 1958 and 2016 in 26 countries, across 181 institutions, and in 46 journals. The median number of citations per article was 268 (IQR 225.75–394.25). Clinical manuscripts were the most common among the top 100 cited articles (n=64) and the most common topic was genital conditions (e.g., penile, inguinal, or testis but not including hypospadias) (n=19; 16.5%; total citations=6591). When using bibliometric software to analyse relatedness among the top 100 articles based on citation of one another, we identified 11 clusters of 3 or more articles which corresponded to topics like those we defined a priori (Summary Figure). We found that a greater proportion of articles describing surgical techniques were published prior to 1987 (n=6, 38%) as compared to after 1987 (n=11, 13%), while the proportion of basic science articles has increased.

Discussion:

This is the first study to analyse the most cited articles in pediatric urology. There was a lower median citation per article and fewer prospective studies in this list compared to other urologic sub-specialties. Similar to other clinical specialties, the focus has moved from describing and comparing operative techniques to exploring mechanisms of disease. This study is limited by using a single parameter (citation rate) and a single citation database.

Conclusion:

The list of top 100 most cited articles in pediatric urology is an important resource for clinicians and trainees to understand the body of knowledge and trajectory of this field. It charts the evolution of the field and highlight areas of potential investigation. This objective approach to literature review can facilitate future research and education efforts.

Introduction

Bibliometric research is the objective evaluation of published scientific articles and allows one to determine the influence of a publication and to follow the development of new fields of science and technology^1,2. The number of times an article is cited in other articles helps to measure the impact of the primary article or its author on the scientific community³. Moreover, a summary of the most cited articles in a field allows the novice student to familiarize themselves with the most important contributing manuscripts to a particular field.

The last 10 years has seen a number of bibliometric analyses in urology^4–7. Many of these analyses used broad search terms. This strategy often identified urologic oncologic articles due to the prevalence of urologic cancers. The predominance of urologic oncology articles among the highest cited articles can diminish the impact of other important articles pertaining to less common urologic conditions, such as those in pediatric urology. To this end, some groups have attempted to identify the most cited articles in specific areas like bladder cancer, urologic emergencies, urethral reconstruction, and andrology^8–13. Though bibliometric analyses have been performed on hypospadias¹⁴ and vesicoureteral reflux¹⁵, to our knowledge an analysis of top cited articles in pediatric urology is not available.

The purpose of this study is to identify and analyse the characteristics of the top 100 most frequently cited articles in pediatric urology.

Methods

We conducted our search using the Web of Science (WOS) core collection, a database providing comprehensive citation data indexing > 21,419 journals and books and conference proceedings (over 79 million records) in the physical-, health-, and social sciences as well as arts and humanities, between 1900 to the present day (December 29, 2020)¹⁶. Titles of foreign-language publications are translated into English. We chose WOS over other commonly used citation databases (Scopus and Google Scholar), as most citations found only by Google Scholar were from non-journal sources¹⁷, and Web of Science core collection covers all the common urology and surgical journals where we expect to find pediatric urology and related articles.

Web of Science was queried using the “OR” search function with the terms outlined in the supplementary file. These terms cover the entire breadth of pathology, surgeries, and patients in pediatric urology. In order to broaden our search to any processes associated with urogenital organs in pediatric patients we queried using the “AND” search function with the term “pediatric” AND “scrotum”, “vas deferens”, “epididymis”, “testicle, “testes”, “kidney”, “renal”, “ureter”, “bladder”, “urethra”, “penis” and “prostate”. Using this search approach, we identified 102,896 records.

The search was completed on December 29, 2020 and was limited to publications (manuscripts, abstracts, conference proceedings, and editorials) between January 1, 1900 and December 29, 2020. We sorted the records by number of citations from all databases available in WOS. We then reviewed the top 500 most cited items. From each item we collected title, journal, all author names, month and year of publication, institution, and total number of citations. Publications were included if they included pediatric patients (i.e., <= 18 years) in their study population. They were also included if they studied a topic that is of clinical relevance to the practice of pediatric urology, although they did not include pediatric patients. For example, the article “Mullerian-Inhibiting Substance Function during Mammalian Sexual Development” by Behringer et al.¹⁸ focuses on the use of mouse subjects, yet is included in this study since it focuses on a topic that is relevant to pediatric urology, specifically sexual differentiation. The titles of the publications were reviewed in order to categorize them. If there was doubt about the contents or study population of the article based on the title, then the article abstract was collected and reviewed independently by two pediatric urologist (AS, RM). Lastly, if the abstract did not clearly identify the patient population, the entire article was reviewed. Differences in agreement regarding an article’s relevance to pediatric urology were adjudicated by a thorough discussion of the entire article. To ensure we captured a substantial number of publications within each category and subcategory, we categorized the top 200 cited publications.

Articles were categorized as being focused on clinical, basic science, or guideline statements. Clinical publications were defined as papers involving clinical subjects including original studies and review articles. Basic science publications were defined as those involving pre-clinical (animal or in-vitro) studies, or translational research with limited clinical subject involvement beyond the acquisition of tissue samples. Guideline statements were defined as position statements or those manuscripts which may have included the term “guideline” in their title, released by medical or surgical associations. Each article was then further categorized within sub-categories defined a priori: hypospadias; vesicoureteral reflux; obstructive uropathy, hydronephrosis, and cystic disease of the kidney; genital conditions (excluding hypospadias) such as circumcision, orchiopexy/undescended testicle, and varicocele; neurogenic bladder, lower urinary tract symptoms, and voiding dysfunction; urinary tract infections; major genitourinary birth defects (excluding hypospadias and disorders of sexual differentiation (DSD)) such as bladder exstrophy and prune belly syndrome; urolithiasis; pediatric genitourinary cancers; and DSD/intersex. Studies pertaining to anesthesia in children and renal transplantation were excluded. If manuscripts covered more than a single category or subcategory, they were assigned an additional category, up to a maximum of two categories and subcategories.

We reported the top 100 most cited publications. We compared manuscripts published after 1987 to those published prior to and including 1987, noting the frequency of each of the categories of studies published in each time period. The year 1987 was chosen as it represents the midpoint between the publication dates (1958–2016) of the top 100 publications. We also identified those presenting a description or evaluation of surgical techniques in the two time periods.

To evaluate the relatedness among the articles based on the number of times they cite each other, we used VOSViewer^® to group citations among the top 100 most cited publications. VOSViewer^® is software used to construct bibliometric maps¹⁹ based on citation, co-citation, or bibliographic coupling data. In this study, VOSviewer allows us to visualize the interrelatedness of articles based on their citation of each other, and then clusters the publications based on the number of times they cite each other. We expected these individual clusters to correspond to categories like the ones we defined a priori. To identify clusters of related articles we used a resolution of 1 and minimum cluster size of 3 articles per cluster. The strength of the links between items was normalized using the LinLog layout technique and the modularity clustering technique²⁰. This was visualized using a network. Once the clusters were identified, we reviewed the articles within each cluster to identify the topic of discussion.

To understand if the time of publication correlated with impact, we evaluated the correlation between year of publication and citations by calculating the Pearson correlation coefficient. We also evaluated the correlation between the 2019 journal impact factor and number of citations. We collected the impact factors of the journals of the top 100 overall most cited publications from the 2019 Journal Impact factor from the Journal Citation Reports: Science Edition (Version 3.1)²¹.

While citation number is a surrogate of impact, the availability of an article based on the time of its publication may diminish or exaggerate the importance of papers irrespective of actual influence. Thus, to account for the impact of a publication irrespective of its publication date, we used a previously published index which adjusts the citation number for years since publication¹⁵. This was calculated as follows:

$$\mathit{\text{Citation index}}=\frac{\mathit{\text{total citations}}}{\mathit{\text{number of years since publication}}}$$

Using this index, higher values correspond to a higher impact. To visualize the effect of this index on gauging article impact, we generated a bubble plot of adjusted index by publication year, with each individual bubble corresponding to a single publication among the top 100 most cited, and bubble sizes corresponding to the number of citations of that individual publication.

Results

We identified 102,896 records based on our search strategy. We limited the list to the top 100 cited articles in pediatric urology between 1900 and 2020. These are presented in Table 1 in descending order of citation number. The median number of citations among the top 100 most cited articles was 268 (IQR 226–394). These articles were published between 1958 and 2016 in 26 countries, with 68% of the articles originating from the USA (Table 2). The top three research institutions in terms of publications were Boston Children’s Hospital (n=10), Johns Hopkins University (n=7), and Massachusetts General Hospital (n=5) (Table 2). Nine of the ten top cited institutions were in the United States, with the exception being the Karolinska Institute in Stockholm, Sweden which produced 4 publications among the top 100 cited articles. Among the top 100 cited articles, 22 were published in the Journal of Urology, and the next most common journals were Pediatrics (n=12) and the New England Journal of Medicine (n=6).

Table 1.

Top 100 cited articles in pediatric urology. Colors in the “Rank” column correspond to the legend in Figure 3.

Rank	Article title	First Author	Publication Year	Citations	Adjusted Index
1	TESTICULAR DYSGENESIS SYNDROME: AN INCREASINGLY COMMON DEVELOPMENTAL DISORDER WITH ENVIRONMENTAL ASPECTS	SKAKKEBAEK, NE	2001	1461	76.89
2	THE STANDARDIZATION OF TERMINOLOGY OF LOWER URINARY TRACT FUNCTION IN CHILDREN AND ADOLESCENTS: REPORT FROM THE STANDARDISATION COMMITTEE OF THE INTERNATIONAL CHILDREN’S CONTINENCE SOCIETY	NEVEUS, T	2006	942	67.29
3	INTERNATIONAL SYSTEM OF RADIOGRAPHIC GRADING OF VESICOURETERIC REFLUX	LEBOWITZ, RL	1985	802	22.91
4	URINARY TRACT INFECTION: CLINICAL PRACTICE GUIDELINE FOR THE DIAGNOSIS AND MANAGEMENT OF THE INITIAL UTI IN FEBRILE INFANTS AND CHILDREN 2 TO 24 MONTHS	ROBERTS, KB	2011	791	87.89
5	PRACTICE PARAMETER: THE DIAGNOSIS, TREATMENT, AND EVALUATION OF THE INITIAL URINARY TRACT INFECTION IN FEBRILE INFANTS AND YOUNG CHILDREN	BERGMAN, DA	1999	694	33.05
6	CORRELATING TELOMERASE ACTIVITY LEVELS WITH HUMAN NEUROBLASTOMA OUTCOMES	HIYAMA, E	1995	613	24.52
7	CONSENSUS STATEMENT ON MANAGEMENT OF INTERSEX DISORDERS	HUGHES, IA	2006	605	43.21
8	CHARACTERIZATION OF SEVERAL CLONAL LINES OF CULTURED LEYDIG TUMOR-CELLS: GONADOTROPIN RECEPTORS AND STEROIDOGENIC RESPONSES	ASCOLI, M	1981	560	14.36
9	AN OPERATIVE TECHNIQUE FOR THE CORRECTION OF VESICOURETERAL REFLUX	POLITANO, VA	1958	550	8.87
10	CRYPTORCHIDISM IN MICE MUTANT FOR INSL3	NEF, S	1999	548	26.10
11	STEROID 5-ALPHA-REDUCTASE-2 DEFICIENCY	WILSON, JD	1993	545	20.19
12	TARGETED DISRUPTION OF THE INSL3 GENE CAUSES BILATERAL CRYPTORCHIDISM	ZIMMERMANN, S	1999	516	24.57
13	THE GENE MUTATED IN AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE ENCODES A LARGE, RECEPTOR-LIKE PROTEIN	WARD, CJ	2002	508	28.22
14	2007 GUIDELINE FOR THE MANAGEMENT OF URETERAL CALCULI	PREMINGER, GM	2007	505	38.85
15	POLYCYSTIC KIDNEY DISEASE	HARRIS, PC	2009	493	44.82
16	MUTATION OF THE PAX2 GENE IN A FAMILY WITH OPTIC NERVE COLOBOMAS, RENAL ANOMALIES AND VESICOURETERAL REFLUX	SANYANUSIN, P	1995	493	19.72
17	MULLERIAN INHIBITING SUBSTANCE FUNCTION DURING MAMMALIAN SEXUAL DEVELOPMENT	BEHRINGER, RR	1994	485	18.65
18	THE CHROMOSOME CONSTITUTION OF A HUMAN PHENOTYPIC INTERSEX	HUNGERFORD, DA	1959	465	7.62
19	TUBULARIZED, INCISED PLATE URETHROPLASTY FOR DISTAL HYPOSPADIAS	SNODGRASS, W	1994	464	17.85
20	FAMILIAL INCOMPLETE MALE PSEUDOHERMAPHRODITISM, TYPE 2. DECREASED DIHYDROTESTOSTERONE FORMATION IN PSEUDOVAGINAL PERINEOSCROTAL HYPOSPADIAS	WALSH, PC	1974	462	10.04
21	THE MOLECULAR BASIS OF FOCAL CYST FORMATION IN HUMAN AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE TYPE I	QIAN, F	1996	453	18.88
22	IDENTIFICATION IN RATS OF A PROGRAMMING WINDOW FOR REPRODUCTIVE TRACT MASCULINIZATION, DISRUPTION OF WHICH LEADS TO HYPOSPADIAS AND CRYPTORCHIDISM	WELSH, M	2008	442	36.83
23	HYPOSPADIAS TRENDS IN TWO US SURVEILLANCE SYSTEMS	PAULOZZI, LJ	1997	409	17.78
24	PEDIATRIC VESICOURETERAL REFLUX GUIDELINES PANEL SUMMARY REPORT ON THE MANAGEMENT OF PRIMARY VESICOURETERAL REFLUX IN CHILDREN	ELDER, JS	1997	400	17.39
25	IMAGING STUDIES AFTER A FIRST FEBRILE URINARY TRACT INFECTION IN YOUNG CHILDREN	HOBERMAN, A	2003	395	23.24
26	WT1 MUTATIONS CONTRIBUTE TO ABNORMAL GENITAL SYSTEM DEVELOPMENT AND HEREDITARY WILMS TUMOR	PELLETIER, J	1991	394	13.59
27	EXPRESSION OF THE WILMS TUMOR GENE WT1 IN THE MURINE UROGENITAL SYSTEM	PELLETIER, J	1991	389	13.41
28	EXPRESSION OF THE MOUSE ANTI MULLERIAN HORMONE GENE SUGGESTS A ROLE IN BOTH MALE AND FEMALE SEXUAL DIFFERENTIATION	MUNSTERBERG, A	1991	383	13.21
29	CLINICAL SIGNIFICANCE OF PRIMARY VESICOURETERAL REFLUX AND URINARY ANTIBIOTIC PROPHYLAXIS AFTER ACUTE PYELONEPHRITIS: A MULTICENTER, RANDOMIZED, CONTROLLED STUDY	GARIN, EH	2006	371	26.50
30	INTERNATIONAL TRENDS IN RATES OF HYPOSPADIAS AND CRYPTORCHIDISM	PAULOZZI, LJ	1999	364	17.33
31	DIFFERENCE IN PREVALENCE OF CONGENITAL CRYPTORCHIDISM IN INFANTS BETWEEN TWO NORDIC COUNTRIES	BOISEN, KA	2004	353	22.06
32	PREVALENCE OF URINARY TRACT INFECTION IN CHILDHOOD: A META-ANALYSIS	SHAIKH, N	2008	343	28.58
33	AGE OF OCCURRENCE OF GONADAL TUMORS IN INTERSEX PATIENTS WITH A Y CHROMOSOME	MANUEL, M	1976	339	7.70
34	DELETION OF THE TSC2 AND PKD1 GENES ASSOCIATED WITH SEVERE INFANTILE POLYCYSTIC KIDNEY DISEASE: A CONTIGUOUS GENE SYNDROME	BROOKCARTER, PT	1994	329	12.65
35	INSL3/LEYDIG INSULIN-LIKE PEPTIDE ACTIVATES THE LGR8 RECEPTOR IMPORTANT IN TESTIS DESCENT	KUMAGAI, J	2002	321	17.83
36	SUMMARY OF THE AUA GUIDELINE ON MANAGEMENT OF PRIMARY VESICOURETERAL REFLUX IN CHILDREN	PETERS, CA	2010	303	30.30
37	MALIGNANCIES IN BLADDER AUGMENTATIONS AND INTESTINAL CONDUITS	FILMER, RB	1990	303	10.10
38	LAPAROSCOPIC PYELOPLASTY: THE FIRST 100 CASES	JARRETT, TW	2002	301	16.72
39	THE RELATIONSHIP AMONG DYSFUNCTIONAL ELIMINATION SYNDROMES, PRIMARY VESICOURETERAL REFLUX AND URINARY TRACT INFECTIONS IN CHILDREN	KOFF, SA	1998	299	13.59
40	PREVALENCE AND NATURAL HISTORY OF CRYPTORCHIDISM	BERKOWITZ, GS	1993	296	10.96
41	CIRCUMCISION POLICY STATEMENT	LANNON, CM	1999	295	14.05
42	THE SOCIETY FOR FETAL UROLOGY CONSENSUS STATEMENT ON THE EVALUATION AND MANAGEMENT OF ANTENATAL HYDRONEPHROSIS	NGUYEN, HT	2010	292	29.20
43	THE STANDARDIZATION OF TERMINOLOGY OF LOWER URINARY TRACT FUNCTION IN CHILDREN AND ADOLESCENTS: UPDATE REPORT FROM THE STANDARDIZATION COMMITTEE OF THE INTERNATIONAL CHILDREN’S CONTINENCE SOCIETY	AUSTIN, PF	2014	287	47.83
44	ASSOCIATION OF DIETHYLSTILBESTROL EXPOSURE IN UTERO WITH CRYPTORCHIDISM, TESTICULAR HYPOPLASIA AND SEMEN ABNORMALITIES	GILL, WB	1979	284	6.93
45	EPIDEMIOLOGY OF WILMS TUMOR	BRESLOW, N	1993	279	10.33
46	ANATOMICAL AND FUNCTIONAL ASPECTS OF TESTICULAR DESCENT AND CRYPTORCHIDISM	HUTSON, JM	1997	276	12.00
47	LEYDIG CELL TUMORS OF THE TESTIS - A CLINICOPATHOLOGICAL ANALYSIS OF 40 CASES AND REVIEW OF THE LITERATURE	KIM, I	1985	276	7.89
48	ANTENATAL HYDRONEPHROSIS AS A PREDICTOR OF POSTNATAL OUTCOME: A META-ANALYSIS	LEE, RS	2006	272	19.43
49	A CRITICAL DEVELOPMENTAL SWITCH DEFINES THE KINETICS OF KIDNEY CYST FORMATION AFTER LOSS OF PKD1	PIONTEK, K	2007	271	20.85
50	GENETIC ANALYSIS OF THE MULLERIAN INHIBITING SUBSTANCE SIGNAL TRANSDUCTION PATHWAY IN MAMMALIAN SEXUAL DIFFERENTIATION	MISHINA, Y	1996	269	11.21
51	SINGLE EXPOSURE TO HEAT INDUCES STAGE SPECIFIC GERM CELL APOPTOSIS IN RATS: ROLE OF INTRATESTICULAR TESTOSTERONE ON STAGE SPECIFICITY	LUE, YH	1999	267	12.71
52	MEDICAL VERSUS SURGICAL TREATMENT OF PRIMARY VESICOURETERAL REFLUX	LEVITT, SB	1981	267	6.85
53	HORMONES AND TESTIS DEVELOPMENT AND THE POSSIBLE ADVERSE EFFECTS OF ENVIRONMENTAL CHEMICALS	SHARPE, RM	2001	265	13.95
54	URINARY INCONTINENCE AND URINARY TRACT INFECTION AND THEIR RESOLUTION WITH TREATMENT OF CHRONIC CONSTIPATION OF CHILDHOOD	LOENINGBAUCKE, V	1997	263	11.43
55	GERM CELL TUMORS IN THE INTERSEX GONAD: OLD PATHS, NEW DIRECTIONS, MOVING FRONTIERS	COOLS, M	2006	263	18.79
56	EXPRESSION CLONING AND REGULATION OF STEROID 5 ALPHA-REDUCTASE, AN ENZYME ESSENTIAL FOR MALE SEXUAL DIFFERENTIATION	ANDERSSON, S	1989	259	18.50
57	ROLE OF THE ANGIOTENSIN TYPE 2 RECEPTOR GENE IN CONGENITAL ANOMALIES OF THE KIDNEY AND URINARY TRACT, CAKUT, OF MICE AND MEN	NISHIMURA, H	1999	253	12.05
58	AGE AT SURGERY FOR UNDESCENDED TESTIS AND RISK OF TESTICULAR CANCER	PETTERSSON, A	2007	253	19.46
59	TREATMENT OF VESICOURETERIC REFLUX BY ENDOSCOPIC INJECTION OF TEFLON	ODONNELL, B	1984	251	6.97
60	RELATIONSHIP OF INFANTILE VESICOURETERIC REFLUX TO RENAL DAMAGE	ROLLESTON, GL	1970	246	4.92
61	RESULTS OF 212 CONSECUTIVE ENDOPYELOTOMIES - AN 8-YEAR FOLLOW-UP	MOTOLA, JA	1993	246	9.11
62	PHENOTYPIC FEATURES, ANDROGEN RECEPTOR BINDING, AND MUTATIONAL ANALYSIS IN 278 CLINICAL CASES REPORTED AS ANDROGEN INSENSITIVITY SYNDROME	AHMED, SF	2000	246	12.30
63	FETAL SURGERY FOR CONGENITAL HYDRONEPHROSIS	HARRISON, MR	1982	244	6.42
64	ENDOSCOPIC TREATMENT OF VESICOURETERAL REFLUX WITH A CHONDROCYTE-ALGINATE SUSPENSION	ATALA, A	1994	237	9.12
65	ANTIMICROBIAL PROPHYLAXIS FOR CHILDREN WITH VESICOURETERAL REFLUX	HOBERMAN, A	2014	235	39.17
66	SINGLE PORT ACCESS NEPHRECTOMY AND OTHER LAPAROSCOPIC UROLOGIC PROCEDURES USING A NOVEL LAPAROSCOPIC PORT (R-PORT)	RANE, A	2008	235	19.58
67	DISAPPEARANCE OF VESICOURETERIC REFLUX DURING LONGTERM PROPHYLAXIS OF URINARY TRACT INFECTION IN CHILDREN	EDWARDS, D	1977	233	5.42
68	ANTIBIOTIC PROPHYLAXIS AND RECURRENT URINARY TRACT INFECTION IN CHILDREN	CRAIG, JC	2009	233	21.18
69	RECURRENT URINARY TRACT INFECTIONS IN CHILDREN - RISK FACTORS AND ASSOCIATION WITH PROPHYLACTIC ANTIMICROBIALS	CONWAY, PH	2007	233	17.92
70	IS ANTIBIOTIC PROPHYLAXIS IN CHILDREN WITH VESICOURETERAL REFLUX EFFECTIVE IN PREVENTING PYELONEPHRITIS AND RENAL SCARS? A RANDOMIZED, CONTROLLED TRIAL	PENNESI, M	2008	232	19.33
71	DIAGNOSIS OF BILATERAL ABDOMINAL CRYPTORCHIDISM BY LAPAROSCOPY	CORTESI, N	1976	232	5.27
72	LONG-TERM OUTCOME OF BOYS WITH POSTERIOR URETHRAL VALVES	PARKHOUSE, HF	1988	231	7.22
73	TRANSVERSE PREPUTIAL ISLAND FLAP TECHNIQUE FOR REPAIR OF SEVERE HYPOSPADIAS	DUCKETT, JW	1980	230	5.75
74	PERCUTANEOUS NEPHROLITHOTOMY IN INFANTS AND PRESCHOOL AGE CHILDREN: EXPERIENCE WITH A NEW TECHNIQUE	JACKMAN, SV	1998	229	10.41
75	AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE: THE CLINICAL EXPERIENCE IN NORTH AMERICA	GUAY-WOODFORD, LM	2003	227	13.35
76	MOLECULAR-BASIS OF MAMMALIAN SEXUAL DETERMINATION ACTIVATION OF MULLERIAN INHIBITING SUBSTANCE GENE EXPRESSION BY SRY	HAQQ, CM	1994	222	8.54
77	HEAT STRESS CAUSES TESTICULAR GERM CELL APOPTOSIS IN ADULT MICE	YIN, YZ	1997	222	9.65
78	UROLITHIASIS IN PEDIATRIC PATIENTS: A SINGLE CENTER STUDY OF INCIDENCE, CLINICAL PRESENTATION AND OUTCOME	VANDERVOORT, K	2007	222	17.08
79	THE MODIFIED STING PROCEDURE TO CORRECT VESICOURETERAL REFLUX: IMPROVED RESULTS WITH SUBMUCOSAL IMPLANTATION WITHIN THE INTRAMURAL URETER	KIRSCH, AJ	2004	220	13.75
80	PEDIATRIC ROBOT ASSISTED LAPAROSCOPIC DISMEMBERED PYELOPLASTY: COMPARISON WITH A COHORT OF OPEN SURGERY	LEE, RS	2006	219	15.64
81	NUTCRACKER PHENOMENON AND NUTCRACKER SYNDROME	KURKLINSKY, AK	2010	219	21.90
82	LOWERING OF PKD1 EXPRESSION IS SUFFICIENT TO CAUSE POLYCYSTIC KIDNEY DISEASE	LANTINGA-VAN LEEUWEN, IS	2004	218	13.63
83	LONG-TERM FOLLOWUP OF CHILDREN TREATED WITH DEXTRANOMER/HYALURONIC ACID COPOLYMER FOR VESICOURETERAL REFLUX	LACKGREN, G	2001	216	11.37
84	WILMS TUMOR AND THE WT1 GENE	LEE, SB	2001	215	11.32
85	GLOBAL DISORDERS OF SEX DEVELOPMENT UPDATE SINCE 2006: PERCEPTIONS, APPROACH AND CARE	LEE, PA	2016	215	53.75
86	THE DYSFUNCTIONAL VOIDING SCORING SYSTEM: QUANTITATIVE STANDARDIZATION OF DYSFUNCTIONAL VOIDING SYMPTOMS IN CHILDREN	FARHAT, W	2000	214	10.70
87	UROLITHIASIS IN PEDIATRIC PATIENTS	MILLINER, DS	1993	213	7.89
88	RENAL SCARRING AFTER ACUTE PYELONEPHRITIS	JAKOBSSON, B	1994	212	8.15
89	HYPOSPADIAS: ANATOMY, ETIOLOGY, AND TECHNIQUE	BASKIN, LS	2006	210	15.00
90	COMPLETE ANDROGEN INSENSITIVITY SYNDROME: LONG-TERM MEDICAL, SURGICAL, AND PSYCHOSEXUAL OUTCOME	WISNIEWSKI, AB	2000	209	10.45
91	RISK OF RENAL SCARRING IN CHILDREN WITH A FIRST URINARY TRACT INFECTION: A SYSTEMATIC REVIEW	SHAIKH, N	2010	207	20.70
92	A MATERNAL VEGETARIAN DIET IN PREGNANCY IS ASSOCIATED WITH HYPOSPADIAS	NORTH, K	2000	207	10.35
93	ANTIBIOTIC PROPHYLAXIS FOR THE PREVENTION OF RECURRENT URINARY TRACT INFECTION IN CHILDREN WITH LOW GRADE VESICOURETERAL REFLUX: RESULTS FROM A PROSPECTIVE RANDOMIZED STUDY	ROUSSEY-KESLER, G	2008	206	17.17
94	GASTROCYSTOPLASTY - AN ALTERNATIVE SOLUTION TO THE PROBLEM OF UROLOGICAL RECONSTRUCTION IN THE SEVERELY COMPROMISED PATIENT	ADAMS, MC	1988	206	6.65
95	THE LONG-TERM FOLLOWUP OF NEWBORNS WITH SEVERE UNILATERAL HYDRONEPHROSIS INITIALLY TREATED NONOPERATIVELY	ULMAN, I	2000	203	10.15
96	ENDOSCOPIC THERAPY FOR VESICOURETERAL REFLUX: A META-ANALYSIS. I. REFLUX RESOLUTION AND URINARY TRACT INFECTION	ELDER, JS	2006	203	14.50
97	MAGPI (MEATOPLASTY AND GRANULOPLASTY): A PROCEDURE FOR SUBCORONAL HYPOSPADIAS	DUCKETT, JW	1981	202	5.18
98	HYPOSPADIAS AND ENDOCRINE DISRUPTION: IS THERE A CONNECTION?	BASKIN, LS	2001	202	10.63
99	TESTICULAR HEATING AND ITS POSSIBLE CONTRIBUTIONS TO MALE-INFERTILITY - A REVIEW	MIEUSSET, R	1995	202	8.08
100	NORDIC CONSENSUS ON TREATMENT OF UNDESCENDED TESTES	RITZEN, EM	2007	201	15.46

Table 2.

Institution and country of origin of the 100 most frequently cited pediatric urology publications.

Country or Institution	Publications
USA	68	(68.0%)
England	10	(10.0%)
Sweden	7	(7.0%)
Denmark	5	(5.0%)
Australia	4	(4.0%)
Canada	4	(4.0%)
Germany	4	(4.0%)
Netherlands	4	(4.0%)
France	3	(3.0%)
Boston Children’s Hospital	10
Johns Hopkins University	7
Massachusetts General Hospital	5
Mayo Clinic	5
University of Pittsburgh	5
University of Texas South Western	5
Karolinska Insitute, Sweden	4
University of Philadelpha (including Children’s Hospital of Philadelphia [n=3])	4
Children’s Healthcare of Atlanta	3

The most cited paper was “Testicular dysgenesis syndrome: an increasingly common developmental disorder with environmental aspects” by Skakkebaek NE et al. from 2001 with 1461 citations. Using the adjusted index which accounts for publication date as well as the number of citations, the article with the highest index (index = 87.9) was “Urinary Tract Infection: Clinical Practice Guideline for the Diagnosis and Management of the Initial UTI in Febrile Infants and Children 2 to 24 Months” by Roberts KB et al from 2011. Among the top 100 most cited articles, there were four randomized clinical trials (See Table 1, article rank 29, 65, 68, and 70). There was also a single prospective non-randomized study (“Imaging Studies after a First Febrile Urinary Tract Infection in Young Children” by A Hoberman et al in 2003).

Clinical manuscripts were the most common among the top 100 cited articles (n=64). The most common subcategories among the top 100 cited articles were genital conditions (excluding hypospadias) (n=19; 16.5%; total citations=6591), vesicoureteral reflux (n=18; 15.7%; total citations =5465), and DSD/intersex (n=18; 15.7%; total citations = 5148). The distribution of categories and subcategories is seen in Figure 1. Among publications in the top 100 published prior to and including 1987, there were 13 (81%) articles categorized as clinical studies, 6 (38% of total articles in this time period) of which described or evaluating surgical procedures and 2 (13%) articles categorized as basic science. After 1987 there were 51 (61%) articles categorized as clinical, 11 (13%) of which were surgical papers, and 21 (25%) articles categorized as basic science. There was one clinical guideline published prior to 1987 (“International system of radiographic grading of vesicoureteric reflux” by Lebowitz RL et al. in 1985), and 12 guidelines published after 1987.

Figure 1.

Distribution of categories and subcategories of all top 100 cited articles in pediatric urology from 1900 – 2020. Total number of citations is summarized in the label along each bar. Genital conditions exclude hypospadias. Note: Total numbers sum to more than the number of publications since articles can be categorized in more than one category and subcategory.

Abbreviations: VUR – vesicoureteral reflux, UTI – urinary tract infection, DSD – disorders of sexual differentiation, NGB – neurogenic bladder, VD – voiding dysfunction, LUTS -lower urinary tract symptoms, GU – genitourinary, OU – obstructive uropathy, Hydro - hydronephrosis, Cystic Kidney – cystic kidney disease.

To determine the relatedness among the articles based on the number of times they cite each other we used VOSviewer. We identified 11 distinct clusters of related articles containing 3 or more publications (Figure 2). Not all the publications had identifiable links (n=23 publications were not assigned to a cluster; i.e., they did not cite and were not cited by another article within the top 100 cited articles). We identified common themes and topics within each cluster. The largest cluster contained 15 articles on imaging and antibiotic prophylaxis for urinary tract infections and vesicoureteric reflux. The next largest cluster contained 13 articles that discussed the epidemiology, mechanisms, and management of hypospadias. The topics of the clusters generated by the VOSviewer (Figure 2) were different yet related to most of the a priori defined topics devised for categorization.

Figure 2.

Network map of clustering among the top 100 most cited pediatric urology publications. Clustering and linkages are based on the number of times articles cite each other.

In evaluating if there was a correlation between year of publication and citations, the Pearson correlation coefficient was −0.0535 (p=0.60). Although technically a negative correlation, the relationship between publication date and number of citations was weak and non-significant (R²=0.0029). Thus, there does not appear to be any relationship between publication date and number of citations received by a specific publication. There also appeared to be a non-significant positive correlation between number of citations of a publication and the 2019 impact factor of the journal it was published in (r=0.0096; p=0.92). To evaluate the impact of publications while adjusting for their publication date, we used a previously published index¹⁵where higher values of the adjusted index correspond to a higher impact,shown in Table 1. A bubble plot of adjusted index by publication year is shown in Figure 3, with each bubble representing one publication and bubble sizes corresponding to the number of citations for that specific publication. For example, the purple bubble in the right upper quadrant with the highest index (index = 87.9) represents “Urinary Tract Infection: Clinical Practice Guideline for the Diagnosis and Management of the Initial UTI in Febrile Infants and Children 2 to 24 Months” by Roberts KB et al from 2011. The largest sized light blue bubble near the top right of the graph represents “Testicular dysgenesis syndrome: an increasingly common developmental disorder with environmental aspects” by Skakkebaek NE et al. from 2001 with 1461 citations (index = 78.89). It has a high adjusted index, although not the highest, despite having the highest number of citations. The adjusted index demonstrated a positive significant correlation with publication date (r= 0.672; p<0.00001; R²=0.28), stronger than that seen for number of citations versus year publication. Overall, we could not observe a clear pattern of adjusted index among the different subcategories.

Figure 3.

The distribution of time adjusted impact index by the publication year for the top 100 cited publications in pediatric urology 1900–2020.

Discussion

In this bibliometric review of the most cited pediatric urology articles from 1900 to 2020, we identified the top 100 articles were published between 1958 and 2016 in 26 countries, across 181 institutions, and in 46 journals. Clinical manuscripts were the most common category and articles covering genital conditions (excluding hypospadias) were the most common subcategory of articles among the top 100 cited articles. These articles naturally cluster around important topics when their relatedness was measured. The number of citations was not significantly correlated with publication date. The use of an adjusted index which accounts for publication date may facilitate the ability to evaluate a paper’s impact. Among this list, the article types over time have shifted from those describing and comparing operative techniques to those exploring mechanisms of disease.

Several previous studies have reported bibliometric analysis of top cited papers in various areas of urology. To our knowledge, this is the first paper to perform this analysis for the top cited publications in pediatric urology, with stratification by publication type (clinical, guideline, or basic science) and subcategory. Attempts at identifying the most impactful manuscripts in the field are fraught with subjectivity. Bibliometric citation analysis is one possible approach to quantifying a paper’s impact. This approach allows us to build a useful reference for pediatric urologists and trainees to understand the evolution of knowledge within the field. Since “pediatric urology” is not a recognized search term, we searched for each “disease” or “category” of disease within pediatric urology. Our selection of different pediatric urology diseases/categories is supported by bibliometric clustering techniques that showed clustering among the top cited articles corresponding to topics which were similar to the a priori subcategories we devised.

Pediatric urology is a relatively small subspecialty, and many of the topics of interest within the subspecialty are of limited interest to the wider urological and medical community. It is no surprise then that 57% of the articles within the top 100 most cited articles in this study cover four main topics which are commonly encountered by pediatricians and general practitioners (genital conditions excluding hypospadias, vesicoureteral reflux, obstructive uropathy and hydronephrosis, and urinary tract infections). The low prevalence of pediatric urologic diseases relative to all diseases in urology (i.e., all adult and pediatric conditions, both benign and malignant) helps explain why pediatric urology manuscripts are not highly cited. In the most recent analysis of the top 100 most cited articles in urology⁷, none of the articles covered pediatric urology. Among the top 25 most cited urology guidelines, only 8% represented pediatric urology⁷.

Compared to other urological subspecialties, we observed a relatively low number of citations per article in this analysis. A contemporary analysis of urological papers identified the median number of citations in the top 100 cited clinical papers from 1788–2020 was 1,463 (IQR 1186–1821)⁷ compared to 339 (range 1461–201) in this study. This is likely explained by a smaller audience for pediatric urology as described above, the relatively low prevalence of pediatric urologic diseases, and a lack of prospective trials, which tend to be highly citable, as seen in other subspecialties such as urologic oncology. In this study we found only five prospective clinical trials. This contrasts with other subspecialties in urology. Gabrielson et al. identified that the top 100 cited contemporary clinical papers were also predominantly (81%) within the field of urologic oncology, many of which were prospective trials⁷. In a bibliometric analysis of the top 100 cited manuscripts in bladder cancer, 29% were interventional clinical studies¹³.

The evolution of studies we observe in this analysis is like that seen in other bibliometric analysis in pediatric urology. We observed a higher proportion of papers which covered surgical techniques published prior to and including 1987 (midpoint of the study period), as compared to after 1987. Likewise, there was a lower proportion of papers covering basic science topics prior to 1987 compared to after. Similar trends have been observed by other authors evaluating citations in pediatric urology. O’Kelly et al identified that within the hypospadias literature, 60% of the manuscripts in the 1940–50s focused on operative techniques, which dropped to 20% by 1970, and 6% by 2000. They also noted an inverse trend in the prevalence of studies about the molecular biology, psychology and environmental factors associated with hypospadias¹⁴.

Some of the limitations of this study are common among all bibliometric analyses. Citation number is used in this study as a surrogate for impact, although there are many variables that affect citation rates, including self-citations²², omission bias²³, and incomplete citing. We attempt to address the time factor, whereby older studies have been available to cite longer, using an adjusted index to measure impact. We also identify that there is no correlation among the top 100 articles between citation number and year of publication. Fernandes et al. used an adjusted index to account that articles published earlier may have more citations because of the duration of availability¹⁵. Countering this effect may be the “obliteration by incorporation” effect as described by Garfield et al., where older publications see fewer citations as their findings become incorporated into the accepted knowledge²¹. These represent competing effects which affect citations over time. There are also limitations in this analysis based on the comprehensiveness of the WOS core collection. Although this database covers all the common journals where we originally expected to find pediatric urology articles, seminal works were omitted if they were published in lower impact journals. For example, the article describing the Fowler-Stephens orchiopexy²⁴ was omitted from this list despite having more than 245 citations, since it was published in the Australian and New Zealand journal of surgery, which is not included in WOS core collection. This same issue occurs with highly cited non-English language articles which appear in journals outside of WOS core collection, such as the French article describing the Mitrofanoff principle published in Chirurgie Pediatrique in 1980 with 571 citations²⁵. This shortcoming could be resolved by repeating our analysis using all the databases available within the WOS, or other citation databases. Another weakness of this study is the omission of papers that would be considered seminal in the field but do not include pediatric patients, such as Lapides seminal work on clean intermittent catheterization²⁶. To address this, previous studies have combined traditional bibliometric citation analysis with expert opinion²⁷, which was outside the scope of this study and could introduce selection bias, caused by choosing a non-random sample of data for further analysis. Despite employing a broad search strategy in this study, it appears that there is not a one-size-fits-all strategy that captures all the impactful works in the field.

Using objective bibliometric citation analysis, we identify the 100 most cited articles in pediatric urology presented in this study. This list can provide pediatric urologists and trainees with a valuable resource to understand the body of knowledge and trajectory of this field and it can facilitate future research and education efforts.

Abbreviations:

IQR

interquartile range

WOS

Web of Science

VUR

vesicoureteral reflux

UTI

urinary tract infection

DSD

disorders of sexual differentiation

NGB

neurogenic bladder

VD

voiding dysfunction

GU

genitourinary

OU

obstructive uropathy

Hydro

hydronephrosis