Int Urol Nephrol DOI 10.1007/s11255-013-0588-7

UROLOGY - ORIGINAL PAPER

A systematic review and meta-analysis of new onset hypertension after extracorporeal shock wave lithotripsy Cui Yu • Liu Longfei • Wang Long • Zeng Feng • Niu Jiping • Li Mao • Qi Lin Chen Hequn



Received: 19 September 2013 / Accepted: 14 October 2013 Ó Springer Science+Business Media Dordrecht 2013

Abstract Objective Previous studies on the association between extracorporeal shock wave lithotripsy (SWL) and new onset hypertension have only illustrated contradictory results. In order to illustrate the association between SWL and new onset hypertension, a meta-analysis of case–control and cohort studies was conducted. Methods Relevant literature was searched using PubMed, EMBASE, and the Cochrane Central Search Library. A meta-analysis of the association between SWL and new onset hypertension was performed. Studies were pooled, and summary relative risk was calculated. Subgroup analyses were also conducted. Results Eleven studies were eligible for our analysis. No statistical significance was detected between SWL and new onset hypertension (RR = 1.06, 95 % CI 0.83–1.35). No association was observed when stratified analyses were performed on age, gender, study design, bilateral SWL, and different machines. Conclusion Our analysis indicated that no association was found between SWL and the development of hypertension.

Introduction Since its introduction in the 1980s, extracorporeal shock wave lithotripsy (SWL) has revolutionized stone treatment and has become the mainstay procedure for urinary tract calculi [1]. However, the side effects of SWL have created much controversy in recent years. Strong evidence has developed that implicates SWL as a cause of transient acute renal damage and damage to surrounding tissues. Hypertension following SWL has been an ongoing controversy since the original reports of acute onset hypertension following SWL were published in the mid to late 1980s [2, 3]. However, subsequent studies with intermediate follow-up did not demonstrate these effects on blood pressure [4, 5]. The inconsistent results across the studies may be due to the small sample size in each study and different study design. To fully evaluate the association between SWL and new onset hypertension, we systemically reviewed all published papers and performed a metaanalysis by pooled analyses of all studies.

Methods Keywords Hypertension  Extracorporeal shock wave lithotripsy  Meta-analysis

Study search strategy

C. Yu  L. Longfei  W. Long  Z. Feng  N. Jiping  L. Mao  Q. Lin  C. Hequn (&) Department of Urology, Xiangya Hospital, Central South University, Changsha 410000, Hunan, China e-mail: [email protected]

In accordance with the PRISMA guidelines [6], a systematic review of the literature was performed in May 2013 using MEDLINE, EMBASE, and the Cochrane Central Search Library. We used the search terms Extracorporeal Shock Wave Lithotripsy, SWL combined with hypertension, blood pressure, high. Additional studies were identified by manual search from the references of original studies or review articles on this topic. Full texts or abstracts of all related reports were then reviewed. The

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Int Urol Nephrol Fig. 1 Flow chart of article selection

Records identified through database searching (n = 214)

Additional records identified through other sources (n = 23 )

Records after duplicates removed (n = 167)

Records screened (n = 68 )

Full-text articles assessed for eligibility (n =26 )

Records excluded (n =42)

15 studies excluded for not meeting inclusion criteria (e.g. no comparison group, lack of data, and so on)

Studies included in qualitative synthesis (n =11 )

Studies included in quantitative synthesis (meta-analysis) (n = 11 )

literature retrieval was performed by three independent reviewers (Cui Yu, Liu Longfei, and Wang Long). Selection criteria Each recruited publication was reviewed to evaluate whether the following criteria were met: (1) cohort or case– control study assessing the association between SWL and new onset hypertension; (2) exact data in both case and control groups should be determined; (3) articles reported between 1980 and May 2013 written in English; (4) results including relative risk (RR), rate ratio or hazard ratio and its 95 % CIs, or providing us with sufficient information to calculate them. Studies with overlapping or insufficient data were excluded. Figure 1 illustrated the process of identifying and selecting articles. Data extraction Two investigators independently assessed and extracted the data into a standardized data extraction form from each

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publication. Disagreements were resolved by a third author. We did not contact authors of the original studies in the case of missing data. Relevant data included the first author’s last name, publication year, year of the study conducted, study design, study location, source population, sample size (cases and controls or cohort size), length of follow-up, variables adjusted in the analysis, and the risk estimates with corresponding 95 % CIs. From each study, we extracted the RR estimate that was adjusted for the greatest number of potential confounders. Statistical analysis We included in this meta-analysis studies reporting different measures of relative risks: rate ratio, relative risk, or hazard ratio. In practice, these measures of effect yield similar estimates of RR. The variance in the log RR from each study was calculated by converting the 95 % CI to its natural logarithm by taking the width of the CI and dividing by 3.92. Summary relative risk estimates with corresponding 95 % CIs were derived using the method of

Int Urol Nephrol Table 1 Characteristics of patients in the studies included Study

Design

Cases/ controls

Population

Median follow-up

Participants source

Machines

Variables of adjustment

Main results (RR)

Barbosa et al. [10]

Case– control

1,892/ 1,758

American

6 years

PCC

Medstone STS electrohydraulic lithotripter

Age, gender, bilateral SWL, family history of hypertension

1.16 [1.06, 1.27]

Chew et al. [11]

Case– control

261/ 200

American

20 years

PCC

Original Dornier HM-3/ modified Dornier HM-3

Age, gender, bilateral SWL, history of smoking

Claro Jde et al. [12]

Case– control

102/ 100

Brazilian

22 months

PCC

NA

NA

1.63 [1.28, 2.09] 0.98 [0.25, 3.81]

Eassa et al. [13]

Case– control

82/ 6,733

Egyptian

43 months

PCC

Dornier MFL 5000/Dornier Lithotripter S

BMI, GFR

0.14 [0.05, 0.42]

El-Assmy et al. [14]

Case– control

89/ 6,733

Egyptian

12 months

PCC

Dornier MFL 5000/Dornier Lithotripter S

GFR, serum creatinine

0.13 [0.04, 0.39]

Elves et al. [15]

Cohort

113/ 115

British

At least 1 year

NA

Siemens Lithostar tubeC/Siemens Multiline tube-M

Diastolic, systolic

1.60 [0.64, 3.98]

Janetschek et al. [16]

Case– control

57/ 1,000

Australian

26 months

PCC

Dornier HM-5 Lithotripter

Age, resistive index level

1.97 [1.09, 3.58]

Jewett et al. [5]

Cohort

74/80

Canadian

3 years

NA

Siemens Lithostar

Diastolic, systolic

1.08 [0.16, 7.48]

Krambeck et al. [17]

Case– control

288/ 288

American

19 years

HCC

HM-3 Lithotripter

Gender, bilateral SWL

1.30 [1.02, 1.66]

Krambeck et al. [18]

Case– control

400/ 4,328

American

Greater than 90 days

PCC

NA

Age, gender

0.99 [0.86, 1.14]

Lingeman et al. [19]

Case– control

429/ 106

American

2 years

HCC

Dornier HM-3

Age, gender, diastolic, systolic

0.71 [0.33, 1.54]

NA not applicable, PCC population-based case–control, HCC hospital-based case–control, BMI body mass index, GFR glomerular filtration rate

DerSimonian and Laird with the assumptions of a randomeffects model, which considers both within study and between-study variations. A fixed-effect model was used to provide summary estimation when no heterogeneity was found; otherwise, the random-effect model was used for pooling instead. The RR and 95 % CI were calculated to assess the risk of hypertension. Stratified analyses were performed on age, gender, bilateral SWL, study design, and geographic regions. The extent of heterogeneity across the eligible studies was quantified using a Q test and I2 test [7], with the statistical significance level set at 0.05. Publication bias was evaluated by Egger’s [8] and Begg’s test [9], with the statistical significance level set at 0.05. All analysis was performed by the Stata version 12.0 software.

Results Eligible studies Eleven studies [5, 10–19] were identified according to the inclusion criteria of the meta-analysis. The characteristics of the included studies are summarized in Table 1. The publication dates in this study ranged between 1990 and 2011. Nine of them were case–control studies [10–14, 16, 17, 19], and the other two were cohort studies [5, 15]. Among the nine case–control studies, seven studies were population-based case–control (PCC) [10–14, 16, 18]. Besides, the other were hospital-based case–control (HCC) [17, 19]. Among these 11 studies, 8 studies did not demonstrate a significantly increased risk of hypertension in patients treated with SWL [5, 11–15, 18, 19], and the rest

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Fig. 2 Forest plots of association between SWL and new onset hypertension

Table 2 Results of subgroup analyses: relative risk (RR), number of studies, and heterogeneity Subgroup analysis

Number of studies

RR (95 % CI)

Heterogeneity (p, I2)

Age

2

1.00 (0.98, 1.02)

0.81

0%

Gender

2

1.06 (0.87, 1.28)

0.57

0%

Bilateral SWL Study design

2

1.31 (0.76, 2.27)

0.12

60 %

Cohort studies

2

1.49 (0.65, 3.40)

0.72

0%

Case–control studies

9

1.03 (0.80, 1.33) \0.0001

84 %

studies reported a significantly increased risk of hypertension in individuals treated with SWL [10, 16, 17]. Quantitative synthesis

Geographic regions North America

6

1.19 (1.01, 1.40)

0.02

67 %

Egypt

2

0.13 (0.06, 0.29)

0.92

0%

Britain

1

1.60 (0.64, 3.98)

NA

Australia

1

1.97 (1.09, 3.58)

NA

Brazil

1

0.98 (0.25, 3.81)

NA

HM3

3

1.34 (0.96, 1.87)

0.07

Non-HM3

6

0.69 (0.31, 1.53) \0.0001

Machine

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63 % 86 %

As illustrated in Fig. 2, no statistically significantly association was found between SWL and risk of hypertension, and the summary RR with 95 % CI was 1.06 (95 % CI 0.83–1.35) in a random-effects model. There was statistically significant heterogeneity among these studies (p \ 0.001, I2 = 80 %). In analysis stratified by study design, the summary RR with 95 % CI was 1.03 (95 % CI 0.80–1.33) and 1.49 (95 % CI 0.65–3.38) in case–control and cohort studies, respectively. There was statistically significant heterogeneity among the case–control studies (p \ 0.001, I2 = 84 %). No significant heterogeneity was found among the cohort studies (p = 0.72, I2 = 0 %). The number of trials, number of participants, and effect sizes for subgroups are reported in Table 2. No association was observed when stratified analyses were performed on age, gender, study design, bilateral SWL, and different machines. In stratified analysis by geographic regions, a

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by sequentially excluding each study in one turn. In our meta-analysis, we found no study could possibly influence the summary of risk estimate (Fig. 4).

Discussion

Fig. 3 Funnel plot of studies evaluating the association between SWL and new onset hypertension

modest but statistically significantly increased risk of hypertension for studies conducted in America was found. Publication bias There was no funnel plot asymmetry for the association between SWL and risk of hypertension. p values for Begg’s adjusted rank correlation test was 0.35 and the Egger’s regression asymmetry test was 0.430, suggesting a low probability of publication bias (Fig. 3). Sensitivity analyses Simultaneously, sensitivity analyses were conducted to assess the effect of one single study on the overall estimate

Shock wave lithotripsy has a major role in the treatment for urolithiasis, particularly for renal and upper ureteral stones. High success rates for treatment for renal stones have been achieved worldwide [20–23]. More than 20 years after the introduction of the HM3 lithotriptor, it is time to review long-term adverse medical events. In this meta-analysis, we found that compared with nonSWL or general population, individuals treated with SWL may have no increased risk of hypertension. There were no differences in the summary RR among different study designs. The summary estimate in cohort studies and case– control studies did not indicate a risk of hypertension in these cases compared with the control population. The strength of the study includes that, on an international scale, there is a large number of individuals treated with SWL in our study. No association was observed when stratified analyses were performed on age, gender, study design, and bilateral SWL. In stratified analysis by geographic regions, a modest but statistically significantly increased risk of hypertension for studies conducted in America was found. Many environmental and personal determinants are related, including genetic factors, lifestyle (eating habits, physical activities, somatotype characteristics), environmental factors (environmental pollution, stress, socioeconomic status), public health services, and so

Fig. 4 Sensitivity analyses of studies evaluating the association between SWL and new onset hypertension

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on. With the gradual improvement in medical conditions, early screening and diagnosis rates of hypertension are greatly improved. These factors are all attributable to the regional differences. Our study also has several potential limitations of the available data. Thus, caution is needed when interpreting these results. Statistical heterogeneity across studies was found in all analyses. Despite the use of appropriate metaanalytic techniques with random-effect models, we could not account for these differences. Inherent in any meta-analysis of published data is the possibility of publication bias, that is small studies with null results tend not to be published. However, the results obtained from funnel plot analysis and formal statistical tests did not provide evidence for such bias. The machines used in six studies were the second or third generation lithotriptor, while other three studies used the HM3, which has a larger focal zone with increased theoretical effects on the surrounding tissue. However, no association was observed when stratified analyses were performed on HM3 and non-HM3 machine. Outcome data of two studies on controls were collected by retrospective review of patients followed at clinic. This could have introduced collection bias in the results. The length of follow-up was ranged from 90 days to 25 years. Because the length of time to develop hypertension is unknown, the short-term follow-up for patients in both cohorts may not be sufficient to identify a significant difference. Future studies are required to long-term follow-up to assess the association between SWL and prevalence of hypertension. Other potentially contributing factors such as smoking status and a family history of hypertension were assessed in one study, and these factors significantly alter the relationship between SWL and risk of hypertension (p = 0.003, p \ 0.01 respectively). Future studies should assess the potentially contributing factors such as smoking status, a family history of hypertension, sodium intake, as well as blood pressure assessment procedures, and other methodological issues.

Conclusion Our analysis indicated that no association was found between SWL and the development of hypertension. Additional more studies (especially the cohort studies and studies from more countries) with long follow-up are needed to provide a more definitive conclusion. Conflict of interest of interest.

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The authors declare that they have no conflict

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A systematic review and meta-analysis of new onset hypertension after extracorporeal shock wave lithotripsy.

Previous studies on the association between extracorporeal shock wave lithotripsy (SWL) and new onset hypertension have only illustrated contradictory...
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