Trends and inequalities in the surgical management of ureteric calculi in the USA

Authors


Abstract

Objective

  • To assess trends in the surgical management of ureteric calculi over a 10-year period.

Materials and Methods

  • An analysis of the 5% Medicare Public Use Files, from 2001, 2004, 2007 and 2010, was performed to assess the use of ureteroscopy (URS), extracorporal shockwave lithotripsy (ESWL) and ureterolithotomy (UL) in treating ureteric calculi.
  • Patients were identified using International Classification of Diseases 9th edition (Clinical Modification) and Current Procedure Terminology codes.
  • Statistical analyses using the Fisher and chi-squared tests, and multivariate logistic regression analysis (dependent variables: URS, ESWL, UL, treatment, no treatment; independent variables: age, gender, ethnicity, geography and year of treatment) were performed.

Results

  • A total of 299 920 patients with ureteric calculi were identified. Of these, 115 200 underwent surgery.
  • Men (odds ratio [OR] = 1.15, P < 0.001) were more likely, while patients from ethnic minorities (OR = 0.84, P = 0.004) were less likely to be treated. Patients in the West of the USA were also less likely to be treated (OR = 0.76, P < 0.001) as were patients aged <65 or >84 years old (P = 0.29).
  • The predominant surgical approach was URS (65.2%), followed by ESWL (33.6%) and UL (1.2%).
  • The use of URS increased over time, while the use of ESWL and UL declined.
  • Women (OR = 1.25, P < 0.001) were more likely to undergo URS. Patients in the South of the USA (OR = 1.51, P < 0.001) and patients from ethnic minorities were more likely to undergo ESWL (OR = 1.23, P = 0.03).

Conclusions

  • The surgical treatment of ureteric calculi changed significantly between 2001 and 2010.
  • The use of URS expanded at the expense of ESWL and UL.
  • Multiple inequalities existed in overall surgical treatment rates and in the choice of treatment; age, gender, ethnicity and geography influenced both whether patients underwent surgical intervention and the type of surgical approach used.

Introduction

Upper urinary tract calculi represent a common condition in patients presenting to urology departments. It has been estimated that 8.8–15% of the populations of Northern America and Europe develop upper urinary tract calculi [1-4]. Indeed, the incidence and prevalence of urolithiasis has been increasing [4-6]. In the USA, one in 20 patients self-reported a history of stone disease in the period 1994–1998, increasing to one in 11 patients by 2007–2010 [4, 7].

Demographic factors such as age, gender, ethnicity and geographical region represent known risk factors for stone formation [4, 5, 8-11]. Men, for example, have been shown to have higher prevalence rates of stone disease (10.6–12%) than women (4.8–7.1%) [4, 8]. Hispanic and Black people have a 40 and 63% lower likelihood of stone disease, respectively, than White people [4, 8, 9]. People aged ≥65 years are 2.5 times more likely to have stone disease than 35–49 years olds [5]. Patients living in the ‘stone belt’, particularly in the Southeast of the USA, report a higher incidence and prevalence of urolithiasis [11].

Surgical intervention for ureteric calculi includes ureteroscopy (URS), ESWL and ureterolithotomy (UL). Although risk factors for the development of stone disease have been identified, studies assessing differences in treatment practice patterns are lacking. In the present study, we sought to assessnational trends in the surgical management of ureteric calculi over time.

Materials and Methods

After institutional review board approval, Medicare claims data for the years 2001, 2004, 2007 and 2010 were obtained from the Centers for Medicare and Medicaid Services. the Public Use files included multiple datasets encompassing physician and hospital inpatient and outpatient medical claims from a 5% national random sample of beneficiaries. Patients with a diagnosis of ureteric calculi were identified on the basis of International Classification of Diseases, 9th Edition (ICD-9 [Appendix 1]). Patients who underwent surgical stone procedures, specifically URS, ESWL and UL, were identified on the basis of Current Procedure Terminology (CPT) and ICD-9 (Clinical Modification) codes. Patients with a combined diagnosis of kidney and ureteric calculi or those with unknown stone location within the upper urinary tract were excluded. Individual de-identified subjects were tracked using encrypted beneficiary identification numbers to link data across the multiple datasets representing care in inpatient and outpatient settings; this accounted for patients who underwent multiple procedures during the study period. National estimates of service use were obtained by multiplying counts by a constant weight of 20 [12]. Patients were categorized according to gender, age, ethnicity and geographical location within the USA [13].

Statistical tests used included the chi-squared and Fisher's tests and multivariate logistic regression analyses. Statistical analyses were performed using sas v9.3 (SAS Institute Inc., Cary, NC, USA) and spss v20 (IBM Corp., Armonk, NY, USA).

Results

A total of 299 920 patients with a diagnosis of ureteric calculi were identified over the 10-year study period. the number of patients diagnosed with ureteric calculi rose from 57 120 to 90 660 (an increase of 59%) between 2001 and 2010; however, the percentage of such patients treated surgically each year remained roughly constant at ∼38% (P = 0.78; Fig. 1).

Figure 1.

Diagnosis of ureteric calculi and surgical treatment rates from 2001 to 2010. the percentage of patients diagnosed and treated remained roughly the same (38%, P = 0.78)

Of the 115 200 patients undergoing surgery, 64.4% (n = 74 160) underwent URS, 29.6% (n = 34 080) underwent ESWL, 0.5% (n = 520) underwent UL and 5.6% (n = 6440) had multiple claims with both URS and ESWL. Over time, a shift towards URS and away from ESWL and UL was observed. URS was initially performed in 62.9% of patients in 2001, increasing to 70.2% by 2010 at the cost of a declining use of ESWL (34.9 to 29.3%) and UL (2.2 to 0.5) (P < 0.001; Fig. 2 and Table 1).

Figure 2.

The use of URS, ESWL and UL from 2001 to 2010.

Table 1. Distribution of surgical treatments by year.
 URS%ESWL%UL%P
2001       
Gender      <0.001
Male10 54060.26 54037.44202.4
Female5 70068.72 46029.61401.7
Ethnicity      <0.001
White15 14064.08 04034.04802.0
Minorities1 08052.494045.6401.9
Age, years)      <0.001
<65 years2 24061.91 22033.71604.4
65–69 years4 50062.02 66036.61001.4
70–74 years3 56059.12 34038.91202.0
75–79 years3 56066.91 70032.0601.1
80–84 years1 52065.570030.21004.3
>84 years86068.338030.2201.6
Geography      <0.001
Northeast2 78062.11 60035.71002.2
Midwest4 08066.91 90031.11202.0
South7 48062.44 26035.62402.0
West1 80060.81 12037.8401.4
2004       
Gender      <0.001
Male12 82059.48 40038.93801.8
Female7 58064.34 04034.41601.4
Ethnicity      <0.001
Whites18 62061.311 32037.34401.4
Minorities1 72059.31 10037.9802.8
Age      <0.001
<65 years3 94064.62 12034.8400.7
65–69 years5 80062.03 38036.11801.9
70–74 years4 46057.93 14040.81001.3
75–79 years3 28058.22 24039.71202.1
80–84 years1 84066.288031.7602.2
>84 years1 08060.068037.8402.2
Geography      <0.001
Northeast3 42066.51 66032.3601.2
Midwest5 88065.32 94032.71802.0
South8 74056.56 50042.02401.6
West2 30064.21 24034.6401.1
2007       
Gender      <0.001
Male13 26062.87 68036.41600.8
Female8 42068.83 72030.41000.8
Ethnicity      <0.001
Whites19 86065.510 26033.82200.7
Minorities1 82061.11 14038.3200.7
Age      <0.001
<65 years4 36068.31 92030.11001.6
65–69 years5 58061.63 44038.0400.4
70–74 years4 20061.42 64038.600.0
75–79 years3 30064.21 76034.2801.6
80–84 years2 70068.91 22031.100.0
>84 years1 54077.042021.0402.0
Geography      <0.001
Northeast4 38075.51 34023.1801.4
Midwest5 48066.02 74033.0801.0
South9 22060.26 06039.6400.3
West2 56066.71 22031.8601.6
2010       
Gender      <0.001
Male18 04069.07 96030.41600.6
Female10 18072.73 78027.0400.3
Ethnicity      <0.001
Whites26 14070.610 72029.01600.4
Minorities2 04065.81 02032.9401.3
Age      <0.001
<65 years5 96071.82 30027.7400.5
65–69 years7 20068.63 24030.8600.6
70–74 years6 16068.82 76030.8400.4
75–79 years4 10068.61 86031.1200.3
80–84 years3 22071.21 26027.9400.9
>84 years1 58082.334017.700.0
Geography      <0.001
Northeast5 06073.31 82026.4200.3
Midwest8 28076.02 54023.3800.7
South11 46064.66 22035.1600.3
West3 36074.01 16025.6200.4
Total       
Gender      <0.001
Male54 66063.330 58035.41 1201.3
Female31 88068.814 00030.24401.0
Ethnicity      <0.001
Whites79 76065.740 34033.21 3001.1
Minorities6 66060.34 20038.01801.6
Age      <0.001
<65 years16 50067.67 56031.03401.4
65–69 years23 08063.812 72035.23801.0
70–74 years18 38062.210 88036.92600.9
75–79 years14 24064.57 56034.22801.3
80–84 years9 28068.54 06030.02001.5
>84 years5 06072.51 82026.11001.4
Geography      <0.001
Northeast15 64070.16 42028.82601.2
Midwest23 72069.210 12029.54601.3
South36 90061.023 04038.15801.0
West10 02067.24 74031.81601.1
Years      <0.001
200116 24062.99 00034.95602.2
200420 40061.112 44037.35401.6
200721 68065.011 40034.22600.8
201028 22070.211 76029.32000.5
Total86 54065.244 60033.61 5601.2

The choice of treatment was associated with multiple demographic factors (Table 1). Specifically, URS was performed more often in women across all years (68.7–72.7%, P < 0.001). URS also was performed more commonly among White patients (61.3–70.2%), whereas ESWL was used more commonly in patients from ethnic minorities (32.9–45.6% P < 0.001). Patients aged ≥80 years underwent URS more frequently than those aged <80 years old (60.0–82.3%, P < 0.001). URS was more commonly performed in the Northeast (62.2–75.5%, P < 0.001) and least often in the South (56.5–64.6%, P < 0.001) where ESWL was more commonly performed. No significant differences were seen for UL in terms of gender, ethnicity, age or geography.

Logistic regression analysis was carried out to evaluate the influence of demographic factors and time on whether patients underwent surgical treatment for stone disease (Table 2). Men were more likely to undergo surgery than women (OR = 1.15, P < 0.001). Patients from ethnic minorities (OR = 0.84, P = 0.004) and, in particular, Black patients (OR = 0.77, P = 0.001) were less likely to undergo surgical treatment than White patients. Patients aged <65 or >84 years old had a lower probability of being treated (OR = 0.92–1.0) than those aged 65–84 years. Patients in the West were less likely to receive surgical treatment than in other parts of the country (OR = 0.76, P < 0.001). the year of diagnosis had no impact on the likelihood of receiving treatment (P > 0.05).

Table 2. Multivariate logistic regression analysis examining likelihood of surgical treatment for ureteric stone disease.
CategoriesTreatment vs no treatment
ORCIP
Gender   
Male1.151.07–1.29<0.001
Female1.00  
Patient ethnicity   
White1.000.66–0.900.001
Black0.770.75–0.950.004
Ethnic minorities (including Black patients)0.84  
Geography   
Northeast1.000.89–1.100.89
Midwest0.990.86–1.040.27
South0.950.67–0.86<0.001
West0.76  
Age   
<65 years1.001.12–1.36<0.001
65–69 years1.231.18–1.45<0.001
70–74 years1.311.14–1.42<0.001
75–79 years1.271.12–1.44<0.001
80–84 years1.270.79–1.080.29
>84 years0.92  
Year   
20011.000.91–1.100.95
20041.000.91–1.100.99
20071.000.91–1.090.98
20101.00  

Logistic regression analysis was also carried out to evaluate the influence of demographic factors and time on the choice of stone procedure if patients were treated surgically (Table 3). Female gender was more likely to be associated with treatment via URS (OR = 1.25, P < 0.001), while minority ethnicity was associated with lower odds of treatment with URS (OR = 0.79, P = 0.01). Patients aged 65–80 years were less likely to be treated with URS (OR = 0.63–69, P = 0.001–0.009) as were patients residing in the South (OR = 0.68, P < 0.001). Treatment in later years of the study was associated with higher odds of being treated with URS (OR = 1.33 P = 0.009).

Table 3. Multivariate logistic regression analysis examining the likelihood of type of surgical treatment for ureteric stone disease.
CategoriesURSESWLUL
ORCIPORCIPORCIP
Gender        0.19
Female1.251.12–1.40<0.0010.810.72–0.91<0.0010.670.37–1.23 
Male1.00  1.00  1.00  
Patient ethnicity      1.00  
White1.000.59–0.960.021.001.00–1.630.0472.190.85–5.660.11
Black0.750.66–0.950.011.281.02–1.480.031.970.91–4.250.09
Ethnic minorities (including Black patients)0.79  1.23     
Age         
<65 years0.820.62–1.070.151.200.91–1.590.191.700.37–7.810.49
65–69 years0.680.53–0.890.0041.451.12–1.890.0061.440.32–6.350.63
70–74 years0.630.49–0.830.0011.591.21–2.070.0011.050.23–4.920.95
75–79 years0.690.53–0.910.0091.431.09–1.880.011.470.32–0.680.62
80–84 years0.830.61–1.120.201.170.87–1.580.292.380.50–11.340.28
>84 years1.000.66–0.95 1.00  1.00  
Geography         
Northeast1.000.82–1.150.721.000.87–1.220.761.000.53–2.430.74
Midwest0.970.58–0.79<0.00011.031.30–1.76<0.0011.140.33–1.440.32
South0.680.74–1.110.351.510.91–1.380.270.690.23–1.960.47
West0.91  1.12  0.68  
Year         
20011.000.79–1.070.131.000.95–1.290.211.000.45–1.530.41
20040.920.92–1.250.861.110.84–1.150.790.830.15–0.720.002
20071.071.14–1.550.0090.980.69–0.940.0050.330.04–0.36<0.001
20101.33  0.80  0.12  

Discussion

The prevalence of stone disease is increasing in the US population. In the present study, we examined nationwide trends in ureteric stone disease and accompanying surgical treatments from 2001 to 2010 by using data from Medicare beneficiaries. While the prevalence of ureteric calculi increased by 59% from 2001 to 2010 in the Medicare population, the rate of surgical treatment remained constant at ∼38%.

Notable changes in the choice of treatment methods for ureteric calculi were seen over the study period. the use of URS procedures increased (OR = 1.33, P = 0.009) compared with ESWL, whose use declined over time. UL played only a limited role in treatment. the change in treatment patterns between URS and ESWL may be a reflection of improvements in URS. Although the 2007 Joint European Association of Urology and AUA Nephrolithiasis Guideline Panel states that both URS and ESWL represent acceptable first-line treatments for proximal ureteric calculi, recent data have highlighted better proximal and distal stone-free rates for URS compared with ESWL [14]. Salem [15], for example, reported a 25% higher stone-free rate after URS compared with ESWL for proximal ureteric stones <10 mm in size in a randomized controlled trial of 200 patients (P < 0.05). A meta-analysis reported by Aboumarzouk et al. [16], encompassing 1205 patients from seven randomized controlled trials, showed that URS resulted in a stone clearance rate six times greater than ESWL regardless of stone size or location (OR = 6.18, P < 0.001), although at the cost of a doubled complication rate (P = 0.01). Several randomized controlled trials also showed higher stone-free rates with URS for distal ureteric stone disease [17-20]. For instance, Zeng et al. [20] reported a 93.3% stone clearance with URS vs 78.1% with ESWL in 390 patients (P < 0.05); retreatment rates were higher in patients treated with ESWL (11.9 vs 2.2%, P < 0.05). Similarly, Peschel et al. [18] reported that treatment with URS resulted in a faster stone-free rate (0.2 vs 10.8 days, P < 0.001) compared with ESWL. Interestingly, given the superior performance of URS over ESWL, several studies have also reported the superior cost performance of URS over ESWL in the treatment of ureteric calculi [17, 21-23]. For instance, Wolf et al. [22] reported higher costs for using ESWL to treat distal ureteric calculi ($6754 vs $5555) when the costs of complications and retreatment were considered, while Parker et al. [21] reported not only a lower initial cost burden of treatment with URS vs ESWL ($7575 vs $9507, P < 0.001) but also a lower overall cost of treatment ($9378 vs $15 583, P < 0.001) for proximal ureteric calculi. Time to convalescence, however, has been reported to be equal between URS and ESWL (5.3 vs 5.8 days, P = 0.32) [17].

Multiple factors influenced whether patients underwent surgical treatment. Indeed, locoregional, racial and gender-based variation in the treatment of disease have been reported in the past, which has been at least partially attributed to the lack of consensus among physicians regarding which services are required and to differing styles of practice [24-29]. In the present study, patients at the extremes of the age range in the study cohort, i.e. <65 or >84 years old had a lower probability of being surgically treated for stone disease (OR = 0.92–1.0). This may be attributable to increased attempts at spontaneous stone passage because of better health (patients <65 years) or poorer surgical candidacy (patients >84 years). If patients were treated, those aged 65–79 years old were more likely to be treated with ESWL, perhaps suggesting a greater role for non-invasive surgery in elderly patients. The geographical distribution of increased URS treatment of ureteric calculi in the Northeast vs less frequent URS use in the South mirrors that of the geographical variations in treatment patterns previously reported by Wang et al. [30] who noted that ESWL predominated over URS in the South and the West, while URS predominated in the Northeast and Midwest.

Most interestingly, men were more likely to undergo surgical treatment than women (OR = 1.15, P < 0.001), while patients from ethnic minorities, in particular Black patients, were less likely to undergo this (OR = 0.77, P = 0.001). If patients were surgically treated, however, female gender was more likely to be associated with treatment via URS (OR = 1.25, P < 0.001), while minority ethnicity was instead associated with a high odds of treatment with ESWL (OR = 1.23, P = 0.03). These discrepancies in care may reflect persistent differences in the availability of medical services, financial barriers, differences in patient perception stemming from culture, language and acceptance of treatment, as well as divergent provider beliefs and behaviours [31, 32]. the unequal use of surgical techniques according to ethnicity has also been reported for other surgical treatments. Yu et al. [33] reported that White Medicare beneficiaries were more likely to be treated with newer procedures for BPH, such as transurethral needle ablation (OR = 2.33, P < 0.001), transurethral microwave therapy (OR = 1.96, P < 0.0001) and laser prostatectomy (OR = 1.36, P < 0.001) compared with Black Medicare beneficiaries. Similarly, Small et al. [34] noted that Hispanic patients were less likely than White patients to undergo nephron-sparing surgery for Stage I kidney cancer in the USA (OR = 0.90, P < 0.001). Anger et al. [35] reported that Asian-American/Pacific Islanders and Black women underwent fewer sling procedures for stress urinary incontinence than White women (2.5 and 7.1 vs 13.1%, respectively; P < 0.01). Additionally, women from ethnic minorities experienced a higher likelihood of non-urological complications (OR = 2.02, P < 0.05) and urinary obstruction (OR = 2.3, P < 0.05).

The most similar study to the present study was reported by Scales et al. [36], who assessed the use of ESWL and URS in Medicare beneficiaries from 1997 to 2007 for upper urinary tract calculi, where both renal and ureteric calculi were considered jointly. Contrary to our findings, they reported that women were less likely to undergo URS (OR = 0.84, P = 0.006). Neither race, age, income, education, nor the presence of comorbidities influenced the choice of surgical procedure. the present study may have yielded different results because of the different timeframe studied or the consideration of additional factors such as patient income, surgical setting, surgeon volume and facility volume by Scales et al. the Scales et al. study, for example, focused on the influence of provider and facility volume as well as duration of practice on initial procedure selection, whereas such factors were not considered in the present study.

The present study has several limitations. First, the trends seen in this Medicare-based population may not be generalizable to the general population, as Medicare beneficiaries are mainly aged >65 years, but stone disease tends to peak between 40–50 and 60–70 years of age [9, 37]. While these trends also reflect the US experience, which may be different from that in other countries, evidence does exist of the increasing use of URS at the expense of ESWL in European countries. For instance, Turney et al. [38] noted that the use of ESWL for ureteric calculi remained roughly stable in the UK from 2000 to 2010, while the use of URS more than doubled. Next, the dataset used did not contain provider-level data to ascertain potential provider bias. Childs et al. [39] reported that treatment selection for urolithiasis could be significantly affected by surgeon-specific factors; for example, a greater use of URS was associated with academic urology practices and more recent urological training, whereas ESWL was associated with longer time since training, community practice settings, and shockwave lithotripter ownership. Scales et al. [36] also noted an increased use of URS in urologists who had completed training recently (OR = 1.05 per year, P = 0.023); this may be partially attributable to the fact that all US endourology programmes have quotas for percutaneous surgery and ureteroscopy but urologists only have to perform 10 ESWLs annually, implying that recent graduates of residency programmes would be more comfortable with URS than with ESWL. This was confirmed by Matlaga et al. [40] who reported that urologists mainly used URS immediately after training (52.0 vs 36.7%), while more senior urologists tended to favour ESWL in the management of upper urinary tract calculi (60.5 vs 41.2%). These factors may also have influenced the increasing use of URS as seen in the later years of our study (OR for URS = 1.33, P = 0.009, in 2010). Our dataset unfortunately did not contain this type of provider-level data, or other associated elements, such as surgeon volume or physician ownership of lithotripsy units, to further explore this possible source of bias which may have also influenced geographical biases toward the type of surgical treatment offered to patients. Another critical limitation of this study is that stone size and location were unavailable as the Medicare Public Use files represent only a billing-oriented claims database. Medicare billing codes may not reliably distinguish between renal and ureteric calculi [41]. The study was retrospective and non-randomized in nature, although sample size was large. In addition, the role of patient preferences, e.g. for non-invasive techniques such as ESWL, could be not be assessed [17].

In conclusion, the surgical treatment of ureteric calculi changed significantly between 2001 and 2010. the use of URS expanded at the expense of ESWL and UL. Multiple inequalities existed in overall surgical treatment rates and in the choice of treatment. Age, gender, ethnicity and geography influenced both whether patients underwent surgical intervention and the type of surgical approach used.

Conflict of Interest

None declared.

Abbreviations
URS

ureteroscopy

UL

ureterolithotomy

OR

odds ratio

ICD-9

International Classification of Diseases 9th edition

CPT

Current Procedure Terminology

Appendix: Appendix 1 ICD-9 and CPT Codes for Stone Disease Diagnosis and Treatment and Covariates

Diagnosis codes for stone disease:
ICD-9 diagnosis codes: calculus of kidney 592.0; uric acid nephrolithiasis 274.11; calculus of ureter 592.1; urinary calculus, unspecified 592.9;
Procedure codes for stone disease:
ICD-9 Clinical Modification procedure codes:
URS 56.0; ESWL 98.5, 98.51;
UL 56.2;
CPT-codes:
URS 52352, 52 353; ESWL 50590; UL 50610, 50 620, 50 630, 50 945;
Covariates:
Gender: male, female; Age: <65, 65–69, 70–74, 75–79, 80–84, >84 years; Ethnicity: White patients, patients from ethnic minorities (Black, Asian, Hispanic, Native North- American, other patients); Year of treatment: 2001, 2004, 2007, 2010; Geography: Northeast (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, Pennsylvania, New Jersey), Midwest (Wisconsin, Michigan, Illinois, Indiana, Ohio, Missouri, North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Iowa), South (Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Kentucky, Tennessee, Mississippi, Alabama, Oklahoma, Texas, Arkansas, Louisiana), West (Idaho, Montana, Wyoming, Nevada, Utah, Colorado, Arizona, New Mexico, Alaska, Washington, Oregon, California, Hawaii)

Ancillary