An investigation into the clinical accuracy of twinkling artifacts in patients with urolithiasis smaller than 5 mm in comparison with computed tomography scanning

Prevalence and clinical association of hyperechoic crystal deposits on ultrasonography in patients with chronic kidney disease: a cross-sectional study from a single center

BACKGROUND

Hyperechoic crystal deposits can be detected in the kidney medulla of patients with gout by ultrasonography examination. Chronic kidney disease (CKD) is usually accompanied with hyperuricemia. Whether hyperechoic crystal deposition could be detected by ultrasonography in CKD patients, and its clinical association are unknown.

METHODS

Five hundred and fifteen consecutive CKD patients were included in this observational study. Clinical, biochemical and pathological data were collected and analyzed.

RESULTS

Altogether, 234 (45.4%) patients were found to have hyperuricemia and 25 patients (4.9%) had gout history. Hyperechoic crystal deposits in kidney medulla were found in forty-four (8.5%) patients, on ultrasonography. Compared with patients without hyperechoic crystal deposits, patients with deposits were more likely to be male, younger, with gout history and presenting with higher serum uric acid level, lower estimated glomerular filtration rate, lower urine pH, lower 24 h-urinary citrate and uric acid excretion, and with a higher percentage of ischemic nephropathy (all p < 0.05). On multivariable logistic analysis, the hyperechoic depositions were associated with age [0.969 (0.944, 0.994), p = 0.016], serum uric acid level [1.246 (1.027, 1.511), p = 0.026], Sqrt-transformed 24 h-urine uric acid excretion [0.923 (0.856, 0.996), p = 0.039], and ischemic nephropathy [4.524 (1.437, 14.239), p = 0.01], respectively.

CONCLUSIONS

Hyperechoic crystal deposition can be detected in kidney medulla by ultrasonography; in CKD patients their presence was associated with hyperuricemia as well as with ischemic nephropathy.

A new way to visualize prostate brachytherapy needles using ultrasound color Doppler and needle surface modifications

PURPOSE

Suboptimal ultrasound conspicuity of the brachytherapy applicator can lead to inaccurate image reconstructions of the applicator resulting in decreased tumor control or increased normal tissue dose. This feasibility study aims to improve ultrasound conspicuity of high-dose rate (HDR) brachytherapy needles by modifying the surface of the needles to produce a color Doppler twinkling signature.

MATERIALS AND METHODS

Surface modifications of standard 17-gauge titanium HDR brachytherapy needles included laser-scribing, application of polymethyl methacrylate (PMMA), and coating with a commercially available echogenic coating. Laser-scribing was performed with variable widths (0.1-1 mm) and depths (10-100 μm). The echogenic coating was applied with 3 different thicknesses (27, 40, and 64 μm). Unmodified and modified needles were imaged under B-mode and color Doppler ultrasound in phantom and cadaver, and the signal strength was recorded.

RESULTS

Laser-scribed, PMMA-coated, and echogenic-coated brachytherapy needles produced a twinkling signature along the needle shaft on color Doppler ultrasound. Twinkling was observed with laser-scribe depths >20 μm and widths >0.1 mm and from echogenic coatings 40 μm and 64 μm thick. Twinkling was not observed with unmodified needles. The twinkling signature had a spectral composition with a uniform magnitude between the velocities of 2 to 16 cm/s.

CONCLUSIONS

Color Doppler ultrasound of surface-modified brachytherapy applicators may improve applicator conspicuity aiding applicator placement and digitization. HDR brachytherapy needles may be modified to produce the twinkling signature via laser-scribing, PMMA rings, or applying an echogenic coating.

Diagnostic accuracy of Doppler twinkling artifact for identifying urolithiasis: a systematic review and meta-analysis

OBJECTIVE

The goal of this study was to perform a comprehensive meta-analysis to assess the overall diagnostic value of Doppler twinkling for the diagnosis of urolithiasis.

METHODS

We systematically searched the PubMed, EMBASE, and Cochrane Library databases from inception through May 31, 2021. Studies including patients with urolithiasis who underwent color flow Doppler sampling to highlight the twinkling artifact and computed tomography were included. Diagnostic test meta-analysis was performed with a bivariate model. We used summary receiver operating characteristic curves to summarize the overall diagnostic performance. The weighted sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were calculated.

RESULTS

Sixteen studies involving 4572 patients were included in the systematic review and meta-analysis. The weighted sensitivity was 0.86 (95% confidence interval [CI] 0.72-0.94), specificity 0.92 (95% CI 0.75-0.98), positive likelihood ratio 11.3, negative likelihood ratio 0.2, and diagnostic odds ratio 75.5.

CONCLUSION

The Doppler twinkling artifact has good diagnostic value for the diagnosis of urolithiasis and should be used as a complementary tool in the diagnosis of urolithiasis.

Does twinkle artifact truly represent a kidney stone on renal ultrasound?

INTRODUCTION

Nephrolithiasis is detected on ultrasound by the presence of an echogenic focus, posterior acoustic shadowing and/or twinkle artifact (TA). TA has been shown to be highly predictive of nephrolithiasis in adults with renal colic and ureteral stones. We sought to evaluate if TA is reliable for diagnosing nephrolithiasis in the pediatric population.

METHODS

We reviewed renal ultrasound reports indicating presence or absence of TA associated with a single echogenic focus in the kidney or ureter. Exclusion criteria were age >18, multiple echogenic foci or medullary calcinosis, no follow-up, or TA located outside the kidney or ureter. Stone was confirmed either by CT within 3 months of color Doppler ultrasound, visualization on ureteroscopy, or patient report of passing the stone.

RESULTS

Five hundred and ninety-nine ultrasound reports were reviewed and 293 met inclusion criteria. Sixty-nine had diffuse twinkle without echogenic focus and 224 showed TA with single echogenic focus. 135 patients had confirmatory information available (Summary Table). Nephrolithiasis was diagnosed using TA and confirmed on confirmatory studies for 49 ultrasounds. The majority of confirmed stones were in the kidney (n = 40; 82%) and mean size of confirmed stones on ultrasound was 5 mm (range 1.5-10). Sensitivity, specificity, positive predictive value and negative predictive value of TA for detecting nephrolithiasis were 83%, 78%, 74% and 86% respectively.

CONCLUSIONS

Compared to the adult literature, TA in children has lower sensitivity, specificity and positive predictive value, but similar negative predictive value for diagnosing nephrolithiasis. This may be related to renal location and smaller stone size. The presence of TA should be weighed in the setting of other clinical and radiographic evidence of nephrolithiasis.

A cross-sectional study of 502 patients found a diffuse hyperechoic kidney medulla pattern in patients with severe gout

We have previously shown that ultrasonography can detect hyperechogenic crystal deposits in the kidney medulla of patients with gout. In this cross-sectional study we investigated the frequency and clinical correlates of hyperechogenic kidney medulla in 502 consecutive primary consultants for gout (ACR/EULAR criteria) at the Vien Gut medical center in Ho Chi Minh City, Vietnam. None of these patients received urate-lowering drugs. Kidney medulla echogenicity on B-mode ultrasonography was compared to that of the kidney cortex. Overall, 36% patients showed a hyperechoic pattern of Malpighi pyramids. On univariate analysis, the pattern was significantly associated with age, estimated gout duration, steroid-dependency, clinical tophi, urate arthropathy, double contour thickness at the scanned joints, coronary heart disease, arterial hypertension, hyperuricemia, proteinuria, leukocyturia, and decreased estimated glomerular filtration rate. On multivariable analysis, the hyperechoic pattern was associated with estimated disease duration, clinical tophi, urate arthropathy, double contour thickness and decreased estimated glomerular filtration rate. No hyperechoic pattern was observed in 515 consecutive consultants without gout. Thus, hyperechoic kidney medulla was frequently demonstrated in Vietnamese patients with tophaceous gout and associated with features of tubulointerstitial nephritis. This finding revives the hypothesis of microcrystalline nephropathy of gout, predominantly seen in untreated gouty patients, which could be an important target for urate-lowering therapy.

Diagnostic Accuracy of Doppler Twinkling Artifact for Identifying Urinary Tract Calculi

Introduction

Flank pain is a frequent cause of emergency department visits and is often due to renal or ureteric colic. Ultrasound is often the initial imaging study used for the detection of urinary tract calculi. Twinkling artifact is a Doppler artifact usually seen on echogenic rough surfaces such as calculi. Its presence can improve the sensitivity and specificity of ultrasound in stone detection. The objective of the current study was to determine the diagnostic accuracy of the Doppler twinkling artifact for detecting urinary calculi using non-contrast computed tomography as the gold standard.

Materials and methods

In this cross-sectional study, both male and female patients of any age having flank pain, burning micturition with or without hematuria were included. Ultrasound was performed and the presence or absence of Doppler twinkling artifact on calculus was noted. Following ultrasound, patients underwent plain CT scan and findings of stones were documented. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of Doppler twinkling artifact was calculated considering CT findings as the gold standard.

Results

Out of the total 221 patients, 146 (66.1%) were males and 75 (33.9%) were females. The mean age of the patients was 45.98 ± 16.30 years. Urinary tract calculi on ultrasound were observed in 74 (33.50%) patients, while on CT urinary tract calculi were observed in 127 (57.50%) patients. Diagnostic accuracy of Doppler twinkling artifact was found to be 71.49% with sensitivity, specificity, positive predictive value, and negative predictive value of 54.33%, 94.68%, 93.24%, and 60.54%, respectively.

Conclusion

Doppler twinkling artifact has low sensitivity, high specificity, and suboptimal diagnostic accuracy for the diagnosis of urinary tract calculi. Integration of this artifact has a lower sensitivity as compared to non-contrast CT scan. Multicentric studies with larger sample size and focusing on interobserver and intraobserver variability are recommended to have a consensus regarding Doppler twinkling artifact in the evaluation of renal and ureteric calculi.