Shockwave lithotripsy

Shockwave lithotripsy (SWL) has historically been the most common treatment method for small renal and ureteral stones. Selecting patients who are more likely to succeed with SWL may improve the clinical and cost-effectiveness of this treatment. Favorable characteristics include smaller stones, lower Hounsfield units (<1000), shorter skin-to-stone distance (<10 cm), and, in the case of lower pole stones, favorable lower pole anatomy, including infundibulopelvic angle and length. Also, evidence demonstrates that slowing SWL rate significantly improves treatment efficiency and reduces the cost of SWL by 50%. Although extra time is required for the treatment, there is higher treatment success and less need for auxiliary treatment.

Ureteroscopy

Use of endoscopy has become more common in recently trained urologists. Although the literature comparing ureteroscopy with SWL has been limited, studies demonstrate a clinical advantage of ureteroscopy for distal ureteral stones, with a lack of rigorous evidence to definitively compare outcomes for stones in other locations. Studies of economic outcomes of ureteroscopy versus SWL have found that, despite the heterogeneity and limited quality of the evidence, ureteroscopy may be cost-effective compared with SWL.

Flexible ureteroscopy, in particular, has enabled access to all renal calyces and direct visualization and removal of stones by a retrograde approach. Options for treatment include active extraction of fragments, typically with a ureteral access sheath, or a “dusting” technique with stent placement enabling small fragments to pass spontaneously over time. There is no consensus on the optimal technique, and studies regarding the comparative effectiveness of these approaches are ongoing. Future studies of the cost-effectiveness of these approaches will need to include short-term costs (eg, operating room time, supplies) and long-term costs (eg, future stone events and/or interventions).

Although flexible ureteroscopy is effective for small-to-medium size stones, the cost of the instruments, as well as maintenance, can be substantial. Furthermore, after one repair, the risk of requiring additional maintenance increases significantly, such that it may be cost advantageous to replace a damaged scope rather than repair it repeatedly. There are important techniques for maximizing the longevity of flexible ureteroscopes; these are likely to benefit both the provider and health system in reducing costs and ensuring functional equipment. These include displacing lower pole stones to more accessible calyces to prevent excessive torque, ensuring that the Holmium laser fiber is not advanced through a curved scope, and taking care not to fire the laser in the channel. Also, use of nitinol devices, smaller caliber laser fibers (ie, 200 μgm), and use of a ureteral access sheath for larger stone burdens may minimize strain on the scope. Careful supervision and education of trainees is needed to ensure these lessons are inculcated and the equipment is preserved. Finally, it may be that having the urology staff process and clean ureteroscopes themselves may reduce processing-related damages and save costs compared with central processing.

An area of investigation has been the cost-effectiveness of prestenting patients undergoing ureteroscopy. Chu and colleagues retrospectively studied 104 patients with upper tract (primarily ureteral) stones with a wide range of stone sizes (0.3–4 cm; median 1 cm). The investigators found that prestenting significantly reduced the total costs (direct and indirect) for treatment of patients with stones greater than 1 cm, even when assuming a cost of prestenting up to 6.2 times the current cost. A limitation of this study was use of reimbursement data, instead of actual cost data. Nonetheless, there seemed to be a cost advantage for prestenting patients with larger stone burdens undergoing ureteroscopy. Additional research is needed to better delineate the cost-effectiveness of endoscopic treatments for larger stone burdens, in terms of timing of stent placement, the use of staged procedures, and comparison with alternative approaches such as percutaneous surgery.

Percutaneous nephrolithotomy

Percutaneous nephrolithotomy (PCNL) remains the standard of care for treatment of large (>2 cm) and/or complex renal calculi. In addition to superior stone clearance for larger burdens, there is evidence that PCNL is cost-effective for these patients. Although PCNL does incur higher costs in the short-term based on an inpatient hospitalization and higher disposable costs, superior stone eradication leads to a long-term cost advantage.

Certain investigators have examined ways to further improve the cost-effectiveness of PCNL. Investigating predictors of cost of this procedure, Bagrodia and colleagues found that only stone burden independently predicted cost, and the main impact of large stone size related to the use of second-look flexible nephroscopy (SLFN). Follow-up study of the cost-effectiveness of SLFN was performed by Raman and colleagues, who reported that this procedure was cost advantageous for residual fragments greater than 4 mm but not for those less than or equal to 4 mm, based on future risk of stone events requiring treatment. The investigators discussed how their cost benefit analysis was dramatically influenced by assumptions regarding likelihood of stone events, the need for surgical treatment, and surgical costs.

There is also some evidence that increased surgical experience enables more efficient and effective treatment of PCNL. Hyams and colleagues reported a lower rate of 30-day mortality and ICU hospitalization for high-volume providers in a Maryland state database. Also, increased surgical experience has been associated with decreased operative time, which may have cost implications. This may also reflect the experience of the operating room staff because troubleshooting instrumentation for PCNL and overall efficiency can be improved with experienced personnel. Finally, operating and fluoroscopy time have been showed to decrease up to 60 cases within a learning curve. These data suggest that referral for treatment of PCNL to higher volume providers and/or institutions may be cost advantageous, though additional research in this area is needed.

The cost-effectiveness of PCNL has been compared with ureteroscopy for treatment of larger renal stones. Hyams and Shah recently demonstrated lower cost associated with ureteroscopy for 2 to 3 cm stones versus PCNL in a retrospective analysis with medium term follow-up. Higher cost for PCNL was based primarily on a high rate of second-stage treatment with PCNL, though there was superior stone clearance in this group of patients. The investigators framed a tradeoff in cost and stone-free rate, with the caveat that long-term follow-up was needed to assess the need for future interventions in patients with small residual fragments. The investigators concluded that, although PCNL was the standard of care, the cost-profile and clinical outcomes of ureteroscopy made it a reasonable option for patients with contraindications to or preference against percutaneous surgery.

In patients with bilateral large stone burdens, it is not clear whether simultaneous or staged PCNL is cost-advantageous. There has been one study in this area by Bagrodia and colleagues, who reported that synchronous bilateral PCNL decreased cumulative operative room time, length of stay, and cost, and thus was advantageous to patients and third-party payers. The investigators noted that physician reimbursement was significantly less compared with staged procedures, providing a disincentive to perform this procedure. This is an important point because a reimbursement scheme can influence practice patterns and provide a disincentive to render care that might be a cost-effective approach overall.

Finally, tubeless PCNL has become increasingly popular to decrease the morbidity and hasten the recovery from PCNL without conceding patient safety. Literature has demonstrated improvements in hospital stay, postoperative analgesic use, and urinary leakage, as well as in operative time. Although tubeless procedures may be cost-effective in properly selected patients, investigation in this area is needed because these patients frequently have ureteral stents placed and may have subsequent retrograde procedures and/or SWL.

Primary prevention

Primary prevention of stone disease has been considered in populations that may be at increased risk based on geography (ie, warmer climates), familial or medical risk factors, genetic testing, or changes in environment (eg, military deployment). Lotan and Pearle investigated the cost-effectiveness of primary prevention strategies using a decision-analysis model. They found that primary prevention of stones may be cost-effective depending on assumptions of cost, risk, and efficacy. Specifically, an intervention would be cost-effective if the incidence of disease was at least 1%, cost did not exceed $20 per person per year, and the strategy was at least 50% effective at stone prevention. Thus, these interventions may be worthwhile in certain populations, depending on risk, because there are low-cost interventions, such as education regarding water consumption, which can be considered. Indeed, Lotan and colleagues reported a cost model in which increased water intake would theoretically be cost-effective for a national payer system for prevention of stone disease.

Secondary prevention

First-time stone formers generally are counseled on conservative treatment measures, including dietary manipulations, to decrease risk of recurrence. These inexpensive interventions include increased water intake and dietary changes that have been shown to modulate stone risk. For recurrent stone formers, conservative treatment is generally insufficient because of the high rate of recurrence. Medical therapy is considered in these patients and has been shown to reduce risk of recurrence in certain patients. Importantly, however, these medications have side effects, inconvenience, and cost that can affect patient compliance. Although older studies found that screening and treating stone patients with medical therapy lowered costs, these studies did not necessarily account for the benefit of conservative treatment alone, the costs of metabolic evaluation, and that not all recurrent stones necessitate treatment. Nonetheless, more recent studies have concluded that medical treatment in known stone formers is likely to be cost-effective depending on assumptions regarding effectiveness, cost of therapy, and rate of stone recurrence.

Lotan and colleagues investigated the cost-effectiveness of conservative therapy versus drug treatment for first-time versus recurrent stone formers. In a decision-analysis model, they concluded that conservative treatment was cost-effective for first-time stone formers, whereas the higher cost of drug treatment strategies was justified for recurrent stone formers. Lotan and colleagues also performed an international comparison of cost-effectiveness of medical management strategies for recurrent stone disease. Contrastingly, they found that dietary treatment was the most cost-effective approach because of the relatively low cost of surgery (which was required infrequently) compared with medication (which was required daily). Empiric and directed medical therapy were more effective at controlling stone disease; however, they were not cost-effective because of the low likelihood of surgical intervention and the relatively low cost of surgery. This was true except in the United Kingdom where medication costs were sufficiently low so that empiric therapy was more cost-effective than conservative therapy. Thus, improving cost-effectiveness of medical therapy requires additional research to reduce costs of medical therapy, improve compliance, identify patients who are most likely to benefit, and to improve the efficacy of medical management itself.