Evaluation of patients with suspected ureteral calculi using sonography as an initial diagnostic tool: how can we improve diagnostic accuracy?

Dynamics of crevice microbubbles that cause the twinkling artifact

The Doppler ultrasound twinkling artifact, a rapid color shift, appears on pathological mineralizations and is theorized to arise from scattering off micron-sized crevice microbubbles. However, the influence of crevice number and size as well as the bubble dynamics on twinkling is not well-understood. Cylinders with diameters of 0.8-1.2 µm and depths of 1 µm were etched into a silicon wafer and crevice bubbles were driven at 0.75, 2.5, and 5.0 MHz while monitoring with high-speed photography. Experimental results were compared to a derived crevice bubble model. On three separate wafers, cylindrical crevices (10 or 100) with diameters of 1, 10, or 100 µm and depths of 10 µm were etched and imaged with a research ultrasound system in Doppler mode at 5, 7.8, and 18.5 MHz. Within the pressure ranges studied here (∼1MPa), no bubble oscillation was observed for the 0.8-1.2 µm crevice bubbles which matched computational results. Crevices with 1 and 10 µm diameters produced more twinkling than 100 µm crevices at 5 and 7.8 MHz. In contrast, 100 µm crevices produced more twinkling than 1 or 10 µm crevices at 18.5 MHz (p < 0.001 in all cases). These results provide better insight into how crevice bubbles cause twinkling on pathological mineralizations.

Urolithiasis diagnosed with endovaginal ultrasound after vaginal prolapse repair surgery using mesh: A case report

Pain after vaginal prolapse repair surgery with mesh is generally attributed to the mesh fixation, particularly to mesh erosion, dislocation or the development of hematoma. However, once all the causes have been excluded, the urinary system, bladder and ureters should be accurately examined by means of endovaginal ultrasound. This report concerns the case of a 72-year-old woman who had undergone mesh-supported prolapse surgery 3 months prior, with no other relevant diseases, who visited the emergency department complaining of dull, right-sided colic pain. The endovaginal ultrasound examination revealed a prevesical ureteral calculus on the right side with consequent dilatation of the proximal ureter. Computed tomography of the abdomen and pelvis confirmed the calculus in the distal right ureter and revealed a right renal lower pole calculus. The patient underwent treatment via an operative ureterorenoscopy with removal of stones and placement of a double-J-stent. Two months later, a second ureterorenoscopy was performed with double-J-stent removal and concomitant stone extraction. It appears that no similar cases have been reported in the literature. This is why, during the urogynecological postoperative follow-up, it is of paramount importance to examine the entire urogenital system with endovaginal ultrasound. This case report highlights how, through a simple, non-invasive, radiation-free examination, like ultrasound, most of the post-operative complications of vaginal prolapse repair surgery using mesh, including urolithiasis, can be excluded.

Effect of ambient gas and crystal features on Doppler ultrasound twinkling of pathological mineralizations

Color Doppler twinkling on kidney stones and other pathological mineralizations is theorized to arise from stable microbubbles, which suggests twinkling will be sensitive to ambient gas. Here, lab-grown cholesterol, calcium phosphate, and uric acid crystals were imaged with ultrasound in water while varying oxygen, carbon dioxide, and nitrogen levels. Twinkling was found to increase on cholesterol in elevated oxygen, cholesterol and calcium phosphate in elevated carbon dioxide, and no crystals in elevated nitrogen. These results support the crevice microbubble theory of twinkling and suggest gases may be varied to enhance twinkling on some mineralizations.

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.

The effect of crystal composition and environment on the color Doppler ultrasound twinkling artifact

Objective.Pathological mineralizations form throughout the body and can be difficult to detect using conventional imaging methods. Color Doppler ultrasound twinkling highlights ∼60% of kidney stones with a rapid color shift and is theorized to arise from crevice microbubbles as twinkling disappears on kidney stones at elevated pressures and scratched acrylic balls in ethanol. Twinkling also sometimes appears on other pathological mineralizations; however, it is unclear whether the etiology of twinkling is the same as for kidney stones.Approach.In this study, five cholesterol, calcium phosphate, and uric acid crystals were grownin vitroand imaged in Doppler mode with a research ultrasound system and L7-4 transducer in water. To evaluate the influence of pressure on twinkling, the same crystals were imaged in a high-pressure chamber. Then, the effect of surface tension on twinkling was evaluated by imaging crystals in different concentrations of surfactant (1%, 2%, 3%, 4%) and ethanol (10%, 30%, 50%, 70%), artificial urine, bovine blood, and a tissue-mimicking phantom.Main results. Results showed that all crystals twinkled in water, with cholesterol twinkling significantly more than calcium phosphate and uric acid. When the ambient pressure was increased, twinkling disappeared for all tested crystals when pressures reached 7 MPa (absolute) and reappeared when returned to ambient pressure (0.1 MPa). Similarly, twinkling across all crystals decreased with surface tension when imaged in the surfactant and ethanol (statistically significant when surface tension <22 mN m^-1) and decreased in blood (surface tension = 52.7 mN m^-1) but was unaffected by artificial urine (similar surface tension to water). In the tissue-mimicking phantom, twinkling increased for cholesterol and calcium phosphate crystals with no change observed in uric acid crystals.Significance.Overall, these results support the theory that bubbles are present on crystals and cause twinkling, which could be leveraged to improve twinkling for the detection of other pathological mineralizations.

Evaluation of Stone Features That Cause the Color Doppler Ultrasound Twinkling Artifact

The color Doppler ultrasound twinkling artifact is a rapid color shift that appears on 43%-96% of kidney stones. Surface microbubbles on kidney stones are theorized to cause twinkling as exposure to elevated static pressures of 0.41-1.13 MPa (approximately 0.5-1 times diagnostic ultrasound pressure and 5-10 times ambient pressure) reduced twinkling. However, it is unclear what external and internal stone features support bubbles. Thirteen ex vivo kidney stones were scanned with color Doppler ultrasound at 2.5, 5 and 18.5 MHz. Select stones were imaged with environmental scanning electron microscopy or underwater micro-computed tomography to evaluate features that may cause twinkling. Results revealed that the lower frequencies produced larger volumes of twinkling. Condensation first occurred in the smallest (∼1 µm diameter) surface pores and may be indicative of where bubbles form. Gas pockets were seen inside two of three tested stones that may contribute to twinkling. Overall, these results provide evidence of cavity structures both externally and internally and their correlation to the twinkling artifact. This indicates that microbubbles may be present on and within kidney stones and may contribute to the twinkling artifact.

Value of the color Doppler imaging mode in improving physicians' diagnostic performance in patients with mid-ureteric stones larger than 5 mm: a retrospective study

The aim of this study was to retrospectively evaluate the value of the color Doppler flow imaging mode compared to the gray-scale mode for diagnosing mid-ureteric stones larger than 5 mm. We consecutively collected images from 79 patients possibly suffering from mid-ureteric stones under gray-scale and color Doppler flow imaging modes. Using computed tomography as the gold standard, all the included images were reviewed in a blinded manner for the confirmation of ureteral stones by 15 physicians divided into three groups according to their clinical experience level (resident, attending, and senior). During the evaluation process, the evaluation consistency was calculated and compared using Kendall's coefficient of concordance (Kendall's W). Moreover, diagnostic performance considering gray-scale and color imaging modes was compared. Especially for the diagnosis of mid-ureteric stones larger than 5 mm, the Kendall's W for the combined gray-scale and color Doppler flow imaging ultrasound scanning modes was greater than that for the gray-scale mode (P < 0.05). Additionally, significant improvements in the diagnostic sensitivity, negative predictive value, and accuracy were noted with color Doppler imaging (P < 0.05). Under isolated gray-scale mode, the resident group had reduced diagnostic sensitivity and negative predictive value and poorer accuracy compared with the attending and senior groups (P < 0.05). In contrast, no significant differences in the combined gray-scale and color Doppler flow imaging modes were noted among all groups (P > 0.05). In summary, the color Doppler flow imaging mode is useful for the diagnosis of mid-ureteric stones larger than 5 mm, especially in the resident group.

Ureter Visualization With Transvaginal Ultrasound: A Learning Curve Study

OBJECTIVES

To evaluate the learning curve of gynecologic surgical fellows (ie, in training) to properly identify the ureters in real time while simultaneously performing and interpreting transvaginal ultrasound (TVUS) examinations.

METHODS

We performed a prospective study, which took place at 2 centers in Sydney, Australia, from December 2017 to December 2018. Three fellows (F1-F3), of varying prestudy ultrasound (US) experience, were recruited to participate. One hundred fifty predetermined examinations were planned. A TVUS examination was performed by the study reference standard (an expert in gynecologic US). Subsequently, the fellows performed a focused component to identify bilateral ureters, having been blinded to the patient's clinical history and reference standard findings. Immediate feedback and hands-on teaching were provided after each of the fellow's evaluations were complete. To evaluate the number of scans needed to gain competency, the cumulative summation test for the learning curve was used.

RESULTS

A total of 150 examinations were performed on 145 patients. One patient had a single ureter, and 1 patient had US evidence of hydroureter. The cumulative summation test for the learning curve for bilateral ureter identification showed that F1 did not reach competency by 50 TVUS examinations, whereas F2 and F3 required 41 and 31 TVUS examinations to reach competency, respectively.

CONCLUSIONS

Contrary to other studies on the topic, this study suggests that although it is feasible for surgical fellows to learn TVUS identification of bilateral ureters, not all fellows can reach competency during a program based on a predefined number of scans. We advocate for an individualized, competency-based medical education model in learning US for identifying the ureters.

Is Combined Ultrasound with Radiography Sufficient for the Diagnosis of Obstructive Ureteric Stone in Patients with Acute Flank Pain?

Context

Ultrasound (US) is excellent for detection of hydronephrosis but has poor sensitivity for stone detection. In contrast, radiography of the kidney-ureter-bladder has better sensitivity for detection of stone but limited sensitivity for hydronephrosis detection. A combination of these two modalities may improve both sensitivity and specificity for the diagnosis of obstructive ureteric stone.

Aims

This study aims to investigate the diagnostic accuracy of combined US with radiography for the diagnosis of obstructive ureteric stone in adult patients.

Settings and Design

Retrospective study with retrospective data collection performed in a 1500-bed university hospital.

Materials and Methods

A total of 90 patients were included. The electronic medical record, radiological reports, laboratory results, and patient management were extracted and analyzed.

Statistical Analysis Used

The diagnostic performance of US, radiography, and combined US with radiography were calculated and compared. The computed tomography was used as diagnostic reference.

Results

US alone had a sensitivity of 73.5%, specificity of 92.7%, and negative predictive value (NPV) of 74.5% for hydronephrosis. When US showed both ureteric stone and hydronephrosis, sensitivity dropped to 14.3% but specificity increased to 100%. Radiography alone had a sensitivity of 34.7%, specificity of 100%, and NPV of 56.2% for the detection of ureteric stone. Combining radiography with US raised the sensitivity for diagnosis of obstructive ureteric stone to 88% with a specificity of 93% and accuracy of 90%.

Conclusions

Combined US with radiography was accurate for the diagnosis of obstructive ureteric stone in patients presenting with acute flank pain.

Evidence of Microbubbles on Kidney Stones in Humans

The color Doppler ultrasound twinkling artifact has been found to improve detection of kidney stones with ultrasound; however, it appears on only ∼60% of stones. Evidence from ex vivo kidney stones suggests twinkling arises from microbubbles stabilized in crevices on the stone surface. Yet it is unknown whether these bubbles are present on stones in humans. Here, we used a research ultrasound system to quantify twinkling in humans with kidney stones in a hyperbaric chamber. Eight human patients with non-obstructive kidney stones previously observed to twinkle were exposed to a maximum pressure of 4 atmospheres absolute (ATA) while breathing air, except during the 10-min pause at 1.6 ATA and while the pressure decreased to 1 ATA, during which patients breathed oxygen to minimize the risk of decompression sickness. A paired one-way t-test was used to compare the mean twinkle power at each pressure pause with baseline twinkling, with p < 0.05 considered to indicate significance. Results revealed that exposure to 3 and 4 ATA of pressure significantly reduced twinkle power by averages of 35% and 39%, respectively, in 7 patients (p = 0.04); data from the eighth patient were excluded because of corruption. This study supports the theory that microbubbles are present on kidney stones in humans.

Nongynecologic Causes of Pelvic Pain: Ultrasound First

Ultrasonography (US) is often the first-line imaging study used to evaluate women who present with acute or chronic pelvic pain. Detection of nongynecologic causes of pelvic pain is critical, because delay in diagnosis can cause significant morbidity and mortality. Evaluation of these entities requires a variety of transducers to achieve optimal imaging depth and changes in patient positioning. Specific imaging techniques (such as graded compression) may be required if bowel pathology is suspected. Contrast-enhanced ultrasonography is increasingly used to improve detection of certain entities. The US appearance of common gastrointestinal and urinary tract-related causes of pelvic pain is reviewed.

[CME Sonography 91: Differential Diagnosis of Lower Abdominal Pain]

CME Sonography 91: Differential Diagnosis of Lower Abdominal Pain Abstract. Pain in the lower abdomen is a frequent reason for further imaging clarification by sonography. The most frequent causes are appendicitis and diverticulitis, in addition to ureteral stones, ovarian and tubal pathology as well as various hernias. Appendicitis has a characteristic clinical presentation and can be diagnosed by CT or ultrasound. In children, the differential diagnosis is that of mesenteric lymphadenitis. Diverticulitis, often right-sided, can also be reliably diagnosed with CT or ultrasound. Not to be forgotten is the left-sided diverticulitis, which occurs more frequently in Asian persons. Appendicitis epiploica should be recognized to avoid unnecessary operations. The iliopsoas syndrome, which is diagnosed by sonopalpation, often remains undetected.

Imaging Modalities in Genitourinary Emergencies

Emergency physicians rely on a multitude of different imaging modalities in the diagnosis of genitourinary emergencies. There are many considerations to be taken into account when deciding which imaging modality should be used first, as oftentimes several diagnostic tools can be used for the same pathologic condition. These factors include radiation exposure, sensitivity, specificity, age of patient, availability of resources, cost, and timeliness of completion. In this review, the strengths and weaknesses of different imaging tools in the evaluation of genitourinary emergencies are discussed.

Ultrasound versus computed tomography for the detection of ureteral calculi in the pediatric population: a clinical effectiveness study

OBJECTIVE

To determine the diagnostic performance of ultrasound for diagnosing ureteral calculi in children using a clinical effectiveness approach.

METHODS

Billing records and imaging reports were used to identify children (≤ 18 years old) evaluated for suspected urolithiasis using ultrasound between March 2012 and March 2017. Patients without unenhanced CT within 24 h (reference standard) were excluded. Imaging (ultrasound and CT) reports were reviewed for presence, number, size, and location of calculi. Diagnostic performance of ultrasound (versus CT) was calculated on an individual ureter basis both by direct calculus visualization as well as direct visualization combined with suspected presence of ureteral stone based on indirect ultrasound findings.

RESULTS

41 ureteral calculi were present in 38 of 69 (55.1%) patients. Mean patient age was 14.7 ± 3.6 years, and 35 of 69 (51%) patients were boys. Based on direct calculus visualization, ultrasound had a sensitivity of 12.8% (95% CI 5.6-26.7%), specificity of 100% (95% CI 96.3-100%), positive predictive value (PPV) of 100% (95% CI 56.6-100%), and negative predictive value (NPV) of 74.4% (95% CI 66.4-81.1%). When ultrasound examinations reported as suspicious for ureteral calculi based on indirect findings also were considered positive, ultrasound had a sensitivity of 41.0% (95% CI 27.1-56.6%), specificity of 95.0% (95% CI 88.7-97.8%), PPV of 76.2% (95% CI 54.9-89.4%), and NPV of 80.3% (95% CI 72.2-86.5%).

CONCLUSIONS

In clinical practice, ultrasound has low sensitivity for directly visualizing ureteral calculi subsequently identified by CT, although sensitivity improves when considering suspicious examinations as positive.

Epidemiological and imaging features that can affect the detection of ureterolithiasis on ultrasound

Objective

To identify, in patients with clinical suspicion of ureterolithiasis, epidemiological and imaging features that affect calculus detection on ultrasound, as well as to compare ultrasound with multidetector computed tomography (MDCT).

Materials and Methods

We searched our database for patients who underwent ultrasound, followed by MDCT (if the ultrasound was negative), for suspected ureterolithiasis in an emergency setting. Patients were divided into three groups: positive ultrasound (US+); negative ultrasound/positive MDCT (US−/MDCT+); and negative ultrasound/negative MDCT (US−/MDCT−). We evaluated age, gender, ureterolithiasis laterality, location of the calculus within the ureter, body mass index, calculus diameter, and calculus attenuation on MDCT.

Results

Of a total of 292 cases of suspected ureterolithiasis, 155 (53.1%) were in the US+ group, 46 (15.7%) were in the US−/MDCT+ group, and 91 (31.2%) were in the US−/MDCT− group. There were no significant differences among the groups in terms of age, gender, ureterolithiasis laterality, and mean MDCT attenuation values. Distal ureterolithiasis was most common in the US+ group, and calculi at other ureteral locations were more common in the US−/MDCT+ group. The mean body mass index was significantly higher in the US−/MDCT+ group than in the US+ group, and the mean calculus diameter was significantly greater in the US+ group than in the US−/MDCT+ group.

Conclusion

A high body mass index, large calculus diameter, and calculus location in the distal third of the ureter are the major factors favoring ureterolithiasis detection on ultrasound.

The usefulness of agent emission imaging - high mechanical index ultrasound mode in the diagnosis of urolithiasis: a prospective preliminary study

PURPOSE

We aimed to determine the feasibility and effectiveness of agent emission imaging - high mechanical index (AEI-High MI) mode ultrasonography (US) compared with gray-scale and color Doppler US, alone or in combination, for the diagnosis of urolithiasis with reference to unenhanced computed tomography (CT).

METHODS

This prospective study included 72 consecutive patients (40 males, 32 females; mean age, 45.9±14.7 years) referred by the department of urology for acute or elective symptoms of urolithiasis and confirmed to have urinary calculi on unenhanced abdominal CT, between January 2015 and June 2015. Gray-scale, color Doppler, and AEI-High MI US were performed by two radiologists to determine the effectiveness of these methods in the diagnosis of urinary stones and to compare them with the reference modality.

RESULTS

A total of 189 calculi were detected on CT examination. Gray-scale US had a sensitivity of 66.1% and positive predictive value (PPV) of 88.7% for detecting calculi, while twinkling artifact of color Doppler had a sensitivity of 70.4% and PPV of 94.3%. The scintillation artifact of AEI-High MI mode had a sensitivity of 75.1% and PPV of 95.9%. When all ultrasound-based modalities were combined, the sensitivity and PPV rose to 83.1% and 88.2%, respectively. When calculi were grouped according to their size ( < 5 mm, 5-10 mm, > 10 mm), AEI-High MI mode had a higher sensitivity (60%) compared with gray-scale (32.5%) and color Doppler (41.3%) for calculi < 5 mm.

CONCLUSION

AEI-High MI mode had a higher sensitivity compared with gray-scale and color Doppler for the detection of calculi smaller than 5 mm, but it did not make a significant contribution to detection of larger calculi. The combined use of gray-scale US with AEI-High MI mode could increase the detection rate of calculi smaller than 5 mm and provide a method for verification of suspected calculi on gray-scale US.

Noninvasive Prediction of Renal Stone Surface Irregularities by Numerical Analysis of the Color Doppler Twinkling Artifact: An Ex Vivo Study

OBJECTIVES

The physical structures of renal stones are highly correlated with their breakability. Noninvasive estimation of stone roughness will be beneficial for management. The intensity of the twinkling artifact appearing at the site of renal stones on Doppler ultrasound imaging is also influenced by the stone's roughness level. This article proposes a quantitative method for roughness prediction of ex vivo renal stones based on a twinkling analysis of their color Doppler images.

METHODS

Twenty surgically removed renal stones were first spatially modeled by an optical method, and 12 standard roughness measures were extracted from them. Stones were then embedded in an agar-based phantom and Doppler imaged with a calibrated ultrasound system. The images were preprocessed, and 11 twinkling intensities were measured numerically. The twinkling data along with the roughness labels were then analyzed by multiple linear regressions, and finally, a linear roughness predictor was trained for renal stones.

RESULTS

The core height measure of roughness had the best linear fit to the twinkling data among other roughness parameters. The results of the multiple linear regression analysis indicated a strong linear relationship between twinkling data and stones' roughness, with an R² value of 83.29% and high statistical significance of F_(11,868)  = 393.36 and P < .001.

CONCLUSIONS

It was possible to predict the core roughness of renal stones using the proposed method and the twinkling artifact data acquired from the color Doppler images ex vivo.

The value of X-ray digital tomosynthesis in the diagnosis of urinary calculi

Urinary calculus is a common and recurrent condition that affects kidney function. The present study evaluated the use of digital tomosynthesis (DTS) and Kidneys-Ureters-Bladder (KUB) radiography as methods of diagnosing urinary calculi. Unenhanced multidetector computed tomography (UMDCT) was used in the diagnosis of calculi. KUB radiography and DTS procedures were conducted on patients prior to and following bowel preparation to detect kidney, ureteral and bladder calculi. Differences in diagnostic performance of KUB radiography and DTS imaging on prepared and unprepared bowel were evaluated using the χ² test. The consistency of diagnostic results between two examining physicians was analyzed using the κ test. A total of 138 calculi from 80 patients were detected via UMDCT. The calculi detection rates of KUB prior to and following bowel preparation were 47.8 and 66.7% respectively, and the calculi detection rate of DTS prior to and following bowel preparation were 94.2 and 96.4%, respectively. The detection rates of calculi >5 mm via KUB prior to and following bowel preparation were 56.6 and 73.5% respectively, and in DTS they were 100% prior to and following bowel preparation. Economically, DTS performed on the unprepared bowel was the most cost effective, followed by DTS on the prepared bowel, KUB on the unprepared bowel and KUB on the prepared bowel. Therefore, the current study concluded that DTS may be an appropriate first-line imaging technique in patients with urinary calculi.

The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact

The color Doppler ultrasound twinkling artifact, which highlights kidney stones with rapidly changing color, has the potential to improve stone detection; however, its inconsistent appearance has limited its clinical utility. Recently, it was proposed stable crevice bubbles on the kidney stone surface cause twinkling; however, the hypothesis is not fully accepted because the bubbles have not been directly observed. In this paper, the micron or submicron-sized bubbles predicted by the crevice bubble hypothesis are enlarged in kidney stones of five primary compositions by exposure to acoustic rarefaction pulses or hypobaric static pressures in order to simultaneously capture their appearance by high-speed photography and ultrasound imaging. On filming stones that twinkle, consecutive rarefaction pulses from a lithotripter caused some bubbles to reproducibly grow from specific locations on the stone surface, suggesting the presence of pre-existing crevice bubbles. Hyperbaric and hypobaric static pressures were found to modify the twinkling artifact; however, the simple expectation that hyperbaric exposures reduce and hypobaric pressures increase twinkling by shrinking and enlarging bubbles, respectively, largely held for rough-surfaced stones but was inadequate for smoother stones. Twinkling was found to increase or decrease in response to elevated static pressure on smooth stones, perhaps because of the compression of internal voids. These results support the crevice bubble hypothesis of twinkling and suggest the kidney stone crevices that give rise to the twinkling phenomenon may be internal as well as external.

Imaging of Female Pelvic Emergencies

Pelvic pain is a common complaint in female patients who present to the emergency department. Although encountered frequently, the path to a definitive diagnosis is not always a straightforward one, and imaging offers a valuable tool to aid in this diagnostic challenge. Radiologists must be familiar with the most common etiologies of female pelvic pain in the emergency setting, their imaging characteristics, and the best way to further evaluate challenging clinical presentations. This allows the radiologist to serve as a valuable asset to the treating physician, aiding in accurate diagnosis, and in guiding the course of treatment, all while ensuring the "Image Wisely" principle. A sonographic approach to female patients presenting to the emergency setting with pelvic pain has been presented in this article and some example entities along with their imaging findings have also been reviewed.

Investigating the clinical significance of twinkling artifacts in patients with urolithiasis smaller than 5 mm

PURPOSE

Our aim was to evaluate the effectiveness of twinkling artifacts (TA) in detecting calculi <5 mm in diameter in patients with renal colic pain who had undergone urinary grayscale ultrasonography (US) and computed tomography (CT) imaging assays.

MATERIALS AND METHODS

In this retrospective study, a total of 76 calculi <5 mm detected in 60 patients were evaluated. Whole data were established using an ultrasound (US) probe at frequencies 1.5-4.5 MHz and noncontrast CT. In US, echogenicity and posterior-shadow (PS) parameters were evaluated and compared with color-Doppler ultrasonography (CDUS) and CT signs.

RESULTS

The mean size of measured calculi was 3.9 ± 0.8 mm (range 2-5 mm). The calculus localization rates detected by CT imaging were as follows: kidneys (n = 61, 80.3 %), proximal ureter (n = 4, 5.3 %), middle ureter (n = 3, 3.9 %) and distal ureter (n = 8, 10.5 %). CT detected the calculus in all 76 cases. There was a statistically significant difference in US-CT and CDUS-CT comparisons (p < 0.001 and p = 0.023, respectively); however, no difference was found when comparing both US methods with CT (p = 0.083).

CONCLUSIONS

TA can be regarded as a significant marker of urolithiasis, and co-operative usage of Doppler and grayscale methods can yield satisfactory results comparable with CT.

Detection of Ureteral Stones With Transvaginal Sonography

Transabdominal sonography has proved to be an efficacious imaging technology to diagnose urolithiaisis. However, the location of the calculus may cause a sonographic examination to be limited. Since the majority of ureteral stones are located in the distal ureter, calculi may not always be visualized transabdominally, especially if the bladder is not full. This case study demonstrates the use of transvaginal sonography in the diagnosis of distal ureterolithiasis and discusses the optimal visualization of a ureteral stone in a female patient using transvaginal sonography. The case demonstrates the importance of this imaging method when distal urinary tract stones are suspected.

A novel approach for quantification and analysis of the color Doppler twinkling artifact with application in noninvasive surface roughness characterization: an in vitro phantom study

OBJECTIVES

The twinkling artifact is an undesired phenomenon within color Doppler sonograms that usually appears at the site of internal calcifications. Since the appearance of the twinkling artifact is correlated with the roughness of the calculi, noninvasive roughness estimation of the internal stones may be considered as a potential twinkling artifact application. This article proposes a novel quantitative approach for measurement and analysis of twinkling artifact data for roughness estimation.

METHODS

A phantom was developed with 7 quantified levels of roughness. The Doppler system was initially calibrated by the proposed procedure to facilitate the analysis. A total of 1050 twinkling artifact images were acquired from the phantom, and 32 novel numerical measures were introduced and computed for each image. The measures were then ranked on the basis of roughness quantification ability using different methods. The performance of the proposed twinkling artifact-based surface roughness quantification method was finally investigated for different combinations of features and classifiers.

RESULTS

Eleven features were shown to be the most efficient numerical twinkling artifact measures in roughness characterization. The linear classifier outperformed other methods for twinkling artifact classification. The pixel count measures produced better results among the other categories. The sequential selection method showed higher accuracy than other individual rankings. The best roughness recognition average accuracy of 98.33% was obtained by the first 5 principle components and the linear classifier.

CONCLUSIONS

The proposed twinkling artifact analysis method could recognize the phantom surface roughness with average accuracy of 98.33%. This method may also be applicable for noninvasive calculi characterization in treatment management.

Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone--the STONE score: retrospective and prospective observational cohort studies

OBJECTIVE

To derive and validate an objective clinical prediction rule for the presence of uncomplicated ureteral stones in patients eligible for computed tomography (CT). We hypothesized that patients with a high probability of ureteral stones would have a low probability of acutely important alternative findings.

DESIGN

Retrospective observational derivation cohort; prospective observational validation cohort.

SETTING

Urban tertiary care emergency department and suburban freestanding community emergency department.

PARTICIPANTS

Adults undergoing non-contrast CT for suspected uncomplicated kidney stone. The derivation cohort comprised a random selection of patients undergoing CT between April 2005 and November 2010 (1040 patients); the validation cohort included consecutive prospectively enrolled patients from May 2011 to January 2013 (491 patients).

MAIN OUTCOME MEASURES

In the derivation phase a priori factors potentially related to symptomatic ureteral stone were derived from the medical record blinded to the dictated CT report, which was separately categorized by diagnosis. Multivariate logistic regression was used to determine the top five factors associated with ureteral stone and these were assigned integer points to create a scoring system that was stratified into low, moderate, and high probability of ureteral stone. In the prospective phase this score was observationally derived blinded to CT results and compared with the prevalence of ureteral stone and important alternative causes of symptoms.

RESULTS

The derivation sample included 1040 records, with five factors found to be most predictive of ureteral stone: male sex, short duration of pain, non-black race, presence of nausea or vomiting, and microscopic hematuria, yielding a score of 0-13 (the STONE score). Prospective validation was performed on 491 participants. In the derivation and validation cohorts ureteral stone was present in, respectively, 8.3% and 9.2% of the low probability (score 0-5) group, 51.6% and 51.3% of the moderate probability (score 6-9) group, and 89.6% and 88.6% of the high probability (score 10-13) group. In the high score group, acutely important alternative findings were present in 0.3% of the derivation cohort and 1.6% of the validation cohort.

CONCLUSIONS

The STONE score reliably predicts the presence of uncomplicated ureteral stone and lower likelihood of acutely important alternative findings. Incorporation in future investigations may help to limit exposure to radiation and over-utilization of imaging.

TRIAL REGISTRATION

www.clinicaltrials.gov NCT01352676.

Effect of provider experience on clinician-performed ultrasonography for hydronephrosis in patients with suspected renal colic

STUDY OBJECTIVE

Hydronephrosis is readily visible on ultrasonography and is a strong predictor of ureteral stones, but ultrasonography is a user-dependent technology and the test characteristics of clinician-performed ultrasonography for hydronephrosis are incompletely characterized, as is the effect of ultrasound fellowship training on predictive accuracy. We seek to determine the test characteristics of ultrasonography for detecting hydronephrosis when performed by clinicians with a wide range of experience under conditions of direct patient care.

METHODS

This was a prospective study of patients presenting to an academic medical center emergency department with suspected renal colic. Before computed tomography (CT) results, an emergency clinician performed bedside ultrasonography, recording the presence and degree of hydronephrosis. CT data were abstracted from the dictated radiology report by an investigator blinded to the bedside ultrasonographic results. Test characteristics of bedside ultrasonography for hydronephrosis were calculated with the CT scan as the reference standard, with test characteristics compared by clinician experience stratified into 4 levels: attending physicians with emergency ultrasound fellowship training, attending physicians without emergency ultrasound fellowship training, ultrasound experienced non-attending physician clinicians (at least 2 weeks of ultrasound training), and ultrasound inexperienced non-attending physician clinicians (physician assistants, nurse practitioners, off-service rotators, and first-year emergency medicine residents with fewer than 2 weeks of ultrasound training).

RESULTS

There were 670 interpretable bedside ultrasonographic tests performed by 144 unique clinicians, 80.9% of which were performed by clinicians directly involved in the care of the patient. On CT, 47.5% of all subjects had hydronephrosis and 47.0% had a ureteral stone. Among all clinicians, ultrasonography had a sensitivity of 72.6% (95% confidence interval [CI] 65.4% to 78.9%), specificity of 73.3% (95% CI 66.1% to 79.4%), positive likelihood ratio of 2.72 (95% CI 2.25 to 3.27), and negative likelihood ratio of 0.37 (95% CI 0.31 to 0.44) for hydronephrosis, using hydronephrosis on CT as the criterion standard. Among attending physicians with fellowship training, ultrasonography had sensitivity of 92.7% (95% CI 83.8% to 96.9%), positive likelihood ratio of 4.97 (95% CI 2.90 to 8.51), and negative likelihood ratio of 0.08 (95% CI 0.03 to 0.23).

CONCLUSION

Overall, ultrasonography performed by emergency clinicians was moderately sensitive and specific for detection of hydronephrosis as seen on CT in patients with suspected renal colic. However, presence or absence of hydronephrosis as determined by emergency physicians with fellowship training in ultrasonography yielded more definitive test results. For clinicians without fellowship training, there was no significant difference between groups in the predictive accuracy of the application according to experience level.

B-mode ultrasound versus color Doppler twinkling artifact in detecting kidney stones

PURPOSE

To compare color Doppler twinkling artifact and B-mode ultrasonography in detecting kidney stones.

PATIENTS AND METHODS

Nine patients with recent CT scans prospectively underwent B-mode and twinkling artifact color Doppler ultrasonography on a commercial ultrasound machine. Video segments of the upper pole, interpolar area, and lower pole were created, randomized, and independently reviewed by three radiologists. Receiver operator characteristics were determined.

RESULTS

There were 32 stones in 18 kidneys with a mean stone size of 8.9±7.5 mm. B-mode ultrasonography had 71% sensitivity, 48% specificity, 52% positive predictive value, and 68% negative predictive value, while twinkling artifact Doppler ultrasonography had 56% sensitivity, 74% specificity, 62% positive predictive value, and 68% negative predictive value.

CONCLUSIONS

When used alone, B-mode is more sensitive, but twinkling artifact is more specific in detecting kidney stones. This information may help users employ twinkling and B-mode to identify stones and developers to improve signal processing to harness the fundamental acoustic differences to ultimately improve stone detection.

Incidental genitourinary findings on obstetrics/gynecology ultrasound

Ultrasound is the standard-of-care imaging modality for initial imaging in obstetrics and gynecology. Given the close proximity of the genitourinary system to the uterus and adnexa, it is not surprising that these studies can result in the discovery of incidental genitourinary findings such as ureterocele, ectopic ureter, bladder mass, ureteral stones, cystitis, bladder diverticulum, and pelvic kidney. Recognition of the etiology of these findings is important for appropriate diagnosis and, at times, patient care. Many of these findings are truly incidental and clinically unimportant but other times can be related to the patient's chief complaint.

Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment

PURPOSE

This technology assessment addresses the optimal use of imaging in the evaluation and treatment of patients with suspected or documented ureteral stones.

MATERIALS AND METHODS

A comprehensive literature search addressing 4 guiding questions was performed for full text in English articles published between January 1990 and July 2011. The search focused on major subtopics associated with the imaging of ureteral calculi, and included specific imaging modalities used in the diagnosis and management of ureteral calculous disease such as unenhanced (noncontrast) computerized tomography, conventional radiography, ultrasound, excretory urography, magnetic resonance imaging and nuclear medicine studies. Protocols (in the form of decision tree algorithms) were developed based on this literature review and in some instances on panel opinion. The 4 questions addressed were 1) What imaging study should be performed for suspected ureteral calculous disease? 2) What information should be obtained? 3) After diagnosis of a ureteral calculus, what followup imaging should be used? 4) After treatment of a ureteral calculus, what followup imaging studies should be obtained?

RESULTS

Based on these protocols, noncontrast computerized tomography is recommended to establish the diagnosis in most cases, with a low energy protocol advocated if body habitus is favorable. Conventional radiography and ultrasound are endorsed for monitoring the passage of most radiopaque stones as well as for most patients undergoing stone removal. Other studies may be indicated based on imaging findings, and patient, stone and clinical factors.

CONCLUSIONS

The protocols generated assist the clinician in establishing the diagnosis of ureteral calculous disease, monitoring stone passage and following patients after treatment. The protocols take into account not only clinical effectiveness but also cost-effectiveness and risk/harm associated with the various imaging modalities.

Systematic analysis of factors related to display of the twinkling artifact by a phantom: an optimized investigation

OBJECTIVES

The purpose of this study was to analyze factors related to display of the twinkling artifact by a phantom.

METHODS

An in vitro phantom made of sandpaper was designed to mimic rough physiologic surfaces prone to generating the twinkling artifact. Sandpaper strips embedded in a plastic box were scanned through a water path under different machine settings with only 1 parameter varied each time. After choosing the best settings for displaying the twinkling artifact, 4 types of sandpaper with different roughness were scanned. The resulting images were recorded at random, and the number of color pixels in the color box of each image was calculated by a custom-designed program developed using commercially available software. All data were then evaluated by regression analysis, a paired 2-tailed Student t test, and single-factor analysis of variance.

RESULTS

The highest color write priority and color gain, which were just below the threshold for color noise, a focus depth setting below the sandpaper, a maximum wall filter under a higher pulse repetition frequency, and a color box adjusted properly in the fundamental imaging mode (P < .001) were found to most readily improve the twinkling artifact intensity. The roughness of the sandpaper was shown to be highly correlated with the twinkling artifact intensity (R(2) = 0.832; P < .001).

CONCLUSIONS

The twinkling artifact was influenced by some machine parameters and the roughness of the sandpaper. By adjusting some ultrasound machine parameters, a better image reflecting the twinkling artifact can be shown in clinical practice and research.

Nephrolithiasis: what surgeons need to know

OBJECTIVE

In this article, we review the standard of care for imaging of nephrolithiasis as well as new technology and radiation concerns from the perspective of the urologic surgeon.

CONCLUSION

Nephrolithiasis is a common cause of morbidity with a lifetime prevalence of 5-10% worldwide. Increasingly, diagnostic evaluation and planning for medical or surgical intervention have become reliant on imaging.

Color Doppler twinkling artifacts in various conditions during abdominal and pelvic sonography

OBJECTIVE

The aims of this study were to describe the mechanisms likely to be responsible for color Doppler twinkling artifacts and their associated machine factors and to illustrate the various conditions that cause twinkling artifacts and those pitfalls.

METHODS

We evaluated various sonographic machine-associated factors that influence artifact appearance and identified various conditions that display twinkling artifacts during abdominal and pelvic sonography.

RESULTS

The presence of twinkling artifacts was found to be dependent on focal zones, gray scale gains, color write priorities, and pulse repetition frequencies. Twinkling artifacts were found to be associated with calcified lesions in the liver, gallbladder adenomyomatosis, hepatic bile duct hamartoma, gallstones and choledocholithiasis, chronic pancreatitis, urinary stones, encrusted indwelling urinary stents, bowel gas, and metallic foreign bodies. However, some of the twinkling artifacts were found to be associated with false-negative and -positive results.

CONCLUSIONS

Color Doppler twinkling artifacts are additional useful sonographic signs in the diagnosis of calcified lesions, urinary and biliary stones, gallbladder adenomyomatosis, and some miscellaneous conditions.

Treatment of bladder diverticula, impaired detrusor contractility, and low bladder compliance

Bladder diverticula are common enough to be encountered by most urologists in practice but are reported less frequently in the literature than they were 50 years ago. Some patients can be managed nonoperatively, whereas others will need surgical intervention consisting of bladder outlet reduction and possibly removal of the diverticulum itself. In addition to the decision to operate, the timing of each intervention deserves careful consideration. Cystoscopy, computed tomography with contrast, urodynamic studies, cytology, and voiding cystourethrography play important roles in informing the clinician. Many new techniques for treatment of the bladder outlet and the diverticulum are available, such as laparoscopy and robotic surgery.