Visualization of urinary tract dilatation: value of single-shot MR urography

The purpose of this study was to evaluate detection of urinary tract dilatation, depiction of obstruction level and determination of cause with single-shot MR imaging in an acquisition time of 2.8 s. Heavily T2-weighted single-shot MR images in 50 patients with ureterohydronephrosis as suspected by ultrasound were prospectively compared with IV urography and clinical outcome. Imaging techniques were obtained within a maximum time interval of 4 h and assessed independently on the same day. Single-shot MR urography was able to demonstrate dilatation and obstruction levels in 96 % of urinary tracts in accordance with X-ray urograms. In 4 patients with a unilaterally negative IV urogram, obstruction levels were demonstrated in single-shot MR urography. Single-shot MR urography did not depict 2 of 7 collecting systems with mild dilatation and contralateral undilated ureters were not adequately visible. Single-shot MR urography consistently visualizes dilated urinary tracts and obstruction levels in moderate and severe dilatation. Single-shot MR urography may be an alternative for IV urography in cases of renal impairment, when iodinated contrast or the application of X-rays is contraindicated, and may help in avoiding direct ureteropyelography. Single-shot MR urography rarely allows determination of the cause of urinary tract dilatation. Received 19 July 1996; Revision received 4 November 1996; Accepted 5 February 1997     

MR urography: examination techniques and clinical applications

Modern MR urography is performed on the basis of two different imaging strategies, which can be used complementarily to cover almost all aspects in the diagnosis of upper urinary tract diseases. The first technique utilizes unenhanced, heavily T2-weighted pulse sequences to obtain static-fluid images of the urinary tract. T2-weighted MR urograms have proved to be excellent in the visualization of the markedly dilated urinary tract, even if the renal excretory function is quiescent. Static-fluid MR urography is less suitable for imaging of disorders that occur in the nondilated collecting system. The second MR urography technique is analogous to the methodology of conventional intravenous pyelography and is, therefore, designated as excretory MR urography. For this purpose, a non-nephrotoxic gadolinium chelate is intravenously administered and after its renal excretion, the gadolinium-enhanced urine is visualized using fast T1-weighted gradient-echo sequences. The combination of gadolinium and low-dose furosemide (5–10 mg) is the key for achieving a uniform distribution of the contrast material inside the entire urinary tract and, secondly, to avoid high endoluminal gadolinium concentrations, which cause signal loss of the urine due to T2^* effects. Gadolinium excretory MR urography allows to obtain high-quality images of both nondilated and obstructed urinary tracts in patients with normal or moderately impaired renal function. This article reviews the principles of T2- and T1-weighted MR urography in detail and informs how to use these techniques safely in potential clinical applications such as chronic urolithiasis, intrinsic and extrinsic tumor diseases, and congenital anomalies. Magnetic resonance urography performed in combination with standard MR imaging offers a potential to reduce the need for invasive retrograde pyelography. Although the economic aspect is still problematic, it is obvious that MR urography will continue to increase its role in clinical uroradiology. Received: 7 July 2000 Revised: 21 August 2000 Accepted: 21 August 2000     

磁共振泌尿系造影的相关技术和临床应用探讨

目的评价磁共振泌尿系造影（ＭＲＵ）的成像技术对揭示尿路梗阻部位及原因的价值和限度，并推广应用半傅立叶转换快速自旋回波序列（ＦＡＳＥ）行ＭＲＵ检查的技术方法。方法１８例尿路梗阻、８例非尿路梗阻性疾患及５例健康志愿者，应用ＦＡＳＥ技术行ＭＲＵ检查。无尿路梗阻者１３例检查前口服速尿２０ｍｇ。所有图像后处理均采用最大信号强度投影（ＭＩＰ）技术。结果尿路梗阻病人均能显示梗阻部位和程度，诊断敏感率达１００％，诊断正确率为８３％（１５／１８）。口服速尿增强ＭＲＵ提供了良好的肾脏形态和尿路解剖结构。结论ＭＲＵ是一种方便快捷的技术，可提供高分辨尿路图像     

Urinary tract infections in children: renal ultrasound evaluation

Ultrasound may replace urography in screening pediatric patients with uncomplicated urinary tract infections but without vesicoureteral reflux. A child undergoing a first radiographic evaluation for urinary tract infection is initially examined by voiding cystourethrography. If reflux is present, urography is performed. If no reflux is present, the kidneys are evaluated by real-time ultrasound; urography may also be performed if the ultrasound examination is abnormal, equivocal, or inadequate. A total of 192 patients was evaluated with this protocol; 146 (76%) had no reflux and therefore were examined with ultrasound. One patient was found to have hydronephrosis and underwent surgical correction. This group of patients was compared with a similar group of 223 patients without reflux who were evaluated by urography prior to the institution of the ultrasound protocol; there was no significant difference between the two groups in upper urinary tract findings that influenced patient management.     

Computed tomography and magnetic resonance imaging of the female lower urinary tract.

Computed tomography (CT) and magnetic resonance (MR) imaging have become invaluable imaging modalities in the diagnosis of diseases involving the lower urinary tract. Both CT and MR imaging are able to accurately stage bladder carcinoma, with MR imaging able to distinguish between superficial and deep muscle invasion of tumor. CT and MR are also the studies of choice for evaluating retroperitoneal fibrosis, which often affects the urinary tract; MR imaging is often able to detect the presence of active inflammation and occasionally rule out a malignant cause. MR imaging holds promise for the evaluation of stress urinary incontinence and urethral disease. Although diseases of the distal ureter continue to be most accurately diagnosed by intravenous urography and retrograde studies, CT and MR imaging may serve a helpful secondary role.     

磁共振泌尿系造影对尿路梗阻性病变的诊断价值

目的 评估ＭＲ泌尿系造影对尿路梗阻性病变的诊断价值。方法 ３１０例用重Ｔ２ＷＩ快速自旋回波（ＦＳＥ）序列作ＭＲ泌尿系造影,采集资源影后作最大信号强度投影（ＭＩＰ）处理,发现１５７例为梗阻性尿路扩张。结果 １５７例梗阻性尿路扩张包括：输尿管癌２０例,输尿管结石３１例,输尿管良性狭窄３３例,先天性狭窄４８例,外在性病变致梗阻１０例,膀胱病变致梗阻１５例,ＭＲ泌尿系造影均清楚显示尿路影像,能确定有无梗阻     

单激发厚层投射技术在MR水成像的应用

目的：探讨单激发厚层投射技术在MR水成像中的应用价值。方法：在低场磁共振采用T2WI单激发TSE序列,厚层投射直接成像技术做MRU检查40例,MRCP检查20例,结果：40例MRU检查中15例未见异常,其余病例及20例MRCP检查的较满意地显示了梗阻部位和尿路或胆管扩张的形态,结论：本方法成像时间短,图像质量高,可为临床诊断和治疗提供有益的帮助。     

Urinary tract infection in infants and children evaluated by ultrasound

Fifty-nine pediatric patients with urinary tract infection (UTI) underwent renal ultrasonography, excretory urography, and voiding cystourethrography. The imaging procedures were analyzed retrospectively to determine their relative effectiveness in detecting abnormalities that might predispose the patient to UTI. Voiding cystourethrography provided valuable information, particularly the presence or absence of vesicoureteral reflux, that could not be obtained from the other procedures. Excretory urography was less specific than ultrasonography in the majority of patients, with the exception of those who had renal scarring. The authors recommended ultrasonography as the initial imaging procedure in the evaluation of children with UTI. When the sonogram is normal, excretory urography is not considered necessary, but voiding cystourethrography is thought to be essential. If sonography is abnormal, excretory urography and/or other follow-up studies are indicated.     

Cyclic cystography: diagnostic yield in selected pediatric populations.

PURPOSE: To test the hypothesis that the diagnostic yield of cyclic cystography is related to the prevalence of vesicoureteral reflux (VUR) in the population being evaluated. MATERIALS AND METHODS: Two groups of children were examined prospectively: 124 with severe urinary tract infection, defined as patient hospitalization or a maximum temperature greater than 39.5 degrees C, and 135 with previously diagnosed VUR. Nuclear cystography was performed in 249 patients, and fluoroscopic cystography was performed in 10. If VUR was not seen during the first cycle of bladder filling and voiding, a second cycle was performed. RESULTS: VUR was present during cycle 1 in 40 (32%) of 124 patients with severe urinary tract infection and 90 (67%) of 135 children in the VUR follow-up group (P < .001). VUR was demonstrated during cycle 2 in seven (9%) of 76 of the severe urinary tract infection group and eight (24%) of 34 of the VUR follow-up group (P = .045). Of 15 patients with VUR during cycle 2, two had grade III VUR and 13 had grade I or II VUR. CONCLUSION: The second cycle of cyclic cystography has a higher diagnostic yield in patients undergoing VUR follow-up than in patients with severe urinary tract infection. The decision to perform a second cycle of bladder filling and voiding should take into account the pretest probability of VUR in the child being examined.     

Radiographic manifestations of congenital anomalies of the lower urinary tract

The evaluation of anomalies of the lower urinary tract (ureter, bladder, and urethra) requires high quality ultrasonography, voiding cystourethrography, and, occasionally, intravenous urography and contrast sinography. Infants with these anomalies present because of abnormal intrauterine ultrasonographic examinations, urinary tract infections, or obvious external malformations. With a solid embryologic knowledge of the development of the lower urinary tract the radiologist can tailor the imaging procedures to demonstrate almost all aspects of the anomaly and the presence or absence of frequently associated malformations.     

Functional and morphologic evaluation of congenital urinary tract dilatation by using combined static-dynamic MR urography: findings in kidneys with a single collecting system

PURPOSE: To assess combined static-dynamic magnetic resonance (MR) urography in the evaluation of congenital urinary tract dilatation in infants and children. MATERIALS AND METHODS: Sixty-two patients with urinary tract dilatation underwent prospective examination with combined static-dynamic MR urography. A combination examination involved use of a static T2-weighted three-dimensional inversion-recovery fast spin-echo sequence and a dynamic T1-weighted two-dimensional fast field-echo sequence with gadopentetate dimeglumine-DTPA and furosemide application. Twelve additional patients underwent examination with only static MR urography. Thus, both image quality and morphologic features were assessed in 74 patients with the use of MR urography. The results were compared with those of ultrasonography and, when available, conventional urography or surgery. In 62 patients, the dynamic sequence was used to calculate split renal function from renograms generated from parenchymal regions of interest and to assess urinary excretion from whole-kidney renograms. Results were compared with those of diuretic renal scintigraphy (DRS) for split function (Spearman rank correlation coefficient) and urinary excretion (kappa coefficient). RESULTS: Stenoses at the ureteropelvic (n = 33) and ureterovesical (n = 31) junctions and within the ureter (n = 3) and nonstenotic dilatation (n = 23) were clearly depicted, while the normal urinary tract (n = 51) was depicted in its entirety in 47 of 51 examinations. Image quality was considered good or excellent in 95% of the kidney-ureter units. For split renal function, dynamic MR urography and DRS showed significant correlation (r = 0.92, P <.001). For urinary excretion, MR urography and DRS showed strong agreement (kappa = 0.67), with concordant classification of urinary excretion in 59 (81%) of 73 abnormal kidney-ureter units and in all 47 (100%) normal kidney-ureter units. CONCLUSION: Combined static-dynamic MR urography provides high-quality depiction of the urinary tract in infants and children, while allowing accurate determination of single-kidney function and reliable evaluation of urinary excretion.     

MR泌尿系成像的技术和应用

目的：估价ＭＲ泌尿系成像的技术和应用价值。材料与方法：用重Ｔ２加权快速自旋回波（ＦＳＥ）序列和脂肪抑制技术作ＭＲ泌尿系成像９５例。所有图像均作最大信号强度投影（ＭＩＰ）处理。结果：９５例均清楚显示肾实质和泌尿系集合系统高质量的影像。７１例阳性，２４例阴性。阳性病种包括：肾癌７例，肾囊肿１７例，肾脓肿１例，肾盂癌４例，肾盏血块１例，肾结核７例，输尿管癌６例，输尿管结石３例，狭窄２例，非梗阻性输尿管扩张和膀胱癌各４例，前列腺病３例，以及各种先天异常等１２例。结论：ＭＲ泌尿系成像是一种很可靠的、非侵袭性的检查方法，它不用造影剂，可避免碘副反应。在形态上，它能较好地显示泌尿系的解剖结构，补充了泌尿系影像学检查方法，是技术上的一大进步。     

What is left of i.v. urography?

Since its introduction into clinical practice in the early 1930s, intravenous urography (IVU) was the primary imaging technique for the investigation of urinary system disorders for many years, until the advent of digital cross-sectional-imaging techniques gradually started to undermine many of its indications. Intravenous urography has been superseded for some indications such as renovascular arterial hypertension, prostatic dysuria, renal failure, palpable abdominal masses and recurrent urinary tract infection in women. Intravenous urography has been reduced, in the sense that it is no longer a primary examination, for other clinical indications such as renal colic, renal trauma, uroseptic fever, asymptomatic haematuria, medical haematuria, obstructive uropathies and follow-up of various disorders. Intravenous urography is indicated and often mandatory in congenital anomalies of the urinary tract, prior to endourological procedures, possible fistulas, renal transplantation, tuberculosis and ureteral pathology. In conclusion, IVU is still the examination of choice where there is a need to visualize the entire urinary system and to evaluate the state of the papillae and calyces. Computed tomography urography and MR urography are the imaging modalities ready in the near future to replace IVU.     

低场磁共振泌尿系成像临床应用探讨

目的评价低场磁共振泌尿系成像（MRU）的成像技术的临床应用。方法25例尿路梗阻,5例非尿路梗阻疾患。应用低场磁共振水成像术检查,所有图像后处理均采用最大信号强度投影（MIP）技术。结果尿路梗阻病人梗阻部位诊断敏感率达100%,诊断正确率为80%。结论MRU是一种无创伤的诊断方法,可作为制定手术方案的补充手段。     

Vesicoureteral reflux in boys: review of 196 cases

To determine the frequency of vesicoureteral reflux (VUR) in boys, the authors retrospectively studied 724 boys who underwent voiding cystourethrography for the first time. VUR was identified in 196 of these patients (27.0%). Urinary tract infection was the indication for cystourethrography in 188 patients (25.9%), 80 of whom (42.5%) had VUR. Hypospadias was the second most frequent indication (179 patients [24.7%]), with VUR present in 32 (17.8%). A significant frequency of VUR was demonstrated in boys studied for various other conditions. Excretory urography in 588 boys revealed congenital anomalies of the upper urinary tract in 72, with VUR in 26 (36.1%), which was significantly higher than that in boys with hypospadias (P greater than .01). There was no significant difference between the frequency of VUR in boys with hypospadias with or without meatal stenosis (P greater than .9) and in boys with meatal stenosis with or without hypospadias (P greater than .9); thus, VUR seems to be independent of mild urethral obstruction and hypospadias. VUR was more frequent in boys with posterior urethral valves (62.5%, P less than .002). VUR in boys with urinary tract infection is as common as in girls. In most cases, its frequency in many apparently unrelated conditions is suggestive of its primary nature.     

Intravenous urographic technique

In these times of rapid advances in radiographic imaging, intravenous urography should be performed in an optimal way. The urographic examination should involve consultation between the referring physician and the radiologist. Necessary patient information should be accessible. McClennan said "patient selection for urographic studies should be efficacious with the radiologist exerting appropriate control so that the urogram is truly a consultative imaging service integrated into the total patient management." We share this view, and it is an extension of the philosophy of practice emphasized by other leaders in uroradiology. Cost containment, new imaging technologies, risk/benefit considerations, and evolving patterns of patient care have had a significant influence on genitourinary tract imaging. In addition, current debate about contrast media, digital radiography, efficacy, and utilization will undoubtedly have an influence on imaging during the next decade. Utilization of intravenous urography has decreased significantly in the past 15 years. Our volume of examinations has declined approximately 50% since 1970. This decline in our practice is attributed to several complex factors such as previous overutilization of screening urography for hypertension; the impact of US and CT for evaluation of obstruction, retroperitoneal disease (adenopathy and fibrosis), renal failure, and renal masses; concern about contrast medium-induced renal failure; and fewer repeat studies because of improved quality of intravenous urography in general radiology practice. In addition, overutilization of urography in patients with hematuria, prostatism, history of urinary tract infection, etc, continues to be debated in the medical community. In our integrated group practice, we have also observed overutilization of "high-tech" procedures in lieu of urography for evaluation of suspected urinary tract disease. Swings of the pendulum are inevitable in diagnostic imaging because of evolving technology and the art of medical practice. Although some differences of opinion about the details of urographic technique and indications for urography may exist, most would agree on the philosophy of producing a high-quality urographic examination. That philosophy focuses on producing the highest quality examination in each patient so that a diagnosis of normal or abnormal can be made accurately and confidently. Failure to demonstrate the entire urinary tract is a common cause of diagnostic error and one that can largely be eliminated by careful attention to the technical details of the examination.     

MR-Urographie: Prinzipien, Untersuchungstechniken, Indikationen

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.     

Assessment of painful ureterohydronephrosis during pregnancy by MR urography

The purpose of this study was to assess the value of the fast imaging sequence called RARE (rapid acquisition with relaxation enhancement) MR urography (or RMU) In pregnant women with painful ureterohydronephrosis. A total of 17 pregnant women with an acute flank pain were examined with RMU. Results were compared with those of US, X-rays and the evolution of symptoms. The gold standard techniques used to evaluate the results of MR urography were US when it showed the entire dilated urinary tract and the nature of the obstruction (9 cases), limited intravenous urography (IVU) when performed (3 cases) or endoscopic procedure (5 cases). The accuracy of RMU in the detection of urinary tract dilatation and the localization of the level of obstruction was excellent (sensitivity 100% in our series). The determination of the type of obstruction, intrinsic vs extrinsic, was always exact. The RMU technique alone could not specify the exact nature of the obstruction. The RMU technique is able to differentiate a physiological from a pathological ureterohydronephrosis during pregnancy. It could be considered as the procedure of choice when US failed to establish the differential diagnosis.Correspondence to: C. Roy     

Feasibility and utility of respiratory-gated, gadolinium-enhanced T1-weighted magnetic resonance urography in children

RATIONALE AND OBJECTIVES: To evaluate the feasibility and utility of respiratory-gated, gadolinium-enhanced T1-weighted magnetic resonance (MR) urography in children. METHODS: In a prospective study, 30 consecutive children, aged 3 weeks to 13.8 years, underwent MR urography. After intravenous injection of low-dose furosemide and gadopentetate dimeglumine, respiratory-gated, coronal, T1-weighted 3D-gradient-echo sequences were obtained at 1.5 T 5 to 30 minutes after contrast administration. Postprocessing of the data was performed using a maximum-intensity projection algorithm. In addition, precontrast half-Fourier rapid acquisition with relaxation enhancement MR urograms were obtained in 29 children. RESULTS: Respiratory-gated, T1-weighted MR urography was successfully performed in all children without the need for sedation. Compared with the final diagnosis, prospective analysis of MR urography images revealed the correct diagnosis in 56 of 58 pelvicaliceal systems (96%). The ureteral morphology was correctly evaluated in 59 of 64 ureters (92%). The method showed limited efficiency for evaluating nonfunctioning renal units. CONCLUSIONS: Respiratory-gated, gadolinium-enhanced T1-weighted MR urography is a feasible and effective diagnostic tool in the assessment of upper urinary tract morphology in children. It is especially useful in depicting nondilated collecting systems and ureters.     

MR-Bildgebung der Nieren Neue Ansätze in der Diagnostik*

AIM: New diagnostic strategies for evaluation of the kidney by fast MR imaging techniques. MATERIAL AND METHODS: A comprehensive morphologic and functional evaluation of the kidney is proposed using fast MR imaging of renal morphology, multiphase 3D gadolinium MR angiography, MR urography and MR flow measurements. A single MR examination is designed to grade renovascular disease and assess the hemodynamic and functional significance, detect and characterize renal lesions and evaluate the urinary tract. RESULTS: The combined analysis of morphologic and functional data allows reliable assessment of renal artery stenosis, benign and malignant renal masses and diseases of the renal collecting system and ureters, as well as congenital abnormalities in good agreement to the results of conventional imaging modalities. The improved tissue contrast and additional functional information compensates for the disadvantage of a lower spatial resolution. CONCLUSION: Combined morphologic and functional MR examination represents a reliable, non-invasive and cost-effective alternative imaging modality for comprehensive diagnostic evaluation of renal disease.