scientific studies play an important role among them ( 1 ) . during the past two decades , iran has enjoyed considerable expansion of trained individuals in the fields of medicine ( 2 ) for being a developed and industrial country . therefore , the policy of iranian governors changed in the recent years to provide a good condition for scientists and training researchers and increase science production . iran has been successful in its agenda to improve its international profile in biomedical sciences by constantly increasing the quantity and quality of articles published in peer - reviewed biomedical journals indexed in pubmed . however , to date , little is known about contributions of iranian medical researchers and their quality in the field of nephrology and urology . by examining various aspects of such investigations regarding quality and quantity of articles in the field of nephrology and urology , we would be able to reflect iran 's scientific progress and impact on world science production . this is one of the earliest studies assessing iran research productivity in the field of urology and nephrology . moreover , a precise and extensive view of the overall research productivity at regional and international level is presented here . the aim of this study was to evaluate the quality and quantity of iranian papers in the field of nephrology and urology indexed in pubmed in the past two decades . this can help scientists and governors to compare this study with other counties and better future planning in nephrology and urology field . we conducted a retrospective study to determine quality and quantity of nephrology and urology research output in the past two decade by iranian scientists . two faculty members of baqiyatallah university of medical sciences ( one nephrologist and one urologist ) helped us to find all relevant keywords in the field of nephrology and urology . we did an online search in abstract / title part of articles with 129 obtained keywords such as kidney , renal , hemodialysis , transplant , nephrology , glomerulonephritis , ureteral , nephrolithiasis , and etc . endnote software version 7 ( bld 7072 ) was used searching pubmed database from november 1993 to november 2013 . all articles in which iran was the affiliation of at least one of the authors were selected . after deleting duplicate records , two investigators evaluated title and abstracts of searched articles and excluded papers unrelated to nephrology and urology . in case of disagreement between investigators regarding excluding or including an article , final decision was made by the professor of nephrology ( b e ) . we gathered a total of 4064 relative articles as an offline database for further evaluation . the final offline database of iranian articles in the field of nephrology and urology was analyzed as follows : 1 ) name of originated institution according to the first author address , 2 ) field of study , categorized as transplantation , hemodialysis , peritoneal dialysis , nephrology , urology , and other issues , 3 ) total number of publications , 4 ) type of study ( retrospective , prospective , clinical trial , case report and etc . ) , 5 ) collaboration rate of iranian nephrologists and urologists for every year and the whole studied period , 6 ) annual publication of iranian articles in five journals with highest impact factor ( if ) regarding nephrology and urology , 6 ) name of journals publishing most iranian papers , 7 ) articles published in journals with if  1 , between 1 and 3 and more than 3 in each five years , and 8) the average of iranian articles if in each five years . all data were analyzed using spss analytical software version 19.0 ( pasw , spss inc . we used one - way anova to compare categorized if obtained in each year in case of normality ; otherwise , kruskal - wallis - h test was used . we conducted a retrospective study to determine quality and quantity of nephrology and urology research output in the past two decade by iranian scientists . two faculty members of baqiyatallah university of medical sciences ( one nephrologist and one urologist ) helped us to find all relevant keywords in the field of nephrology and urology . we did an online search in abstract / title part of articles with 129 obtained keywords such as kidney , renal , hemodialysis , transplant , nephrology , glomerulonephritis , ureteral , nephrolithiasis , and etc . endnote software version 7 ( bld 7072 ) was used searching pubmed database from november 1993 to november 2013 . all articles in which iran was the affiliation of at least one of the authors were selected . after deleting duplicate records , two investigators evaluated title and abstracts of searched articles and excluded papers unrelated to nephrology and urology . in case of disagreement between investigators regarding excluding or including an article , final decision was made by the professor of nephrology ( b e ) . we gathered a total of 4064 relative articles as an offline database for further evaluation . the final offline database of iranian articles in the field of nephrology and urology was analyzed as follows : 1 ) name of originated institution according to the first author address , 2 ) field of study , categorized as transplantation , hemodialysis , peritoneal dialysis , nephrology , urology , and other issues , 3 ) total number of publications , 4 ) type of study ( retrospective , prospective , clinical trial , case report and etc . ) , 5 ) collaboration rate of iranian nephrologists and urologists for every year and the whole studied period , 6 ) annual publication of iranian articles in five journals with highest impact factor ( if ) regarding nephrology and urology , 6 ) name of journals publishing most iranian papers , 7 ) articles published in journals with if  1 , between 1 and 3 and more than 3 in each five years , and 8) the average of iranian articles if in each five years . all data were analyzed using spss analytical software version 19.0 ( pasw , spss inc . we used one - way anova to compare categorized if obtained in each year in case of normality ; otherwise , kruskal - wallis - h test was used . our entire search results with 129 keywords were 27,503 articles . deleting duplicate records yielded 8,602 papers . slightly more than 80% of papers published within seven recent years ( 2007 - 2013 ) . figure 1 shows the increase in the annual number of iranian articles in the field of nephrology and urology in the past two decades . the first five journals that published iranian papers in the field of nephrology and urology were as follows : urology journal ( 9.7% ) , iranian journal of kidney disease ( 8.4% ) , saudi journal of kidney disease and transplantation ( 6.5% ) , journal of endourology ( 1.9% ) and experimental and clinical transplantation ( 1.7% ) . an overall of 1070 ( 28.3% ) iranian articles were published in the mentioned five journals . there was a significant difference between the mean if of journals published in iranian papers in different years ( p = 0.03 ) . we also categorized if of journals to less than one , between one and three and more than three and then evaluated them in five years ( 1994 , 1998 , 2003 , 2008 and 2013 ) . abbreviation : if : impact factor . transplantation ( 44.6% ) , nephrology ( 20.9% ) , hemodialysis ( 16.4% ) , and infertility ( 11.8% ) were the most prevalent topics of papers . however , chronic ambulatory peritoneal dialysis ( 1.7% ) and other topics ( 4.6% ) contributed to a small proportion of publications . figure 2 demonstrates the institutional affiliation of corresponding authors who published more than ten papers in the past two decades in nephrology and urology . most iranian nephrology and urology papers were from the capital city , tehran ( 50.03% ) , particularly from tehran university of medical sciences ( ums ; 18% ) , shahid beheshti ums ( 13.3% ) , baqiyatallah ums ( 6.3% ) , iran ums ( 3.1% ) , royan institute for reproductive biomedicine ( 1.8% ) , tarbiat modares university ( 1.4% ) , avicenna research institute ( 0.83 ) , pasteur institute ( 0.4% ) , and other institutes in tehran ( 4.9% ) . of all papers evaluated in this study , 26.1% were fundamental ( basic science ) and 53.7% were retrospective articles . iranian publications in the field of nephrology and urology have been increased during the past two decades . as shown in figure 1 , the number of iranian indexed publications in pubmed had a considerable increase since 2006 ; publications number increased from less than 200 publications in 2006 to more than 300 publications in 2007 . since that year , iranian researchers have had a significant growth in science production . in our study , the total number of publications was 3,771 between 1993 and 2013 ( average of 188 papers per year ) . a recent paper ( 3 ) showed the total number of urology and nephrology publications in arab countries ( 21 countries ) for 40 years from 1972 - 2011 as 224,479 in web of science database ( average of 267 papers per year for each country ) . however , these results are not comparable due to their differences in years and database . during 2000 - 2009 , according to the findings of the present study , the number of articles written by iranians was 1,777 , while at the same time ( in a decade ) , the number of articles in china and saudi arabia were 3,100 and 462 , respectively ( 3 , 4 ) . some studies proposed that lack of funding may be the cause of low scientific research output in the arab world ( 5 , 6 ) . it is also , possible that the overall growth of published articles of iranians or some other scientific societies is partly due to increased number of foreign international conferences , which can significantly affect the rate of publication in internationally published journals . furthermore , nourbala and his coworkers ( 7 ) showed that iran had the maximum number of publications in the field of transplantation after turkey among muslim counties in a period of eight years ( 2000 - 2007 ) . we also showed that transplantation was the most prevalent topic in nephrology and urology papers ( 44.6% , 1682 papers ) . some reasons for the rising trend observed in the quantity might be firstly the huge population , secondly funding in the field of nephron - urology , thirdly increased number of researchers and subspecialists in this field and finally publishing articles in domestic journals and fourthly , government overall policies to promote research in iran . nevertheless , the number of publications derived from medline - indexed journals can not be a good representative of all iranian scientific nephrology and urology population and this amount merely reflects the overall estimation . we showed that the mean journals impact factor ( if ) within five years decreased slightly . figure 3 shows a steep decline from 1994 to 2008 in the mean if for journals in which iranian articles were published . the jumps observed within five years might be due to increasing number of iranian international journals indexed in isi and increase in their impact factor during these years . it is hoped that this upward trend would be continued . despite the high level of mean impact factor in the past years however , the mean of impact factor is reduced , the amount of articles published in high impact factor journals are significantly increased . due to the wide variety of nephrology and urology , certainly a lot of complex issues in these areas are unknown and remain unknown and require further investigation . we found that the subject of kidney transplantation has received the most attention in the recent years and most papers topics in our study were about transplantation ( 44.6% ) . the number of transplant centers and transplanted patients increased during the past two decades in iran ( 8) . iran has been the most active country in the field of transplantation in the middle east . the annual rate of kidney transplantation in iran ranks the highest among the middle eastern countries ( 9 ) . regarding the type of articles published in journals , our results were relatively similar to previous studies to a large extent . most of these studies were retrospective articles , while a few contributed to clinical trial studies . zhou et al . ( 4 ) reported that based upon a ten year - analysis in china , the most published articles in the field of nephrology and urology were case reports , randomized control trials and clinical trial articles , respectively . the researcher analyzes patients records and therefore , has lower scientific value than prospective studies . most sources of error due to confounding factors and bias are more prevalent in retrospective studies than prospective ones ( 10 ) , so , more attention should be paid in these cases . it can add to our knowledge about the etiology , pathogenesis , natural history and treatment of rare diseases , and is so useful for training junior investigators ( 11 ) . given less time requirement to write and present this paper and easier publishing process than other types of articles in journals , many researchers are willing to publish case reports ( 12 ) . however , performing a randomized controlled trial or analytical epidemiological studies requires long time , manpower and high cost ( 13 ) . the results of this study showed that tehran university of medical sciences has the greatest amount of participation , cooperation and contribution in nephrology and urology published - articles among iranian universities and scientific institutes . a study conducted by einollahi et al . in 2007 showed that most iranian biomedical papers ( according to the first author in the field of nephrology ) were from tehran city ( 55.2% ) , particularly from some academic centers such as iran university ( 15.0% ) , shahid beheshti university ( 13.0% ) , tehran university ( 11.2% ) and baqiyatallah university ( 10.2% ) . in the present study , we examined publications of urologists and nephrologists together . therefore , tehran university with 18% had the highest number of articles and also the highest growth among the universities from 2007 up to now . iranian universities are very competitive to publish research articles and more important promote medical sciences . some , if not the only , reasons for research activities and positive movement made in iranian research community might be increasing encouragement system for researchers , well - development of research culture , fellowship training in nephrology and urology and also setting up a research phd degree in universities however , some articles are not included in this database and accordingly were not analyzed in our study . in pubmed , only the address of the first author is presented , so it may limit the researcher to understand other centers and affiliations involved in the project . in conclusion , iranian publications in the field of nephrology and urology have had a considerable and significant increase in the recent years in middle eastern countries , but there is a wide distance to be a science exporter country in the world .