MR urography using HASTE imaging in the assessment of ureteric obstruction

ACR Appropriateness Criteria® Acute Onset Flank Pain-Suspicion of Stone Disease (Urolithiasis)

Noncontrast CT (NCCT) is the imaging study of choice for initial evaluation of patients with acute onset of flank pain and suspicion of stone disease without known prior stone disease. NCCT can reliably characterize the location and size of an offending ureteral calculus, identify complications, and diagnose alternative etiologies of abdominal pain. Although less sensitive in the detection of stones, ultrasound may have a role in evaluating for signs of obstruction. Radiography potentially has a role, although has been shown to be less sensitive than NCCT. For patients with known disease and recurrent symptoms of urolithiasis, NCCT remains the test of choice for evaluation. In pregnancy, given radiation concerns, ultrasound is recommended as the initial modality of choice with potential role for noncontrast MRI. In scenarios where stone disease suspected and initial NCCT is inconclusive, contrast-enhanced imaging, either with MRI or CT/CT urogram may be appropriate. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Three-dimensional static-fluid MR urography with gradient- and spin-echo (GRASE) at 3.0T: comparison of image quality and diagnostic performance with respiratory-triggered fast spin-echo (FSE)

Purpose

To compare the performance of 3D MRU based on a breath-hold gradient- and spin-echo (BH-GRASE) technique with conventional 3D respiratory-triggered FSE (RT-FSE) sequence in patients with urinary tract dilation.

Methods

We prospectively included 90 patients with urinary tract dilation who underwent both 3D BH-GRASE and RT-FSE MRU at 3T. The acquisition time of two MRU sequences was recorded. Three readers blinded to the protocols reviewed the image quality using a five-point scale and assessed the diagnostic performance related to urinary tract dilation. The relative contrast ratio (CR) between the urinary tract and adjacent area was measured quantitatively.

Results

Acquisition time was 14.8 s for BH-GRASE MRU and 213.6 ± 52.2 s for RT-FSE MRU. The qualitative image analysis demonstrated significant equivalence between the two MRU protocols. 3D BH-GRASE MRU better depicted bilateral renal calyces than RT-FSE MRU (p < 0.05). The CR values of the urinary tract were lower on BH-GRASE MRU compared with RT-FSE MRU (p < 0.05). There were excellent agreements in the assessment of urinary tract dilation between BH-GRASE and RT-FSE MRU, including the dilated degree, obstructive level, and obstructive imaging features (inter-sequence κ = 0.924–1).

Conclusion

3D BH-GRASE MRU significantly decreased the acquisition time and achieved comparable image quality, urinary tract visualization, and diagnostic performance with conventional 3D RT-FSE MRU. Breath-hold 3D MRU with GRASE may provide a feasible evaluation of urinary tract dilation.

Graphical abstract

Dynamic Contrast Enhanced-MR CEST Urography: An Emerging Tool in the Diagnosis and Management of Upper Urinary Tract Obstruction

Upper urinary tract obstructions (UTOs) are blockages that inhibit the flow of urine through its normal course, leading to impaired kidney function. Imaging plays a significant role in the initial diagnosis of UTO, with anatomic imaging (primarily ultrasound (US) and non-contrast computed tomography (CT)) serving as screening tools for the detection of the dilation of the urinary collecting systems (i.e., hydronephrosis). Whether hydronephrosis represents UTO or a non-obstructive process is determined by functional imaging (typically nuclear medicine renal scintigraphy). If these exams reveal evidence of UTO but no discernable source, multiphase contrast enhanced CT urography and/or dynamic contrast enhanced MR urography (DCE-MRU) may be performed to delineate a cause. These are often performed in conjunction with direct ureteroscopic evaluation. While contrast-enhanced CT currently predominates, it can induce renal injury due to contrast induced nephropathy (CIN), subject patients to ionizing radiation and is limited in quantifying renal function (traditionally assessed by renal scintigraphy) and establishing the extent to which hydronephrosis is due to functional obstruction. Traditional MRI is similarly limited in its ability to quantify function. DCE-MRU presents concerns regarding nephrogenic systemic fibrosis (NSF), although decreased with newer gadolinium-based contrast agents, and regarding cumulative gadolinium deposition in the basal ganglia. DCE-MR CEST urography is a promising alternative, employing new MRI contrast agents and imaging schemes and allowing for concurrent assessment of renal anatomy and functional parameters. In this review we highlight clinical challenges in the diagnosis and management of UTO, identify key advances in imaging agents and techniques for DCE-MR CEST urography and provide perspective on how this technique may evolve in clinical importance.

Management of ureteric stone in pregnancy: a review

Background

Urolithiasis in pregnancy is a major health concern and is one of the most common causes for non-obstetrical abdominal pain and subsequent hospital admission during pregnancy. The incidence of urinary calculi during pregnancy varies in the range of 1/200 to 1/2000. Acute ureteric colic in pregnancy is associated with significant potential risks to both mother and fetus. Significant anatomic and functional changes occur in pregnancy which not only lead to stone formation but also create diagnostic dilemma. The diagnosis of ureteric calculi can be incorrect in about 28% of pregnant patients.

Main body

Management of ureteric stone during pregnancy is remaining to be a challenge for the treating urologist. Because of the inability to use good imaging options for the diagnosis confirmation and more invasive approach for the treatment, management continues to be difficult. The main threats are preterm labor with delivery and premature rupture of membranes. Other pregnancy complications are obstructive uropathy, gestational diabetes mellitus, recurrent abortions and pre-eclampsia. Management of diagnosed ureteric stone is unique in the pregnant population and requires multi-disciplinary care. It should be individualized for each patient and moves preferably from conservative to invasive approaches sequentially. With continued advancements in endourological techniques, few definitive treatment options are also available for such patients.

Conclusion

There are several lacunae related with the diagnostic imaging, medical expulsive therapy, reliability of ureteral stent/percutaneous nephrostomy insertions and safety of ureteroscopy during pregnancy. Herein, we review the management of ureteric stone during pregnancy, the various diagnostic modalities and treatment options with their advantages and disadvantages. We also proposed our management algorithm to deal with such clinical scenario in this particular population.

Utility of MR Imaging in Abdominopelvic Emergencies

Acute abdominopelvic pain, a common symptom in emergency department patients, is challenging given the spectrum of differential diagnoses encompassing multiple organ systems, ranging from benign self-limiting to life-threatening and emergent. Diagnostic imaging is critical given its high accuracy and management guidance. A contrast-enhanced computed tomography (CT) scan is preferred given its widespread availability and speed of acquisition. MR imaging may be appropriate, usually performed for specific indications with tailored protocols. It is accurate for diagnosis and may be an alternative to CT. This article discusses the advantages and disadvantages, protocols, and appearances of MR imaging of common diagnoses.

Renal Colic Imaging: Myths, Recent Trends, and Controversies

There has been a substantial increase in the utilization of imaging, particularly of multi-detector computed tomography (MDCT), for the evaluation of patients with suspected urolithiasis over the past 2 decades. While the diagnostic accuracy of computed tomography (CT) for urolithiasis is excellent, it has also resulted in substantial medical expenditures and increased ionizing radiation exposure. This is especially concerning in patients with known nephrolithiasis and in younger patients. This pictorial review will focus on recent trends and controversies in imaging of patients with suspected urolithiasis, including the current roles of ultrasound (US), MDCT, and magnetic resonance imaging, the estimated radiation dose from MDCT and dose reduction strategies, as well as imaging of suspected renal colic in pregnant patients. The current epidemiological, clinical, and practice management literature will be appraised.

Value of Magnetic Resonance Urography Versus Computerized Tomography Urography (CTU) in Evaluation of Obstructive Uropathy: An Observational Study

BACKGROUND

Obstructive uropathy is a common public health issue that requires imaging research for providing necessary information. The data is important for determining treatment options, and may influence selective management choices.

OBJECTIVE

The aim of the study is to determine whether magnetic resonance urography or computerized tomography urography is the best imaging modality among patients with suspected obstructive uropathy.

METHODS

Seventy patients; referred from the emergency department for the evaluation of renal colic or hematuria that highly suggested urinary tract abnormalities, were prospectively enrolled. Thirty five women and 35 men were categorized with a mean age of 43.52 years and the mean body weight of 61.31 kg. All participants underwent abdominal ultrasonography and clinical examination to detect the causes of urinary obstruction. Pregnant women were excluded from the study. Both magnetic resonance urography and computerized tomography urography were performed within 30 days of each analysis.

RESULTS

Only 54.3% of the participants had urinary stones. Mean size of the renal stone was 11 mm; while mean size of the ureteral stone was 3.8 mm. The approach of magnetic resonance is not only limited to diagnosis, but is also effectively involved in the real time investigations. MRU has more reliability in terms of the diagnosis and anatomic presentation of the kidneys along with the vasculature. All cases of urinary stones were detected by computed tomography (100%); whereas, 78.9% cases were detected by magnetic resonance urography.

CONCLUSION

Computerized tomography urography is more sensitive in detecting kidney stones; whereas, magnetic resonance urography is better in detecting pathology behind the development of kidney stones.

Urolithiasis in pregnancy

Urolithiasis in pregnancy is a major health concern and can potentially affect the well-being of both mother and foetus. Management of this condition often entails simultaneous multidisciplinary involvement of obstetrician, radiologist and urologist. Additionally, adverse effects with usage of anaesthesia, radiation, medications and surgery on mother and foetus, limit utilisation of the full armamentarium of diagnostic and therapeutic modalities that are commonly used in non-pregnant women. This review was conducted using an electronic literature search of peer reviewed journal articles. Clinical studies were identified in the bibliographic database- PubMed (Medline), Ovid and eMedicine(WebMD) using the keywords: hydronephrosis, urolithiasis, kidney stone, urinary tract infection, pregnancy and ultrasound, incidence and epidemiology of renal stones.

Acute Urinary Tract Disorders

Acute urinary tract disorders often manifest as flank pain and are a common complaint of patients who present to the emergency department. The pain is often a vague, poorly localized sensation that may have a variety of causes. Laboratory and clinical findings, such as hematuria, are neither sensitive nor specific for determining the cause of the flank pain. Accordingly, imaging is an important tool in determining a diagnosis and management plan. Patients with acute urinary tract disorders who present with pain include those with calculi as well as renal infection, vascular disorders, and hemorrhage.

High temporal resolution dynamic MRI and arterial input function for assessment of GFR in pediatric subjects

PURPOSE

To introduce a respiratory-gated high-spatiotemporal-resolution dynamic-contrast-enhanced MRI technique and a high-temporal-resolution aortic input function (HTR-AIF) estimation method for glomerular filtration rate (GFR) assessment in children.

METHODS

A high-spatiotemporal-resolution DCE-MRI method with view-shared reconstruction was modified to incorporate respiratory gating, and an AIF estimation method that uses a fraction of the k-space data from each respiratory period was developed (HTR-AIF). The method was validated using realistic digital phantom simulations and demonstrated on clinical subjects. The GFR estimates using HTR-AIF were compared with estimates obtained by using an AIF derived directly from the view-shared images.

RESULTS

Digital phantom simulations showed that using the HTR-AIF technique gives more accurate AIF estimates (RMSE = 0.0932) compared with the existing estimation method (RMSE = 0.2059) that used view-sharing (VS). For simulated GFR > 27 mL/min, GFR estimation error was between 32% and 17% using view-shared AIF, whereas estimation error was less than 10% using HTR-AIF. In all clinical subjects, the HTR-AIF method resulted in higher GFR estimations than the view-shared method.

CONCLUSION

The HTR-AIF method improves the accuracy of both the AIF and GFR estimates derived from the respiratory-gated acquisitions, and makes GFR estimation feasible in free-breathing pediatric subjects.

Stone disease in pregnancy: imaging-guided therapy

Renal colic is the most frequent nonobstetric cause for abdominal pain and subsequent hospitalization during pregnancy. The physio-anatomical changes in the urinary tract and the presence of the fetus may complicate the clinical presentation and management of nephrolithiasis. Ultrasound (US) is the primary radiological investigation of choice. Magnetic resonance urography (MRU) and low-dose computed tomography (CT) have to be considered as a second- and third-line test, respectively. If a study that uses ionizing radiation has to be performed, the radiation dose to the fetus should be as low as possible. The initial management of symptomatic ureteric stones is conservative during pregnancy. Intervention will be necessary in patients who do not respond to conservative measures. Therefore, it is crucial to obtain a prompt and accurate diagnosis to optimize the management of these patients. Teaching Points • In pregnancy, renal colic is the most frequent nonobstetric cause for abdominal pain and hospitalization. • Magnetic resonance urography should be considered when ultrasound is nondiagnostic. • Low-dose CT should be considered as a last-line test during pregnancy.

MR urography (MRU) of non-dilated ureter with diuretic administration: Static fluid 2D FSE T2-weighted versus 3D gadolinium T1-weighted GE excretory MR

•

T2w-MRU with multiple orientations and diuretic is sufficient to identify non-dilated ureter.

•

T2w-MRU offers information on ureteral contractions and could be proposed to detect initial obstruction before hydronephrosis occurs (for instance in cases of endometriosis).

•

T2w-MRU could also be used to evaluate potential renal donors or in patients unable to receive gadolinium.

•

CE-MRU rapidly produces an overdistended bladder with a risk of false positive diagnosis of mild obstruction.

•

CE-MRU is less convenient for patients.

Objective

The goal of this prospective study was to compare the efficiency of two types of MRU after diuretic administration to identify the non-dilated ureter.

Methods

MR pelvic examinations were performed in 126 patients after receiving furosemide. Each patient underwent in addition to their protocol for context, two types of MRU: 2D T2-weighted FSE (T2w-MRU) and 3D Gd T1-weighted GE (CE-MRU). Four segments were checked for each ureter.

For the first part of the analysis, readers evaluated the whole image quality using a four points subjective scale and for the second part, they were asked to score separately each ureteral segment as present or absent.

Results

1008 ureteral segments were checked. For the image quality, readers did not find any significant difference (3.8 ± 0.5 vs 3.6 ± 0.7, p value: 0.13) between MRU methods. The interobserver agreement was excellent with a κ correlation coefficient as high as 0.89 for T2w-MRU and 0.92 for CE-MRU, respectively.

For the detection of the segments and considering the 9 rotations for the T2W MRU, there were no statistically significant differences between the two groups.

Conclusion

T2-weighted MRU with multiple orientations and diuretic is sufficient to identify the non-dilated ureter. It offers information on ureteral peristaltism. It can be suggested that this sequence is able to detect an initial obstruction before hydronephrosis occurs.

MR imaging for acute nontraumatic abdominopelvic pain: rationale and practical considerations

Medical imaging is becoming an increasingly vital component of patient care in the emergency department. Computed tomography has been the diagnostic imaging method of choice for emergency department patients with acute abdominopelvic pain; however, the use of ionizing radiation and the potential need for exogenous contrast material adversely affect patient safety and work flow efficiency, respectively. Magnetic resonance (MR) imaging holds promise as an alternative for the evaluation of acute abdominopelvic pain. Critical causes of abdominopelvic pain may be detected with MR imaging without exogenous contrast material. MR imaging is sensitive for depicting tissue or fluid changes related to inflammation, a common process in causes of acute abdominopelvic pain. Fat suppression allows the detection of abnormal signal caused by inflamed tissue. MR imaging has proved sensitive in the detection of acute inflammatory diseases of the gallbladder and bile ducts, liver, pancreas, kidneys, collecting system, bowel, and pelvic soft tissues. Moreover, MR imaging without exogenous contrast material may be safely used in pregnant patients. Evolving roles for emergency department MR imaging include the assessment of vascular disease (including thromboembolic disease) and right upper quadrant pain. Emergency department MR imaging currently has limited availability, and its continued use will require further education regarding operation and image interpretation as well as further validation of cost-effectiveness. Nevertheless, current understanding of the diagnostic utility of this imaging method warrants continued study and the increased use of MR imaging in the evaluation of emergency department patients with acute abdominopelvic pain.

Kidney stones and pregnancy

Kidney stones are common and do not spare the pregnant population. Although a simple stone event is usually straightforward in the general population, it is complex during pregnancy. Acute nephrolithiasis is associated with a unique set of complications during pregnancy and, because of imaging limitations, diagnosis is challenging. Multidisciplinary care is the key in proper management decisions. The pathophysiology of kidney stone formation in the pregnant state is also unique. Herein, we discuss the complexity of kidney stones and pregnancy.

The role of static magnetic resonance urography in the evaluation of obstructive uropathy

OBJECTIVE

To assess the diagnostic accuracy of static magnetic resonance urography (MRU) in hydronephrosis and to compare parameters of hydronephrosis in MRU with intravenous urography (IVU).

MATERIALS AND METHODS

Sixty-nine patients were included in this study of which 55 patients with a total of 63 hydronephrotic units underwent both IVU and MRU. MRU was performed on a 1.5 T scanner using heavily T2-weighted sequences. The level, grade, and cause of obstruction on each modality were interpreted by 2 radiologists. These were compared with the final diagnosis based on other appropriate modalities including imaging, intraoperative and histopathologic diagnosis.

RESULTS

The sensitivity and specificity MRU in detecting hydronephrosis were 95% and 100%, respectively. In determining the level of obstruction, the strength of agreement between IVU and MRU using kappa statistics was κ = 0.66, which corresponds to a good level of agreement. The Spearman correlation coefficient for the grade of hydronephrosis on MRU and IVU was 0.92 (95% confidence interval 0.86-0.95), with a P value of < .0001. The correct diagnosis was made in 89.2% of the cases by IVU and in 93.8% of the cases by MRU.

CONCLUSION

Along with a high sensitivity and specificity in detecting the presence, level, and grade of hydronephrosis, MRU without contrast also shows a good agreement with IVU. Static MRU can reliably replace IVU when the latter is contraindicated or technically difficult.

Acute abdominal pain: is there a potential role for MRI in the setting of the emergency department in a patient with renal calculi?

Acute flank pain is a frequent clinical presentation encountered in emergency departments, and a work-up for obstructive urolithiasis in this setting is a common indication for computed tomography (CT). However, imaging alternatives to CT for the evaluation of renal colic are warranted in some clinical situations, such as younger patients, pregnancy, patients that have undergone multiple prior CT exams and also patients with vague clinical presentations. MRI, although relatively insensitive for the direct detection of urinary calculi, has the ability to detect the secondary effects of obstructive urolithiasis. Using rapid, single shot T2-weighted sequences without and with fat saturation provides an abdominopelvic MR examination that can detect the sequelae of clinically active stone disease, in addition to alternate inflammatory processes that may mimic the symptoms of renal colic. In addition, MR nephro-urography (MRNU) has the ability to provide quantitative analysis of renal function that has the potential to direct clinical management in the setting of obstructing calculi. This review describes the potential utility and limitations of MRI in the emergency setting for diagnosing causes of flank pain and renal colic, particularly in patients with unusual presentations or when an alternative to CT may be warranted.

Magnetic resonance urography

Excellent contrast resolution and lack of ionizing radiation make magnetic resonance urography (MRU) a promising technique for noninvasively evaluating the entire urinary tract. While MRU currently lags behind CT urography (CTU) in spatial resolution and efficiency, new hardware and sequence developments have contributed to a resurgence of interest in MRU techniques. By combining unenhanced sequences with multiphase contrast-enhanced and excretory phase imaging, a comprehensive assessment of the kidneys, ureters, bladder, and surrounding structures is possible with image quality rivaling that obtained with other techniques. At the same time, formidable challenges remain to be overcome and further clinical validation is necessary before MRU can replace other forms of urography. In this article, we demonstrate the current potential of MRU to demonstrate a spectrum of urologic pathology involving the kidneys, ureters, and bladder while discussing the limitations and current status of this evolving technique.

[Functional MR urography in children]

MR Urography (MRU) provides both morphologic and functional information without radiation exposure. It enables the assessment of split renal function, excretion, and quantification of obstruction. MRU is thus complementary to ultrasonography in the assessment of pre- and post-natal obstructive uropathies in children. If available, MRU should be definitely preferred to intravenous urography.

Imaging in diagnosis, treatment, and follow-up of stone patients

Imaging has an essential role in the diagnosis, management, and follow-up of patients with stone disease. A variety of imaging modalities are available to the practicing urologist, including conventional radiography (KUB), intravenous urography (IVU), ultrasound (US), magnetic resonance urography, and computed tomography (CT) scans, each with its advantages and limitations. Traditionally, IVU was considered the gold standard for diagnosing renal calculi, but this modality has largely been replaced by unenhanced spiral CT scans at most centers. Renal US is recommended as the initial imaging modality for suspected renal colic in pregnant women and children, but recent literature suggests that a low-dose CT scan may be safe in pregnancy. Intraoperative imaging by fluoroscopy or US plays a large part in assisting the urologist with the surgical intervention chosen for the individual stone patient. Posttreatment imaging of stone patients is recommended to ensure complete fragmentation and stone clearance. Plain radiography is suggested for the follow-up of radiopaque stones, with ultrasound and limited IVU reserved for the follow-up of radiolucent stones to minimize cumulative radiation exposure from repeated CT scans. Patients with asymptomatic calyceal stones who prefer an observational approach should have a yearly KUB to monitor progression of stone burden. Current research has been aimed toward the development of a micro-CT scan and coherent-scatter analysis to determine stone composition in vivo. This may have a significant impact on the future clinical management of renal calculi by facilitating selection of the most appropriate surgical intervention based on stone composition at the time of presentation.

Application of magnetic resonance urography in diagnosis of congenital urogenital anomalies in children

Magnetic resonance urography (MRU) has become a useful adjuvant in evaluating urogenital anomalies. In present study, we evaluated the ability of MRU in diagnosis of different congenital urogenital anomalies when the results of conventional imaging modalities were inconclusive. A total of 90 children were included in this series. The children were evaluated with T2-weighted and contrast-enhanced T1-weighted MRU sequences. The results were compared with findings obtained with ultrasonography, intravenous urography, renal nuclide scan, and voiding cystourethrography. MRU was requested in these children because conventional imaging modalities were equivocal or a co-existing urogenital anomaly was suspected. Only those cases that underwent surgery were included in this study and the surgical findings were set as the reference standard in statistical evaluation. The records of 61 boys with mean (range) age of 2.3 years (2 months-12 years) and 29 girls with mean (range) age of 3.3 years (3 months-12 years) were reviewed. The final diagnosis was ureteropelvic junction obstruction (n = 25), vesicoureteral junction obstruction (n = 16), ureterocele (n = 19), ectopic kidney (n = 11), posterior urethral valve (n = 17), and polycystic kidney (n = 2). The overall sensitivity of MRU, intravenous urography, renal nuclide scan, ultrasonography, and voiding cystourethrography in diagnosis of the aforementioned anomalies were 86, 63, 50, 44, and 41%, respectively. MRU was much more sensitive than other imaging modalities in diagnosis of end-ureteral dilation (100%) and ureterocele (89%). MRU provides a reliable noninvasive technique for imaging of the congenital anomalies in the urinary tract of children with T2-weighted MRU sequences providing unenhanced static-water images of the urinary tract as well as depicting adjacent soft-tissue lesions, and T1-weighted MRU technique imitating conventional intravenous urography. Both MRU sequences can be combined for a comprehensive examination of the urinary tract.

MR urography: techniques and clinical applications

Magnetic resonance (MR) urography comprises an evolving group of techniques with the potential for allowing optimal noninvasive evaluation of many abnormalities of the urinary tract. MR urography is clinically useful in the evaluation of suspected urinary tract obstruction, hematuria, and congenital anomalies, as well as surgically altered anatomy, and can be particularly beneficial in pediatric or pregnant patients or when ionizing radiation is to be avoided. The most common MR urographic techniques for displaying the urinary tract can be divided into two categories: static-fluid MR urography and excretory MR urography. Static-fluid MR urography makes use of heavily T2-weighted sequences to image the urinary tract as a static collection of fluid, can be repeated sequentially (cine MR urography) to better demonstrate the ureters in their entirety and to confirm the presence of fixed stenoses, and is most successful in patients with dilated or obstructed collecting systems. Excretory MR urography is performed during the excretory phase of enhancement after the intravenous administration of gadolinium-based contrast material; thus, the patient must have sufficient renal function to allow the excretion and even distribution of the contrast material. Diuretic administration is an important adjunct to excretory MR urography, which can better demonstrate nondilated systems. Static-fluid and excretory MR urography can be combined with conventional MR imaging for comprehensive evaluation of the urinary tract. The successful interpretation of MR urographic examinations requires familiarity with the many pitfalls and artifacts that can be encountered with these techniques.

Avaliação das fístulas urogenitais por urorressonância magnética

OBJETIVO: As fístulas vesicovaginais e ureterovaginais são complicações incomuns, secundárias a doenças ou a cirurgias pélvicas. O sucesso terapêutico dessas fístulas depende de adequada avaliação pré-operatória para o diagnóstico e visualização do seu trajeto. Este trabalho tem o objetivo de demonstrar o potencial da urorressonância no diagnóstico das fístulas urogenitais e na visualização dos seus trajetos. MATERIAIS E MÉTODOS: Foram analisados, retrospectivamente, os prontuários médicos e as imagens radiológicas e de urorressonância magnética de sete pacientes do sexo feminino com diagnóstico de fístula urogenital. Para a urorressonância foram realizadas seqüências 3D-HASTE com saturação de gordura. RESULTADOS: Seis pacientes apresentavam fístula vesicovaginal e uma paciente tinha diagnóstico de fístula ureterovaginal à direita. Com a utilização da urorressonância magnética, foi possível demonstrar o trajeto da fístula em seis das sete pacientes (85,7%), sem a necessidade de cateterização vesical ou da injeção de contraste. CONCLUSÃO: Este estudo demonstra o potencial e a aplicabilidade da urorressonância na avaliação dessas fístulas.

MR imaging of acute right lower quadrant pain in pregnant and nonpregnant patients

The use of magnetic resonance (MR) imaging in the evaluation of acute abdominal pain is increasing, particularly in those circumstances where computed tomography (CT) is not desirable (eg, pregnancy, allergy to iodinated contrast material). Although ultrasonography (US) is considered the imaging study of choice for evaluation of abdominal pain in pregnant patients, MR imaging is a valuable adjunct to US in evaluation of pregnant patients with acute right lower quadrant (RLQ) pain who have inconclusive US results. MR imaging is also frequently used in patients with renal failure, in whom the use of iodinated contrast material is contraindicated, as well as in cases where CT results are inconclusive. In patients with acute RLQ pain, the breadth of abnormalities visible at MR imaging is very broad, with pathologic conditions potentially originating from multiple organ systems, but most commonly from the gastrointestinal and genitourinary systems. MR imaging is an excellent imaging modality for evaluation of RLQ pain and should be strongly considered in those patients in whom use of iodinated contrast media or radiation is not desirable.

Imaging of the renal transplant: comparison of MRI with duplex sonography

Renal transplantation is an established treatment for patients with end-stage renal disease. Many causes of graft dysfunction are treatable, making prompt detection and diagnosis of complications essential. Sensitive, noninvasive imaging procedures, which do not use iodinated contrast media, are therefore highly desirable to evaluate graft function. Duplex sonography (US) has traditionally been the initial investigation of graft dysfunction. US offers many advantages, particularly during the postoperative period, when it can be performed portably regardless of renal function and can guide percutaneous procedures. However, US lacks specificity in assessing hydronephrosis, cannot differentiate parenchymal causes of dysfunction, and may have difficulty assessing transplant vessels. Recently comprehensive magnetic resonance imaging (MRI) protocols including MR urography, gadolinium-enhanced MR angiography, and MR renography have evolved as a "one-stop" diagnostic technique in the evaluation of the entire graft and peritransplant region. Multiplanar capabilities enable MRI to identify the site of urinary obstruction and assess renal vessels in their entirety. The evolving technique of MR renography may also differentiate parenchymal causes of dysfunction. By combining these three components into a single examination, further information may be obtained regarding the graft when compared with US and other conventional studies, with improved patient convenience, less morbidity, and a potential cost saving.

3D excretory MR urography: Improved image quality with intravenous saline and diuretic administration

PURPOSE

To assess the effect of diuretic administration on the image quality of excretory magnetic resonance urography (MRU) obtained following intravenous hydration, and to determine whether intravenous hydration alone is sufficient to produce diagnostic quality studies of nondilated upper tracts.

MATERIALS AND METHODS

A total of 22 patients with nondilated upper tracts were evaluated with contrast-enhanced MRU. All patients received 250 mL of saline intravenously immediately prior to the examination. A total of 11 patients received 10-20 mg furosemide in addition to saline. Imaging was performed with a three-dimensional (3D) and two-dimensional (2D) breathhold spoiled gradient-echo sequences. Excretory MRU images were acquired five minutes after the administration of 0.1 mmol/kg gadolinium and were independently reviewed by two radiologists, who were blinded to the MRU technique. Readers evaluated the calyces, renal pelvis, and ureters qualitatively for degree of opacification, distention, and artifacts on a four-point scale. Statistical analysis was performed using a permutation test.

RESULTS

There was no significant disagreement between the two readers (P=0.14). Furosemide resulted in significant improvement in calyceal and renal pelvis distention (P<0.005), and significant artifact reduction in all upper tract segments (P<0.001) compared to the effect of saline alone.

CONCLUSION

Intravenous furosemide significantly improves the image quality of excretory MRU studies obtained following intravenous hydration. Intravenous saline alone is insufficient to produce diagnostic quality studies of the non-dilated upper tracts.

(Paediatric) magnetic resonance urography: just fancy images or a new important diagnostic tool?

PURPOSE OF REVIEW

Magnetic resonance urography has become an established imaging tool in uroradiology. Its potential to assess anatomy and function makes it an ideal tool for evaluation of urinary tract malformations, renal cysts, genito-urinary tract tumours, infections and renal transplants. This review tries to highlight the potential of magnetic resonance urography in the light of new advances, particularly focusing on paediatric applications.

RECENT FINDINGS

Technical innovations such as diaphragmatic tracking, parallel or propeller imaging, faster gradients and higher field strength improve applicability in infants and children. Dynamic studies enable assessment of renal functional parameters such as split renal function, glomerular filtration rate or urinary drainage. Recent advances in magnetic resonance spectroscopy, diffusion imaging and perfusion imaging and new contrast agents promise to widen the potential of magnetic resonance urography as a functional imaging tool, not only in paediatrics but also for other magnetic resonance applications in the genito-urinary tract, such as prostate imaging or in the staging of ovarian and endometrial cancer.

SUMMARY

Besides ultrasound being used as the initial imaging method, particularly in children (and as computed tomography in adults), magnetic resonance urography can be envisioned as the major imaging modality for almost all (paediatric) uroradiological queries, consequently creating a growing demand for available equipment and procedural expertise.

Uso de la urografía por resonancia magnética en el estudio del aparato urinario frente a la urografía convencional

Conventional urography (IVU) is an essential examination for the assessment of urinary tract but it is not free of complications, such as adverse reactions to contrast agents used (vasovagal and anaphylactic reactions), neurotoxicity, nephrotoxicity, as well as the damage due to the ionizing irradiation applied to the patient. For this reason, alternative imaging techniques such as magnetic resonance (MR) urography or uro-resonance have been developed.

OBJECTIVE

We present a case study assessing the diagnostic accuracy, specificity and sensitivity of uro-resonance and IVU as a morphological and functional examination of the urinary tract: and a quality study of the urographic images obtained with MR versus IVU.

MATERIALS AND METHODS

150 patients have submited to a MR study, 63 of them with an IVU study already performed, acquiring high-intensity signals at T2 corresponding to abdominal and retroperitoneal fluid, initially using furosemide at low doses and, in a final study, administering gadolinium at a rate of 0.1 mg/Kg. The test was indicated in patients with antecedents of adverse reactions to iodine contrast, acute or chronic kidney failure, functional cancellation of the kidneys, pregnant patients and those in paediatric age. The capacity of diagnosis of urinary obstruction and the aetiology of this obstruction of both tests was studied, as well as the quality of the images obtained by the urographic study using MR.

RESULTS

High resolution images were obtained of all the upper urinary tracts using MR, especially in the renal pelvis, without artefacts caused by peristalsis or intestinal fluid interposition. In 83.3% of cases, examinations revealed urological pathology. The diagnostic accuracy of the involvement cause of the urinary tract was 83.3%, with a sensitivity of 89.6%, a specificity of 69.2%. a positive predictive value of 86.6% and a negative predictive value of 75%.

CONCLUSION

MR urography is a high sensitive technique for the study of urinary tract, used as an alternative to conventional urography particularly in cases of the contraindication of ionizing radiation or allergy to the contrast agent, as well as in patients with renal failure, and offers a wider morphological and functional study, with a high image quality, able to displace conventional examinations in the short or medium term.

Magnetic resonance urography: a pictorial overview

Magnetic resonance urography (MRU) can be performed on the basis of two different imaging strategies: static-fluid MRU, based on heavily T2 weighted turbo spin echo (TSE) sequences, and gadolinium-enhanced excretory MRU. Both MR urographic techniques in combination with standard MRI permit a comprehensive examination of the entire urinary tract. This pictorial review illustrates the MRU features of the a wide spectrum of pathological conditions affecting the urinary tract.

[Functional and morphological MR imaging of the upper urinary tract in the pediatric age group]

MR imaging is being increasingly used for the diagnosis of congenital urinary tract obstruction. The following conditions have to be fulfilled to provide an MR urography technique which is useful for the pediatric age group: (1) the combination of morphology and function, (2) a high-resolution morphological image, (3) a morphological image independent of kidney function, (4) reliable determination of split renal function and (5) of urinary excretion. This is best accomplished with a combination of a T1-weighted fast GE sequence post-contrast and a heavily T2-weighted 3D IR-TSE sequence. Selected sequence parameters are important for optimization as well as for a correct functional assessment. Then MR urography is superior to the conventional methods of excretory urography, ultrasound, and scintigraphy in the morphological depiction of the urinary tract even of complex malformations as well as in a detailed functional assessment. In particular, this method is useful in the situation of complicated duplex kidneys, dystopic kidneys, unclear morphology, or discrepant former results and perioperative assessment. The main advantages are avoiding radiation and obtaining a simultaneous functional-morphological diagnosis.

Contrast-enhanced dynamic MR nephrography using the TurboFLASH navigator-gating technique in children

The purpose of this work was to test the feasibility of an MR examination protocol for the comprehensive assessment of renal morphology, excretion and split renal function using a navigator-gated TurboFLASH sequence. A navigator-gated T1-weighted single-slice TurboFLASH sequence suitable for dynamic MR urography and nephrography was implemented. A protocol was developed allowing for assessment of urinary excretion and split renal function by recording the renal clearance of a gadolinium (Gd) diethylene-triamine-pentacetic-acid (DTPA) bolus. Ten patients aged between 14 months and 14 years (mean age 4.8+/-4.6 years) were evaluated with the following indications: pelvicalyceal dilatation (n=4), follow-up after pyeloplasty (n=1), duplex systems (n=3), large renal cyst (n=1), and renal insufficiency (n=1). Dynamic MR urography and MR split renal function were compared to MAG3 scintigraphy. Evaluation of morphology, excretion and function required 50-60 minutes examination time, plus 10 minutes for post-processing. The TurboFLASH sequence yielded image acquisition at nearly identical diaphragm positions allowing for accurate region-of-interest evaluation within the renal parenchyma and the urinary passage. Static and dynamic MR urography showed the morphology of the urinary tract and excretion with sufficient diagnostic imaging quality, and the results were in diagnostic compliance with scintigraphy. MRI and scintigraphy yielded similar results for split renal function with a correlation coefficient of R=0.968 determined by linear regression. Our conclusions were that the method is robust, easy to perform on a clinical 1.5 T MRI system, rapid to evaluate and post-process and, therefore, easy to incorporate into clinical routine. Compared to scintigraphy, the higher spatial resolution of the MR examination provides additional important information improving the management of the pediatric patients without the application of radioactive tracers.

Imagerie de la lithiase urinaire : « Trois en un »

Urinary lithiasis is very common among the general population, with a high prevalence level. In rich countries it is mainly located inside the upper urinary tract. Helical CToperated with newer devices is the most accurate modality to provide all needed information: diagnosis of stone without contrast medium injection, morphology (size, number) and localization, diagnosis of urinary obstruction, urinary tract aspect and all kind of differential diagnosis in emergency. It must be used during follow up to diagnose residual fragments. Multiplanar reconstructions are essential for the clinicians; but diagnosis is interpreted by scrolling axial views with dynamic analysis on computer screen. Low-dose helical CT is today available. Helical CT provides an "all-in-one" examination. It should soon replace combined plain film-ultrasonography performed in an emergency context of renal colic and intravenous urography for pre- and post-treatment assessments.

[MR urography: principles, examination techniques, indications]

MR urography is an evolving and promising technique in the evaluation of the urinary tract. MR urography is currently considered the method of choice for imaging of the renal parenchyma and the collecting systems in patients who cannot undergo routine radiographic studies such as pregnant women, pediatric patients, patients allergic to iodinated contrast agents, or patients with impaired renal function. The future development of MR urography in terms of functional, cellular, and molecular imaging is presently the subject of research. The ability of MR imaging to provide quantitative functional information (e.g., on blood flow, perfusion, glomerular filtration rate, and excretion as well as urine drainage) in addition to morphologic assessment of the parenchyma and the collecting system could lead to a single, "all-in-one approach" examination technique.

Acute ureteric calculus obstruction: unenhanced spiral CT versus HASTE MR urography and abdominal radiograph

The aim of this study is to compare the performance of unenhanced spiral CT to the combination of HASTE MR urography (MRU) and plain abdominal radiography (KUB) in patients suspected of having acute calculus ureteric obstruction. 64 patients with suspected acute calculus ureteric obstruction were evaluated. The presence of perirenal fluid, presence and level of ureteric obstruction and calculi were assessed on both techniques. 44 of 64 (69%) patients had acute calculus ureteric obstruction based on clinical, radiographic or surgical findings. MRU showed perirenal fluid in acute ureteric obstruction (77%) with a greater sensitivity than CT showed stranding (45%). The combination of fluid and ureteric dilation on MRU showed a sensitivity of 93% (CT 80%), specificity of 95% (CT 85%), and accuracy of 94% (CT 81%). There were 61 findings of either fluid or ureteric dilatation on MRU in 44 acutely obstructed kidneys compared with 37 similar findings on CT (p<0.005). Although there was excellent reproducibility (Kappa=/>0.75) in the finding of perirenal fluid on MRU, there was only fair interobserver agreement (Kappa<0.4) regarding perirenal stranding on CT. MRU/KUB showed ureteric calculi in 21/29 (72%) of patients with calculi seen by CT. Overall, MRU/KUB revealed 2.4 abnormalities per acutely obstructed ureter compared with 1.8 abnormalities detected by CT. MRU/KUB using HASTE sequences can diagnose the presence of acute calculus ureteric obstruction with similar accuracy to spiral CT. The technique has less observer variability and is more accurate than CT in detecting evidence of obstruction such as perirenal fluid.

Diagnostic value of diuretic-enhanced excretory MR urography in patients with obstructive uropathy

PURPOSE

Ultrasonography and conventional intravenous urography are most common methods in diagnosis of obstructive uropathies. The disadvantage of ultrasonography is inability of visualizing middle and lower one thirds of ureter, while intravenous urography is using radiation, also functionally extra loading effect on kidneys. In this study, the diagnostic value of MR urography on obstructive uropathy were investigated.

MATERIALS AND METHODS

Forty five patients who were suffered from obstructive uropathy examined by ultrasonography, intravenous urography and diuretic-enhanced excretory MR urography by using MR-contrast-agent.

RESULTS

MR urography established accuracy rate of 92.8% for stone diseases which formed the largest group in this study, however, in other causes of obstructive uropathy, MR urography provide 100% correct diagnosis.

CONCLUSION

MR urography provide high quality images for diagnosing and determining causes of urinary obstruction defining position and severity of dilatations as well as showing localization of the pathology. We think that MR urography should be a primary investigation in patients with obstructive uropathy who have contrast agent and X-ray contrindication.

Diagnosis of ureteral obstruction in patients with compromised renal function: the role of noninvasive imaging modalities

We compared the role of noncontrast computerized tomography (NCCT), magnetic resonance urography (MRU), and combined abdominal radiography (KUB) and ultrasonography (US) in the diagnosis of the cause of ureteral obstruction in patients with compromised renal function.

MATERIALS AND METHODS

The study included 149 patients, of whom 110 had bilateral obstruction and 39 had obstruction of a solitary kidney. Therefore, the total number of renal units was 259. All patients had renal impairment with serum creatinine greater than 2.5 mg/dl. Besides conventional KUB and US all patients underwent NCCT and MRU. The gold standard for diagnosis of the cause of obstruction included retrograde or antegrade ureterogram, ureteroscopy and/or open surgery. The sensitivity, specificity and overall accuracy of NCCT, MRU, and combined KUB and US in the diagnosis of ureteral obstruction were calculated in comparison with the gold standard.

RESULTS

The definitive cause of ureteral obstruction was calculous in 146 and noncalculous in 113 renal units, including ureteral stricture in 65, bladder or ureter in 43, extraurinary collection in 3 and retroperitoneal fibrosis in 2. The site of stone impaction was identified by NCCT in all 146 renal units (100% sensitivity), by MRU in 101 (69.2% sensitivity), and by combined KUB and US in 115 (78.7% sensitivity) with a difference of significant value in favor of NCCT (p <0.001). Ureteral strictures were identified by NCCT in 18 of the 65 cases (28%) and by MRU in 54 of 65 (83%). Bladder and ureteral tumors causing ureteral obstruction could be diagnosed in approximately half of the patients by NCCT (22 of 43) and in all except 1 by MRU (42 of 43). NCCT and MRU could identify all extraurinary causes of obstruction. Overall of the 113 kidneys with noncalculous obstruction the cause could be identified by MRU in 101 (89% sensitivity), by NCCT in 45 (40% sensitivity), and by combined KUB and US in only 20 (18% sensitivity) with a difference of significant value in favor of MRU (p <0.001).

CONCLUSIONS

In patients with renal impairment due to ureteral obstruction NCCT has superior diagnostic accuracy for detecting calculous causes of obstruction but MRU is superior for identifying noncalculous lesions.

Diagnosis of noncalcareous hydronephrosis: role of magnetic resonance urography and noncontrast computed tomography

OBJECTIVES

To evaluate the role of magnetic resonance urography (MRU) and noncontrast computed tomography (NCCT) in the diagnosis of noncalcareous hydronephrosis when excretory urography (intravenous urography) is either contraindicated or inconclusive.

METHODS

A total 108 consecutive patients with noncalcareous hydronephrosis were included in this study. In all patients, intravenous urography was either contraindicated or could not determine the diagnosis. In all patients, calculus obstruction was excluded by NCCT and all underwent heavily T2-weighted MRU. The final definitive diagnosis was established by retrograde or antegrade ureterography, endoscopy, or open surgery and was considered the reference standard for the diagnosis of obstruction. Normal kidneys in patients with unilateral obstruction were considered the reference standard for the absence of obstruction. The results of MRU were compared with those of NCCT regarding sensitivity, specificity, and overall accuracy.

RESULTS

Of the 108 patients, 5 had bilateral obstruction and the remaining 103 had unilateral obstruction. Of the latter group, 5 had a solitary kidney; therefore, the total number of renal units was 211 (113 obstructed and 98 normal units). Ureteral strictures were identified by NCCT in 15 (28%) of 54 and by MRU in 45 (83%) of 54 patients. Bladder, ureter, or prostate tumors causing ureteral obstruction could be diagnosed in one half of the 54 patients with such tumors by NCCT (27 of 54) and in all but 2 patients by MRU (52 of 54). Both NCCT and MRU could identify all extraurinary causes of obstruction. Overall, of the 113 kidneys with noncalculus obstruction, the cause could be identified by MRU in 102 (sensitivity of 90%) and by NCCT in 47 (sensitivity of 42%), a difference of statistically significant value in favor of MRU (P <0.001). The specificity of T2-weighted MRU and NCCT was 100% and 99%, respectively (not a statistically significant difference). The overall accuracy of T2-weighted MRU and NCCT was 95% and 68%, respectively (P <0.001).

CONCLUSIONS

In patients with ureteral obstruction in whom intravenous urography is not helpful and after NCCT has excluded stone disease, heavily T2-weighted MRU is a sensitive and specific method in the identification of the cause of obstruction.

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.