Difficulties with access in percutaneous renal surgery

Predicting the Stone-Free Status of Percutaneous Nephrolithotomy with the Machine Learning System

Purpose

The study aimed to create a machine learning model (MLM) to predict the stone-free status (SFS) of patients undergoing percutaneous nephrolithotomy (PCNL) and compare its performance to the S.T.O.N.E. and Guy's stone scores.

Patients and Methods

This is a retrospective study that included 320 PCNL patients. Pre-operative and post-operative variables were extracted and entered into three MLMs: RFC, SVM, and XGBoost. The methods used to assess the performance of each were mean bootstrap estimate, 10-fold cross-validation, classification report, and AUC. Each model was externally validated and evaluated by mean bootstrap estimate with CI, classification report, and AUC.

Results

Out of the 320 patients who underwent PCNL, the SFS was found to be 69.4%. The RFC mean bootstrap estimate was 0.75 and 95% CI: [0.65-0.85], 10-fold cross-validation of 0.744, an accuracy of 0.74, and AUC of 0.761. The XGBoost results were 0.74 [0.63-0.85], 0.759, 0.72, and 0.769, respectively. The SVM results were 0.70 [0.60-0.79], 0.725, 0.74, and 0.751, respectively. The AUC of Guy's stone score and the S.T.O.N.E. score were 0.666 and 0.71, respectively. The RFC external validation set had a mean bootstrap estimate of 0.87 and 95% CI: [0.81-0.92], an accuracy of 0.70, and an AUC of 0.795, While the XGBoost results were 0.84 [0.78-0.91], 0.74, and 0.84, respectively. The SVM results were 0.86 [0.80-0.91], 0.79, and 0.858, respectively.

Conclusion

MLMs can be used with high accuracy in predicting SFS for patients undergoing PCNL. MLMs we utilized predicted the SFS with AUCs superior to those of GSS and S.T.O.N.E scores.

Non-papillary prone percutaneous nephrolithotomy for renal abnormalities: single-institution experience

PURPOSE

To evaluate the effectiveness and safety of non-papillary prone PCNL for the treatment of patients with renal abnormalities.

METHODS

An observational retrospective cohort study including PCNL cases of patients with renal abnormalities was performed. The following inclusion criteria were applied: renal stones > 1.5 cm with maximal diameter, anatomical malformations of affected kidney (malrotated kidneys, horseshoe kidneys and kidneys with complete duplicated systems, medullary sponge kidney), patients treated with standard (30Fr) PCNL or mini-PCNL (22Fr). The lithotripsy was performed using the Lithoclast Master or the Lithoclast^® Trilogy (EMS Medical, Nyon, Switzerland).

RESULTS

Overall, 57 patients, 35 males, and 22 females with any renal malformation underwent non-papillary prone PCNL. Our study included 25 patients with horseshoe kidneys, 21 with malrotated kidneys, 9 with kidneys with duplicated pelvicalyceal systems and 2 with medullary sponge kidneys. The mean cumulative stone size was 36 ± 1.4 mm and most of the stones were in the lower calyceal group (36.9%) and in the pelvis (27.2%). The stone-free rate (SFR) was 84.2% and the mean hospitalization time was 2.7 ± 0.7 days. In total, postoperative complications were developed in six patients (10.5%), half of them presenting fever and the other half requiring blood transfusion (Grade II).

CONCLUSION

The PCNL is the method of choice for treating large stones in anomalous kidneys. The generally accepted panacea that only a papillary puncture is safe is questioned by our results. Based on our experience, a non-papillary puncture proved to be a safe and effective procedure.

On Surgical Planning of Percutaneous Nephrolithotomy with Patient-Specific CTRs

Percutaneous nephrolithotomy (PCNL) is considered a first-choice minimally invasive procedure for treating kidney stones larger than 2 cm. It yields higher stone-free rates than other minimally invasive techniques and is employed when extracorporeal shock wave lithotripsy or uteroscopy are, for instance, infeasible. Using this technique, surgeons create a tract through which a scope is inserted for gaining access to the stones. Traditional PCNL tools, however, present limited maneuverability, may require multiple punctures and often lead to excessive torquing of the instruments which can damage the kidney parenchyma and thus increase the risk of hemorrhage. We approach this problem by proposing a nested optimization-driven scheme for determining a single tract surgical plan along which a patient-specific concentric-tube robot (CTR) is deployed so as to enhance manipulability along the most dominant directions of the stone presentations. The approach is illustrated with seven sets of clinical data from patients who underwent PCNL. The simulated results may set the stage for achieving higher stone-free rates through single tract PCNL interventions while decreasing blood loss.

Preoperative Virtual Reality Surgical Rehearsal of Renal Access during Percutaneous Nephrolithotomy: A Pilot Study

Percutaneous Nephrolithotomy (PCNL) is a procedure used to treat kidney stones. In PCNL, a needle punctures the kidney through an incision in a patient’s back and thin tools are threaded through the incision to gain access to kidney stones for removal. Despite being one of the main endoscopic procedures for managing kidney stones, PCNL remains a difficult procedure to learn with a long and steep learning curve. Virtual reality simulation with haptic feedback is emerging as a new method for PCNL training. It offers benefits for both novices and experienced surgeons. In the first case, novices can practice and gain kidney access in a variety of simulation scenarios without offering any risk to patients. In the second case, surgeons can use the simulator for preoperative surgical rehearsal. This paper proposes the first preliminary study of PCNL surgical rehearsal using the Marion Surgical PCNL simulator. Preoperative CT scans of a patient scheduled to undergo PCNL are used in the simulator to create a 3D model of the renal system. An experienced surgeon then planned and practiced the procedure in the simulator before performing the surgery in the operating room. This is the first study involving survival rehearsal using a combination of VR and haptic feedback in PCNL before surgery. Preliminary results confirm that surgical rehearsal using a combination of virtual reality and haptic feedback strongly affects decision making during the procedure.

Comparison outcomes of percutaneous nephrolithotomy in prone and flank position in obese patients: A randomized clinical trial

BACKGROUND

The aim of this study was to compare the complications of percutaneous nephrolithotomy (PCNL) surgery in Flank and Prone positions in patients with a BMI above 30.

METHODS

In this randomized clinical trial patients were randomly assigned to PCNL treatment in one of two groups undergoing PCNL under fluoroscopic guidance in Flank or Prone positions. Patient demographic information, stone number, size and location, stent duration, hospital stay, blood loss, Creatinine, hemoglobin, hematocrit changes, and arterial blood gas changes and acid-base hemostasis were collected.

RESULTS

In this study, 60 patients were examined, which were divided into two groups of 29 people, prone and 31 people. Mean stone size was 3.16 ± 0.82 cm. arterial blood gases did not differ significantly between two groups. The SFR (stone free rate) in the prone and flank groups was 91.02% and 86.89%, respectively. However, SFR and Complications in the prone and flank groups were not significantly different (p value of 0.081 and 0.13, respectively).

CONCLUSIONS

According to the results of this study, PCNL complications and acid-base changes is not significantly different in flank and prone positions in obese patients. However, SFR is slightly lower in flank group. Thus, PCNL in flank position is not superior to prone position in obese Patients. It is recommended to choose each of these surgical methods according to the surgeon's facilities and skills.

Application of S.T.O.N.E. Nephrolithometry Score for Prediction of Stone-Free Status and Complication Rates in Patients Who Underwent Percutaneous Nephrolitotomy for Renal Stone

Background: Renal stone disease is a common disorder in urology practice. Kidney stone has various treatment methods such as extracorporeal shock wave lithotripsy, retrograde intrarenal surgery, and percutaneous nephrolithotomy (PCNL). In this study, we aimed to determine the value of S.T.O.N.E. nephrolithometry score, which is considered as a new scoring system for predicting residual stone rate and complications in patients undergoing PCNL due to renal calculi. Materials and Methods: A total of 120 patients >18 years old who underwent PCNL were evaluated prospectively. Five parameters available from preoperative noncontrast-enhanced computed tomography were measured: stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E) and then S.T.O.N.E. nephrolithometry score was calculated. The prediction of the stone-free rates and complication rates of this scoring was evaluated statistically. Results: When the age, gender, body mass index, comorbidities, and American Society of Anesthesiologists scores of the patients were evaluated according to the patients' postoperative stone-free status, no statistical difference was found between the groups. Patients had a stone-free rate of 78%. Patients' mean neuropilitometry score was calculated to be 7.75 S.T.O.N.E. nephrolithometry score statistically significant (P = .001) for prediction of stone-free status. S.T.O.N.E. nephrolithometry score was significantly correlated with operation time, estimated blood loss, duration of fluoroscopy, duration of hospital stay, and number of punctures. Complications were seen in 13 patients. Conclusions: S.T.O.N.E. nephrolithometry score can be used as an objective criterion for predicting the complexity of the PCNL process. In addition, this scoring system is expected to provide more objective preoperative counseling and can provide standardization in academic studies.

Percutaneous nephrolithotripsy: C-arm CT with 3D virtual navigation in non-dilated renal collecting systems

PURPOSE

We aimed to evaluate the clinical superiority of using C-arm computed tomography (CT) to establish percutaneous nephrolithotripsy (PCNL) access for patients with non-dilated renal collecting systems.

METHODS

From May 2014 to May 2015, 33 patients underwent C-arm CT-guided puncture to establish PCNL access after failed attempts of ultrasonography-guided nephrostomy. Technical success, procedure details, radiation exposure, complications, and stone-free rate were recorded.

RESULTS

The technical success rate was 97% (32/33) with a mean puncture score of 4.5/5. Mean puncture, dilation, and fragmentation times were 17.9±6.0, 12.6±3.9, and 33.1±8.8 minutes, respectively. Mean radiation exposure was 4.8±2.1 mSv without serious complications. Stone-free rate was 93.8%.

CONCLUSION

C-arm CT is a useful tool to establish PCNL access, particularly in cases of upper pole access or complicated anatomy.

Nephrolithiasis in a 17-Year-Old Male With Seckel Syndrome and Horseshoe Kidneys: Case Report and Review of the Literature

We report the case of a 17-year-old male with Seckel syndrome and horseshoe kidneys which had a 7 mm kidney stone in the lower pole calyx of the right moiety. The patient had a history of rotoscoliosis with 60° dextroconvex curvature and hepatic steatosis. Attempted ureteroscopy was unsuccessful due to stone location and anatomy. Percutaneous nephrolithotomy was ultimately required. This case highlights the difficulties of endoscopic treatments of renal calculi in patients with abnormal renal anatomy and dysmorphia. To our knowledge, this is the first reported case of nephrolithiasis in a patient with Seckel syndrome and horseshoe kidneys.

Predictability and Practicality of Image-Based Scoring Systems for Patient Assessment and Outcome Stratification During Percutaneous Nephrolithotomy: a Contemporary Update

Preoperative nomograms offer systematic and quantitative methods to assess patient- and stone-related characteristics and their impact on successful treatment and potential risk of complication. Discrepancies in the correlation of perioperative variables to patient outcomes have led to the individual development, validation, and application of four independent scoring systems for the percutaneous nephrolithotomy: Guy's stone score, S.T.O.N.E. nephrolithometry, Clinical Research Office of the Endourology Society nomogram, and Seoul National University Renal Stone Complexity. The optimal nomogram should have high predictive ability, be practically integrated into clinical use, and be widely applicable to urinary stone disease. Herein, we seek to provide a contemporary evaluation of the advantages, disadvantages, and commonalities of each scoring system. While the current data is insufficient to conclude which scoring system is destined to become the gold standard, it is crucial that a nephrolithometric scoring system be incorporated into common practice to improve surgical planning, patient counseling, and outcome assessment.

Flat detector cone beam CT-guided nephrostomy using virtual navigation in patients with iatrogenic ureteral injury

PURPOSE

To evaluate the feasibility of flat detector cone beam computed tomography (CBCT)-guided nephrostomy using virtual navigation in patients with iatrogenic ureteral injury.

MATERIALS AND METHODS

A retrospective review of percutaneous nephrostomy (PN) revealed the use of CBCT with 3D virtual navigation guidance in 42 procedures (40 patients) for patients with iatrogenic ureteral injury. All procedures were shown as second-line interventions after failed ultrasound-guided nephrostomy. Data on technical success rate, procedure time, puncture performance, radiation exposure, complications, and clinical success were collected.

RESULTS

The technical success rate was 95.2% (40/42). The mean puncture performance score was 4.4 ± 1.0, and the procedure time was 25.2 ± 3.1 min, resulting in a mean effective exposure dose of 5.9 ± 2.3 mSv. There were no serious complications. During the mean follow-up periods of 11.4 months (range 6-19), clinical success rates following drainage were 72.5% (29/40), and ten cases (25%) had secondary surgical treatments.

CONCLUSION

CBCT with 3D virtual navigation is a feasible technique for PN with reasonable exposure dose and can serve as a second-line intervention after failed ultrasound guidance.

Nephrolithometric Scoring Systems to Predict Outcomes of Percutaneous Nephrolithotomy

Currently, there is no single agreement upon an ideal predictive model that characterizes the complexity of renal stones and predicts surgical outcomes following percutaneous nephrolithotomy (PCNL). New predictive tools have recently emerged to systematically and quantitatively assess kidney stone complexity to predict outcomes following PCNL: the Guy's Stone Score, the CROES nomogram, S.T.O.N.E. nephrolithometry, and S-ReSC score. An ideal scoring system should include variables that both influence surgical planning and are predictive of postoperative outcomes. This review discusses the strengths, weaknesses, and commonalities of each of the above scoring systems. Additionally, we propose future directions for the development and analysis of surgical treatment for stone disease, namely, the importance of assessing radiation exposure and patient quality of life when counseling patients on treatment options.

Balloon dilator versus telescopic metal dilators for tract dilatation during percutaneous nephrolithotomy for staghorn stones and calyceal stones

Objective

To compare the results of balloon dilatation (BD) vs. telescopic metal dilators (TMDs) in establishing the tract for percutaneous nephrolithotomy (PCNL) in patients with calyceal stones or staghorn stones, but with no hydronephrosis.

Patients and methods

Data from selected patients over 4 years were recorded retrospectively. Patients with complex staghorn stones, an undilated targeted calyx, or the stone filling the targeted calyx, were included in the study. In all, 97 patients were included, of 235 undergoing PCNL between March 2010 and March 2014, and were divided into two groups according to the technique of primary tract dilatation. Group A included patients who had BD and group B those treated using TMDs.

Results

In group A (BD, 55 patients) dilatation was successful in 34 (62%). The dilatation failed or there was a need for re-dilatation using TMD in 21 patients (38%). In one of these 21 patients the dilatation failed due to extravasation. In group B (TMD, 42 patients) dilatation was successful in 38 (90%) patients, with incomplete dilatation and a need for re-dilatation in four (10%) patients, and no failed procedures. Group A had a significantly higher failure rate than group B (P < 0.001). Differences in operative duration, blood loss, stone-removal success rate and complication rate were statistically insignificant.

Conclusion

BD has a higher failure rate than TMD when establishing access for calyceal stones or staghorn stones that have little space around them.

Fluoroscopy guided percutaneous renal access in prone position

Percutaneous nephrolithotomy is a very commonly done procedure for management of renal calculus disease. Establishing a good access is the first and probably the most crucial step of this procedure. A proper access is the gateway to success. However, this crucial step has the steepest learning curve for, in a fluoroscopy guided access, it involves visualizing a three dimensional anatomy on a two dimensional fluoroscopy screen. This review describes the anatomical basis of the renal access. It provides a literature review of all aspects of percutaneous renal access along with the advances that have taken place in this field over the years. The article describes a technique to determine the site of skin puncture, the angle and depth of puncture using a simple mathematical principle. It also reviews the common problems faced during the process of puncture and dilatation and describes the ways to overcome them. The aim of this article is to provide the reader a step by step guide for percutaneous renal access.

Factors affecting complications according to the modified Clavien classification in complete supine percutaneous nephrolithotomy

INTRODUCTION

An increase in percutaneous nephrolithotomy (PCNL) has been accompanied by an increase in complications. We identified the parameters affecting the severity of complications using the modified Clavien classification (MCC).

METHODS

From 2008 to 2013, 330 patients underwent complete supine PCNL using subcostal access, one-shot dilation, rigid nephroscopy, and pneumatic lithotripsy. We assessed the impact of the following factors on complication severity based on the MCC: age, gender, body mass index, hypertension, diabetes, previous stone surgery and extracorporeal shock wave lithotripsy, preoperative hemoglobin, renal dysfunction (creatinine >1.4 mg/dL), preoperative urinary tract infection, anatomic upper urinary tract abnormality (AUUTA), significant (moderate-severe) hydronephrosis, stone-related parameters (opacity, number, burden, location, staghorn, complex stones), anesthesia type, kidney side, imaging and calyx for access, tract number, tubeless approach, operative time, postoperative hemoglobin, and hemoglobin drop and stone-free results.

RESULTS

The complication rate was 19.7% (MCC: 0=80.3%, I=6.4%, II=11.2%, ≥III=2.1%). On univariate analyses, only the following factors affected MCC: gender, preoperative hemoglobin, AUUTA, significant hydronephrosis, imaging for access, calyx for access, tract number, postoperative hemoglobin, hemoglobin drop and stone-free result. Renal dysfunction was accompanied by higher complications, yet the results were not statistically significant. Multivariate logistic regression analysis demonstrated renal dysfunction, absence of significant hydronephrosis, AUUTA, multiple tracts, lower postoperative hemoglobin, and higher postoperative hemoglobin drop as the significant parameters which affected MCC and predicted higher grades. The paper's limitations include a low number of cases in the higher Clavien grades and some subgroups of variables, and not applying some techniques due to surgeon preference.

INTERPRETATION

Many of the complete supine PCNL complications were in the lower Clavien grades and major complications were uncommon. Renal dysfunction, AUUTA, significant hydronephrosis, tract number, postoperative hemoglobin, and hemoglobin drop were the only factors affecting MCC.