US detection of renal and ureteral calculi in patients with suspected renal colic

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.

Diagnostic utility of ultrasonography for detection of the cause and location of ureteral obstruction in cats: 71 cases (2010-2016)

OBJECTIVE To assess the utility of ultrasonography to detect the cause and location of ureteral obstruction in cats and to identify factors associated with agreement between ultrasonographic and surgical findings. STUDY DESIGN Retrospective case series. ANIMALS 71 cats. PROCEDURES Medical records were searched to identify cats that had ureteral obstruction diagnosed ultrasonographically and that subsequently underwent exploratory laparotomy. Patient signalment, ultrasonographic findings, interventions performed, and surgical findings were recorded. Cause and location of ureteral obstruction as assessed by ultrasonography were compared with surgical findings. Sensitivity, specificity, and positive predictive value of ultrasonography for detection of ureteroliths and strictures were calculated. Statistical analysis was performed to identify factors associated with agreement between ultrasonographic and surgical findings. RESULTS There was significant, moderate agreement between ultrasonographic and surgical findings for the cause and location of ureteral obstruction. Signalment variables, ureter affected (left vs right), and presence of retroperitoneal effusion were not associated with this agreement. Sensitivity was 98% and 44%, specificity was 96% and 98%, and positive predictive value was 98% and 88% for detection of ureteroliths and strictures, respectively, by ultrasonography. CONCLUSIONS AND CLINICAL RELEVANCE Ultrasonography was highly sensitive for detection of ureteroliths that caused ureteral obstruction but was considerably less sensitive for detection of ureteral strictures in the study population. Future prospective studies are needed to determine the role of advanced imaging in assessing cats with ureteral abnormalities. (J Am Vet Med Assoc 2019;254:710-715).

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.

Imaging patients with renal colic-consider ultrasound first

Renal colic is a common disease in Europe and a common cause of visit to the Emergency Department. Clinical diagnosis is usually confirmed by imaging modalities. Unenhanced computed tomography (CT) is considered the best diagnostic test due to its excellent accuracy detecting ureteral stones. However, ultrasound (US) should be considered as the primary imaging technique. It is a reproducible, non-invasive and non-expensive imaging technique, achieving accurate diagnosis in most cases without the need for radiation. Diagnosis is based on the presence of ureteral stones, but indirect findings such as the asymmetry or absence of ureteric jet, an increase of the resistive index or a colour Doppler twinkling artefact may help to suggest the diagnosis when the stone is not identified.

MAIN MESSAGES

• Renal colic diagnosis is usually confirmed by imaging modalities. • Imaging diagnosis of renal colic is based on the detection of ureteral stones. • CT is the most accurate imaging technique to identify ureteral stones. • US allows correct diagnosis in most cases without using radiation. • US should be used as the first imaging modality in patients with renal colic.