Diagnosis and management of acute ureterolithiasis: CT is truth

Identification of Clinically Insignificant Renal Calculi on Sonography

OBJECTIVE

To determine factors predicting if a radiologists... report of a .. stone... on ultrasound (US) was not actually a clinically significant stone, based on subsequent computed tomogram (CT). US often overestimates stone size and various pathologic entities are also hyperechoic;.ßthus, a subsequent CT without a clinically significant stone may represent unnecessary radiation exposure. A decision-tree and nomogram were developed to predict when stones are unlikely on subsequent CT.

METHODS

Retrospective analysis of patients, of any age, receiving CT within 24.ßhours of a sonographic report documenting a single renal stone, during 2019...2020, in any phase of care, at one institution. Novel stone-likelihood-systems for US and CT (US-SLS, CT-SLS) were devised and validated to classify stones as clinically significant or insignificant, with CT as the gold standard. Binomial logistic regression predicting clinically significant stones was performed with sonographic and patient characteristics.

RESULTS

Eight hundred twenty patients had US followed by CT, 228 (27.8%) reported documented stones, 140 (17.1%) reported a single stone. Clinically significant stones were associated with larger stone size (P: .002), location (P: .002), hydronephrosis (P: .04), shadowing-artifact (P: .02) depth.ßto.ßstone (P: .008), and Body mass Index (BMI) (P: .01). US-SLS had higher sensitivity (95.4%) and negative-predictive-value (81.8%) compared to a multivariate model of significant variables.

CONCLUSION

US-SLS appears to exclude clinically irrelevant .. stones... better than established criteria including twinkle or shadow in this retrospective analysis. A diagnostic algorithm and nomogram are presented. US-SLS and the associated decision tree can assist providers in avoiding unnecessary radiation when clinically significant stones are unlikely.

Enhancing sizing accuracy in ultrasound images with an alternative ADMIRE model and dynamic range considerations

Ultrasound imaging can struggle with sizing accuracy, especially when the targets have a significantly different amplitude compared to the surrounding background. In this work, we consider the challenging task of accurately sizing hyperechoic structures, and specifically kidney stones, where accurate sizing is critical for determining medical intervention. AD-Ex, an extended alternative model of our aperture domain model image reconstruction (ADMIRE) pre-processing method, is introduced and is designed to improve clutter removal and improve sizing accuracy. We compare this method against other resolution enhancing methods such as minimum variance (MV) and generalized coherence factor (GCF), and against those methods using AD-Ex as a pre-processing tool. These methods are evaluated among patients with kidney stone disease, with the task of accurately sizing the stones against the gold standard, computed tomography (CT). Stone ROI's were selected using contour maps as reference from which the lateral stone size was estimated. Among the in vivo kidney stone cases we processed, AD-Ex+MV had the overall lowest sizing error among the methods, with an average error of 10.8% compared to the next best method AD-Ex which had an average error of 23.4%. For reference, DAS had an average error of 82.4%. Though dynamic range was evaluated to determine optimal thresholding for sizing applications, variability between stone cases was too high for any conclusions to be drawn at this time.

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.

In-Office Ultrasound Facilitates Timely Clinical Care at a Multidisciplinary Kidney Stone Center

Introduction

A considerable publication record exists comparing sensitivity and specificity of radiological ultrasound (including point of care ultrasound) to computerized tomography for stone disease. However, the practical application of in-office ultrasound to support the growing number of kidney stone centers around the world represents a nuanced topic that is ripe for study and discussion.

Methods

We provide a descriptive analysis of how in-office ultrasound is being used as an adjunct to clinical care based on our experience during 50 days in clinic at an institutionally affiliated, multidisciplinary kidney stone center. Clinic subjects gave consent and underwent ultrasound as part of research studies. Ultrasonograms were shared with and verified by the treating physician before the patient was discharged from care. We counted the number of times research imaging altered the care plan.

Results

Of the 60 patients enrolled the clinician used the information obtained from the studies in 20 (33%) to determine the course of clinical care that resulted in a change in treatment or process.

Conclusions

Ultrasound has the potential to be a cost-effective and valuable tool that can provide more efficient workflow within a kidney stone center or urology clinic.

In vitro feasibility of next generation non-linear beamforming ultrasound methods to characterize and size kidney stones

Ultrasound imaging for kidney stones suffers from poorer sensitivity, diminished specificity, and overestimation of stone size compared to computed tomography (CT). The purpose of this study was to demonstrate in vitro feasibility of novel ultrasound imaging methods comparing traditional B-mode to advanced beamforming techniques including plane wave synthetic focusing (PWSF), short-lag spatial coherence (SLSC) imaging, mid-lag spatial coherence (MLSC) imaging with incoherent compounding, and aperture domain model image reconstruction (ADMIRE). The ultrasound techniques were evaluated using a research-based ultrasound system applied to an in vitro kidney stone model at 4 and 8 cm depths. Stone diameter sizing and stone contrast were compared among the different techniques. Analysis of variance was used to analyze the differences among group means, with p < 0.05 considered significant, and a Student's t test was used to compare each method with B-mode, with p < 0.0025 considered significant. All stones were detectable with each method. MLSC performed best with stone sizing and stone contrast compared to B-mode. On average, B-mode sizing error ± SD was > 1 mm (1.2 ± 1.1 mm), while those for PWSF, ADMIRE, and MLSC were < 1 mm (- 0.3 ± 2.9 mm, 0.6 ± 0.8, 0.8 ± 0.8, respectively). Subjectively, MLSC appeared to suppress the entire background thus highlighting only the stone. The ADMIRE and SLSC techniques appeared to highlight the stone shadow relative to the background. The detection and sizing of stones in vitro are feasible with advanced beamforming methods with ultrasound. Future work will include imaging stones at greater depths and evaluating the performance of these methods in human stone formers.

Ultrasound vs. Computed Tomography for Severity of Hydronephrosis and Its Importance in Renal Colic

Introduction

Supporting an “ultrasound-first” approach to evaluating renal colic in the emergency department (ED) remains important for improving patient care and decreasing healthcare costs. Our primary objective was to compare emergency physician (EP) ultrasound to computed tomography (CT) detection of hydronephrosis severity in patients with suspected renal colic. We calculated test characteristics of hydronephrosis on EP-performed ultrasound for detecting ureteral stones or ureteral stone size >5mm. We then analyzed the association of hydronephrosis on EP-performed ultrasound, stone size >5mm, and proximal stone location with 30-day events.

Methods

This was a prospective observational study of ED patients with suspected renal colic undergoing CT. Subjects had an EP-performed ultrasound evaluating for the severity of hydronephrosis. A chart review and follow-up phone call was performed.

Results

We enrolled 302 subjects who had an EP-performed ultrasound. CT and EP ultrasound results were comparable in detecting severity of hydronephrosis (x²=51.7, p<0.001). Hydronephrosis on EP-performed ultrasound was predictive of a ureteral stone on CT (PPV 88%; LR+ 2.91), but lack of hydronephrosis did not rule it out (NPV 65%). Lack of hydronephrosis on EP-performed ultrasound makes larger stone size >5mm less likely (NPV 89%; LR− 0.39). Larger stone size > 5mm was associated with 30-day events (OR 2.30, p=0.03).

Conclusion

Using an ultrasound-first approach to detect hydronephrosis may help physicians identify patients with renal colic. The lack of hydronephrosis on ultrasound makes the presence of a larger ureteral stone less likely. Stone size >5mm may be a useful predictor of 30-day events.

Non-invasive differentiation of kidney stone types using X-ray dark-field radiography

Treatment of renal calculi is highly dependent on the chemical composition of the stone in question, which is difficult to determine using standard imaging techniques. The objective of this study is to evaluate the potential of scatter-sensitive X-ray dark-field radiography to differentiate between the most common types of kidney stones in clinical practice. Here, we examine the absorption-to-scattering ratio of 118 extracted kidney stones with a laboratory Talbot-Lau Interferometer. Depending on their chemical composition, microscopic growth structure and morphology the various types of kidney stones show strongly varying, partially opposite contrasts in absorption and dark-field imaging. By assessing the microscopic calculi morphology with high resolution micro-computed tomography measurements, we illustrate the dependence of dark-field signal strength on the respective stone type. Finally, we utilize X-ray dark-field radiography as a non-invasive, highly sensitive (100%) and specific (97%) tool for the differentiation of calcium oxalate, uric acid and mixed types of stones, while additionally improving the detectability of radio-lucent calculi. We prove clinical feasibility of the here proposed method by accurately classifying renal stones, embedded within a fresh pig kidney, using dose-compatible measurements and a quick and simple visual inspection.

Diagnostic efficiency of split-bolus dual-energy computed tomography for patients with suspected urinary stones

OBJECTIVE

The objective of this study was to evaluate the efficiency of virtual noncontrast image (VNCI) generated from dual-energy split-bolus computed tomographic urography (DE-SBCTU) for urinary stones detection.

METHODS

Three hundred fifty-six patients underwent true noncontrast image (TNCI) and DE-SBCTU. Two radiologists evaluated opacification scores of DE-SBCTU as well as iodine subtractions and image noise on VNCI. Diagnostic performance of the VNCI was evaluated using TNCI as a reference standard, according to diameter and image quality. The results were compared between patient groups with body mass index of less than 25 and 25 kg/m2 or greater.

RESULTS

Agreements for opacification, iodine subtraction, and image noise between the radiologists were excellent, and there were no significant difference in the 2 patients groups. A total of 499 stones were detected on VNCI, with a sensitivity and diagnostic accuracy of 95.1% (468/492) and 92.9% (499/537). Mean (SD) diameter was significantly smaller on VNCI (3.6 [2.3] mm) than on TNCI (4.4 [2.0] mm) (P = 0.01). The stone diameter with false interpretation was less than 4 mm in 48 of 51 patients. The diameter and image quality on VNCI had no significant difference between the 2 patients groups.

CONCLUSIONS

Virtual noncontrast image displays high accuracy for detecting urinary stones, regardless of body mass index.

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.

Detection of urolithiasis using low-dose CT--a noise simulation study

How does an acquisition at reduced doses using automatic tube current modulation techniques compare to the normal standard dose CT? Does it affect the sensitivity for detection of calcifications? CT raw data of 54 patients with suspected urolithiasis acquired with automatic tube current modulation techniques were used for image noise simulations with 100%, 50% and 25% dose simulated. Data were analyzed by independent readers with regard to the presence of urolithiasis, stone location, size, density and differential diagnoses. The mean effective dose per standard examination/50%/25% simulation was 7.3 mSv/3.8 mSv/1.9 mSv. Sensitivities/specificities for detection of urolithiasis were calculated for all dose simulations and resulted in 0.94/0.98 in the 50% dose level group and 0.82/0.97 in the 25% dose level group. Low-dose CT with tube current modulation can be used as a standard procedure for the evaluation of patients with suspected acute renal colic.

Diagnostic performance of low-dose CT for the detection of urolithiasis: a meta-analysis

OBJECTIVE

The objective of our study was to perform a meta-analysis to evaluate the diagnostic performance of low-dose CT for the diagnosis of urolithiasis (seven studies, 1,061 patients).

MATERIALS AND METHODS

The medical literature from 1995 to 2007 was searched using PubMed, Medline, and Cochrane Library databases for articles on studies that used low-dose CT (< 3 mSv dose applied for the entire CT examination) as a diagnostic test for the detection of urolithiasis. Prospective and retrospective studies were included if they separately reported the rate of true-positive, true-negative, false-positive, and false-negative diagnoses of urolithiasis from low-dose CT compared with the positive and negative rates of normal-dose CT or a combination of diagnostic tests. Two readers assessed the quality of the studies.

RESULTS

The pooled sensitivity and specificity of low-dose CT for the diagnosis of urolithiasis were 0.966 (95% CI, 0.950-0.978) and 0.949 (95% CI, 0.920-0.970), respectively.

CONCLUSION

The results of this meta-analysis suggest that a low-dose CT protocol can be used as the initial imaging technique in the workup of patients with suspected urolithiasis.

Comparison between ultrasound and noncontrast helical computed tomography for identification of acute ureterolithiasis in a teaching hospital setting

CONTEXT AND OBJECTIVE

Recent studies have shown noncontrast computed tomography (NCT) to be more effective than ultrasound (US) for imaging acute ureterolithiasis. However, to our knowledge, there are few studies directly comparing these techniques in an emergency teaching hospital setting. The objectives of this study were to compare the diagnostic accuracy of US and NCT performed by senior radiology residents for diagnosing acute ureterolithiasis; and to assess interobserver agreement on tomography interpretations by residents and experienced abdominal radiologists.

DESIGN AND SETTING

Prospective study of 52 consecutive patients, who underwent both US and NCT within an interval of eight hours, at Hospital São Paulo.

METHODS

US scans were performed by senior residents and read by experienced radiologists. NCT scan images were read by senior residents, and subsequently by three abdominal radiologists. The interobserver variability was assessed using the kappa statistic.

RESULTS

Ureteral calculi were found in 40 out of 52 patients (77%). US presented sensitivity of 22% and specificity of 100%. When collecting system dilatation was associated, US demonstrated 73% sensitivity, 82% specificity. The interobserver agreement in NCT analysis was very high with regard to identification of calculi, collecting system dilatation and stranding of perinephric fat.

CONCLUSIONS

US has limited value for identifying ureteral calculi in comparison with NCT, even when collecting system dilatation is present. Residents and abdominal radiologists demonstrated excellent agreement rates for ureteral calculi, identification of collecting system dilatation and stranding of perinephric fat on NCT.

Avaliação da concordância interobservador na análise da tomografia computadorizada sem contraste no diagnóstico da urolitíase em pacientes com cólica renal aguda

OBJETIVO: Avaliar a reprodutibilidade da tomografia computadorizada sem contraste na avaliação da litíase ureteral e os sinais secundários de obstrução do sistema coletor em pacientes com cólica renal aguda. MATERIAIS E MÉTODOS: Estudo prospectivo de 52 pacientes com diagnóstico clínico de cólica renal aguda submetidos a exame de tomografia computadorizada de abdome sem contraste. Os exames foram realizados com técnica helicoidal e posteriormente analisados por três observadores independentes, com a concordância interobservador avaliada pelo método estatístico kappa (kapa). Foram analisados os parâmetros: a) presença, localização e mensuração dos cálculos ureterais; b) dilatação do sistema coletor intra-renal; c) heterogeneidade da gordura perirrenal; d) dilatação ureteral; e) edema da parede ureteral (sinal do halo). RESULTADOS: Foram encontrados 40 cálculos ureterais na tomografia computadorizada (77%). A concordância interobservador para a identificação do cálculo ureteral e da dilatação ureteral foi quase perfeita (kapa = 0,89 e kapa = 0,87, respectivamente), substancial para dilatação do sistema coletor intra-renal (kapa = 0,77) e moderada para heterogeneidade da gordura perirrenal e para edema da parede ureteral (kapa = 0,55 e kapa = 0,56, respectivamente). CONCLUSÃO: A tomografia computadorizada de abdome sem contraste apresenta elevada reprodutibilidade na avaliação da litíase ureteral e dos sinais secundários de obstrução do sistema coletor.

Unexplained renal colic: What is the utility of IV contrast?

PURPOSE

The aim of this study was to evaluate the benefit of intravenous (IV) contrast in patients with suspected renal colic and unremarkable unenhanced MDCT.

MATERIALS AND METHODS

One thousand two hundred and four patients with suspected ureterolithiasis were evaluated with unenhanced MDCT. Seven hundred and eight patients that had additional imaging following IV contrast were our study group.

RESULTS

Of the patients, 9.4% (67/708) had abnormalities seen only on contrast-enhanced exams. In 53.1% (376/708) of the patients, no additional finding was identified after IV contrast.

CONCLUSION

IV contrast in patients with renal colic is rarely helpful.

Progress in the Use of Helical CT for Imaging Urinary Calculi

Helical CT has become the preferred method to diagnose urinary calculi in patients presenting with abdominal or flank pain. Recent in vitro studies have shown that CT also can display the internal structure in stones with remarkable detail. Because some stones respond better to SWL than others, knowing stone structure at diagnosis could be helpful in choosing among treatment options. This paper examines the potential for CT to be used in this way. Older CT technology proved to be problematic, in that all studies using low-resolution CT will suffer from an artifact in which stone size affects apparent CT attenuation values. Thus, the observation that stones with low measured CT attenuation break more easily than stones with high attenuation could be attributable entirely to an artifact of stone size. Most stones are composed of more than one mineral, and heterogeneity of composition may contribute to variability in stone response to SWL. Older technology is not useful in evaluating stone composition, but current and emerging CT machines have sufficient resolution to determine the composition and structure of stones inside the patient, provided proper viewing windows are used. Continuing improvement in image resolution in helical CT promises to provide information about stone composition and structure that will ultimately lead to better care for patients with stone disease.

Avaliação dos métodos de imagem no diagnóstico da urolitíase: revisão da literatura

O objetivo deste trabalho foi comparar a tomografia computadorizada helicoidal com os métodos imaginológicos atualmente disponíveis para a abordagem dos pacientes com dor lombar aguda e revisar brevemente as características fisiopatológicas da urolitíase e a evolução da sua abordagem diagnóstica. Foi revista a literatura publicada nos últimos 30 anos, comparando os seguintes métodos: radiografia simples de abdome, urografia excretora, ultra-sonografia e tomografia computadorizada helicoidal. Esta última se mostrou método de alta sensibilidade e especificidade para o diagnóstico de urolitíase, sendo que, virtualmente, todos os cálculos são identificados por este método, exceto em pacientes em uso de indinavir. A radiografia simples de abdome associada à ultra-sonografia têm acurácia semelhante à tomografia computadorizada helicoidal, contudo, esta foi superior como método de avaliação isolado. A literatura sugere que a tomografia computadorizada helicoidal é útil na avaliação de pacientes com dor lombar aguda quando disponível, possibilitando também o diagnóstico diferencial entre as várias doenças que simulam os sintomas de urolitíase.

Combined magnetic resonance urography and targeted helical CT in patients with renal colic: A new approach to reduce delivered dose

PURPOSE

To determine whether magnetic resonance urography (MRU), obtained before helical computed tomography (CT) in patients with acute renal colic, can help delimit the obstructed area to be subsequently examined by a targeted CT scan, thus reducing the dose of radiation.

MATERIALS AND METHODS

Patients (51) with symptoms of acute renal colic underwent MRU and a total urinary tract helical CT. CT images from the 5 cm below the level of ureteral obstruction as demonstrated by MRU were selected out. Combined interpretation of MRU and selected CT images constituted protocol A. Protocol B consisted of the entire unenhanced helical CT of the urinary tract. The two protocols were compared regarding the following points: 1) sensitivity in diagnosing the presence of obstructing urinary stones, and 2) the delivered radiation dose.

RESULTS

Protocol A and protocol B had, respectively, 98% and 100% sensitivity in demonstrating ureteral stone as a cause of renal colic. Estimated average dose calculated from phantom study was 0.52 mSv for protocol A and 2.83 mSv for protocol B. Therefore, the effective radiation dose was 5.4 times lower in protocol A compared to protocol B.

CONCLUSION

Combined MRU and short helical CT has a high sensitivity in detecting ureteral calculi with a reduced radiation dose.

CT evaluation of urinary lithiasis

Unenhanced CT has been demonstrated to be the most accurate and efficient diagnostic imaging means to evaluate urinary lithiasis, with capability of directing management, and has become well accepted by radiologists, urologists, and emergency department physicians such that it is now the standard of practice. It is the duty of the radiologist to be aware of proper technique and the details of interpretation. The radiologist also has a duty to be aware of the limitations of unenhanced CT for detection and evaluation of various nonstone disorders, particularly with poor patient selection, and to extend the examination if appropriate. Controversies and future developments include cost containment with care for the selection of patients. Further attempts to reduce radiation exposure should be made. Optimal CT technique is not needed in general merely to detect urinary lithiasis. A consensus should be developed regarding use of CT in pregnant patients. Further improvements in the digital scout view would be useful for following patients.

Patients with acute flank pain: comparison of MR urography with unenhanced helical CT

PURPOSE

To compare unenhanced helical computed tomography (CT) and magnetic resonance (MR) urography, by using T2-weighted and contrast material-enhanced T1-weighted imaging to examine patients with acute flank pain, with reference to excretory urography and final clinical diagnosis.

MATERIALS AND METHODS

Forty-nine patients underwent CT, MR urography (with T2-weighted and gadopentetate dimeglumine-enhanced T1-weighted sequences), and excretory urography. CT and MR urographic findings were evaluated separately and independently by two radiologists each (CT, observers A and B; MR urography, observers C and D) for the presence, cause, level, and degree of obstruction. The final conclusive diagnosis was based on the combination of excretory urographic, clinical, and interventional results.

RESULTS

At final diagnosis, 32 (65%) patients were found to have ureteral stones causing unilateral obstruction. In ureteral stone detection, the sensitivity and specificity of CT were 90.6% (29 of 32 patients) and 100.0% (17 of 17 patients), respectively (observer A) and 90.6% (29 of 32 patients) and 94.1% (16 of 17 patients), respectively (observer B), while those of MR urography were 93.8% (30 of 32 patients) and 100.0% (17 of 17 patients), respectively (observer C) and 100.0% (32 of 32 patients) and 100.0% (17 of 17 patients), respectively (observer D). Spearman correlation coefficients for stone size at CT were 0.76 (P <.001) and 0.75 (P <.001) and at MR urography, 0.49 (P =.005) and 0.51 (P =.004).

CONCLUSION

In routine clinical practice, CT is the modality of choice in the evaluation of patients with acute flank pain. MR urography is an accurate and suitable alternative imaging technique in selected patients.

Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography

OBJECTIVE

The purpose of this study was to compare the accuracy of unenhanced helical CT with combined sonography and unenhanced radiography in patients with acute flank pain suggestive of ureteral colic.

SUBJECTS AND METHODS

From January 1997 to December 1999, 181 consecutive patients with acute flank pain underwent unenhanced radiography, sonography, and unenhanced helical CT (protocol A). From January 2000 to December 2000, 96 consecutive patients arriving at the emergency department with acute flank pain were alternately submitted either to primary unenhanced helical CT (protocol B, 48 patients) or to unenhanced radiography and sonography with the addition of helical CT in unclear cases (protocol C, 48 patients).

RESULTS

When compared with the diagnostic accuracy for ureterolithiasis of the combined sonography and radiography in the same group of subjects (protocol A), CT had a greater sensitivity (92% vs 77%), negative predictive value (87% vs 68%), and overall accuracy (94% vs 83%). Among patients who underwent primary CT (protocol B), we found three false-negatives (all with spontaneous stone passage) and no false-positives. Among patients initially examined with unenhanced radiography and sonography (protocol C), we found one false-positive (leading to patient admission and needless repeated radiographic and sonographic studies) and six false-negatives (all followed by an uncomplicated course and spontaneous passage); CT depicted four of these stones but did not result in change in treatment. Fourteen percent of the patients in protocol C required invasive treatment, but combined sonography and radiography showed stones and hydronephrosis in all these patients.

CONCLUSION

Unenhanced CT was the most accurate modality for determining the presence of ureterolithiasis. The combination of abdominal radiography and sonography, however, yielded comparable results with no clinically important misdiagnoses and thus can be used as an alternative when CT resources are limited.

Torsion of a normal ovary in a post-pubertal female: unenhanced helical CT appearance

This case report presents the CT features of torsion of normal adnexa in an adult woman. Unenhanced helical CT, initially performed for clinically suspected acute ureterolithiasis, established the diagnosis.