Drivers of Cost Variability of Ureteroscopy with Laser Lithotripsy at an Academic Institution

Abstract

Objective:

Ureteroscopy with laser lithotripsy (URS/LL) requires significant disposable equipment including wires, baskets, lasers, and stents. Surgeons choose this equipment based on preference, with higher- and lower-cost options available. We sought to explore factors that affect cost variability among urologists performing URS/LL within a single academic medical center.

Patients and Methods:

We retrospectively reviewed all patients who underwent URS/LL at our institution between September 2022 and June 2023. A weighted cost for each item’s contribution to total cost was generated. Bivariate and then multivariate median regression models were generated to identify variables associated with higher total surgical cost. Statistical significance was considered p < 0.05.

Results:

A total of 311 patients underwent URS/LL during the study period with 14 different surgeons. The total median cost of disposable equipment for the entire cohort was $1488/operation. On multivariate regression, basket cost above the cohort median or specialized catheter cost above the cohort median was associated with increased total surgical cost (p < 0.001). Fellowship training in endourology was associated with a decreased cost of $90.40 per case (p < 0.05).

Conclusions:

There is significant variability in the cost of ureteroscopy, even at a single institution where all surgeons have access to identical supplies. Attention to specific categories of equipment, which appear to be associated with higher total cost, as well as the potential differences in technique between surgeons with varied training, may help to identify opportunities for institutional cost savings.

Introduction

Nephrolithiasis is a chronic condition that leads to high health care costs, given its prevalence of up to 8.8% of the U.S. population.¹ Approximately 10% to 15% of patients diagnosed with nephrolithiasis will require surgical intervention each year.^2,3 The most common surgical treatment is ureteroscopy with laser lithotripsy (URS/LL).^4,5 URS/LL is minimally invasive, leads to high stone-free rates, and has a lower risk of renal injury than do more invasive procedures such as percutaneous nephrolithotomy.^4,6

The total direct health care cost of nephrolithiasis in the United States is estimated to be $4.5 billion per year.⁷ There is significant variability in the cost of surgery between surgeons performing the same procedure, even within the same department, suggesting that the method in which a procedure is performed may have significant potential to affect total costs.⁸ Surgeons often choose equipment based on personal preference, with higher- and lower-cost options available and with different preferences for items in order to complete identical surgical procedures.^9,10 Disposable equipment is estimated to account for approximately 50% of costs generated by activity within the operating room (OR).¹¹

Surgeons have demonstrated cost variability within the same department for many surgical procedures, including URS/LL.¹² Although several studies have identified that such cost variation exists, the drivers of this variability have not been identified. The aim of this study was to evaluate the factors associated with cost variability among surgeons performing URS/LL within a single institution.

Patients and Methods

We retrospectively reviewed the records of all patients who underwent URS/LL for the treatment of kidney stones at an urban, academic medical center between September 2022 and June 2023. All patients over age 18 who underwent URS/LL during the study period were eligible for inclusion. The study was approved by our institutional review board.

Patient demographic data such as age, sex, race/ethnicity, and preferred language were recorded. Records were also reviewed for clinical variables including prior stent, prior stone history, size of the largest kidney or ureteral stone, body mass index (BMI), and anesthesia time. The identity of the attending surgeon was recorded. Surgeon-specific data were recorded including the number of cases performed during the study period, the surgeon’s years of experience, and if the surgeon had completed fellowship training in endourology.

Total surgery costs were collected from cost receipts generated by the electronic health record, which represents a list of the institutional procurement cost of each item used. The costs of operative time and personnel were excluded as they were outside the scope of this study. All disposable items used during the study period were assigned to one of eight categories: baskets, specialty catheters, lasers, sheaths, stents, wires, miscellaneous, and single-use ureteroscopes. The miscellaneous category included low-cost surgical items such as gauze and saline. Specialty catheters included open-ended ureteral catheters, dual-lumen catheters, and urethral catheters.

Median costs were calculated for the equipment used in each category per surgery. To better understand the factors associated with cost differences between surgeons, an item-weighted cost was used to identify which disposables were being used and the frequency at which they were used. A weighted cost for each item’s contribution was created, as has been done previously to analyze the cost variability of surgical procedures.^13
–15 This value was created to represent the percentage of total cost that each disposable item category contributed to the overall cost of surgery on average. The item-weighted cost values were generated by totaling up the cost of all disposable items used by a surgeon across operations and then dividing by the total number of operations that were performed.

Categorical variables were compared using Chi-squared analysis. A Shapiro–Wilk analysis revealed that the cost data were not normally distributed. Therefore, disposable cost variables were modeled using median values to avoid potential outlier cases from skewing the results of the analysis. A bivariate median regression model assessed the association of 12 different potential variables with cost. All single-use ureteroscopes that were used had identical costs, so they were not considered as a potential variable (only one model of disposable scope was used).

Variables that had a p < 0.1 in bivariate analyses were then selected for the multivariate median regression. The multivariate model containing both continuous (e.g., anesthesia time) and categorical variables was constructed to identify variables associated with total surgery cost differences. Endourology fellowship training and disposable item costs used above the median cohort cost for baskets and catheters were included as categorical variables. Anesthesia time, basket cost above median, and catheter cost above median were all variables selected based on statistically significant bivariate median regression results. Endourology fellowship training was included in the multivariate regression because of its potential to be a confounding variable in the model. Statistical significance for all tests and models was considered p < 0.05. Statistical analyses were conducted utilizing IBM SPSS Statistics for Mac, version 29 (IBM Corp., Armonk, NY, USA).

Results

In total, 311 patients underwent URS/LL during the study period. One hundred and sixty-eight patients (54.0%) identified as Spanish/Hispanic/Latino, and 80 patients (25.7%) indicated Spanish as their preferred language. Two hundred and thirty-five patients (75.6%) had a prior history of nephrolithiasis, and 121 patients (38.9%) had a stent placed previously in their lifetime that was documented within the electronic medical record (Table 1). The median size for the largest stone in the kidney or ureter on the operative side was 8 mm (interquartile range [IQR] 6–11), with most stones measuring between 6 mm and 10 mm (56.0%). Median BMI was 29.2 (IQR 25.8–34.6), median age was 55 (IQR 43–65), and the median anesthesia time was 97 minutes (IQR 79–123). The median total cost of disposable equipment used was $1488 (IQR $1114–$2098; Table 1). The median cost of disposable equipment by category is shown in Table 2. Most of the cases (88.7%) were done by surgeons who were in the “high-volume” category, which meant that they performed >20 cases in the study period. Two of these six surgeons had formal endourology fellowship training.

Table 1.

Patient Demographic Data and Median Characteristics

	n (%)
Patients	311
Median age at procedure (IQR)	55 (43–65)
Race
White	46 (14.8%)
Black	54 (17.4%)
Asian	12 (3.9%)
Other	161 (51.8%)
Patient unavailable/declined	38 (12.1%)
Ethnicity
Not Spanish/Hispanic/Latino	117 (37.6%)
Spanish/Hispanic/Latino	168 (54.0%)
Patient unavailable/declined	26 (8.4%)
Preferred language
English	221 (71.1%)
Spanish	80 (25.7%)
Other	10 (3.2%)
Prior stent
Yes	121 (38.9%)
No	190 (61.1%)
Prior stone history
Yes	235 (75.6%)
No	76 (24.4%)
Largest stone
≤5 mm	42 (14.3%)
6–10 mm	164 (56.0%)
>10 mm	87 (29.7%)

Clinical characteristics	Median (IQR)
Largest stone size, mm	8 (6–11)
BMI	29.2 (25.8–34.6)
Age, years	55 (43–65)
Anesthesia time, minutes	97 (79–123)
Total surgery cost, $	1488 (1114–2098)

BMI = body mass index, IQR = interquartile range.

Table 2.

Median Total Cost Categorized by Disposable Item Group Type

Disposable item category	Median cost in $ (IQR)	Median number of items used in category per case (IQR)
Basket	377.63 (298.94–577.63)	1 (1–2)
Catheter	120.63 (118.75–137.47)	2 (1–2)
Laser	283.33 (263.00–546.33)	1 (1–2)
Sheath	174.68 (0–287.78)	1 (0–2)
Stent	202.35 (116.90–202.35)	1 (1–1)
Wire	152.76 (142.32–188.84)	2 (2–3)
Miscellaneous	124.22 (104.04–189.32)	8 (7–10)

URS/LL was performed by 14 surgeons during the study period. The total item-weighted cost of disposable equipment for the entire cohort was $1598/operation, of which $386.47 (24.2%) was attributed to lasers, $374.67 (23.4%) to baskets, $171.16 (10.7%) to stents, $165.29 (10.3%) to sheaths, $156.97 (9.8%) to wires, $111.97 (7.0%) to catheters, $159.48 (10.0%) to miscellaneous items, and $72.35 (4.5%) to single-use ureteroscopes. Single-use ureteroscopes used in this cohort each individually contributed $1500 in cost, but owing to the low frequency of their use, they represented a small portion of the item-weighted cost. Of the 311 cases, multiple baskets were used in 83 (26.7%) cases and multiple catheters were used in 179 (57.6%) of cases.

A total of 12 independent variables were selected for bivariate median regression analysis using total surgery cost as the outcome of interest (Table 3). The variables that had a p < 0.1 were anesthesia time, and a basket or catheter supply cost was above the cohort median. Other variables such as largest stone size, surgeon years of experience, and median laser cost had p-values >0.1.

Table 3.

Bivariate Median Regression for Total Surgery Cost

Predictors	Coefficient (β)	p-Value
Anesthesia time	6.41	<0.001^*
Stone size	15.00	0.214
Years of experience	−7.16	0.290
Endourology fellowship training	−37.00	0.747
URS case volume (>20 cases)	244.00	0.166
Median basket cost >377.63	837.00	<0.001^*
Median catheter cost >120.63	722.00	<0.001^*
Median laser cost >283.33	−105.00	0.352
Median sheath cost >174.68	−94.00	0.386
Median stent cost >202.35	−117.00	0.466
Median wire cost >152.76	−51.00	0.675
Median misc cost >124.22	100.00	0.382

p-Value considered significant <0.05. Coefficient values are reported in dollars. Anesthesia time, stone size, and years of experience are continuous variables. Endourology fellowship training, URS volume, and cost variables represent categorical dummy variables.

URS, ureteroscopy.

p-values bolded in the table represent a statistically significant difference at the p < 0.05 value.

From these 12 variables, only 4 independent variables were chosen to create a multivariate median regression model on the dependent variable of total surgery cost (Table 4). The four variables chosen were anesthesia time, basket and catheter cost above cohort median, and endourology fellowship training. Results showed that higher than median costs of basket or specialized catheter equipment were associated with increased total cost (p < 0.001), when controlling for all other variables in the model. Endourology training was associated with decreased total surgery cost (p < 0.05). The pseudo R ² of the model was 0.336.

Table 4.

Multivariate Median Regression Model for Total Surgery Cost

Predictors	Coefficient (β)	p-Value
Anesthesia time	3.60	<0.001^*
Endourology fellowship training	−90.40	0.033^*
Median basket cost >377.63	586.60	<0.001^*
Median catheter cost >120.63	391.20	<0.001^*
Pseudo R ²	0.336

p-Value considered significant <0.05. Coefficient values are reported in $. Anesthesia time is a continuous variable. Endourology training and cost variables represent categorical dummy variables.

p-values bolded in the table represent a statistically significant difference at the p < 0.05 value.

Discussion

In this retrospective review of URS/LL performed by multiple urologists at a single institution, we demonstrate high variability in the use of endourological disposables, despite all surgeons having access to identical equipment. The use of stone baskets and specialty catheters more expensive than the group median for those categories was associated with increased total surgery cost, whereas endourology fellowship training was associated with decreased cost.

Standardization of operative equipment among surgeons within a department has been shown to reduce cost.^19,20 Simon et al. demonstrated that the creation of a standardized pick list led to decreased disposable costs of 32% among surgeons performing laparoscopic cholecystectomy.²¹ Our findings suggest that kidney stone surgery—with a high and varied amount of disposable supplies—may be particularly amenable to improvement via such efforts.

Okike et al. demonstrated that orthopedic surgeons performing a variety of surgical procedures have varied preferences for disposable equipment but that they cannot accurately estimate the cost of these supplies.²² It is perhaps not surprising that this leads to wide variability in costs within other surgical fields as well. Farber et al. found that neither residents nor attending urologists were able to accurately estimate the cost of commonly used disposable devices used in ureteroscopy.²³ Educating surgeons on the cost of disposable equipment used during surgery represents one possible avenue for reducing cost.^24,25 Gitelis et al. demonstrated that educating surgeons on the cost of disposable supplies resulted in a 10% reduction in supplies used.²⁴ Such cost savings may be possible in URS/LL through targeted education.

A reduction in surgery cost after the completion of fellowship training is a novel finding in kidney stone surgery but has been demonstrated in studies of other surgical specialties. For example, Stahl et al. demonstrated that minimally invasive surgical fellowship was associated with decreased cost for laparoscopic cholecystectomy and that years of surgeon experience did not contribute to cost variation.¹⁶ Interestingly, this study found that an increased number of cholecystectomy cases performed were associated with decreased cost, whereas the findings of our study found no such variation when controlling for other variables within the multivariate model.

Our bivariate median regression analysis also did not find the largest stone size to be associated with total surgery cost. This finding corroborates data from Mondschein et al., who found that after adjusting for operative time, there were no differences in the cost of disposable equipment based on stone size.¹⁵ Disagreement exists as to the extent to which the largest stone diameter best represents stone burden,^17,18 rather than stone volume or other such measurements, and so it is possible that our approach obscures an association between stone burden and surgical cost that may exist.

There are significant limitations in the present study. First, our definition of total surgical cost only captured the cost of disposable equipment but not upstream costs such as capital equipment or downstream costs such as those resulting from complications. Total cost also excluded OR time and personnel. Although these costs likely eclipse those of disposable supplies, they are less immediately under a surgeon’s control. Second, only two of the surgeons within this sample had completed an endourology fellowship. It is possible that the cost savings associated with their cases were influenced by individual preferences independent of their fellowship training. However, given the reproducibility of this finding across other surgical fields, it is worth exploring further. Third, there is likely substantial unmeasured variation in the complexity of surgical cases chosen by stone surgeons. Stone volume and complexity are particularly poorly quantified by maximum stone diameter, though this remains the most commonly reported metric (cyst). Further research is needed to identify variables that are more able to accurately measure surgical complexity in endourology. Finally, although the present study highlights the association between expensive stone baskets/specialty catheters and total surgical cost, it is difficult to translate this finding to specific recommendations for optimized supply lists. This is particularly the case across organizations that may have preferential pricing with particular vendors.

These limitations notwithstanding, we demonstrate significant cost variability in cases of URS/LL associated with varied use of disposable equipment in a group of surgeons. Attention to the cost of disposable supplies, selective standardization, and surgeon education regarding equipment cost may present opportunities to achieve cost savings in the surgical treatment of kidney stones.

Conclusions

This study demonstrates that there is significant variability in the cost of ureteroscopy, even at a single institution where all surgeons have access to identical equipment. Multivariate regression demonstrated that endourology fellowship training was associated with cost savings, whereas the use of expensive stone baskets or specialty catheters was associated with increased total costs.

Footnotes

Authors’ Contributions

T.B.: Data curation, formal analysis, methodology, writing—original draft, and writing—review and editing. I.A.: Investigation, methodology, supervision, and writing—review and editing. A.C.S.: Supervision, methodology, and writing—review and editing. D.R.: Conceptualization, supervision, methodology, and writing—review and editing.

Ethics

This study was approved by Albert Einstein College of Medicine IRB (2022-13966).

Author Disclosure Statement

The authors have no conflicts of interest, financial or otherwise, to report related to this study.

Funding Information

This study was funded by the Albert Einstein College of Medicine Summer Scholarly Fellowship.

Supplementary Material

Supplementary Table S1

Abbreviations Used

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Supplementary Material

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