Contrast Enhanced Ultrasound as a Radiation-Free Alternative to Fluoroscopic Nephrostogram for Evaluating Ureteral Patency

Radiation exposure of urologists during endourological procedures: a systematic review

INTRODUCTION

Ionizing radiation is used daily during endourological procedures. Despite the dangers of both deterministic and stochastic effects of radiation, there is a lack of knowledge and awareness among urologists. This study reviewed the literature to identify the radiation exposure (RE) of urologists during endourological procedures.

METHODS

A literature search of the Medline, Web of Science, and Google Scholar databases was conducted to collect articles related to the radiation dose to urologists during endourological procedures. A total of 1966 articles were screened. 21 publications met the inclusion criteria using the PRIMA standards.

RESULTS

Twenty-one studies were included, of which 14 were prospective. There was a large variation in the mean RE to the urologist between studies. PCNL had the highest RE to the urologist, especially in the prone position. RE to the eyes and hands was highest in prone PCNL, compared to supine PCNL. Wearing a thyroid shield and lead apron resulted in a reduction of RE ranging between 94.1 and 100%. Educational courses about the possible dangers of radiation decreased RE and increased awareness among endourologists.

CONCLUSIONS

This is the first systematic review in the literature analyzing RE to urologists over a time period of more than four decades. Wearing protective garments such as lead glasses, a thyroid shield, and a lead apron are essential to protect the urologist from radiation. Educational courses on radiation should be encouraged to further reduce RE and increase awareness on the harmful effects of radiation, as the awareness of endourologists is currently very low.

Hydrostatic pressure of the renal pelvis as a radiation-free alternative to fluoroscopic nephrostogram following percutaneous nephrolithotomy

Background

We evaluated the hydrostatic pressure of the renal pelvis (RPP) as a radiation-free alternative to fluoroscopic nephrostogram to assess ureteral patency after percutaneous nephrolithotomy (PCNL).

Methods

Retrospective non-inferiority study analyzing 248 PCNL-patients (86 female (35%) and 162 males (65%)) between 2007 and 2015. Postoperatively, RPP was measured using a central venous pressure manometer in cmH2O. The primary endpoint was to assess RPP depending on the patency of the ureter and the nephrostomy tube removal. Secondary, the upper limit of normal RPP of $$\le$$ ≤ 20 cmH2O was assessed as an indicator of an unobstructed patency.

Results

The median procedure duration was 141 min (112–171.5) with a stone free rate of 82% (n = 202). RPP was significantly higher in patients with obstructive nephrostogram with 25.0 mmH2O (21.0–32.0) versus 20.0 mmH2O (16.0–24.0; p < 0.001). The pressure was lower in successful nephrostomy removal with 18 cmH2O (15–21) versus 23 cmH2O (20–29) in the leakage group (p < 0.001). The analysis of a cut-off of $$\le$$ ≤ 20 cmH2O showed a sensitivity of 76.9% (95% CI [60.7%; 88.9%]) and a specificity of 61.5% (95% CI [54.6%; 68.2%]). The negative predictive value was 93.4% (95% CI: [87.9%; 97.0%]) and the positive predictive value 27.3% (95% CI [19.2%; 36.6%]). The accuracy of the model showed an AUC = 0.795 (95% CI [0.668; 0.862]).

Conclusion

The hydrostatic RPP seems to allow a bedside evaluation of ureteral patency after PCNL.

Urinary tract obstruction: Ultrasound-guided intervention

Introduction

Urinary tract obstruction (UTO) is a common clinical problem of which there are many potential causes. The aim of this feature article is to explore the role of ultrasound in diagnosing UTO, during guided interventional procedures and the potential procedural complications.Topic description and discussion: Ultrasound is an integral imaging modality throughout the management pathway of a patient with UTO and is often utilised as a first-line test in diagnosis and treatment. Percutaneous nephrostomy is an interventional technique, usually performed by radiologists or interventional sonographers, as either a short- or long-term management strategy. It can either be used in isolation or to gain access to the renal collecting system prior to more complex interventional or surgical techniques. Ultrasound-guided interventional techniques to relieve UTO can be employed in a number of clinical scenarios each with their own indications, contraindications and complications.

Conclusion

Ultrasound plays a unique role in the planning and active stages of intervention with the provision of dynamic imaging which is crucial for providing safe and effective patient management.

Contrast-enhanced ultrasound in pediatric interventional radiology

There is growing interest in the use of contrast-enhanced ultrasound (CEUS) in diagnostic and interventional radiology. CEUS applications in interventional radiology are performed with intravascular or intracavitary administration of microbubble-based US contrast agents to allow for real-time evaluation of their distribution within the vascular bed or in body cavities, respectively, providing additional information beyond gray-scale US alone. The most common interventional-radiology-related CEUS applications in children have been extrapolated from those in adults, and they include the use of CEUS to guide lesion biopsy and to confirm drain placement in pleural effusions and intra-abdominal fluid collections. Other applications are emerging in interventional radiology for use in adults and children, including CEUS to optimize sclerotherapy of vascular malformations, to guide arthrography, and for lymphatic interventions. In this review article we present a wide range of interventional-radiology-related CEUS applications, emphasizing the current and potential uses in children. We highlight the technical parameters of the CEUS examination and discuss the main imaging findings.

Comparison of contrast-enhanced ultrasound versus conventional ultrasound-guided percutaneous nephrolithotomy in patients with nondilated collecting system: a randomized controlled trial

OBJECTIVE

To compare the safety, effectiveness, and feasibility of contrast-enhanced ultrasound (CEUS) versus conventional ultrasound-guided percutaneous nephrolithotomy (PCNL) in patients with nondilated collecting system.

METHODS

Between July 2018 and July 2020, 160 kidney stone patients with nondilated collecting system planned for PCNL were randomly assigned into two groups, CEUS with retrograde ureteral contrast injection and conventional ultrasound with retrograde ureteral normal saline injection. Patient's demographics, the success rate of puncture, success rate of a single-needle puncture, number of punctures, puncture time, perioperative outcomes, stone-free rate, and incidence of complications were compared.

RESULTS

The success rate of a single-needle puncture for CEUS-guided PCNL was higher than that in the conventional ultrasound group (88.5% vs. 73.7%, p = 0.02). Patients performed with CEUS-guided PCNL required less needle passes (p = 0.02), shorter needle puncture time (p = 0.031), and shorter channel establishment time (p = 0.04) than those guided with conventional ultrasound. The postoperative hemoglobin decrease in the CEUS-guided PCNL group was less than that of the control group (p = 0.02). There was no significant difference in operating time, length of hospital stays, kidney function change, and complications between the two groups (p > 0.05). The 1-month stone-free rate was 94.9% in the CEUS group and 90.8% in the control group (p > 0.05).

CONCLUSIONS

Compared with conventional ultrasound, CEUS-guided PCNL may facilitate ultrasound-guided PCNL for patients without hydronephrosis, and benefited with a higher success rate of a single-needle puncture, less needle passes, shorter puncture time, and lower postoperative Hb drop.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR1800016981 KEY POINTS: • Compared with conventional ultrasound, CEUS-guided PCNL is a safe and efficacious procedure for kidney stone patients with nondilated collecting system. • Compared with conventional ultrasound, CEUS-guided PCNL benefited with a higher success rate of a single-needle puncture, less needle passes, shorter puncture time, and lower postoperative Hb drop. • CEUS-guided PCNL associated with the more accurate needle puncture and acceptable 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.

Assessment of the Contrast-Enhanced Ultrasound in Percutaneous Nephrolithotomy for the Treatment of Patients with Nondilated Collecting System

Purpose: To investigate the clinical value of contrast-enhanced ultrasound (CEUS) in percutaneous nephrolithotomy (PCNL) for kidney stone patients without hydronephrosis. Methods: Patients with nondilated collecting system kidney stones who underwent PCNL between October 2018 and December 2019 at our hospital were enrolled in this study. Patients who met the inclusion criteria were randomized into two groups: a CEUS-guided PCNL group and a conventional ultrasound (US)-guided PCNL group. The operation results of the two groups were compared, including the number of attempts for effective puncture, duration to effective puncture, stone clearance rate, blood loss, postoperative complications, and hospital stay. Results: Fifty-six patients with a nondilated collecting system who underwent PCNL for 60 kidneys were included in this study, including 4 patients who underwent bilateral PCNL due to bilateral renal stones. There were 30 kidneys in each group. All patients successfully underwent PCNL. The CEUS-guided PCNL group had more accurate punctures, with a higher effective rate of one puncture and shorter puncture time. There was no statistically significant difference in stone clearance rate between the two groups. Four cases of double channels were established in the conventional US-guided PCNL group, while there was only one case in the CEUS-guided PCNL group. In the CEUS-guided PCNL group, most cases (96.7%, 29/30) had no or only mild complications, which were significantly better than the conventional US-guided PCNL group (76.7%, 23/30). The mean postoperative hemoglobin loss in the CEUS-guided PCNL group was 9.5 (range 1-25) g/L, which was significantly lower than 15.5 (range 5-52) g/L in the conventional US-guided PCNL group. Conclusion: The CEUS technique can improve visibility of the nondilated renal collecting system, facilitate selection of suitable calix, and identify renal calix fornix. It also benefits needle placement in patients with a nondilated collecting system.

Efficacy of contrast-enhanced percutaneous nephrosonography to evaluate urinary tract patency in children

A novel method known as contrast-enhanced percutaneous nephrosonography (cePNS), using an ultrasound contrast agent administered through the nephrostomy catheter, has been used to evaluate the urinary tract patency in children. Nine cePNS examinations were performed in seven children to evaluate the urinary tract patency prior to further management. The cePNS results were compared with the clinical evaluation of patent urinary tract cases or with surgery results. Both, the technical success rate and accuracy of cePNS examinations were 100%. CePNS is a radiation-free method and can be performed as a continuation of an ultrasound examination.

Role for contrast-enhanced ultrasound in assessing complications after kidney transplant

Kidney transplantation (KT) is an effective treatment for end-stage renal disease. Despite their rate has reduced over time, post-transplant complications still represent a major clinical problem because of the associated risk of graft failure and loss. Thus, post-KT complications should be diagnosed and treated promptly. Imaging plays a pivotal role in this setting. Grayscale ultrasound (US) with color Doppler analysis is the first-line imaging modality for assessing complications, although many findings lack specificity. When performed by experienced operators, contrast-enhanced US (CEUS) has been advocated as a safe and fast tool to improve the accuracy of US. Also, when performing CEUS there is potentially no need for further imaging, such as contrast-enhanced computed tomography or magnetic resonance imaging, which are often contraindicated in recipients with impaired renal function. This technique is also portable to patients' bedside, thus having the potential of maximizing the cost-effectiveness of the whole diagnostic process. Finally, the use of blood-pool contrast agents allows translating information on graft microvasculature into time-intensity curves, and in turn quantitative perfusion indexes. Quantitative analysis is under evaluation as a tool to diagnose rejection or other causes of graft dysfunction. In this paper, we review and illustrate the indications to CEUS in the post-KT setting, as well as the main CEUS findings that can help establishing the diagnosis and planning the most adequate treatment.

Intracavitary contrast-enhanced ultrasonography in children: review with procedural recommendations and clinical applications from the European Society of Paediatric Radiology abdominal imaging task force

Contrast-enhanced ultrasonography (US) has become an important supplementary tool in many clinical applications in children. Contrast-enhanced voiding urosonography and intravenous US contrast agents have proved useful in routine clinical practice. Other applications of intracavitary contrast-enhanced US, particularly in children, have not been widely investigated but could serve as a practical and radiation-free problem-solver in several clinical settings. Intracavitary contrast-enhanced US is a real-time imaging modality similar to fluoroscopy with iodinated contrast agent. The US contrast agent solution is administered into physiological or non-physiological body cavities. There is no definitive list of established indications for intracavitary US contrast agent application. However, intracavitary contrast-enhanced US can be used for many clinical applications. It offers excellent real-time spatial resolution and allows for a more accurate delineation of the cavity anatomy, including the internal architecture of complex collections and possible communications within the cavity or with the surrounding structures through fistulous tracts. It can provide valuable information related to the insertion of catheters and tubes, and identify related complications such as confirming the position and patency of a catheter and identifying causes for drainage dysfunction or leakage. Patency of the ureter and biliary ducts can be evaluated, too. US contrast agent solution can be administered orally or a via nasogastric tube, or as an enema to evaluate the gastrointestinal tract. In this review we present potential clinical applications and procedural and dose recommendations regarding intracavitary contrast-enhanced ultrasonography.

Contrast-Enhanced Ultrasound Guidance for Interventional Procedures

Since its introduction, contrast-enhanced ultrasound (CEUS) has gained an important role in the diagnosis and management of abdominal and pelvic diseases. Contrast-enhanced ultrasound can improve lesion detection rates as well as success rates of interventional procedures when compared to conventional ultrasound alone. Additionally, CEUS enables the interventionalist to assess the dynamic enhancement of different tissues and lesions, without the adverse effects of contrast-enhanced computed tomography, such as exposure to ionizing radiation and nephrotoxicity from iodinated contrast material. This review article describes the various applications and advantages of the use of CEUS to enhance performance of ultrasound-guided interventions in the abdomen and pelvis.

Contrast-enhanced ultrasound (CEUS) nephrostogram: utility and accuracy as an alternative to fluoroscopic imaging of the urinary tract

AIM

To establish the feasibility and accuracy of contrast-enhanced ultrasound (CEUS) nephrostogram in comparison to the reference standard, fluoroscopic nephrostogram, in providing alternative imaging of the urinary tract post-nephrostomy insertion.

MATERIALS AND METHODS

This prospective study was approved by the institutional and national ethics committee. All patients for whom a fluoroscopic nephrostogram was requested were included. Fluoroscopic and CEUS nephrostograms were performed within 24 hours. Image analysis (nephrostomy position, opacification of pelvicalyceal system, ureter, and bladder) was performed by two reviewers, and the diagnostic accuracy of the CEUS nephrostograms was compared to fluoroscopic nephrostograms.

RESULTS

Sixty-two nephrostograms were performed in 48 patients from June 2011 to April 2016, (male: 25/48, 52.1%; mean age 65 years, range 28-90 years). Indications for nephrostomy were: malignancy (29/62; 46.8%), benign ureteric stricture (14/62; 22.6%), urinary diversion (8/62; 12.9%), renal calculus (5/62; 8.1%), haematoma (3/62; 4.8%) or pelvi-ureteric junction obstruction (3/62; 4.8%). Two nephrostomies were identified as displaced by both techniques. The pelvicalyceal system was visualised in 60/60 (100%) examinations in both fluoroscopic and CEUS nephrostograms. The entire ureter was visualised in 30/60 (50%) with CEUS compared to 32/60 (53.3%) fluoroscopically. The distal ureter was the least well-visualised segment for both techniques with no significant difference (p=0.815). Both CEUS and fluoroscopy could be used to correctly identify complications including entero-ureteric fistula or urine leak. Fluoroscopic nephrostogram demonstrated drainage into the bladder in 33/60 (55%), CEUS confirmed drainage in 34/60 (56.7%) cases (p=0.317).

CONCLUSIONS

CEUS nephrostogram can determine the correct positioning of a nephrostomy and assess drainage into the bladder with statistically comparable results to fluoroscopy.

Advanced ultrasound applications in the assessment of renal transplants: contrast-enhanced ultrasound, elastography, and B-flow

Ultrasound is routinely used as the first imaging exam for evaluation of renal transplants and can identify most major surgical complications and evaluate vascularity with color Doppler. Ultrasound is limited, however, in the detection of parenchymal disease processes and Doppler evaluation is also prone to technical errors. Multiple new ultrasound applications have been developed and are under ongoing investigation which could add additional diagnostic capability to the routine ultrasound exam with minimal additional time, cost, and patient risk. Contrast-enhanced ultrasound (CEUS) can be used off-label in the transplant kidney, and can assist in detection of infection, trauma, and vascular complications. CEUS also can demonstrate perfusion of the transplant assessed quantitatively with generation of time-intensity curves. Future directions of CEUS include monitoring treatment response and microbubble targeted medication delivery. Elastography is an ultrasound application that can detect changes in tissue elasticity, which is useful to diagnose diffuse parenchymal disease, such as fibrosis, otherwise unrecognizable with ultrasound. Elastography has been successfully applied in other organs including the liver, thyroid, and breast; however, it is still under development for use in the transplant kidney. Unique properties of the transplant kidney including its heterogeneity, anatomic location, and other technical factors present challenges in the development of reference standard measurements. Lastly, B-flow imaging is a flow application derived from B-mode. This application can show the true lumen size of a vessel which is useful to depict vascular anatomy and bypasses some of the pitfalls of color Doppler such as demonstration of slow flow.

Exposure to Radioactive Emanations of Medical Personnel in Percutaneous Nephrolithotomy

The use of radioactive emanations has been of great importance for the performance of endourology procedures, such as percutaneous nephrolithotomy (NLP). The damage to health caused by radiation has been a sensitive issue. The objective of this work was to determine the dose received by the surgeon during NLP and the total dose generated by the fluoroscope. A cross-sectional study was conducted with data from a cohort study with a duration of 18 months that included 101 patients. Radiation was measured with dosimeter during the last 6 months. During the last 6 months of the study, 34 patients were submitted to surgery. The average age was 47 years. Average fluoroscopy time was 58.3 second (24-122 seconds) in both male and female groups, with 57.16 seconds and 58.95 seconds per case, respectively (P = .6). Radiation emitted during 6 months for the 34 patients was 330.5 mGy. The total radiation measured by the dosimeter was 1 mSv, which is equivalent to 0.3% of the total radiation applied during the procedures. Doses measured by the dosimeter on the surgeon were within the recommended annual doses although dose received by the hands exceeds the authorized limits (500 mSv/y).

Contrast-enhanced ultrasound (CEUS) in abdominal intervention

The introduction of ultrasound contrast agents has rendered contrast-enhanced ultrasound (CEUS) a valuable complementary technique to address clinically significant problems. This pictorial review describes the use of CEUS guidance in abdominal intervention and illustrates such application for a range of clinical indications. Clinical application of CEUS discussed include commonly performed abdominal interventional procedures, such as biopsy, drainage, nephrostomy, biliary intervention, abdominal tumor ablation and its subsequent monitoring, and imaging of vascular complications following abdominal intervention. The purpose of this article is to further familiarize readers with the application of CEUS, particularly its specific strength over alternative imaging modalities, in abdominal intervention.

Endocavitary contrast enhanced ultrasound (CEUS): a novel problem solving technique

Abstract

Contrast-enhanced ultrasound (CEUS) is a technique that has developed as an adjunct to conventional ultrasound. CEUS offers a number of benefits over conventional axial imaging with computerised tomography and magnetic resonance imaging, primarily as a “beside” test, without ionising radiation or the safety concerns associated with iodinated/gadolinium-based contrast agents. Intravascular use of ultrasound contrast agents (UCAs) is widespread with extensive evidence for effective use. Despite this, the potential utility of UCAs in physiological and non-physiological cavities has not been fully explored. The possibilities for endocavitary uses of CEUS are described in this review based on a single-centre experience including CEUS technique and utility in confirming drain placement, as well as within the biliary system, urinary system, gastrointestinal tract and intravascular catheters.

Teaching Points

• CEUS offers an excellent safety profile, spatial resolution and is radiation free.

• Endocavitary CEUS provides real-time imaging similar to fluoroscopy in a portable setting.

• Endocavitary CEUS can define internal architecture of physiological cavities.

• Endocavitary CEUS can confirm drain position in physiological and non-physiological cavities.

Research progress of percutaneous nephrolithotomy

Percutaneous nephrolithotomy (PCNL) is generally accepted as the gold standard treatment for the treatment of large kidney stones (> 2 cm). For nearly 40 years, with the continuous progress of technology and the constant updating of ideas, PCNL has made great progress. In this review, we discuss the current research progress, recent advancement and hot spot of the whole process of PCNL including anesthesia, position, puncture, dilation, lithotripsy approaches, perfusate, tube placement, hospitalization time, drug, treatment of residual stones, prognosis judgment and operation evaluation by summarizing the related research in this article.