Response to: “Re: Using Intraoperative Portable CT Scan to Minimize Reintervention Rates in Percutaneous Nephrolithotomy: A Prospective Trial” by Kirti Singh et al.

Dear Editor:

We thank Kirti Singh et al. (this issue) for their keen interest in our article ¹ and for their generous feedback. We also appreciate the very important questions they have raised and hope they will find this response satisfactory and helpful.

First, it is important to acknowledge that practice patterns in percutaneous nephrolithotomy (PCNL) vary widely across the world, ² and they are often driven by patient expectation, surgeon skills, hospital resources, and various logistical considerations for all three stakeholders. The standard practice at our institution is for the Interventional Radiologists to obtain percutaneous access, followed by PCNL performed by the Urologists. The two providers collaborate to determine the appropriate access point.

While line-item pricing is quite transparent in many countries, that is not typically the case in the United States. The expenses incurred by each patient at the end of the hospital stay are based on a complex calculation that consists of the patient's insurance, deductibles, coinsurance, out-of-pocket maximum, and individual contracts between the hospital and the insurance carrier. For this reason, we could not appropriately perform an analysis of our patients' medical bills and did not include this in the study.

It is absolutely true that reduced-dose CT protocols should be preferred over standard CT in many situations but, when this study was conceived, our Radiology department did not have reduced-dose protocols for CT imaging.

In our portable CT cohort (n = 60), there was only one complete staghorn (2%) and 12 partial staghorns (20%). Complete stone extraction was able to be performed with just one access in 9 of these 13 patients. Nine patients (15%) underwent bilateral PCNL; these renal units were treated as independent entities for the purpose of this study. All intra-operative images were interpreted by our Urologists.

The reason for excluding patients who had recently undergone PCNL within the same renal unit is because the stone burden in a second-look PCNL will typically be less than that in PCNL-naïve patients. Including these patients would inappropriately inflate the stone-free rate.

We also agree that the perfect methodology for this project would be to perform a two-armed randomized trial that includes follow-up standard CT on post-operative day 1 regardless of whether the patient had portable CT. Unfortunately, the idea of potential extra radiation creates a significant enrollment barrier and it did not seem ethical to request this from patients for a project that sought to reduce radiation doses.

Once again, we thank the letter writers for their insightful comments and hope they find this response valuable.