Initial Experience and Evaluation of a Nomogram for Outcome Prediction in Management of Medium-sized (1-2 cm) Kidney Stones

External validation of a nomogram for outcome prediction in management of medium-sized (1-2 cm) kidney stones

BACKGROUND

Stone nomogram by Micali et al., able topredict treatment failure of shock-wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PNL) in the management of single 1-2 cm renal stones, was developed on 2605 patients and showed a high predictive accuracy, with an area under ROC curve of 0.793 at internal validation. The aim of the present study is to externally validate the model to assess whether it displayed a satisfactory predictive performance if applied to different populations.

METHODS

External validation was retrospectively performed on 3025 patients who underwent an active stone treatment from December 2010 to June 2021 in 26 centers from four countries (Italy, USA, Spain, Argentina). Collected variables included: age, gender, previous renal surgery, preoperative urine culture, hydronephrosis, stone side, site, density, skin-to-stone distance. Treatment failure was the defined outcome (residual fragments >4 mm at three months CT-scan).

RESULTS

Model discrimination in external validation datasets showed an area under ROC curve of 0.66 (95% 0.59-0.68) with adequate calibration. The retrospective fashion of the study and the lack of generalizability of the tool towards populations from Asia, Africa or Oceania represent limitations of the current analysis.

CONCLUSIONS

According to the current findings, Micali's nomogram can be used for treatment prediction after SWL, RIRS and PNL; however, a lower discrimination performance than the one at internal validation should be acknowledged, reflecting geographical, temporal and domain limitation of external validation studies. Further prospective evaluation is required to refine and improve the nomogram findings and to validate its clinical value.

Application of AI in urolithiasis risk of infection: a scoping review

INTRODUCTION

Artificial intelligence and machine learning are the new frontier in urology; they can assist the diagnostic work-up and in prognostication bring superior to the existing nomograms. Infectious events and in particular the septic risk, are one of the most common and in some cases life threatening complication in patients with urolithiasis. We performed a scoping review to provide an overview of the current application of AI in prediction the infectious complications in patients affected by urolithiasis.

EVIDENCE ACQUISITION

A systematic scoping review of the literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses for Scoping Reviews (PRISMA-ScR) guidelines by screening Medline, PubMed, and Embase to detect pertinent studies.

EVIDENCE SYNTHESIS

A total of 467 articles were found, of which nine met the inclusion criteria and were considered. All studies are retrospective and published between 2021 and 2023. Only two studies performed an external validation of the described models. The main event considered is urosepsis in four articles, urinary tract infection in two articles and diagnosis of infection stones in three articles. Different AI models were trained, each of which exploited several types and numbers of variables. All studies reveal good performance. Random forest and artificial neural networks seem to have higher AUC, specificity and sensibility and perform better than the traditional statistical analysis.

CONCLUSIONS

Further prospective and multi-institutional studies with external validation are needed to better clarify which variables and AI models should be integrated in our clinical practice to predict infectious events.

Stone decision engine accurately predicts stone removal and treatment complications for shock wave lithotripsy and laser ureterorenoscopy patients

Kidney stones form when mineral salts crystallize in the urinary tract. While most stones exit the body in the urine stream, some can block the ureteropelvic junction or ureters, leading to severe lower back pain, blood in the urine, vomiting, and painful urination. Imaging technologies, such as X-rays or ureterorenoscopy (URS), are typically used to detect kidney stones. Subsequently, these stones are fragmented into smaller pieces using shock wave lithotripsy (SWL) or laser URS. Both treatments yield subtly different patient outcomes. To predict successful stone removal and complication outcomes, Artificial Neural Network models were trained on 15,126 SWL and 2,116 URS patient records. These records include patient metrics like Body Mass Index and age, as well as treatment outcomes obtained using various medical instruments and healthcare professionals. Due to the low number of outcome failures in the data (e.g., treatment complications), Nearest Neighbor and Synthetic Minority Oversampling Technique (SMOTE) models were implemented to improve prediction accuracies. To reduce noise in the predictions, ensemble modeling was employed. The average prediction accuracies based on Confusion Matrices for SWL stone removal and treatment complications were 84.8% and 95.0%, respectively, while those for URS were 89.0% and 92.2%, respectively. The average prediction accuracies for SWL based on Area-Under-the-Curve were 74.7% and 62.9%, respectively, while those for URS were 77.2% and 78.9%, respectively. Taken together, the approach yielded moderate to high accurate predictions, regardless of treatment or outcome. These models were incorporated into a Stone Decision Engine web application (http://peteranoble.com/webapps.html) that suggests the best interventions to healthcare providers based on individual patient metrics.

Predictors of stone-free rate after a single-session extracorporeal shockwave lithotripsy for a single kidney stone measuring 10 to 20 mm: A private center experience

Background

Despite the continuous update of guidelines for the management of kidney stones, the ability to predict a successful response to extracorporeal shockwave lithotripsy (SWL) remains a topic of research. This is due to the need to refine the decision making in the context of technological advancements and current pandemics. This study aimed to determine the predictors of stone-free rate (SFR) after single-session SWL in adult patients with a single kidney stone 10 to 20 mm in diameter.

Materials and methods

A retrospective review of the records of patients with a single kidney stone 10 to 20 mm in diameter was performed at a private SWL center from December 2019 to February 2021. Univariate and multivariate analyses were performed for stone- and patient-related factors, using the Student t and Mann-Whitney U tests for the quantitative variables and the Fisher exact and Pearson correlation tests for the qualitative variables.

Results

A total of 138 patients were eligible for this study, including 92 men and 46 women. The mean age was 38.6 ± 12.4 years, and the mean body mass index (BMI) was 25.9 ± 3.4 kg/m2. Four weeks after SWL, 120 patients (87%) were free of stones, and 18 (13%) needed further treatment. Univariate analyses showed that SFR was negatively correlated with increased BMI (p = 0.0001), maximum stone length (p = 0.0001), transverse diameter of the stone (p = 0.0001), number of shocks per session (p = 0.052), and Hounsfield unit (HU) (p = 0.0001). Multivariate analysis revealed that HU (p = 0.009), maximum stone length (p = 0.01), BMI (p = 0.000), and presence of double-J stent (p = 0.034) were independent risk factors for failure of single-session SWL in the treatment of kidney stones 10 to 20 mm in diameter. The estimated average cost per case was USD 450.5.

Conclusions

Increased HU, maximum stone length, BMI, and presence of double-J stents were independent risk factors for low SFR after single-session SWL for a kidney stone 10 to 20 mm in diameter. The cost of SWL remains an advantage in the private sector.

Asymptomatic bacteriuria in candidates for active treatment of renal stones: results from an international multicentric study on more than 2600 patients

The occurrence of asymptomatic bacteriuria concomitant to urolithiasis is an issue for patients undergoing renal stone treatment. Disposing of a preoperative urine culture is essential to reduce the risk of septic events. The endpoint of the study is to report which characteristics of candidates for renal stone treatment are frequently associated with positive urine culture. 2605 patients were retrospectively enrolled from 14 centers; inclusion criteria were age > 18 and presence of a single renal stone 1-2 cm in size. The variables collected included age, gender, previous renal surgery, comorbidities, skin-to-stone distance, stone size, location, density, presence of hydronephrosis. After a descriptive analysis, the association between continuous and categorical variables and the presence of positive urine culture was assessed using a logistic regression model. Overall, 240/2605 patients (9%) had preoperative bacteriuria. Positive urine culture was more frequent in females, patients with previous renal interventions, chronic kidney disease, congenital anomalies, larger stones, increased density. Multivariate analysis demonstrated that previous renal interventions (OR 2.6; 95% CI 1.9-3.4; p < 0.001), renal-related comorbidities (OR 1.31; 95% CI 1.19-1.4; p < 0.001), higher stone size (OR 1.06; 95% CI 1.02-1.1; p = 0.01) and density (OR 1.00; 95% CI 1.0-1.00; p = 0.02) were associated with bacteriuria; male gender and lower caliceal location were inversely related to it. Beyond expected risk factors, such as female gender, other parameters are seemingly favoring the presence of positive urine culture. The awareness of variables associated with bacteriuria allows to assess which individuals are at increased risk of presenting bacteriuria and reduce the rate of septic complications.

Volume should be used instead of diameter for kidney stones between 10 and 20 mm to determine the type of surgery and increase success

Aim of this study is to categorize stones between 10 and 20 mm according to stone diameter or volume and compare mini percutaneous nephrolithotomy (mPNL) and retrograde intrarenal surgery (RIRS) outcomes. Files of 515 patients who underwent surgery for kidney stones with sizes 10-20 mm were reviewed. Patients were divided into RIRS or mPNL groups. An attempt was made to find the diameter and volume threshold values above which the success of the operation, complication rates and the number of auxiliary treatments deteriorated. Subgroup analysis was performed below and above the threshold value to reveal the optimal treatment methods. RIRS complications increased with volumes above 1064 mm³, number of auxiliary interventions increased with volumes above 1256 mm³, and success of the operation decreased with volumes above 1416 mm³. A subgroup analysis under and over 1064 mm³ was performed in RIRS group. Complication and auxiliary treatment rates were higher, operative success was lower in patients with a stone volume greater than 1064 mm³. In patients who underwent RIRS, for every 1000 mm³ increase in stone volume success of the operation decreased by 2.1 times, while the probability of auxiliary treatment increased by 2.8 times. In patients with kidney stones between 10 and 20 mm, it is more meaningful to use volume instead of diameter to determine the success rate. When mPNL is used instead of RIRS for volumes greater than 1064 mm³, the success rate will be higher, complication rate will be similar, and the need for auxiliary treatment will be lower.

Open nephrectomy: The extreme measure for sepsis after flexible-ureteroscopy (f-URS) procedure

URS is considered a safe method of stone treatment. Complications most often do not exceed grade II of the Clavien Dindo classification. Although it is considered safe, in some cases major complications may occur from grade III onwards. A 50-year-old man underwent f-URS for a 2.7 × 1.2 cm left medium caliceal stone; after surgery patient developed an intraparenchymal renal abscess and concomitant pulmonary and hepatic septic emboli. Despite attempts to treat it conservatively, nephrectomy was the only effective treatment. The f-URS is minimally invasive and effective procedure, although it is not free from complications.