Urolithiasis DOI 10.1007/s00240-014-0643-6
Original Paper
The epidemiology of reno‑ureteral stone disease in Koreans: a nationwide population‑based study Sang Rak Bae · Jong‑Mi Seong · Log Young Kim · Sung Hyun Paick · Hyeong Gon Kim · Yong Soo Lho · Hyoung Keun Park
Received: 13 September 2013 / Accepted: 27 January 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract The objective of this study was to evaluate the annual incidence of upper tract urolithiasis based on a large population-based study in Korea. This study used a subset of the 2009 Health Insurance and Review and Assessment service-National Patient Sample (HIRA-NPS). The 2009 HIRA-NPS contains data for 1,115,721 patients (711,285 inpatients and 404,436 outpatients) from January 2009 to December 2009. Based on these data, we selected patients who had been diagnosed with urolithiasis using the ICD code and calculated the incidence of urolithiasis. The total number of estimated urolithiasis patients was 219,328. The annual incidence of upper tract urolithiasis was estimated to be 457.02 per 100,000 in the overall population, with 589.09 per 100,000 men and 326.64 per 100,000 women. The male-to-female ratio was about 1.8:1. The annual incidence of urolithiasis in Korea was 457 per 100,000. It is higher than that previously reported in Japan, but lower than that in Western countries. Keywords Epidemiology · Incidence · Urolithiasis · Population-based study
S. R. Bae Department of Urology, Konkuk University Medical Center, Seoul, Korea J.-M. Seong Office of Drug Safety Information II, Korea Institute of Drug Safety & Risk Management, Seoul, Korea L. Y. Kim Health Insurance Review and Assessment Service, Seoul, Korea S. H. Paick · H. G. Kim · Y. S. Lho · H. K. Park (*) Department of Urology, School of Medicine, Konkuk University, 4‑12 Hwayang‑dong, Gwangjin‑gu, Seoul, Korea e-mail: [email protected]
Introduction The urinary calculus disease, urolithiasis, is one of the most prevalent diseases in urology. The prevalence and annual incidences of urolithiasis have been reported to a variable degree for different countries or regions. In previous reports, the incidence of urolithiasis in Western countries ranged from 0.2 to 1.5 % [1, 2]. In Asian countries, there have been only a few epidemiology studies about urolithiasis. Yasui et al. [3] reported that the annual incidence of a first-episode upper urinary tract stone in Japan was 134.0 per 100,000, and this incidence was lower than that reported in Western countries. However, previous studies have been limited by restriction to local areas and dependency on patients’ subjective memory about the urolithiasis episode. Korea has a single National Health Insurance program and all citizens are covered under this program, accounting 97 % of the population, approximately 50 million people. Health Insurance and Review and Assessment (HIRA) database contains not only individual beneficiary’s information, but also healthcare service information such as diagnosis, procedures, prescriptions and tests for them. Due to its tremendous size, researchers have had problems in accessing the database to conduct research. To meet this demand, HIRA conducted a study to develop the sample data (NPS) from HIRA database for research [4]. Recently in Korea, National Health Insurance released a large-scale standardized patient data set called the National Patient Sample (NPS). The NPS includes medical records from about 1,100,000 standardized patients who were selected from all Korean population. The objective of this study was to evaluate the annual incidence of reno-ureteral stone disease.
13
Urolithiasis
Materials and methods In Korea, all people are registered with the National Health Insurance system, and their medical records are stored at the HIRA center. In 2012, HIRA provided nationwide patient data called the “Health Insurance and Review and Assessment service-National Patient Sample (NPS) 2009”. NPS was defined as secondary data that was randomly sampled from the raw data of the public health insurance.
Fig. 1 a A diagram showing the extraction from total population, estimation of number of urolithiasis patients and prevalence of urolithiasis. NPS data consisted of 1 % of outpatients and 13 % of inpatients that were extracted from original data. The estimated number of patients was determined that was multiflied a reciprocal number of the extraction ratio by NPS data. b The procedure to estimate overall stone patients incidence
13
Data sample extraction was based on the medical use of all patients in 2009 and performed by systematic sampling and stratification of patients according to gender and age sectors. The numbers of patients of original data were 5,471,423 for inpatients and 40,430,615 for outpatients. An adequate sample size was determined to ensure representativeness and generality with additional consideration for convenience of calculation. The representativeness means a subset of a statistical population that accurately reflects the
Urolithiasis
members of the entire population. Generality of one sample means that the sample has the power to show the same prevalence and same characters of various diseases in comparison to original total population. For example, the minimum sample size of inpatients was 729,904 for the generality, and 488,861 for representativeness. After considering the convenience of calculation, our final sample size was 13 % of the inpatient population, which were about 7.7 million beneficiaries. The sample size of outpatients was determined through the same procedure. As the variance of data in inpatients is low, the extraction rate is determined as 1 %, 4.0 million beneficiaries [4]. In short, the extraction rates were 13 % in inpatients and 1 % in outpatients and final NPS includes 711,285 inpatients and 404,436 outpatients. NPS data included age, sex, diagnosis-based ICD-10. To investigate the incidence of upper tract urolithiasis, patients who were diagnosed as N20.0 (renal stone), N20.1 (ureter stone), and N13.2 (hydronephrosis with renal and ureteral stone) were included. Patients diagnosed with N21 (lower urinary tract stone such as bladder stone or urethral stone) were excluded. The estimate of urolithiasis patients was calculated as follows: Total estimated number of urolithiasis patients = (7.692 × the number of urolithiasis inpatients) + (100 × the number of urolithiasis outpatients) (Fig. 1). Incidence was defined as number of estimated urolithiasis patients divided by total population number in the Korea population census results. Statistical analysis was conducted using SAS, version 9.2 (SAS Institute, Inc, Cary, NC).
Results In total, there were 8,298 inpatients and 1,555 outpatients who were diagnosed with upper tract urolithiasis in NPS 2009 data. After adjusted to weighted value, the total Table 1 Number of patients in original data, NPS data, stone patients in NPS data, and incidence of stone patients Total
Inpatients Outpatients
No. of patients in total population No. of patients in NPS data No. of stone patients in NPS data Estimated no. of patients 2010 Concensus number
45,902,038 5,471,423 40,430,615
219,328 63,828 47,990,761
155,500
Overall incidence (number per 100,000)
457
324
1,115,721 9,853
711,285 8,298
133
404,436 1,555
number of urolithiasis patients diagnosed with urolithiasis was estimated to be 219,328 (63,828 inpatients and 155,500 outpatients) (Table 1). The annual incidence of upper tract urolithiasis was estimated to be 457.02 per 100,000 in the overall population, with 589.09 per 100,000 men and 326.64 per 100,000 women (Table 2). The male-to-female ratio was about 1.80:1. The incidence of urolithiasis in inpatients and outpatients was 133.0 per 100,000 and 324.02 per 100,000, respectively. The incidences of urolithiasis by sex were 158.32 per 100,000 men and 108.01 per 100,000 women in inpatients, 430.78 per 100,000 men and 218.64 women in outpatients, respectively. When stratified by age, the number of urolithiasis patients was largest in the 40- to 49-year-old age group, but the incidence in the 60- to 69-year-old group was higher than that of any other age group (0.81 %) (Table 3; Fig. 2a, b). Stone distribution was renal in 38 % and ureter in 62 % of cases, respectively.
Discussion Urolithiasis is one of the most prevalent diseases in urology. The prevalence and incidence of urolithiasis has been reported to a variable degree depending on the country or region. In previous reports, the prevalence of kidney stones varied greatly between geographic locations, ranging from 4.3 to 5.2 % [1, 2, 5–8]. In Korea, it is estimated that 6.0 % of men and 1.8 % of women will experience urolithiasis during their lifetime [9]. In Taiwan, the prevalence of urolithiasis was 7.4 % in 2010, and these results were similar to those in Western countries [10]. The annual incidence of urolithiasis was reported to range from 0.5 to 1.5 % in Western countries [1, 2]. However, there have been few reports about upper tract urolithiasis in Asia. Yasui et al. [3] showed that the annual incidence of first-episode upper urinary tract stone was 134.0 per 100,000 in Japan, which is lower than that previously described in Western countries [1, 2]. Recently, Huang et al. [10] reported epidemiologic results using a nationwide population-based database in Taiwan. The age-adjusted rate of medical care visits for upper urinary tract was 1,278/100,000. However, these results were just the sum of hospital visits for urolithiasis in a year, and therefore do not indicate the annual incidence of urolithiasis. In the present study, the annual incidence of upper tract urolithiasis was estimated to be 457 per 100,000 in the overall population, with 589 per 100,000 men and 327 per 100,000 women (Table 1). Our incidence was higher than that of Iran (0.15 %) [5] and Japan (0.13 %) [3], but lower than that of Germany
13
13
430
218 108
158 589
327 24,149,865
23,840,896 102,700
52,800 26,083
37,745 140,445
78,883 528
4,907
3,919
3,391
5,934
Female
1,027
324 133 457 155,500 63,828 219,328 1,555 8,298 9,853
Total Gender Male
Inpatients
Outpatients
Inpatients Total Total
Outpatients
47,990,761
2010 Census Data Estimated no. of patients No. of stone patients in NPS data
Table 2 Number of patients in NPS data, estimated number of stone patients, and incidence of stone patients by sex
Overall incidence (number per 100,000)
Incidence of Inpatients (number per 100,000)
Incidence of outpatients (number per 100,000)
Urolithiasis
(1.5 %) [2]. In the case of Japan, the incidence of urolithiasis was lower than in our study because it was not divided by area, but was rather targeted to particular hospitals, and they excluded stone passage state and their survey was collected data by mail. Moreover, annual rate of all stone episodes (first or recurrent) is obviously higher than incidence of first episodes. This can explain difference of our study and Japanese study [3]. In the case of Germany, the incidence of urolithiasis was higher than in our study partly because of the inclusion of bladder calculi. Our study excluded bladder calculi because most bladder calculi cases were correlated with bladder outlet obstruction or neurogenic bladder, rather than pathophysiology of urolithiasis. The difference of risk factors such as systemic disease prevalence, life style, food and race may be possible explanation. Our sample size was over 1,100,000 and was collected by a standardized method. This population is sufficient to represent the national incidence. Moreover, the diagnosis of urolithiasis was made by a clinician, not by patient recall. Typically, KUB, IVP, and non-enhanced CT are covered by insurance, and all physicians must provide evidence of the presence of stone such as radiologic exam results to the insurance center. Therefore, the diagnostic accuracy is thought to be very high in this study. In this study, the total number of upper urinary tract stone was the highest in the 40–49 class ages. However, with adjusting by the population number per age group, the rate of stone incidence was the highest in the 60–69 class ages. This result is different from other reports that showed highest incidence in 40–60 ages. This is maybe because of rapid decline in 60–69 age population in Korea. Hesse et al. [2] reported the high incidence in 50–64 age groups. However, the number of stone patients was so small to represent the age distribution and was not divided by age proportion. Japanese study [3] also reported the high incidence in 40–59 age groups in 2005, but ages were standardized to the population in 1980. In addition, as non-enhanced CT is usually used for diagnosis of urinary stone in Korea, there is possibility of increase of uric acid stone detection that occurred more in old ages. Our study had some limitations. This was a large-scale study, but it lacked certain inclusion criteria other than ICD-10 criteria. Patients who did not visit the hospital or clinic because of asymptomatic urolithiasis or other cause could not be included in this study. There were some differences between the diagnostic methods of each physician, and therefore urolithiasis may have been underestimated by doctors who were not familiar with urolithiasis. This study did not identify the characteristics of urolithiasis such as size, location of stone (upper, mid, and lower), history of previous treatment, stone composition and patients’ treatment outcomes.
Urolithiasis Table 3 The incidence of urolithiasis of inpatients and outpatients according to age Age group
Estimated no. of patients Total
0–9 10–19 20–29 30–39 40–49 50–59 60–69 ≥70
Total
Inpatients
2010 Census Data
Incidence (number per 100,000)
95 % CI
Outpatients
269 4,261 22,554 43,738 53,414 48,899 32,161 14,030
169 1,161 5,454 10,738 14,814 14,599 9,961 6,930
100 3,100 17,100 33,000 38,600 34,300 22,200 7,100
4,613,747 6,611,640 6,594,369 7,794,495 8,204,781 6,564,826 3,994,404 3,612,499
6 64 342 561 651 745 805 388
0.00–0.01 0.05–0.08 0.31–0.38 0.53–0.60 0.62–0.68 0.71–0.78 0.77–0.84 0.34–0.44
219,328
63,828
155,500
47,990,761
457
0.44–0.47
Fig. 2 a The estimated number of urolithiasis patients in year 2009. When stratified by age, the number of urolithiasis patients was largest in the 40- to 49-year-old age group. b The annual incidence of urolithiasis patients in the year 2009. The incidence in the 60- to 69-yearold group was higher than that of any other age group (0.81 %)
13
Urolithiasis
However, this study is very meaningful because this is the one of few studies of urolithiasis incidence using a large sample at a national level. As additional NPS data are made available to the public, we will be able to acquire more accurate data on the annual incidence and other factors of urinary stone disease in the Korean population.
Conclusions The annual incidence of upper tract urolithiasis was estimated to be 457 per 100,000 in the overall population and the incidence of urolithiasis in inpatients and outpatients was 133.0 per 100,000 and 324.02 per 100,000, respectively. The incidence in the 60- to 69-year-old group was higher than that in other age groups. It is higher than that previously reported in Japan, but lower than that in Western countries. Further study is needed to confirm these results. Acknowledgments This work was supported by Konkuk University. Conflict of interest None of the authors have any conflict of interests.
References 1. Indridason OS, Birgisson S, Edvardsson VO, Sigvaldason H, Sigfusson N, Palsson R (2006) Epidemiology of kidney stones in Iceland: a population-based study. Scand J Urol Nephrol 40:215–220
13
2. Hesse A, Brändle E, Wilbert D, Köhrmann K-U, Alken P (2003) Study on the prevalence and incidence of urolithiasis in Germany comparing the years 1979 vs. 2000. Eur Urol 44:709–713 3. Yasui T, Iguchi M, Suzuki S, Kohri K (2008) Prevalence and epidemiological characteristics of urolithiasis in Japan: national trends between 1965 and 2005. Urology 71:209–213 4. Kim L, Sakong J, Kim Y, Kim S, Kim S, Tchoe B et al (2013) Developing the inpatient sample for the national health insurance claims data. Health Policy Manag 23:152–161 5. Safarinejad MR (2007) Adult urolithiasis in a population-based study in Iran: prevalence, incidence, and associated risk factors. Urol Res 35(2):73–82 6. Stamatelou KK, Francis ME, Jones CA, Nyberg LM, Curhan GC (2003) Time trends in reported prevalence of kidney stones in the United States: 1976–1994. Kidney Int 63:1817 7. Scales CD Jr, Smith AC, Hanley JM, Saigal CS; Urological Disease in America Project (2012) Prevalence of kidney stones in the United States. Eur Urol 62:160 8. Boyce CJ, Pickhardt PJ, Lawrence EM, Kim DH, Bruce RJ (2010) Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography. J Urol 183:1017 9. Jo MK, Kwak C, Park SK, Yoo K-Y, Kang D, Lee C (2002) Prevalence and epidemiologic characteristics of urolithiasis in Seoul, Korea. Urology 59:517–521 10. Huang W-Y, Chen Y-F, Carter S, Chang H-C, Lan C-F, Huang K-H (2013) Epidemiology of upper urinary tract stone disease in a Taiwanese population: a nationwide, population-based study. J Urol 189(6):2158–2163
Original Paper
The epidemiology of reno‑ureteral stone disease in Koreans: a nationwide population‑based study Sang Rak Bae · Jong‑Mi Seong · Log Young Kim · Sung Hyun Paick · Hyeong Gon Kim · Yong Soo Lho · Hyoung Keun Park
Received: 13 September 2013 / Accepted: 27 January 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract The objective of this study was to evaluate the annual incidence of upper tract urolithiasis based on a large population-based study in Korea. This study used a subset of the 2009 Health Insurance and Review and Assessment service-National Patient Sample (HIRA-NPS). The 2009 HIRA-NPS contains data for 1,115,721 patients (711,285 inpatients and 404,436 outpatients) from January 2009 to December 2009. Based on these data, we selected patients who had been diagnosed with urolithiasis using the ICD code and calculated the incidence of urolithiasis. The total number of estimated urolithiasis patients was 219,328. The annual incidence of upper tract urolithiasis was estimated to be 457.02 per 100,000 in the overall population, with 589.09 per 100,000 men and 326.64 per 100,000 women. The male-to-female ratio was about 1.8:1. The annual incidence of urolithiasis in Korea was 457 per 100,000. It is higher than that previously reported in Japan, but lower than that in Western countries. Keywords Epidemiology · Incidence · Urolithiasis · Population-based study
S. R. Bae Department of Urology, Konkuk University Medical Center, Seoul, Korea J.-M. Seong Office of Drug Safety Information II, Korea Institute of Drug Safety & Risk Management, Seoul, Korea L. Y. Kim Health Insurance Review and Assessment Service, Seoul, Korea S. H. Paick · H. G. Kim · Y. S. Lho · H. K. Park (*) Department of Urology, School of Medicine, Konkuk University, 4‑12 Hwayang‑dong, Gwangjin‑gu, Seoul, Korea e-mail: [email protected]
Introduction The urinary calculus disease, urolithiasis, is one of the most prevalent diseases in urology. The prevalence and annual incidences of urolithiasis have been reported to a variable degree for different countries or regions. In previous reports, the incidence of urolithiasis in Western countries ranged from 0.2 to 1.5 % [1, 2]. In Asian countries, there have been only a few epidemiology studies about urolithiasis. Yasui et al. [3] reported that the annual incidence of a first-episode upper urinary tract stone in Japan was 134.0 per 100,000, and this incidence was lower than that reported in Western countries. However, previous studies have been limited by restriction to local areas and dependency on patients’ subjective memory about the urolithiasis episode. Korea has a single National Health Insurance program and all citizens are covered under this program, accounting 97 % of the population, approximately 50 million people. Health Insurance and Review and Assessment (HIRA) database contains not only individual beneficiary’s information, but also healthcare service information such as diagnosis, procedures, prescriptions and tests for them. Due to its tremendous size, researchers have had problems in accessing the database to conduct research. To meet this demand, HIRA conducted a study to develop the sample data (NPS) from HIRA database for research [4]. Recently in Korea, National Health Insurance released a large-scale standardized patient data set called the National Patient Sample (NPS). The NPS includes medical records from about 1,100,000 standardized patients who were selected from all Korean population. The objective of this study was to evaluate the annual incidence of reno-ureteral stone disease.
13
Urolithiasis
Materials and methods In Korea, all people are registered with the National Health Insurance system, and their medical records are stored at the HIRA center. In 2012, HIRA provided nationwide patient data called the “Health Insurance and Review and Assessment service-National Patient Sample (NPS) 2009”. NPS was defined as secondary data that was randomly sampled from the raw data of the public health insurance.
Fig. 1 a A diagram showing the extraction from total population, estimation of number of urolithiasis patients and prevalence of urolithiasis. NPS data consisted of 1 % of outpatients and 13 % of inpatients that were extracted from original data. The estimated number of patients was determined that was multiflied a reciprocal number of the extraction ratio by NPS data. b The procedure to estimate overall stone patients incidence
13
Data sample extraction was based on the medical use of all patients in 2009 and performed by systematic sampling and stratification of patients according to gender and age sectors. The numbers of patients of original data were 5,471,423 for inpatients and 40,430,615 for outpatients. An adequate sample size was determined to ensure representativeness and generality with additional consideration for convenience of calculation. The representativeness means a subset of a statistical population that accurately reflects the
Urolithiasis
members of the entire population. Generality of one sample means that the sample has the power to show the same prevalence and same characters of various diseases in comparison to original total population. For example, the minimum sample size of inpatients was 729,904 for the generality, and 488,861 for representativeness. After considering the convenience of calculation, our final sample size was 13 % of the inpatient population, which were about 7.7 million beneficiaries. The sample size of outpatients was determined through the same procedure. As the variance of data in inpatients is low, the extraction rate is determined as 1 %, 4.0 million beneficiaries [4]. In short, the extraction rates were 13 % in inpatients and 1 % in outpatients and final NPS includes 711,285 inpatients and 404,436 outpatients. NPS data included age, sex, diagnosis-based ICD-10. To investigate the incidence of upper tract urolithiasis, patients who were diagnosed as N20.0 (renal stone), N20.1 (ureter stone), and N13.2 (hydronephrosis with renal and ureteral stone) were included. Patients diagnosed with N21 (lower urinary tract stone such as bladder stone or urethral stone) were excluded. The estimate of urolithiasis patients was calculated as follows: Total estimated number of urolithiasis patients = (7.692 × the number of urolithiasis inpatients) + (100 × the number of urolithiasis outpatients) (Fig. 1). Incidence was defined as number of estimated urolithiasis patients divided by total population number in the Korea population census results. Statistical analysis was conducted using SAS, version 9.2 (SAS Institute, Inc, Cary, NC).
Results In total, there were 8,298 inpatients and 1,555 outpatients who were diagnosed with upper tract urolithiasis in NPS 2009 data. After adjusted to weighted value, the total Table 1 Number of patients in original data, NPS data, stone patients in NPS data, and incidence of stone patients Total
Inpatients Outpatients
No. of patients in total population No. of patients in NPS data No. of stone patients in NPS data Estimated no. of patients 2010 Concensus number
45,902,038 5,471,423 40,430,615
219,328 63,828 47,990,761
155,500
Overall incidence (number per 100,000)
457
324
1,115,721 9,853
711,285 8,298
133
404,436 1,555
number of urolithiasis patients diagnosed with urolithiasis was estimated to be 219,328 (63,828 inpatients and 155,500 outpatients) (Table 1). The annual incidence of upper tract urolithiasis was estimated to be 457.02 per 100,000 in the overall population, with 589.09 per 100,000 men and 326.64 per 100,000 women (Table 2). The male-to-female ratio was about 1.80:1. The incidence of urolithiasis in inpatients and outpatients was 133.0 per 100,000 and 324.02 per 100,000, respectively. The incidences of urolithiasis by sex were 158.32 per 100,000 men and 108.01 per 100,000 women in inpatients, 430.78 per 100,000 men and 218.64 women in outpatients, respectively. When stratified by age, the number of urolithiasis patients was largest in the 40- to 49-year-old age group, but the incidence in the 60- to 69-year-old group was higher than that of any other age group (0.81 %) (Table 3; Fig. 2a, b). Stone distribution was renal in 38 % and ureter in 62 % of cases, respectively.
Discussion Urolithiasis is one of the most prevalent diseases in urology. The prevalence and incidence of urolithiasis has been reported to a variable degree depending on the country or region. In previous reports, the prevalence of kidney stones varied greatly between geographic locations, ranging from 4.3 to 5.2 % [1, 2, 5–8]. In Korea, it is estimated that 6.0 % of men and 1.8 % of women will experience urolithiasis during their lifetime [9]. In Taiwan, the prevalence of urolithiasis was 7.4 % in 2010, and these results were similar to those in Western countries [10]. The annual incidence of urolithiasis was reported to range from 0.5 to 1.5 % in Western countries [1, 2]. However, there have been few reports about upper tract urolithiasis in Asia. Yasui et al. [3] showed that the annual incidence of first-episode upper urinary tract stone was 134.0 per 100,000 in Japan, which is lower than that previously described in Western countries [1, 2]. Recently, Huang et al. [10] reported epidemiologic results using a nationwide population-based database in Taiwan. The age-adjusted rate of medical care visits for upper urinary tract was 1,278/100,000. However, these results were just the sum of hospital visits for urolithiasis in a year, and therefore do not indicate the annual incidence of urolithiasis. In the present study, the annual incidence of upper tract urolithiasis was estimated to be 457 per 100,000 in the overall population, with 589 per 100,000 men and 327 per 100,000 women (Table 1). Our incidence was higher than that of Iran (0.15 %) [5] and Japan (0.13 %) [3], but lower than that of Germany
13
13
430
218 108
158 589
327 24,149,865
23,840,896 102,700
52,800 26,083
37,745 140,445
78,883 528
4,907
3,919
3,391
5,934
Female
1,027
324 133 457 155,500 63,828 219,328 1,555 8,298 9,853
Total Gender Male
Inpatients
Outpatients
Inpatients Total Total
Outpatients
47,990,761
2010 Census Data Estimated no. of patients No. of stone patients in NPS data
Table 2 Number of patients in NPS data, estimated number of stone patients, and incidence of stone patients by sex
Overall incidence (number per 100,000)
Incidence of Inpatients (number per 100,000)
Incidence of outpatients (number per 100,000)
Urolithiasis
(1.5 %) [2]. In the case of Japan, the incidence of urolithiasis was lower than in our study because it was not divided by area, but was rather targeted to particular hospitals, and they excluded stone passage state and their survey was collected data by mail. Moreover, annual rate of all stone episodes (first or recurrent) is obviously higher than incidence of first episodes. This can explain difference of our study and Japanese study [3]. In the case of Germany, the incidence of urolithiasis was higher than in our study partly because of the inclusion of bladder calculi. Our study excluded bladder calculi because most bladder calculi cases were correlated with bladder outlet obstruction or neurogenic bladder, rather than pathophysiology of urolithiasis. The difference of risk factors such as systemic disease prevalence, life style, food and race may be possible explanation. Our sample size was over 1,100,000 and was collected by a standardized method. This population is sufficient to represent the national incidence. Moreover, the diagnosis of urolithiasis was made by a clinician, not by patient recall. Typically, KUB, IVP, and non-enhanced CT are covered by insurance, and all physicians must provide evidence of the presence of stone such as radiologic exam results to the insurance center. Therefore, the diagnostic accuracy is thought to be very high in this study. In this study, the total number of upper urinary tract stone was the highest in the 40–49 class ages. However, with adjusting by the population number per age group, the rate of stone incidence was the highest in the 60–69 class ages. This result is different from other reports that showed highest incidence in 40–60 ages. This is maybe because of rapid decline in 60–69 age population in Korea. Hesse et al. [2] reported the high incidence in 50–64 age groups. However, the number of stone patients was so small to represent the age distribution and was not divided by age proportion. Japanese study [3] also reported the high incidence in 40–59 age groups in 2005, but ages were standardized to the population in 1980. In addition, as non-enhanced CT is usually used for diagnosis of urinary stone in Korea, there is possibility of increase of uric acid stone detection that occurred more in old ages. Our study had some limitations. This was a large-scale study, but it lacked certain inclusion criteria other than ICD-10 criteria. Patients who did not visit the hospital or clinic because of asymptomatic urolithiasis or other cause could not be included in this study. There were some differences between the diagnostic methods of each physician, and therefore urolithiasis may have been underestimated by doctors who were not familiar with urolithiasis. This study did not identify the characteristics of urolithiasis such as size, location of stone (upper, mid, and lower), history of previous treatment, stone composition and patients’ treatment outcomes.
Urolithiasis Table 3 The incidence of urolithiasis of inpatients and outpatients according to age Age group
Estimated no. of patients Total
0–9 10–19 20–29 30–39 40–49 50–59 60–69 ≥70
Total
Inpatients
2010 Census Data
Incidence (number per 100,000)
95 % CI
Outpatients
269 4,261 22,554 43,738 53,414 48,899 32,161 14,030
169 1,161 5,454 10,738 14,814 14,599 9,961 6,930
100 3,100 17,100 33,000 38,600 34,300 22,200 7,100
4,613,747 6,611,640 6,594,369 7,794,495 8,204,781 6,564,826 3,994,404 3,612,499
6 64 342 561 651 745 805 388
0.00–0.01 0.05–0.08 0.31–0.38 0.53–0.60 0.62–0.68 0.71–0.78 0.77–0.84 0.34–0.44
219,328
63,828
155,500
47,990,761
457
0.44–0.47
Fig. 2 a The estimated number of urolithiasis patients in year 2009. When stratified by age, the number of urolithiasis patients was largest in the 40- to 49-year-old age group. b The annual incidence of urolithiasis patients in the year 2009. The incidence in the 60- to 69-yearold group was higher than that of any other age group (0.81 %)
13
Urolithiasis
However, this study is very meaningful because this is the one of few studies of urolithiasis incidence using a large sample at a national level. As additional NPS data are made available to the public, we will be able to acquire more accurate data on the annual incidence and other factors of urinary stone disease in the Korean population.
Conclusions The annual incidence of upper tract urolithiasis was estimated to be 457 per 100,000 in the overall population and the incidence of urolithiasis in inpatients and outpatients was 133.0 per 100,000 and 324.02 per 100,000, respectively. The incidence in the 60- to 69-year-old group was higher than that in other age groups. It is higher than that previously reported in Japan, but lower than that in Western countries. Further study is needed to confirm these results. Acknowledgments This work was supported by Konkuk University. Conflict of interest None of the authors have any conflict of interests.
References 1. Indridason OS, Birgisson S, Edvardsson VO, Sigvaldason H, Sigfusson N, Palsson R (2006) Epidemiology of kidney stones in Iceland: a population-based study. Scand J Urol Nephrol 40:215–220
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