Comparison of ultrasound versus computed tomography for the detection of kidney stones in the pediatric population: a clinical effectiveness study

Zero-echo time MRI: an alternative method for the diagnosis of urinary stones in children

OBJECTIVES

To evaluate the potential of zero-echo time-magnetic resonance imaging (ZTE-MRI) in the assessment of urolithiasis and compare ZTE-MRI with computed tomography (CT) in pediatric patients.

MATERIALS AND METHODS

This was a single-center, prospective cross-sectional study conducted between April 2023 and December 2023. 23 patients (12 girls, 11 boys; mean age: 12.3, range 1-18) with urinary tract stones detected on non-enhanced abdominal CT were enrolled. The images were evaluated independently by two radiologists for the presence, and number of stones in the kidneys, ureters, and bladder. In the second session, two radiologists evaluated whether urinary tract stones could be detected by MRI compared to CT, and the maximum diameter of the stones was measured. The CT and MRI results were compared with the Wilcoxon test. The agreement between the results of the observers was examined using Spearman's rho correlation coefficient and the intraclass correlation coefficient.

RESULTS

A total of 58 urinary tract stones were detected by CT and 39 of these were detected by MRI. Most of the stones that MRI could not detect were < 5 mm and the detection sensitivity of MRI increased in correlation with stone size (p < 0.001). There was poor intermodality agreement for stones < 5 mm, substantial agreement for stones 5-10 mm, and almost perfect agreement for stones > 10 mm. Interobserver agreement for stone detection on MRI was almost perfect for stones > 10 mm and 5-10 mm and was substantial for stones < 5 mm.

CONCLUSION

ZTE-MRI is a promising modality for detecting urinary stones without radiation exposure in children.

CLINICAL RELEVANCE STATEMENT

Zero-echo time-magnetic resonance imaging is a potential method for identifying urinary stones in children and other populations who are particularly sensitive to radiation.

KEY POINTS

Urinary system stone disease in children is increasing and imaging is needed for managing urolithiasis. Zero-echo time-magnetic resonance imaging (ZTE-MRI) had an accuracy of 81.8% and 93.7% for stones larger than 5 mm and 10 mm, respectively. ZTE-MRI is a potential non-irradiating method for the diagnosis and management of urolithiasis.

Optimizing Advanced Imaging of the Pediatric Patient in the Emergency Department: Technical Report

Advanced diagnostic imaging modalities, including ultrasonography, computed tomography, and magnetic resonance imaging, are key components in the evaluation and management of pediatric patients presenting to the emergency department. Advances in imaging technology have led to the availability of faster and more accurate tools to improve patient care. Notwithstanding these advances, it is important for physicians, physician assistants, and nurse practitioners to understand the risks and limitations associated with advanced imaging in children and to limit imaging studies that are considered low value, when possible. This technical report provides a summary of imaging strategies for specific conditions where advanced imaging is commonly considered in the emergency department. As an accompaniment to the policy statement, this document provides resources and strategies to optimize advanced imaging, including clinical decision support mechanisms, teleradiology, shared decision-making, and rationale for deferred imaging for patients who will be transferred for definitive care.

Optimizing Advanced Imaging of the Pediatric Patient in the Emergency Department: Technical Report

Advanced diagnostic imaging modalities, including ultrasonography, computed tomography, and magnetic resonance imaging (MRI), are key components in the evaluation and management of pediatric patients presenting to the emergency department. Advances in imaging technology have led to the availability of faster and more accurate tools to improve patient care. Notwithstanding these advances, it is important for physicians, physician assistants, and nurse practitioners to understand the risks and limitations associated with advanced imaging in children and to limit imaging studies that are considered low value, when possible. This technical report provides a summary of imaging strategies for specific conditions where advanced imaging is commonly considered in the emergency department. As an accompaniment to the policy statement, this document provides resources and strategies to optimize advanced imaging, including clinical decision support mechanisms, teleradiology, shared decision-making, and rationale for deferred imaging for patients who will be transferred for definitive care.

Radiation exposure associated with computed tomography for pediatric urolithiasis evaluation: A scoping review of the literature

INTRODUCTION

Computed tomography (CT) imaging is used for assessment of pediatric urolithiasis in cases where ultrasound is inconclusive. The utility of CT imaging must be considered alongside the potential risks of radiation exposure in this patient population due to the increased risk of cancer development. The purpose of this review is to investigate the radiation exposure associated with standard-dose and low-dose computed tomography (CT) imaging for the assessment of pediatric urolithiasis.

METHODS

A scoping literature review over a 23 year period between 2000 and 2023 was conducted of all English-language studies reporting on the use of non-contrast CT imaging for assessment of pediatric urolithiasis. Patients that were specified as pediatric with age ≤20 years at time of intervention and undergoing standard-dose or low/ultra-low-dose CT were included. Low-dose and ultra-low-dose CT were defined as a radiation dose ≤3.0 mSv and ≤1.9 mSv, respectively.

RESULTS

A total of 8121 articles were identified and after screening, 6 articles representing 309 patients were included in this scoping review. Of the articles reviewed, standard non-contrast CT radiation doses for pediatric urolithiasis evaluation ranged from 2.9 to 5.5 mSv and low-dose CT radiation dose was reported to be 1.0-2.72 mSv. Only 2 studies directly evaluated low-dose CT imaging compared to standard-dose CT imaging for pediatric urolithiasis assessment. Radiation reduction approaches did not negatively impact urolithiasis detection or characterization in 2 studies reviewed.

CONCLUSIONS

CT radiation doses for suspected or known pediatric urolithiasis are underreported and vary greatly with underutilization of low-dose/ultra-dose protocols for pediatric urolithiasis especially in comparison to the adult population. Results from this scoping review support that low-dose CTprotocols for pediatric stone disease are feasible to reduce radiation exposure.

A population-based retrospective cohort study of surgical trends and outcomes of pediatric urolithiasis in Ontario, Canada (2002-2019)

INTRODUCTION

The worldwide incidence of pediatric urinary stone disease (PUSD) is increasing. However, there is no commensurate data on whether this translates to an increasing need for surgical intervention for PUSD, given the role of conservative management.

OBJECTIVE

We aimed to evaluate the trends and outcomes of clinically significant PUSD, using administrative databases to identify patients surgically treated for PUSD.

STUDY DESIGN

This retrospective population-based cohort study assessed the incidence and trends of surgically treated PUSD and outcomes in Ontario, Canada in patients <18 years of age who underwent their first PUSD procedure between 2002 and 2019 utilizing administrative databases held at the Institute of Clinical Evaluative Sciences (ICES). We assessed the incidence of surgically treated PUSD, demographics, initial surgical treatment and imaging modality, and risk factors for repeat intervention within 5 years. Statistical analyses summarized demographics, surgical trends, and logistic regression was used to identify risk factors for repeat surgical intervention.

RESULTS

We identified 1149 patients (mean age 11.3 years), with 59.6% older than 12 years. There was a decrease in the number of PUSD procedures performed per year that was close to statistical significance (p = 0.059) and a trend towards increased utilization of ureteroscopy (URS) compared with Shockwave Lithotripsy (SWL). In addition, there was a significant increase in the proportion of females surgically treated with PUSD (p = 0.001). In the 706 patients followed for 5 years, 17.7% underwent a repeat procedure within 6 months, while 20.4% underwent a repeat procedure from 6-months to 5 years. Renal stone location (OR 2.79, 95% confidence interval (CI) 1.62-4.80, p = 0.0002) and index SWL (OR 1.66, 95% CI 1.20-2.31, p = 0.0025) were risk factors for repeat surgical intervention within the first 6-months. There was an increasing utilization of ultrasound (US) compared to computerized tomography (CT) (p = 0.0008).

DISCUSSION

Despite the literature reporting increasing PUSD incidence, we observed a non-significant decrease in the number of surgical PUSD procedures performed. Exclusion of those treated conservatively may explain our results. The increase in the proportion of females treated reflects the narrowing gender gap in stone disease. A trend towards increased URS utilization was observed and re-intervention rates were similar to previous studies.

CONCLUSION

The overall rate of surgically treated PUSD did not show an increasing trend in Ontario, Canada from 2002 to 2019. URS was the most common surgical treatment modality, with a corresponding decline in SWL rates. PUSD was associated with a high surgical re-intervention rate within 6 months.

Imaging urolithiasis: complications and interventions in children

Urolithiasis affects people in all age groups, but over the last decades there has been an increasing incidence in children. Typical symptoms include abdominal or flank pain with haematuria; in acute cases dysuria, fever or vomiting also occur. Ultrasound is considered the modality of choice in paediatric urolithiasis because it can be used to identify most clinically relevant stones. Complementary imaging modalities such as conventional radiographs or non-contrast computed tomography should be limited to specific clinical situations. Management of kidney stones includes dietary, pharmacological and urological interventions, depending on stone size, location or type, and the child's condition. With a very high incidence of underlying metabolic abnormalities and significant recurrence rates in paediatric urolithiasis, thorough metabolic evaluation and follow-up examination studies are of utmost importance.

Paediatric kidney stone surgery: state-of-the-art review

While urolithiasis in children is rare, the global incidence is rising, and the volume of minimally invasive surgeries being performed reflects this. There have been many developments in the technology, which have supported the advancement of these interventions. However, innovation of this kind has also resulted in wide-ranging practice patterns and debate regarding how they should be best implemented. This is in addition to the extra challenges faced when treating stone disease in children where the patient population often has a higher number of comorbidities and for example, the need to avoid risk such as ionising exposure is higher. The overall result is a number of challenges and controversies surrounding many facets of paediatric stone surgery such as imaging choice, follow-up and different treatment options, for example, medical expulsive therapy, shockwave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy. This article provides an overview of the current status of paediatric stone surgery and discussion on the key topics of debate.

Progression of asymptomatic nephrolithiasis in children: How often should patients receive follow-up ultrasound imaging?

INTRODUCTION

The natural history of asymptomatic nephrolithiasis (AN) in children is not well defined. Furthermore, there is no guidance on the utility of repeated renal ultrasound evaluations in this same population. Follow-up ultrasound studies are often obtained as frequently as every 6 months. The goal of this study is to assess the follow-up ultrasound interval in the management of these patients.

METHODS

A retrospective IRB approved chart review was performed for patients seen for non-cysteine AN between 2012 and 2019. AN was defined as patients without obstructive uropathy abdominal, flank pain and/or gross hematuria. Asymptomatic stones were discovered incidentally or after an acute stone event. Patients with pre-existing renal anomalies and the timepoints with stone passage or stone procedure were excluded. Descriptive statistics were used for demographic information. Multiple linear regression was used to analyze risk factors. Statistical significance was set to p < 0.05.

RESULTS

Twenty-nine patients had 90 ultrasounds. The average age at diagnosis was 10.8 ± 6.2 years. The average number of ultrasound studies per patient was 3.2 ± 1.7. The median time between follow-up ultrasounds was 5.2 months [IQR 2.8-10.0]. Median follow-up of patients was 10.6 months [IQR 4.9-21.9]. The change in total stone burden occurred at a rate of 0.11 mm/month (CI [-0.06-0.28], p = 0.20, r² = 0.42) or 0.66 mm/6 months. Patients with more renal stones had almost a threefold increase in stone burden compared to patients with fewer renal stones (2.98 [CI 1.34-4.62], p=0.001, r²=0.33). Patients with a family history of stones had a twofold increase in the size of their largest stone when compared to patients without a family history (1.97 [CI 0.26-3.68], p=0.02, r²=0.60.

CONCLUSION

A complex interplay of multiple factors influence the progression of AN in children. Children with a greater number of stones have a higher increase in total stone burden and children with a family history of stones have a faster increase in largest stone size. These patients may require more frequent imaging studies. The small change in stone size over time favors a longer than 6-month interval for many children.

Ureteroscopy for stone disease in the paediatric population: lessons learned and outcomes in a Nordic setting

Introduction:

Paediatric stone disease is rare in the Nordic communities. Still, the condition can require surgical intervention in the form of ureteroscopy (URS). Here, we report outcomes achieved at a regional (tertiary) centre.

Patients and methods:

Retrospective analysis was performed of consecutive patients (<18 years of age) undergoing URS for stone disease between 2010 and 2021. Outcomes of interest included stone-free rate (SFR) determined using a definition of no residual fragments ⩾ 3 mm on imaging and complications classified according to Clavien–Dindo system.

Results:

In total, 23 patients underwent 47 URS procedures for a total of 31 stone episodes. Mean age was 9 (range 1–17) years and male-to-female ratio was 6:17. Overall, 35% had at least one medical comorbidity. Ultrasound determined preoperative stone status in 87%. Mean largest index and cumulative stone sizes were 9 (range 3–40) and 12 (range 3–40) mm, respectively. Overall, 32% had multiple stones. Lower pole was the commonest stone location (39%). No patients underwent elective pre-operative stenting. Ureteral access sheaths were not used in any cases. Access to upper urinary tract at first procedure was successful in 94%. Initial and final SFR was 61% and 90%, respectively. No intra-operative complications were recorded. Overall post-operative complication rate was 17.5%. Urinary tract infection (CD II) was the commonest adverse event (12.5%).

Conclusion:

Paediatric URS can be delivered in the setting of a regional centre without compromising outcomes. This includes when carried out by adult endourologists, without routine pre-stenting and omitting use of ureteric access sheath.

The gap between ultrasonography and computed tomography in measuring the size of urinary calculi

Objective

Due to a lack of studies regarding the need for computed tomography (CT) in measuring the size of each urinary calculus before surgery, this study was conducted to elucidate the difference between ultrasonography (US) and CT in measuring the size of urinary stones.

Methods

A retrospective review of 100 stones from 83 patients. Each urinary stone was measured using both US and CT; both measurements were then compared.

Results

Of 83 patients, the mean age was 39.29 ± 23.76 years; 47 (56.62%) were male and 36 (43.37%) were female. Most of the urinary stones were <10 mm (50.0%) followed by 11-20 mm (42.0%), (P < 0.001). A cross-tabulation test revealed strong compatibility between US and CT in measuring the size of urinary stones (73.7% in stones <10 mm, 66.7% in stones 11-20 mm and 50% in stones >21 mm), (P < 0.001). Spearman's rho correlation test revealed strong compatibility between stone diameters measured by US and CT (r = 0.755), (P = 0 < 0.001). T-test for equality of means revealed no significant difference in the measured size using US and CT (mean = 11.80 ± 5.83 vs. 11.65 ± 6.59, respectively), mean difference = 0.15, and P = 0.865, 95% confidence interval: -1.584-1.884.

Conclusion

No significant difference in measuring the size of urinary stones using US and CT. However, US may slightly overestimate small stones in some cases.

Imaging modalities and treatment of paediatric upper tract urolithiasis: A systematic review and update on behalf of the EAU urolithiasis guidelines panel

BACKGROUND

Prompt diagnosis and treatment of paediatric urolithiasis are required to avoid long term sequelae of renal damage.

OBJECTIVE

To systematically review the literature regarding the diagnostic imaging modalities and treatment approaches for paediatric urolithiasis.

STUDY DESIGN

PubMed, Science Direct, Scopus and Web of Science were systematically searched from January 1980-January 2019. 76 full-text articles were included.

RESULTS

Ultrasound and Kidney-Ureter-Bladder radiography are the baseline diagnostic examinations. Non-contrast Computed Tomography (CT) is the second line choice with high sensitivity (97-100%) and specificity (96-100%). Magnetic Resonance Urography accounts only for 2% of pediatric stone imaging studies. Expectant management for single, asymptomatic lower pole renal stones is an acceptable initial approach, especially in patients with non-struvite, non-cystine stones<7 mm. Limited studies exist on medical expulsive therapy as off-label treatment. Extracorporeal shock wave lithotripsy (SWL) is the first-line treatment with overall stone free rates (SFRs) of 70-90%, retreatment rates 4-50% and complication rates up to 15%. Semi-rigid ureteroscopy is effective with SFRs of 81-98%, re-treatment rates of 6.3-10% and complication rates of 1.9-23%. Flexible ureteroscopy has shown SFRs of 76-100%, retreatment rates of 0-19% and complication rates of 0-28%. SFRs after first and second-look percutaneous nephrolithotomy (PNL) are 70.1-97.3% and 84.6-97.5%, respectively with an overall complication rate of 20%. Open surgery is seldom used, while laparoscopy is effective for stones refractory to SWL and PNL. Limited data exist for robot-assisted management.

CONCLUSIONS

In the initial assessment of paediatric urolithiasis, US is recommended as first imaging modality, while non-contrast CT is the second option. SWL is recommended as first line treatment for renal stones <20 mm and for ureteral stones<10 mm. Ureteroscopy is a feasible alternative both for ureteral stones not amenable to SWL as well as for renal stones <20 mm (using flexible). PNL is recommended for renal stones >20 mm.

The Prevalence of Incidentally Detected Urolithiasis in Subjects Undergoing Computerized Tomography

Background and objective

Urolithiasis is defined as the presence of calculi in the urinary tract. Multiple studies have shown that urinary tract stones are one of the most common incidental findings in medical imaging. These stones are potentially dangerous and can cause severe impairment to renal function if they remain undiagnosed for a long time. The objective of this study was to determine the prevalence of incidentally detected urolithiasis in patients undergoing abdominopelvic CT scans.

Materials and methods

A retrospective cross-sectional study was conducted, which involved 721 patients selected by consecutive non-randomized sampling. The study population included patients who underwent an abdominopelvic CT scan in the radiology department of a tertiary care hospital in Pakistan. Patients aged below 10 years and those above 90 years were excluded from the study. Patients undergoing kidney, ureter, and bladder (KUB) scan for urolithiasis-associated symptoms and those with already known urolithiasis were also excluded. The data were recorded in a predesigned pro forma and analyzed with SPSS Statistics version 20.00 (IBM, Armonk, NY).

Results

A total of 721 patients underwent an abdominopelvic CT scan during the six months from July to December in the radiology department of the hospital. Out of these, 336 (46.6%) were males, and 385 (53.4%) were females. Incidental stones were found in 20 of these patients. Among these 20 stone formers, 11 were males, and nine were females. Out of them, six had stones in the right kidney, eight in the left kidney, and four patients had bilateral stones. The remaining two patients had stones in their ureters. In most cases, stones were found in lower poles as compared to the mid pole and upper pole of the kidneys.

Conclusion

The prevalence of incidentally detected urolithiasis was found to be 2.8% in this study. Its frequency was much higher in males (3.27%) compared to females (2.33%). Most of the stones were found in the kidneys whereas no stone was detected in the urinary bladder.

Nephrolithiasis: Approach to Diagnosis and Management

Although kidney stones are less common in children than in adults, incidence in children is rising. Kidney stones may lead to significant morbidity in addition to escalating medical costs. Clinical presentation is variable. Bilateral kidney stones in a younger child should prompt work-up for primary hyperoxaluria. Metabolic abnormalities are more frequent in children and can result in frequent stone recurrence. Whole exome sequencing data shows genetic defects in about 30% of stone formers. 24 h urine collection should be conducted when patient receives his usual diet and fluid intake with normal activity. Infrared spectroscopy and X-ray diffraction are used for stone analysis. Urine studies should be delayed by 4-6 wk after stone fragmentation or treatment of any stone related complications. The goal of evaluation is to identify modifiable risk factors for which targeted therapy may be instituted. Primary indications for surgical intervention include pain, infection and obstruction. Extracorporeal shockwave lithotripsy (ESWL), ureteroscopy, and percutaneous nephrolithotomy (PCNL) are most commonly used, and selection is based on stone size, anatomy, composition and anatomy. Advances in technology have allowed a shift to minimally invasive surgeries. Comprehensive management requires multidisciplinary team. Children with kidney stones require long term follow-up with periodic assessment of stone forming activity and ascertaining stone burden. High index of suspicion should be there to diagnose diseases like primary hyperoxaluria, Dent's disease, renal tubular acidosis (RTA) etc. as these diseases have ramifications on kidney function and growth.

Evaluation of a child with suspected nephrolithiasis

PURPOSE OF REVIEW

As the incidence of nephrolithiasis in children doubles every 10 years it is becoming a common disease associated with significant morbidity along with considerable economic burden worldwide. The aim of this review is to summarize current data on the epidemiology and causes of renal stones in children and to provide a frame for the first clinical evaluation of a child with suspected nephrolithiasis.

RECENT FINDINGS

Dietary and environmental factors are the driving force of changing epidemiology. Diagnosis should be based on medical history, presenting signs, examination, first laboratory and radiological workup. Ultrasound should be the initial diagnostic imaging performed in pediatric patients while low-dose computed tomography is rarely necessary for management. Metabolic factors including hypercalciuria, hypocitraturia, low fluid intake as well as specific genetic diseases should be explored after the resolution of initial signs and symptoms.

SUMMARY

Appropriate initial evaluation, imaging technique, identification of risk factors and other abnormalities are essential for early diagnosis and prevention of stone-related morbidity in children with suspected nephrolithiasis.

Detecting Kidney Stones Using Twinkling Artifacts: Survey of Kidney Stones with Varying Composition and Size

In recent years, work has been done to understand the mechanisms of Doppler ultrasound twinkling artifacts (TAs) and why they appear over kidney stones. In the work described here, twinkling artifacts were evaluated as a possible method of locating and characterizing kidney stones. Doppler ultrasound scanning was used to evaluate 47 stones of different types and sizes in the range 1.31-55.76 mm² in cross-sectional area (average = 9.65 mm²). An isolated stone study was used to understand the behavior of the TAs. An ex vivo kidney study was conducted to determine if the renal tissue impeded localization of the TAs to the stones. An ex vivo study of randomly placed stones was used to evaluate the robustness of the method for detecting stones that were placed by an independent party. The TAs were found to be qualitatively consistent in appearance across stone types, sizes and scanning parameters in the isolated stone study. Quantitative assessment of TA amplitude for isolated stones was also found to be consistent for each class of stones across multiple days. The TAs were also found to be isolated to the stone when placed in an ex vivo kidney. The study of randomly placed stones revealed that this method could find all 47 stones used in a clinical situation with only two false positives. A few limitations to this method were noted involving accurate sizing of stones and the specificity of characterizing the stones. Further work will be done to overcome limitations by improving the Doppler acquisition and processing code, as well as by evaluating the use of TAs in human studies.

Clinical Significance of Twinkling Artifact in the Diagnosis of Urinary Stones

The twinkling artifact is a color Doppler artifact, but it could be used in the confirmation of urinary stones. Conventionally, gray-scale criteria (echogenic foci with acoustic shadowing) is used in the diagnosis of urinary stones, but unfortunately, its reliability is very low. If the color Doppler twinkling artifact is applied in conjunction with other provocative measures, then its overall reliability exceeds 95%. To determine the clinical significance of twinkling artifact in the diagnosis of urinary stones, this cross-sectional observational study was conducted at Gilani Ultrasound Center, Lahore, Pakistan. For the determination of clinical significance, 1350 patients were recruited for this study. All the patients had renal stones of variable size and location. All the patients were evaluated with gray-scale sonographic criteria, and then color Doppler was applied to look for the twinkling artifact. The findings were confirmed with other imaging modalities (i.e., plain X-ray, computed tomography scan, etc., or during patient follow up). Sensitivity and specificity of the gray-scale ultrasound criteria in the detection of urinary stones was 96.1% and 57.9%, respectively, while the sensitivity and specificity of the color Doppler twinkling artifact in the detection of urinary stones was 100.0% and 97.4%, respectively. It was concluded that the application of twinkling artifact is useful in the confirmation of urinary stones, but specifically, it is of great diagnostic value in the small (less than 5 mm) renal stones and stones adjacent to a strong reflector (i.e., ureteric stones or stones in the prostatic urethra).

Point-of-Care Ultrasound for the Pediatric Hospitalist's Practice

Point-of-care ultrasound (POCUS) has the potential to provide real-time valuable information that could alter diagnosis, treatment, and management practices in pediatric hospital medicine. We review the existing pediatric POCUS literature to identify potential clinical applications within the scope of pediatric hospital medicine. Diagnostic point-of-care applications most relevant to the pediatric hospitalist include lung ultrasound for pneumothorax, pleural effusion, pneumonia, and bronchiolitis; cardiac ultrasound for global cardiac function and hydration status; renal or bladder ultrasound for nephrolithiasis, hydronephrosis, and bladder volumes; soft tissue ultrasound for differentiating cellulitis from abscess; and procedural-guidance applications, including line placement, lumbar puncture, and abscess incision and drainage. We discuss POCUS applications with reviews of major pathologic findings, research gaps, the integration of POCUS into practice, and barriers to implementation.

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.

Acoustic shadowing in pediatric kidney stone ultrasound: a retrospective study with non-enhanced computed tomography as reference standard

BACKGROUND

The usefulness of acoustic shadowing as a feature of pediatric kidney stone ultrasound (US) may be underestimated.

OBJECTIVE

The hypothesis was that the majority of stones in children have acoustic shadowing and that its specificity is high (>90%) in pediatric kidney stones.

MATERIALS AND METHODS

Our retrospective observational study included children who had undergone abdominal non-enhanced computed tomography (CT) for kidney stones in a pediatric renal stone referral centre between 2015 and 2016. US examinations prior to CT were retrospectively assessed for US features such as acoustic shadowing, twinkle artifact and stone size. These features were compared to CT as reference standard.

RESULTS

Thirty-one patients (median age: 13 years, range: 1-17 years) with 77 suspected kidney stones were included. The median stone size was 5 mm (interquartile range [IQR]: 5 mm). For acoustic shadowing, sensitivity was 70% (95% confidence interval [CI] 56-80%) and specificity was 100% (95% CI 56-100%). All kidney stones with a diameter ≥9 mm demonstrated shadowing. Sensitivity for twinkle artifact was 88% (95% CI 72-96%), but specificity for twinkle artifact could not be calculated due to the lack of true negatives. All false-positive stones on US demonstrated twinkle artifact, but none showed shadowing.

CONCLUSION

Acoustic shadowing was demonstrated in the majority of pediatric kidney stones. Specificity was high, but this was not significant. Twinkle artifact is a sensitive US tool for detecting (pediatric) kidney calculi, but with a risk of false-positive findings.

Imaging features of primary hyperoxaluria

Primary hyperoxaluria (PH) is a group of autosomal recessive diseases that affect the metabolism of glyoxalate and oxalate. As a result of the enzymatic deficiency, there is overproduction and urinary excretion of oxalate with progressive renal damage and subsequent deposition of oxalate salts in various tissues. The definitive treatment in cases of end-stage kidney disease is a combined liver and kidney transplant. Imaging features are diverse and reflect the multiple organs that might be affected. These include nephrolithiasis and nephrocalcinosis, oxalate osteopathy, as well as other findings, such as splenomegaly and oxalate deposition in the heart. In this review article, we present various imaging findings that may appear in patients with PH.