Introduction

The surgical management of kidney and ureteral stones has been and continues to be an important topic of discussion for the urological field and the general population. With a prevalence of over 10% in males and over 7% in females, stone disease is not only common, but the prevalence continues to rise [1]. The increasing stone burden not only leads to more hospitalizations and emergency room visits but continues to increase healthcare expenditure. Over 20 years ago, the cumulative cost of nephrolithiasis was over 2 billion dollars and is projected to reach over 4 billion dollars by 2030 [2]. With an increased healthcare expenditure and prevalence of stone formation it is critical now more than ever to be able to treat stones in an efficient and cost-effective manner.

While there are multiple viable interventions for stone disease, such as ureteroscopy and extracorporeal shock wave lithotripsy, Percutaneous Nephrostolithotomy (PCNL) is the gold standard for larger, treatment refractory stones. What started out as a rudimentary procedure in the 1940’s has become a hallmark of kidney stone management today [3]. Traditionally performed in the hospital setting, PCNL has migrated to an outpatient, ambulatory surgery setting. There have been studies in the literature that have shown an outpatient model to be feasible without higher readmission rates or cost when compared to a hospital setting [4-6]. While current guidelines suggest PCNL be used in the treatment of stones >2 cm, staghorn calculi, and in stones refractory to other procedures, there are still varying opinions about whether PCNL should be performed in a hospital or outpatient setting [7].

In addition to the lack of clarity in operative locations, there is varying opinion on whether to leave a Percutaneous Nephrostomy Tube (PCNT) upon PCNL completion. The AUA suggests clinicians may choose to omit the placement of a nephrostomy tube in those who are stone-free, after an uncomplicated PCNL [8]. The reason for PCNTs in the first-place stems from the thought that they improve hemostasis and drainage of the urinary tract after the procedure [9]. While this remains part of the standard PCNL, there have been modern approaches which involve a ‘tubeless’ approach in which a double JJ stent is used in place of a nephrostomy tube. Other approaches involve ‘totally tubeless’ in which no nephrostomy tube or stent are placed at all. All such modifications have been shown to provide a similar safety profile to the standard PCNL in select patients [9].

We performed PCNLs at our academic institution without placement of a post-operative nephrostomy tube which we have deemed ‘tubeless’. In doing so we evaluated the feasibility and reported readmission rates in previous literature in hopes that other academic medical centers will follow. We also sought to contribute to the notion that tubeless PCNL may allow for quicker discharge times, furthering an ongoing philosophy that PCNLs will eventually be a primarily outpatient procedure.

Materials and Methods

Patient Selection

A retrospective chart review was conducted at a single academic institution. Patients included in the study were above 18 years old and were treated with a PCNL between October 2020 and April 2024 for either primary or refractory stone disease. A total of 98 patients had a scheduled PCNL with 95 having a completed PCNL. Three patients were excluded due to having an aborted procedure during or prior to the scheduled PCNL. Patient demographics, comorbidities, intraoperative metrics, and stone characteristics were all recorded at the time of procedure or in prior clinic visits. Discharge time and readmission data was collected up to 30 days post PCNL. Data was recorded in a retrospective fashion. Operating time was defined as the time between initial fluoroscopic imaging and completion. All procedures were performed at a single academic institution, supervised by a single experienced endourologist. PCNLs were performed primarily by twelve urology residents of varying experience levels who served as primary decision makers in surgical management including whether to place a PCNT.

Surgical Technique

Access is achieved with placement of a nephrostomy tube by interventional radiology prior to the procedure. After informed consent is obtained, patients are taken to the operating room. Time-out, antibiotics, and urethral catheter placement are completed and patients are positioned for prone PCNL and prepped. The tract is dilated with a nephrostomy pressure balloon followed by a working sheath.

Nephroscopy is performed with the offset nephroscope through the working sheath with stone(s) fragmented completely with the option of using ultrasonic, electrohydraulic, and/or laser instrumentation. Patients undergo a final survey with fluoroscopy/pyeloscopy to assure the absence of residual stone fragments. A nephrostogram is performed to evaluate for any contrast extravasation. An antegrade ureteral stent is placed over a wire and decision to place a nephrostomy tube is determined based on the amount of bleeding, presence of extravasation, and other contributing factors. If no nephrostomy tube is left, the skin edges are reapproximated with 3-0 chromic sutures.

Analytics

All statistical analysis were performed using SAS 9.4. The statistical significance was assessed using an alpha level of 0.05. Descriptive statistics (means, standard deviations, frequencies, and percentages) were calculated for all variables. Fisher’s exact tests were calculated to determine if there was an association between nephrostomy tube placement, discharge within 24 hours, and readmission within 30 days. A Mann-Whitney U test was calculated to determine if there was a difference in the number of days until discharge among patients with a nephrostomy tube placement compared to those without.

Logistic regressions were calculated on the outcome, readmission within 30 days, for each independent variable of interest, including BMI, size of the stone, Diabetes Mellitus (DM), Hypertension (HTN), American Society of Anesthesiologists physical status classification system (ASA), Estimated Blood Loss (EBL), and Coronary Artery Disease (CAD). Interactions were assessed for each independent variable with nephrostomy tube placement.

Similarly, logistic regressions were calculated on the outcome, discharged within 24 hours, and for each independent variable of interest, including BMI, size of the stone, DM, HTN, ASA, estimated blood loss, and CAD. Interactions were assessed for each independent variable with nephrostomy tube placement. Operating Room (OR) completion time was categorized into the following categories, 0900-1300, 1301-1600, 1601-2000 hours. A Chi-Square test was calculated to determine if the proportion of patients discharged within 24 hours differed across OR completion time categories.        

Results

Descriptive Statistics

A total of 95 patients underwent a completed PCNL, representing 96.9% of the patients initially investigated in this study. Complete descriptive statistics and patient characteristics are found in Table 1. The population had relatively high rates of comorbidities with the average patient having a BMI >30 and ASA of 2.8. The average stone burden was slightly greater than 3.0 cm with equal distribution in laterality with the left renal system involved in 49.5% of cases.

Table 1: Descriptive Statistics and Patient Characteristics.

Readmissions and Discharge Rate

A total of 72 patients were discharged within 24 hours of their completed PCNL. As seen in Table 2, the patients without a PCNT were statistically more likely to be discharged within 24 hours compared to patients with a PCNT (64 vs 8, p=0.0449). A total of 13 patients were readmitted within 30 days. Of those being readmitted the primary diagnosis was sepsis (15.4%), fever (23%), urinary tract infection (15.4%), flank pain (15.4%), pyelonephritis (6.7%), abdominal pain (6.7%), lethargy (6.7%), and sepsis unrelated to the urinary tract (6.7%). A total of 4 patients returned to the Emergency Department (ED) without requiring admission to the hospital within 30 days. Of those returning to the ED, the primary diagnoses were gross hematuria (50%), abdominal pain (25%), and nephrolithiasis (25%). Those patients without a PCNT were just as likely to be readmitted within 30 days as patients with a PCNT (12 vs 1, p=0.6847). As seen in Table 3, we found that patients with a PCNT were more likely to remain in the hospital for a greater number of days (0.5 vs 2.4, p=0.0087).

Table 2: Results of Fisher’s exact tests to determine if there was an association between post-operative nephrostomy tube placement with (1) discharge within 24 hours and (2) readmission within 30 days.

Table 3: Results of a Mann-Whitney U test were calculated to determine if there was a difference in the number of days until discharge among patients with a nephrostomy tube placement compared to those without.

Confounders of Discharge and Readmission

The average length of operation time was 93.6 minutes with the longest procedure lasting over 4 hours. A total of 21 procedures were completed by 1300 hours, 35 were completed by 1600 hours, and 39 were completed by 2000 hours. As seen in Figure 1, the end time of each procedure’s completion did not significantly impact the discharge rate of patients within 24 hours (p=0.7121). In other words, procedures completed earlier had no influence on the discharge time. Results of interaction from a logistic regression determined that BMI, stone burden, DM, HTN, CAD, ASA classification, and EBL had no impact on readmissions and days until discharge in patients with and without PCNT (p>0.05).

Figure 1: The time the operation was completed was divided amongst three-time intervals. Patients were then assigned to one of these groups based upon when their surgery was completed and were analyzed based on if they were discharged within 24 hours. A Chi-Square test was used and found there to be no significant difference in the proportion of patients discharged within 24 hours across the OR end times (p=0.7121).

Discussion

This study sought to evaluate the feasibility of performing PCNLs without post-op nephrostomy tubes. We found that tubeless PCNLs can be a viable option in patients undergoing PCNLs leading to low readmission rates and adequate discharge times.

For the last two decades there has been an increased effort to move hospital-based surgeries to an ambulatory setting [10,11]. Part of this is driven by a decreasing cost for surgeries at an ambulatory surgery center when compared to hospital-based procedures [12,13]. While finances are a large driver of ambulatory surgery, patient satisfaction and convenience cannot be overlooked [14]. One of the key metrics used by surgeons and hospitals alike is readmission rates, which not only reflects poorly on the hospital but can cause undue financial harm to both the hospital and the patient [15]. The literature places the readmission rate for PCNLs anywhere between 1% and 18.7% [16-18] with reported length of stay around 2.9 days for completely tubeless PCNLs. When looking specifically at ages 26-64, the readmission rates average around 12% [17]. Our findings support previous literature with a 30-day admission rate of 13.7% and show an improvement in length of stay at 0.5 days in patients without a post-op PCNT. The discrepancy seen amongst days until discharge is most likely related to the complexity of the procedure rather than the PCNT itself.

This study demonstrated that patient comorbidities and stone burden did not impact readmission rates in patients with and without post-op PCNTs. This is similar to literature looking at hypertension as a risk factor for readmission but differs from studies showing an increased readmission rate after surgery for those with DM [19,20]. While DM is a known factor in readmission rate, the discrepancy may arise from our limited population size. One study found the presence of multiple stones preoperatively and fragments postoperatively to be the most important risk factor for readmission after PCNL [21]. Other studies have cited complexity of kidney stones and history of complications to be the primary driving factors for readmission [22]. While we did not investigate the number of stones treated, the overall stone burden and EBLwere used as surrogates for stone complexity and intraoperative complications, respectively. We found no effect on readmission rates with respect to stone burden and blood loss because most stones presented in a predictable fashion leading to straightforward PCNLs with an acceptable EBL in most cases.

Interestingly, we did not find a relationship between OR completion times and rates of discharge within 24 hours. One such study investigated length of stay and surgical start times undergoing orthopedic or neurosurgical procedures. They found that a start time before 3 pm predicted a shorter length of stay in patients [23]. While there are several reports suggesting that PCNL patients can be discharged the same day, there is a gap in knowledge about what the ideal time of PCNL completion is. Our finding of no relationship may be attributed to the fact that we set our discharge time to be 24 hours after completion of surgery instead of 12 hours or even shorter. We believe this to be an interesting topic of future research as it could influence future scheduling decisions to ensure patients are discharged by a specific time of day.

This study is not without its limitations. One such limitation is the use of a single academic medical center where results may not be as generalizable to the population at large. Another limitation is the limited number of patients who underwent PCNL. While we believe important conclusions can still be drawn, a follow up analysis with a larger patient population could help solidify the claims made. There is also the possibility that readmitted patients were more likely to be unhealthier at baseline, acting as a potential confounding factor. While there was an attempt to control a few confounding metrics, there are other variables that could have been at play such as anticoagulation status, smoking status, and social situation.

Conclusion

PCNL can be performed safely in select patients without the use of post-op percutaneous nephrostomy tubes. The presence of a PCNT does not influence the rates of readmissions and may increase the discharge rate. Not only can this be applied in the inpatient setting, but we believe it to be adaptable to the outpatient setting where patients go home the same day.

Ethical Considerations

The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of Augusta University (protocol code 2182424-2) on June 5^th, 2024.

Conflict of Interest: The authors declare no conflicts of interest.

Funding: This research received no external funding.

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