Imaging in Urolithiasis

[Imaging for urolithiasis]

The substantial reduction of radiation exposure using (ultra-)low dose programs in native computed tomographic imaging has led to considerable changes in imaging diagnostics and treatment planning in urolithiasis in recent years. In addition, especially in Germany, ultrasound diagnostics is highly available in terms of equipment and with increasing expertise. This can largely replace the previous radiation-associated procedures in emergency and follow-up diagnostics, but also in intraoperative imaging, e.g., in percutaneous stone therapy (intraoperative fluoroscopy). This is reflected in the international guidelines, which recommend these two modalities as first-line diagnostics in all areas mentioned. Continuous technical development enables ever higher resolution imaging and thus improved diagnostics with high sensitivity and specificity. This also enables reliable imaging of particularly vulnerable patient groups, such as children or pregnant women. In addition, methods from the field of artificial intelligence (AI; machine learning, deep learning) are increasingly being used for automated stone detection and stone characterization including its composition. Furthermore, AI models can provide prognosis models as well as individually tailored treatment, follow-up, and prophyaxis. This will enable further personalization of diagnostics and therapy in the field of urolithiasis.

CT of the urinary tract revisited

Computed tomography (CT) of the abdomen is usually appropriate for the initial imaging of many urinary tract diseases, due to its wide availability, fast scanning and acquisition of thin slices and isotropic data, that allow the creation of multiplanar reformatted and three-dimensional reconstructed images of excellent anatomic details. Non-enhanced CT remains the standard imaging modality for assessing renal colic. The technique allows the detection of nearly all types of urinary calculi and the estimation of stone burden. CT is the primary diagnostic tool for the characterization of an indeterminate renal mass, including both cystic and solid tumors. It is also the modality of choice for staging a primary renal tumor. Urolithiasis and urinary tract malignancies represent the main urogenic causes of hematuria. CT urography (CTU) improves the visualization of both the upper and lower urinary tract and is recommended for the investigation of gross hematuria and microscopic hematuria, in patients with predisposing factors for urologic malignancies. CTU is highly accurate in the detection and staging of upper tract urothelial malignancies. CT represents the most commonly used technique for the detection and staging of bladder carcinoma and the diagnostic efficacy of CT staging improves with more advanced disease. Nevertheless, it has limited accuracy in differentiating non-muscle invasive bladder carcinoma from muscle-invasive bladder carcinoma. In this review, clinical indications and the optimal imaging technique for CT of the urinary tract is reviewed. The CT features of common urologic diseases, including ureterolithiasis, renal tumors and urothelial carcinomas are discussed.

Does unenhanced computerized tomography as imaging standard post-retrograde intrarenal surgery paradoxically reduce stone-free rate and increase additional treatment for residual fragments? Outcomes from 5395 patients in the FLEXOR study by the TOWER group

Background

Assessment of residual fragments (RFs) is a key step after treatment of kidney stones.

Objective

To evaluate differences in RFs estimation based on unenhanced computerized tomography (CT) versus X-rays/ultrasound after retrograde intrarenal surgery (RIRS) for kidney stones.

Design

A retrospective analysis of data from 20 centers of adult patients who had RIRS was done (January 2018-August 2021).

Methods

Exclusion criteria: ureteric stones, anomalous kidneys, bilateral renal stones. Patients were divided into two groups (group 1: CT; group 2: plain X-rays or combination of X-rays/ultrasound within 3 months after RIRS). Clinically significant RFs (CSRFs) were considered RFs ⩾ 4 mm. One-to-one propensity score matching for age, gender, and stone characteristics was performed. Multivariable logistic regression analysis was performed to evaluate independent predictors of CSRFs.

Results

A total of 5395 patients were included (1748 in group 1; 3647 in group 2). After matching, 608 patients from each group with comparable baseline and stone characteristics were included. CSRFs were diagnosed in 1132 patients in the overall cohort (21.0%). Post-operative CT reported a significantly higher number of patients with RFs ⩾ 4 mm, before (35.7% versus 13.9%, p < 0.001) and after matching (43.1% versus 23.9%, p < 0.001). Only 21.8% of patients in the matched cohort had an ancillary procedure post-RIRS which was significantly higher in group 1 (74.8% versus 47.6%, p < 0.001). Age [OR 1.015 95% confidence interval (CI) 1.009-1.020, p < 0.001], stone size (OR 1.028 95% CI 1.017-1.040, p < 0.001), multiple stones (OR 1.171 95% CI 1.025-1.339, p = 0.021), lower pole stone (OR 1.853 95% CI 1.557-2.204, p < 0.001) and the use of post-operative CT scan (OR 5.9883 95% CI 5.094-7.037, p < 0.001) had significantly higher odds of having CSRFs.

Conclusions

CT is the only reliable imaging to assess the burden of RFs following RIRS and urologist should consider at least one CT scan to determine the same and definitely plan reintervention only based on CT rather than ultrasound and X-ray combination.

The Role of Radiological Imaging in the Diagnosis and Treatment of Urolithiasis: A Narrative Review

The incidence and prevalence of urolithiasis have been increasing worldwide for the last several decades. This increase could be attributed to many factors, including missed cases of small stones, a sedentary lifestyle, a high BMI, a lack of physical activity, and poor dietary intake. In addition, the increased incidence of co-morbidities such as diabetes, dyslipidemia, infections, and multiple urinary tract surgeries could contribute significantly to the formation of urolithiasis. Radiology has a major role in diagnosing a variety of these stone types and can be used in planning management approaches, either as guidance or as a direct therapeutic method for stones. Because of the availability, safety, cost, and effectiveness of radiological imaging nowadays, urolithiasis is rarely missed; furthermore, the availability of radiological treatment options decreases the need for surgical intervention for urolithiasis, which minimizes hospital stay and surgical-related complications. This review aims to scope and analyze the role of radiological imaging modalities in reaching a diagnosis and planning treatment options for urolithiasis in different circumstances. Information was gathered from relevant peer-reviewed publications in PubMed and thereafter refined and summarized to provide a comprehensive review. The selected indexing terms included "radiological imaging modality," "treatment of urolithiasis," and "diagnosis of urolithiasis," among others.

Audit on Compliance to Guidelines in CT Scanning for Urolithiasis

Introduction

According to the ALARA principle, CT-imaging procedures should be implemented to optimize radiation doses. The purpose of this study is to determine whether a quality control process has an impact on compliance with procedures.

Materials and methods

This retrospective study was conducted in three hospitals, focusing on the selection of the appropriate acquisition protocol and the reduction of acquisition height in abdominal computed tomography (CT) examinations performed to diagnose or rule out urolithiasis. A first audit was conducted to measure the compliance with the procedure. Next, a reminder of the CT-urolithiasis procedure was given to stakeholders. Three months later, a second audit was conducted to measure the impact of the repeat recall information on compliance, and to compare the outcome with an earlier audit conducted five years earlier.

Results

We included 517 'urolithiasis CT examinations'. The compliance ranged from 41.67% to 64.8% for the first audit. After the reminder of the urolithiasis procedure, compliance ranged from 50% to 76.10%. This improvement was statistically significant for hospital A and B (p < 0.001 for hospital A, p = 0.013 for hospital B) but not for hospital C (p = 0.405). Despite prior demonstration that improved compliance persisted at one year from an initial audit, our actual data show that this compliance had decreased at year five, confirming the need to repeat compliance audits more frequently, or to monitor it continuously.

Conclusion

Surveying compliance to procedures can improve compliance but only for a limited duration. Monitoring compliance more frequently or even continuously is recommended.

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.