Non-contrast Computed Tomography After Percutaneous Nephrolithotomy: Findings and Clinical Significance

Costovertebral angle as a novel tool for predicting the thoracic complication risk following percutaneous nephrolithotomy requiring supracostal access

INTRODUCTION

The objective of this study was to determine whether the costovertebral angle (CVA) and other factors can predict the risk of thoracic complications following percutaneous nephrolithotomy (PCNL).

METHODS

The data of patients who underwent prone PCNL with supracostal access at Suleyman Demirel University Hospital between January 2015 and December 2019 were retrospectively reviewed. Patients' demographics information (age, sex, body mass index [BMI], stone size, and stone location), operative data (supracostal access site, renal puncture site, and laterality), and postoperative thoracic complications (pleural injury) were evaluated. The CVA was measured on preoperative posteroanterior chest X-ray images. The mean CVA of patients with and without thoracic complications was evaluated.

RESULTS

A total of 89 patients (mean age 46.12±15.66 years; 59 men and 30 women) with supracostal access were included in the study. Thoracic complications occurred in 17 (19.1%) patients. Nine (52.9%) hemothorax cases, five (29.4%) pneumothorax cases, and three (17.7%) urinothorax cases were detected. There was a statistically significant difference in the complication rate compared to the percutaneous access site (10^th-11^th supracostal vs. 11^th-12^th supracostal, p=0.004). The mean CVA was significantly lower in patients with complications (45.47±3.59) than in those without complications (53.26±5.98) (p=0.000). No association was found (p>0.05) with age, sex, BMI, laterality, stone surface area, and access site among patients with and without thoracic complications.

CONCLUSIONS

Preoperative CVA can be an effective tool in predicting the risk of postoperative thoracic complications.

Impact of Implementing Contrast-Enhanced Ultrasound for Antegrade Nephrostogram After Percutaneous Nephrolithotomy

OBJECTIVES

To report results from a quality improvement (QI) project evaluating diagnostic performance, hospital resource use, and patient response data for postoperative contrast-enhanced ultrasound (CEUS) antegrade nephrostogram after percutaneous nephrolithotomy.

METHODS

For this Health Insurance Portability and Accountability Act-compliant, Institutional Review Board-approved study, QI data were deidentified and analyzed. On the first postoperative day after percutaneous nephrolithotomy, patients underwent both CEUS and fluoroscopic antegrade nephrostogram. For CEUS, 1.0 mL of Lumason (sulfur hexafluoride lipid type A microspheres; Bracco Diagnostics, Inc, Monroe Township, NJ) was injected via an indwelling nephrostomy tube, with ureteral patency confirmed by identifying intravesical ultrasound (US) contrast. Diagnostic performance for ureteral patency and contrast extravasation was calculated (with fluoroscopy as the reference standard). The examination time, room time, physician time, hospital costs, and patient response data were compared. The mean, standard deviation, 95% confidence interval, differences in mean, and 95% confidence interval of differences were calculated.

RESULTS

Eighty-one examinations were performed in 73 patients during the QI period. The sensitivity and specificity of CEUS for ureteral patency were 96% and 57%, respectively. There was no significant difference in time metrics between modalities, and the cost analysis showed lower direct and indirect costs for CEUS. Patient responses revealed lower levels of comfort for CEUS relative to fluoroscopy, without significant differences in reported pain or effort levels.

CONCLUSIONS

Contrast-enhanced US showed very high sensitivity for ureteral patency; the relatively low specificity may have resulted from false-negative results in fluoroscopy. The hospital costs and resource use of CEUS compared favorably to fluoroscopy. Contrast-enhanced US also offers inherent advantages, including portability and lack of ionizing radiation.

Tubeless supra-costal percutaneous nephrolithotomy is associated with significantly less hydrothorax: a prospective randomized clinical study

OBJECTIVES

To evaluate prospectively whether a tubeless (JJ stent-only) percutaneous nephrolithotomy (PCNL) might reduce the risk of hydrothorax, compared to an approach where a nephrostomy tube is left.

MATERIALS AND METHODS

We conducted a two-arm open-label prospective randomized study (NCT02036398) comparing tubeless supra-costal PCNL (with a JJ stent only) to standard PCNL (with nephrostomy tube and JJ stent) using intention-to-treat (ITT) and per-protocol (PP) analyses. All patients underwent a standard single-stage prone supra-costal procedure with single-tract access. Complication data were collected according to the Clavien-Dindo grading system. The primary endpoint was the rate of hydrothorax, and secondary endpoints included stone-free rate (SFR) and complication rate. Multivariable logistic regression analysis identified factors associated with hydrothorax formation.

RESULTS

Out of 101 patients approached, 75 were finally analysed. No differences were observed between the two arms with regard to baseline demographic and stone characteristics. The mean largest stone size ranged between 23 and 24.2 mm. No significant difference was seen in the mean operating time and length of hospital stay. The incidence of hydrothorax was significantly higher in the nephrostomy group in comparison to the tubeless group (37.8% vs 15.8%, P = 0.031, and 38.4% vs 13.8%, P = 0.016, in the ITT and PP analyses, respectively). The SFR and complication rate were similar in both groups using the ITT and PP analyses. Multivariable logistic regression analysis showed that nephrostomy tube placement was the only covariate associated in a statistically significant manner to hydrothorax (odds ratio 3.628, 95% confidence interval 1.073-12.265; P = 0.038).

CONCLUSION

The rate of hydrothorax in supra-costal PCNL is associated with the type of postoperative drainage left. When possible, a tubeless approach should be applied as it may confer a lower risk of hydrothorax.

Residual stones after percutaneous nephrolithotomy: comparison of intraoperative assessment and postoperative non-contrast computerized tomography

OBJECTIVES

To compare the intraoperative surgeon perspective for detection of residual fragments (RFs) after percutaneous nephrolithotomy (PNL) with postoperative NCCT.

METHODS

A prospective study of adult patients who underwent PNL between March and September 2014 was conducted. Stone complexity was evaluated using the Guy's stone score (GSS). All patients were evaluated by pre- and postoperative NCCT. After the procedure, the surgeon had been asked whether there were residual stones or not. The sensitivity, specificity and predictive values were tested against postoperative NCCT. Predictors of accurate intraoperative assessment were determined using univariate and multivariate statistical analyses.

RESULTS

The study included 306 consecutive patients. The surgeons reported no residual stones in 236 procedures; of whom 170 (72%) were reported stone-free by NCCT. On the other hand, 65 out of 70 procedures (93%) reported with residual stones by the surgeons were true by NCCT. The sensitivity was 50% and the NPV was 72%, while the specificity was 97% and the PPV was 93%. On multivariate analysis, only lower GSS (p < 0.001) was independently associated with true negative surgeon opinion.

CONCLUSIONS

Although there was a high surgeon ability to detect post-PNL residual stones, postoperative imaging is mandatory because of the high false negative rates and low NPV. The surgeon opinions can be judged only in stones with lower GSS. The NPV could be enhanced if a consistent definition of clinically significant RFs is introduced.

Pyelocaliceal Distribution of Kidney Stones Used as an Outcome Predictor in Percutaneous Nephrolithotomy After Being Evaluated with Preoperative and Postoperative CT Scan

OBJECTIVE

To identify kidney stone characteristics that will determine either success or failure of a percutaneous nephrolithotomy (PCNL) and design a classification system to predict results according to these characteristics.

MATERIALS AND METHODS

One hundred thirty-eight patients were assessed with multislice abdominal and pelvic CT before and after PCNL. With regard to pyelocaliceal stone distribution, we classified our patients in two groups that we called "no extra stone in middle calix" (NESMC) and "extra stone in middle calix" (ESMC), according to the difficulty in reaching the stones. We did a univariate and a multivariate analysis, as well as a receiving operating curve (ROC) of the proposed classification, based on the foreseen probabilities, to determine the diagnostic yield.

RESULTS

Global residual lithiasis (RL) was 26.08%. The proportion of patients with RL according to classification was NESMC 11.5% and ESMC 59.5%. In the univariate logistic regression analysis of the distribution, number, total volumetry, side, type, radio-opacity of stones, and the presence or not of preoperatory urinary tract infection, the variables related to RL were the distribution (11.3; 95% confidence interval [95% CI] 4.7, 27.4), volumetry (odds ratio [OR] 1.01; 95% CI 1.004, 1.014), and the presence of staghorn stones (OR 6.64; 95% CI 2.463, 17.905). In the multivariate analysis, distribution was statistically significant (OR 8.687; 95% CI 2.69, 28.06), whereas total volumetry and the presence of staghorn stones were not (OR 1; 95% CI 1.000, 1.000 and OR 2.7; 95% CI 0.35, 20.57, respectively). The ROC showed an area under the curve of 0.77.

CONCLUSION

In our experience, the distribution of kidney stones is the most important predictor of RL after PCNL. The results also suggest that the presence of stones in the middle calix has a direct impact on the stone-free rate. We put forward a simple and reproducible classification, easy to apply, and useful to estimate the chances of success of the procedure using preoperatory CT scans.

Cross-sectional imaging of iatrogenic complications after extracorporeal and endourological treatment of urolithiasis

Extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL) and ureteroscopy (URS) currently represent the mainstay treatment options for the vast majority of patients with urolithiasis, with limited contraindications and high success rates. However, minimally invasive extracorporeal and endourological treatments are associated with a non-negligible morbidity including occasional life-threatening occurrences. These complications represent a source of concern for urologists since they may result in prolonged hospitalisation, need for surgical, endoscopic or interventional treatment, long-term renal impairment, and sometimes even medical malpractice claims. Due to the increasing prevalence of urolithiasis and the large number of therapeutic procedures performed, in hospitals with active urologic practices radiologists are increasingly requested to investigate suspected post-procedural complications following ESWL, PCNL or ureteroscopic stone removal. Based upon our experience, this pictorial essay provides an overview of current extracorporeal and endourological treatment modalities for urolithiasis, including indications and possible complications according to the most recent guidelines from the European Association of Urology (EAU). Afterwards, we review the clinical features and cross-sectional imaging appearances of common and unusual complications with case examples, including steinstrasse, subcapsular, perirenal and suburothelial haemorrhages, severe urinary tract infections (such as pyeloureteritis, pyelonephritis, renal abscesses and pyonephrosis), ureteral injuries and delayed strictures.

Teaching points

• Extracorporeal lithotripsy, percutaneous nephrolitotomy and ureteroscopy allow treating urolithiasis.

• Minimally invasive extracorporeal and endourological treatment have non-negligible morbidity.

• Multidetector CT allows confident assessment of stone-free status and postprocedural complications.

• Main complications include steinstrasse, bleeding, severe infections, ureteral injuries and strictures.

• Imaging triage allows the choice among conservative, surgical, endoscopic or interventive treatment.