On June 21, 2022, the US Supreme Court issued a ruling in Marietta Memorial Hospital Employee Health Benefit Plan v. DaVita Inc. that could have major implications for the financing of dialysis care.1 The case centered on an employer-provided health plan that designated all dialysis facilities as out of their preferred network of providers. DaVita Inc., a large US dialysis provider, filed suit, claiming that the health plan violated the Medicare Secondary Payer (MSP) statute by illegally discriminating against patients with kidney failure requiring hemodialysis in the determination of benefits. Resolving split rulings on similar cases by lower courts, the Supreme Court ruled 7–2 in favor of the health plan, which argued that there was no differential treatment of patients with kidney failure since the preferred network restrictions applied to all the plan's beneficiaries. The Court's decision was controversial, with many stakeholders issuing statements strongly critical of the ruling. In addition to controversy over the Court's legal interpretation, the ruling has generated public health concerns. There are several ways in which the widespread adoption of the Marietta health plan's “out-of-network” strategy could affect patients and dialysis facilities. Unlike Medicare, which administers prices, private health insurers must negotiate the prices they pay for dialysis. Two companies currently provide the majority of US dialysis care. Having a significant market share provides dialysis organizations with bargaining leverage, enabling them to charge private insurers higher prices compared with Medicare. An analysis of a large dialysis provider's financial filings found that commercial payers represented only 11% of their payer population but contributed to 33% of their revenue stream.2 Another analysis found that the median price paid by private insurers for dialysis was six times higher than the price paid by Medicare.3 After designating dialysis facilities as out of network, the Marietta health plan agreed to pay facilities 87.5% of Medicare's allowable rate after excluding patient costs. This was substantially less than the typical price paid by other private insurers. If other private insurers follow the Marietta health plan's lead by adopting an out-of-network strategy for dialysis coverage, lower insurance payments would reduce dialysis facility revenues. This would occur regardless of how dialysis providers respond. Dialysis facilities could respond by continuing to care for affected patients while being reimbursed at a fraction of what they otherwise would have received. Incentives to keep facilities operating at or near capacity and to disperse fixed costs could motivate this response. Alternatively, rather than accepting lower out-of-network prices from private insurers, dialysis facilities might refuse to treat patients enrolled in these private health plans from fear that doing so would lead other insurers to take a similar out-of-network approach. This would force patients to discontinue their employer-provided health insurance and make Medicare the primary payer to continue receiving dialysis. Dialysis units would then receive the standard Medicare payment, which is also less than the typical private insurance payment. DaVita shares fell 11% in the wake of the Supreme Court ruling, reflecting concerns about its effect on profits. Decreased dialysis facility revenues resulting from the Court's ruling could interfere with patient care. One way that patients might be affected is through dialysis facility closures. The Medicare margin is the difference between what Medicare pays for dialysis and average dialysis cost reported by a facility. It roughly indicates whether a facility could continue operating from Medicare payment rates alone. A report from the Medicare Payment and Advisory Commission found that the average Medicare margin in 2020 was 2.7%,4 suggesting that many facilities could continue to operate if all of their treatments were reimbursed at Medicare rates. Yet, the average margin in 2020 was negative for rural facilities and for the smallest 40% of facilities, and recent inflationary pressures could erode margins. Up until now, dialysis facility closures have not had a large effect on Medicare's dialysis population. This could change if decreased reimbursement prevents facilities from fully covering dialysis costs. This is important for patients because dialysis facility closures are associated with higher rates of hospitalization and possible increases in mortality.5 Vulnerable patient populations may be most affected by future dialysis facility closures. In adjusted models, dialysis center closures were more likely to affect Medicare beneficiaries of Black race and those with Medicaid and more medical comorbidities.6 These vulnerable populations are also more likely to be “safety-net reliant,” where patients are either uninsured or only qualify for state Medicaid upon the initiation of dialysis. Hospital-based dialysis facilities, which care disproportionately for vulnerable safety-net reliant populations, are at increased risk of closure and may be particularly affected by the ruling.7 Lower revenues could also affect the quality of dialysis care, as has been observed in the hospital setting.8 Since the ESRD Prospective Payment System was first enacted in the 1980s, limited Medicare payment for dialysis has fueled concerns about the quality of US dialysis care. Yet, many of these concerns have not come to pass, and there have been recent improvements in mortality and hospitalization rates among patients receiving dialysis.9 Additional revenue from private insurance may help to maintain quality in the setting of restricted Medicare reimbursement. If so, then a loss of this additional revenue could impair quality for all patients, possibly reversing recent trends in improved health outcomes. If more patients switch to Medicare in the setting of declining facility revenues, then Medicare's quality and value-based initiatives would assume a larger role in helping to maintain quality. While the widespread adoption of an out-of-network strategy by private health plans would likely decrease revenue to dialysis facilities and their parent organizations, the financial effects on patients enrolled in private health plans are less certain. As a secondary payer, Medicare provides coinsurance support for dialysis treatments. This is true even when a dialysis facility is out of network. In the case in question, the Marietta health plan continued to pay for patients to receive dialysis, albeit at a rate more commensurate with Medicare fees. The health plan noted in their brief to the Court that Medicare regulations prevent “balance billing,” where providers bill patients for differences between what the provider charges and what the insurer pays. Taken together, this suggests that patients enrolled in private health plans are protected from higher out-of-network dialysis costs. Yet, the patient in the lawsuit gave up their private insurance and switched to Medicare as their primary insurance provider. In their brief to the court, DaVita Inc. equated out-of-network designation with an absence of coverage, noting that other patients will be forced to forgo their private insurance. Switching from private insurance to Medicare would lead to increased out-of-pocket costs for all health care expenses because patients would be responsible for Medicare's coinsurance. This could add to the financial strain that many dialysis patients already experience. The financial consequences of switching to Medicare could be particularly devastating for patients whose family members are dependents on their private insurance plan. It is difficult to reconcile these two contrasting forecasts of the Court ruling's effects on patient finances. Ultimately, the financial effects on patients will hinge on several factors. Do dialysis facilities continue to accept these patients, despite lower reimbursement? To what extent do protections against balance billing mitigate financial risk to patients and protect patients from uncertainty associated with efforts by dialysis facilities to obtain the full charge? What proportion of higher coinsurance payments does Medicare cover in its role as a secondary payer? The effects of the ruling on patient and provider finances will also depend critically on the number of insurers that follow the Marietta health plan's lead. Several factors might limit the broad adoption of this practice. The case in question involved a self-insured employer-provided health plan, where employers assume insurance risk. Self-insured plans are regulated by the Employee Retirement Income Security Act (ERISA), which has relatively few network adequacy protections. By contrast, the many privately insured patients enrolled in fully insured plans (where an insurer assumes risk) may benefit from state and federal network adequacy protections. Market mechanisms could also limit the number of insurance plans that adopt an out-of-network strategy if health plans decide to keep some dialysis facilities in network for fear of losing customers. In response to the Supreme Court ruling, Fresenius, another large dialysis provider, stated “We do not expect that this case triggers a major change in the relationship between providers and health insurers as the vast majority of those in the industry are interested in the well-being of patients.”10 They cited corporate interests in promoting equity as another reason why major changes were unlikely.10 Uncertainty about the ruling's effects on both patients and dialysis facilities underscores the need to monitor private health plans and patients' access to dialysis services. Policy strategies could also mitigate potential consequences of the ruling. The federal government could enact regulatory reforms to modify the law, exempting ERISA plans from network-adequacy regulations, or to clarify MSP provisions. Recently, Congress proposed legislation aiming to address the ruling by requiring insurers to treat dialysis like other chronic conditions. Protection organizations, such as the National Association of Insurance Commissioners, could help to ensure that consumers have the information they need about dialysis network adequacy. Government and charities could provide financial assistance to patients and dialysis facilities that are most vulnerable to out-of-network designation. A recent Supreme Court ruling may lead private insurers to adopt a strategy of making all dialysis providers out of network. If this practice becomes widespread, it will reduce dialysis facility revenues, which could affect patients' access to dialysis care and the quality of care provided. However, the degree to which other insurers will adopt an out-of-network strategy, and its effects on individual patient finances, remains uncertain.