The results of our study indicate that outpatient ‘day surgery’ after PKB may have lower institutional costs inclusive of all potential complications compared to inpatient observation for low-risk patients. Sensitivity analysis demonstrated that this relationship remained, even at high probabilities of complications and costs. Outpatient management after PKB can be considered in patients with low risk for bleeding, including lack of known risk factors, absence of advanced chronic kidney disease, normal post-procedure ultrasonography, and hemodynamic stability in the immediate hours following PKB.
Outpatient management after PKB is a safe alternative in low-risk patients [3
]. Despite this, routine use of the outpatient approach remains dependent on the practicing clinician. Proponents cite the institutional cost benefits, low complication rates, and the flexibility of risk stratification. It also allows patients to avoid hospitalization and recover at home. In addition, immediate [17
] and/or delayed (1–2 h) postbiopsy ultrasound [15
] could predict bleeding risk, providing additional reassurance prior to discharge. The latter was not modeled in this analysis, but the incremental cost of a limited renal ultrasound would fall well under the incremental cost difference observed in this study. Critics note that while a significant portion of complications will be detected early, there remain a large proportion of adverse events, perhaps as high as one third [16
], that are missed after discharge home. However, the vast majority of complications that occur after 12 h are minor with most major complications (89%) occurring prior to this [16
While the published literature supports the safety of outpatient management after PKB, it is important to recognize that this strategy still bears risk. While the observed risk of complications is low with no deaths reported in the literature among outpatients, it is unrealistic to conclude that ODS is safer than IO. The lower risk of complications and death may stem from the selection of lower risk patients or publication bias. This analysis postulated that the theoretical risk of death among outpatients would be higher than among inpatients, 0.15% compared to 0.10%. This assumption was based on the observation that delayed bleeds do occur [16
] and outpatients may be less likely to promptly recognize the symptoms of a major complication. It also raised the required threshold needed to reject the null hypothesis that IO was less costly inclusive of all complications. Given that this analysis ultimately favored outpatient management, this further strengthens our conclusion that ODS is less costly from the institutional perspective.
Despite the observed safety of outpatient PKB inclusive of these risks of delayed bleeds, some clinicians may prefer the perceived safety of IO, and this preference may remain despite knowledge of the considerable costs associated with this policy. However, it is important to recognize that the strategy of IO does not prevent deaths from occurring, bleeding events can occur after 23 h [16
], and delayed diagnosis can occur even for inpatients. This is why IO is an extremely expensive strategy if the goal was only to prevent patient death. The overall risk of death as presented in this study is 1 per 1,000 and 1.5 per 1,000 for inpatients and outpatients, respectively. Assuming an incremental cost of USD 406 per biopsy for IO inclusive of all complications, the incremental cost for preventing one death through IO exceeds USD 800,000. This may appear to be worth the expense at first glance but it exceeds the base estimate for cost per death by at least USD 300,000. While this may seem reasonable to a clinician who is risk adverse, it constitutes a considerable expense to the institution given PKB has known and unavoidable risks even in the best of monitoring environments. It is also important to acknowledge that despite all the evidence presented in this analysis, some clinicians will remain steadfast in the belief that even a slightly increased risk of death associated with the outpatient strategy would be unacceptable, regardless of the cost savings. The model does not address this ethical question that will come under even greater scrutiny in the near future as we continue to address rising costs in health care.
Assuming one is willing to accept the slightly increased risk of death associated with the outpatient perspective, it is also important to recognize that this analysis is from the institutional perspective. The quantification of cost is therefore based on actual institutional estimates from one center. The IC of an unexpected patient death is very difficult to quantify and can be easily confused with the societal cost of death, which primarily quantifies lost productivity such as wages. It would be inappropriate to estimate societal cost for this analysis as it does not reflect a direct cost to the institution. Similarly, a cost-effectiveness analysis was not performed in this analysis as the majority of costs of the disutility (effectiveness) of a major complication, such as time off work and lost wages, are borne by society and not the institution or payer. An estimate was therefore determined to reflect the IC associated with risk management, increased insurance premiums, and litigation costs. Since these costs can greatly differ at varying institutions, sensitivity analysis is the best way to interpret the impact of the cost of death on the overall cost per biopsy. Despite our belief that the base cost of death is overestimated in this analysis, outpatient management was still favored even if that cost doubled.
This analysis does not address nor does it support the use of ODS for all patients undergoing PKB. The base case specifically considered patients of low-risk profiles and the results and conclusions of this analysis should not be applied to patients with risk factors for a bleeding event. In fact, our findings also suggest that patients with specific risk factors that raise concern for a complication should be observed overnight, especially if the perceived risk for a major complication in an individual patient exceeds 5% (as determined by sensitivity analysis).
This analysis assumed that patients observed through an ODS approach have reliable access to emergency medical care in the event a complication were to occur. For patients who live in outlying or rural areas, or who do not have reliable emergency services in their area of residence, ODS may not be the preferred strategy as the risk of delayed recognition or death may exceed the cost benefit achieved from outpatient management.
This study has several limitations. First, our model is a generalization of a potentially complex hospital course. Each outcome follows a standardized course and does not attempt to analyze real patient encounters or actual cost data, as the latter would be subject to significant cost variation based on provider management style. This limitation, however, is balanced by the strength gained in sensitivity analysis and ability to thoroughly test each assumption. Second, the probability of complications utilized in this model is an estimate based on the available literature and may vary depending on the institution, procedural skill, use of direct ultrasonography, number of cores obtained, and other factors. All costs reported are specific to our institution but could be generalizable to other institutions of similar size in the US. Lastly, the IC of a patient death is very difficult to quantify. Not all patients encountering serious or lethal adverse events choose to pursue litigation nor are most adverse events associated with PKB due to gross negligence or medical malpractice. Therefore, the estimates for IC per death may be overestimated in this study.