Complex cystic renal masses: characterization with contrast-enhanced US

PURPOSE: To prospectively compare contrast material-enhanced ultrasonography (US) with computed tomography (CT) in the classification of complex cystic renal masses with the Bosniak system. MATERIALS AND METHODS: Ethics committee approval and written informed consent were obtained. Forty patients (17 women, 23 men; age range, 31-77 years) with 44 complex cystic renal masses detected with conventional US were prospectively examined by using second-harmonic US with a second-generation contrast agent and multiphasic helical CT. Thirty-six patients had one lesion, and four patients had two lesions. Surgical resection in nine patients and imaging follow-up in 31 patients were used to determine the outcome. RESULTS: On contrast-enhanced US images, masses were classified as Bosniak category II (n = 18), IIF (ie, lesions were classified as category II and follow-up was needed) (n = 16), III (n = 7), or IV (n = 3) lesions. On CT images, masses were classified as Bosniak category II (n = 24), IIF (n = 10), III (n = 7), or IV (n = 3) lesions. Interobserver agreement was high (kappa = 0.86, P < .001) for classification with US. Complete concordance between the readers was found for classification with CT. Complete concordance between contrast-enhanced US and CT was observed in the differentiation of surgical and nonsurgical complex cysts. Complete concordance among the three readers in the assessment of vascularity with contrast-enhanced US was found. Interobserver agreement in the evaluation of enhancement on CT images was high (kappa = 0.88, P < .001). Concordance between contrast-enhanced US and CT in the evaluation of vascularization was high (kappa = 0.77, P < .001). CONCLUSION: The study data suggest that contrast-enhanced second-harmonic US is appropriate for renal cyst classification with the Bosniak system.     

Detection and characterisation of renal lesions by multiphasic helical CT

Purpose: The fast helical CT technique allows examination of the kidneys during different phases of contrast medium enhancement. However, every additional phase increases the radiation dosage to the patients. We investigated the detection rate and characterisation of renal lesions during different phases and evaluated them separately, and considered the possibility of excluding phases without loss of important information.Material and Methods: Sixty patients who underwent contrast-enhanced multiphasic renal helical CT examination were included. Every CT phase was evaluated separately. The number of lesions and the characteristics of the lesions were noted and all lesions were viewed together.Results: A total of 153 cysts and 17 solid lesions were detected. The largest and an equal number of cysts (142/143) was detected in the nephrographic and excretory phases. However, the nephrographic phase detected more cortical cysts and the excretory phase detected more sinus cysts. All solid lesions were detected in all phases. Renal parenchymal tumours were best characterised in the cortical phase and angiomyolipomas in the native phase.Conclusion: The cortical phase was best for characterisation of renal parenchymal tumours. The nephrographic and excretory phases were best in detecting and characterising renal cysts. The nephrographic phase was the phase giving the least diagnostic information.     

Ultrasonography and computerized tomography in the diagnosis of renal metastasis

The US and CT findings of renal metastases are described in a series of 26 patients. US findings were round or oval masses ranging in diameter from 1.5 cm to 8 cm (mean: 4.2 cm); in only 21.2% of cases lesion diameters were less than or equal to 3 cm. In most patients (84.8%) the metastatic lesions were hypo-isoechoic, while in the extant cases they were either mildly hyperechoic or inhomogeneous. CT findings were round masses with variable diameters (1 cm to 8 cm; mean: 2.7 cm); in most cases (86.4%) lesions diameters were less than or equal to 3 cm. The latter finding was in significant disagreement with US results. CT densities were within the soft-tissue range, and always hypodense if compared to normal renal parenchyma in contrast-enhanced scans. Few cases of perirenal metastases were observed. US sensitivity was only 57%, much lower than that of CT; the latter method yielded no false negatives. CT showed metastatic lesions in patients with normal US findings; in 2 cases a greater number of lesions was detected with CT than with US. Our results are in substantial agreement with literature data, as far as US and CT findings are concerned; however, a lower incidence of bilateral cases was observed in our series than in previous reports. Our results support the primary role of CT in the detection of renal metastases thanks to its high sensitivity and to its allowing the simultaneous evaluation of other organs.     

The prevalence of simple renal and hepatic cysts detected by spiral computed tomography

AIM: To provide a definitive evaluation of the prevalence of simple renal and hepatic cysts using spiral computed tomography (CT). PATIENTS AND METHODS: Contrast-enhanced abdominal CT studies from 617 patients (295 women, 322 men) attending for investigations unrelated to renal or hepatic pathology were included. The number of renal cysts, their location and the diameter of the largest cyst were recorded. Hepatic cysts were recorded as being either present or absent. RESULTS: Two hundred and fifty-four patients (41%) were found to have simple renal cysts and 110 patients were found to have simple hepatic cysts (18%). Both renal and hepatic cysts became more common with age. Renal cysts were significantly more common at all ages in men (p=0.001), and increased in both size (p=0.02) and number (p<0.05) with age. CONCLUSION: A major discrepancy has, until now, existed between autopsy prevalence of renal cysts and prevalence as reported by in-vivo third-generation CT or sonography studies. Using newer spiral CT machines, we have generated prevalence data closer to post-mortem findings. We have also shown a significant, but age dependent, association between the presence of simple hepatic and simple renal cysts (p=0.001)     

Renal cysts: is attenuation artifactually increased on contrast-enhanced CT images?

PURPOSE: To determine if the attenuation values of simple renal cysts are artifactually increased on contrast material-enhanced, clinically acquired spiral computed tomographic (CT) images. MATERIALS AND METHODS: Dual-phase renal spiral CT studies (5-mm collimation; pitch, 1.0) were retrospectively analyzed in 24 consecutive patients who had ultrasonographic (US) documentation of simple renal cysts. Forty-eight cysts were identified. The attenuation values of each cyst were measured on nonenhanced, cortical phase, and nephrographic phase images. The size and the location of each cyst in relation to the renal parenchyma were also recorded. RESULTS: The cysts were 0.6-10.8 cm in diameter (mean, 2.6 cm; SD, 2.0). The mean attenuation change in the cysts from nonenhanced to contrast-enhanced images was statistically significant in a comparison of cortical phase and nephrographic phase images (P: <.01): +1.8 HU (SD, 3.8) for cortical phase and +3. 6 HU (SD, 5.6) for nephrographic phase images. Renal cysts 1.0 cm or smaller showed a higher attenuation increase (mean, +4.0 HU for cortical phase and +11.0 HU for nephrographic phase). None of the renal cysts larger than 1.0 cm demonstrated an increase greater than 10 HU (mean, +1.4 HU for cortical phase and +2.3 HU for nephrographic phase). Intraparenchymal cysts showed higher mean attenuation changes than the exophytic cysts. CONCLUSION: Attenuation values in the renal cysts increased artifactually on contrast-enhanced images, but this pseudoenhancement was not substantial and was less than 10 HU when the cyst was larger than 1. 0 cm in diameter.     

Tuberose sclerosis complex: analysis of growth rates aids differentiation of renal cell carcinoma from atypical or minimal-fat-containing angiomyolipoma

AIM: To study the radiological characteristics of renal masses in individuals with tuberous sclerosis complex (TSC) using serial CT, and to examine how renal cell carcinoma (RCC) may be differentiated from indeterminate cysts or masses. METHODS: This was a retrospective study of 12 cases of TSC in which dedicated renal CT followed after US had demonstrated cystic or sonographically unusual renal masses. The CT density of all masses was measured and the masses categorized as simple cysts, complex cysts, angiomyolipomas or indeterminate solid masses. Subjects were maintained on regular follow-up with repeat CT or MRI and interval renal US. Indeterminate masses that showed rapid growth were considered suspicious for renal cell carcinoma and biopsy or nephrectomy followed. RESULTS: Comparative data were available for a median of 4 years. In each case the renal masses were multiple and bilateral; mean mass diameter was 3.6 cm. Among a total of 206 masses, 18 were simple cysts and 3 were complex cysts. Of the complex cysts, 1 proved to be an angiomyolipoma on histology and the other 2 showed no growth. Of the solid masses, 133 were typical angiomyolipomas (AMLs) and 52 were indeterminate. On follow-up, only 3 indeterminate masses showed rapid growth (>0.5 cm/year), of which only 1 proved to be an RCC on biopsy. The other 2 were minimal-fat AMLs, and the remainder of the masses showed no or slow growth. CONCLUSION: Many renal masses associated with TSC are radiologically indeterminate. A growth threshold of >0.5 cm/year identified the only RCC in this study (0.5% of all masses). Yearly radiological follow-up of indeterminate renal masses is recommended for individuals with TSC.     

Radiologisches Staging des Nierenzellkarzinoms

The routine staging work-up for renal cancer includes a contrast-enhanced multiphasic spiral CT and a chest radiograph. If there is doubt regarding the presence and extent of (supradiaphragmatic) IVC thrombus, MR imaging should be performed. Dynamic contrast-enhanced MR imaging should be used in place of CT in any patient with severe renal dysfunction, symptomatic polycystic kidney disease, or a history of allergy to iodinated contrast media. Cavography is no longer needed in the era of (adaptive array detector) spiral CT and MR venography.     

儿童非霍奇金淋巴瘤与白血病肾脏浸润的CT表现

目的：认识儿童非霍奇金淋巴瘤（NHL）及白血病肾脏浸润的各种CT表现。材料和方法：复习病理证实的42例儿童NHL的临床资料,选出其中12例肾脏浸润的病例,分析化疗前后的CT变化,所有病例均行常规胸腹部CT平扫加增强扫描;4例白血病B超提示肾脏浸润,然后行腹部CT平扫加增强扫描。结果：NHL肾脏浸润表现为两侧肾脏多发结节样改变9例,单侧单弛节浸润2例,单侧多结节1例;4例白血病肾脏浸润全部表现为两肾多结节样改变。结论：儿童NHL与白血病肾脏浸润CT表现极其相似,具有一定的特征性,CT能很好显示肾脏浸润情况,正确及时地诊断肾脏浸润有助于NHL的临床分期,也有助于NHL及白血病化疗前后的疗效观察。     

64层螺旋CT后处理技术对马蹄肾血供和合并症的诊断价值

目的:探讨64层螺旋CT后处理技术在马蹄肾血供和合并症中的诊断价值。方法:对25例马蹄肾患者先行64层CT平扫,然后行肾皮质期、实质期及排泄期增强扫描,将扫描数据经薄层重建后传至工作站,采用多平面重组(MPR)、容积再现(VR)及最大密度投影(MIP)技术进行后处理,观察马蹄肾融合的部位及其组织结构以及血供和合并症情况。结果:25例均为下极融合性马蹄肾畸形,24例峡部为肾实质组织,1例峡部为纤维结缔组织。25例患者共观察到71支肾动脉、6支副肾动脉,其中8例观察到2支肾动脉,6例观察到3支肾动脉,4例观察到4支肾动脉,1例观察到5支肾动脉,3例观察到2支肾动脉且另见1支起源于腹主动脉分叉前下壁的副肾动脉,2例观察到3支肾动脉且另见1支起源于骶正中动脉的副肾动脉,1例观察到4支肾动脉且另见1支起源于腹主动脉分叉前壁的副肾动脉。25例中11例合并肾积水,8例合并肾结石,10例合并肾囊肿,10例合并感染,1例合并肾细胞癌。18例有临床症状者均经手术证实其马蹄肾的解剖结构、血供及合并症与CT检查结果相符。结论:64层螺旋CT后处理技术能够清楚显示马蹄肾的整体形态和细微解剖结构,尤其是血供和合并症情况,为临床外科治疗提供解剖学依据,可作为本病的首选检查方法。     

肝、双肾巨大血管平滑肌脂肪瘤的影像诊断及鉴别诊断(附1例报告及文献复习)

目的 探讨肝、肾血管平滑肌脂肪瘤即错构瘤的临床特点、影像诊断以及鉴别诊断.方法 回顾性分析1例51岁女性患者肝、肾错构瘤的临床资料,结合文献报道,对其临床表现、影像特点进行探讨.结果 腹部CT平扫示肝右叶一巨大低密度占位,增强扫描动静脉期自周缘向中心渐进性填充.两肾体积明显增大,呈大小不等、形态各异的蜂巢状混杂密度,可见斑块状、条索状的脂肪密度,增强扫描正常皮髓结构消失,蜂巢壁明显强化,其内见未强化区,双肾动静脉明显受压、移位.结论 肝、肾错构瘤与肝、肾其它良性、恶性病变相比,影像表现较典型,但确诊多数只能通过病理组织学方法.     

病理性肾损伤的影像学诊断及评价

目的:分析病理性肾损伤的影像学表现特征,评价CT和MRI对病理性肾损伤及其病因的诊断价值。方法:回顾性分析9例病理性肾损伤的临床资料及影像学表现,9例均有不同程度的外伤史,全部经CT检查(7/9增强),5例经MRI检查(4/5增强)。结果:病理性肾损伤的病因中,血管平滑肌脂肪瘤3例,肾癌2例,黄色肉芽肿性肾盂肾炎、多发肾囊肿、神经源性膀胱炎伴肾积水、先天性肾盂输尿管连接部狭窄伴肾积水各1例。8例经手术病理证实,1例经临床既往病史证实。CT和MRI检查均清楚显示原发病变及损伤表现。结论:CT和MRI检查对病理性肾损伤的价值显著,但对病因的定性诊断有局限性。     

Rapid MRI assessment of renal space-occupying lesions

The aim of this study was to determine whether rapidly acquired MRI sequences, taking less than 5 min imaging time, can accurately characterise renal masses. All patients found to have a renal space-occupying lesion on CT or ultrasound were asked to participate in a prospective study using rapidly acquired MRI. The MRI technique was performed on a GE Signa (General Electric, Milwaukee, Wis.) 1.5 T magnet using breath-hold coronal and axial T1 GRASS (fast spoiled gradient-recalled acquisition into steady state, FSPGR/30/90) and axial T2 fast spin-echo sequences. The results were analysed by two radiologists unaware of the CT or ultrasound findings. The CT/US was independently viewed by a third radiologist. Lesions were characterised as simple cysts, indeterminate or solid. The MR and CT/US results were correlated and the sensitivity and specificity of MR for the characterisation of simple cysts and solid renal masses calculated. A total of 144 lesions (68 patients; 29 women 39 men, age range 32–78 years, average age 60 years) were studied: 111 simple cysts; 3 hyperdense cysts; 26 renal cell carcinomas; and 4 indeterminate lesions on CT/US. There was agreement between the CT/US and MRI in 82 % of cases. All renal cell carcinomas were correctly characterised on MRI. Of simple cysts, 79 % were correctly identified using this technique. Breath-hold MRI performed in less than 5 min can accurately characterise the majority of renal masses. It is 100 % sensitive in the characterisation of renal carcinoma, and it correctly identified approximately 80 % of simple cysts. If used at the time a renal mass is detected on MRI, it would reduce the need for further investigation of the majority of incidentally detected lesions which are simple cysts. Received: 15 December 1998; Revised: 10 May 1999; Accepted: 2 July 1999     

Differentiation of renal neoplasms from high-density cysts: use of attenuation changes between the corticomedullary and nephrographic phases of computed tomography

PURPOSE: The current study evaluated attenuation changes for proven renal neoplasms between the corticomedullary and the nephrographic phases of a contrast-enhanced computed tomographic (CT) scan as a possible means for differentiating these tumors from the cysts of the kidney when high-density renal masses are detected on a CT scan that does not include a noncontrast baseline. METHODS: We retrospectively reviewed the CT scans performed on 20 patients with 21 biopsy-proven renal neoplasms, which had been done using standard contrast-enhanced computed tomography only. Attenuation values for the 21 renal neoplasms and for 23 simple cysts, used as an internal control, were measured and recorded from the 2 phases of enhancement. The difference in attenuation between the 2 phases of enhancement for each mass was calculated. Data for the neoplasms and cysts were compared with published data for enhancement changes for proven high-density renal cysts. RESULTS: The mean absolute value change in attenuation between the corticomedullary and the nephrographic phases for renal neoplasms was 22 Hounsfield units (HU) (range, 1.0-48 HU) and 1 HU (range, 0.1-3.3 HU) for simple cysts. Only one renal neoplasm (5%) changed to less than 10 HU. CONCLUSIONS: Almost all renal neoplasms studied had an attenuation change of more than 10 HU, either increased or decreased, between 2 phases of a contrast-enhanced CT scan separated by 50 seconds. The results suggest that if the attenuation of a renal tumor changes by more than 10 HU between phases of a contrast-enhanced computed tomography, then the diagnosis of renal neoplasm is very likely. High-attenuation renal masses which change less than 10 HU between the corticomedullary and tubular phases are most likely high-density cysts, but neoplasm is possible.     

Contrast-enhanced second-harmonic sonography in the detection of pseudocapsule in renal cell carcinoma

OBJECTIVE: Our purpose was to assess the capacity of contrast-enhanced second-harmonic sonography to detect a pseudocapsule in renal masses compared with conventional gray-scale sonography. SUBJECTS AND METHODS. Thirty-two patients with 40 renal masses suspicious for renal cancer (mean diameter, 3.1 cm) were prospectively studied with contrast-enhanced second-harmonic sonography during IV administration of a second-generation sonographic contrast agent. The sonographic criteria for the presence of a pseudocapsule were a peritumoral hypoanechoic halo on conventional gray-scale imaging and a rim of perilesional enhancement, increasing in the tardive phase of the examination, on contrast-enhanced second-harmonic imaging. Multiphasic helical CT or dynamic MRI or both were performed in all patients. RESULTS: Final diagnoses of the 40 renal masses were as follows: hemorrhagic cysts, five; angiomyolipomas, four; lymphomas, four; metastasis from lung cancer, one; and renal cell carcinomas (RCCs), 26. Histologic diagnosis of RCC was surgically obtained in all patients. Nephron-sparing surgery was performed in 12 of 26 RCCs, and radical nephrectomy was performed in the remaining 14. At pathologic examination, pseudocapsule was found in 14 (53.8%) of 26 RCCs. On conventional sonography, the presence of a pseudocapsule was detected in 3 of 14 RCCs (sensitivity, 21%). Sonographic contrast-enhanced harmonic imaging revealed the presence of pseudocapsule in 12 of 14 RCCs (sensitivity, 85.7%). In the remaining 12 RCCs with either absent or extensive neoplastic infiltration of pseudocapsule seen at pathologic evaluation, pseudocapsule was not visible on either conventional or contrast-enhanced second-harmonic sonography. The pseudocapsule was not visible in any of the 14 noncancerous renal masses on either conventional or contrast-enhanced sonography. CONCLUSION: Sonographic contrast-specific imaging with a second-generation contrast agent is effective in improving the sonographic visualization of tumoral pseudocapsule. This finding could be useful both in the sonographic diagnosis and in the choice of conservative surgery for renal cell carcinoma. The potential role of second-harmonic contrast-enhanced sonography in the management of renal cell carcinoma should be investigated in larger series and compared with the findings of state-of-the-art MRI and CT.     

CT in the evaluation of complicated autosomal dominant polycystic kidney disease

Purpose: We retrospectively reviewed the CT findings in 24 cases of autosomal dominant polycystic kidney disease (ADPKD) to assess the role of CT in the diagnostic work-up of patients with complicated ADPKD.Material and Methods: Twenty-four patients with ADPKD underwent unenhanced and contrast-enhanced CT for flank pain, haematuria, or fever. The images were retrospectively reviewed for presence of complicated cysts, their morphological features and associated findings in the perinephric space/retroperitoneum.Results: Cyst haemorrhage was present in all patients, seen as high-density cysts, which were mostly bilateral. Most of these cysts had sharply outlined contours, sharp interfaces with adjacent renal parenchyma, imperceptible walls, and homogeneous density, and did not enhance following i.v. contrast administration. However, a few haemorrhagic cysts (9 cysts in 6 patients) showed inhomogeneous density (n=7), dependent layering of high-density blood leading to fluid-fluid level (n=2), and contour irregularity (n=3).CT revealed presence of cyst infection in 6 cases; the involved cysts were larger (average size 4.2 cm) than adjacent cysts, had only a mildly increased or near water density, and showed wall thickening and enhancement. Other findings included air within the infected cyst (n=1), thickening and enhancement of peri- and paranephric fasciae (n=5), and abscesses in the posterior paranephric space and adjoining psoas muscle (n=2). In 2 other patients, although CT suggested cyst infection because of presence of wall enhancement, diagnostic needle aspiration revealed only sterile haemorrhagic fluid. In 1 case, CT revealed a soft tissue density enhancing mass in one of the cysts; this proved to be a renal cell carcinoma by fine-needle biopsy. Calculi were observed in 7 patients, and cyst wall calcification in 11 cases.Conclusion: A combination of unenhanced and contrast-enhanced CT allows correct diagnosis and differentiation amongst the various complications affecting patients with ADPKD. However, in a small subgroup of patients, it may not be possible to differentiate between haemorrhage and infection; such cases require diagnostic needle aspiration for diagnosis.     

CT and ultrasound imaging of retropharyngeal abscesses in children.

PURPOSE: To show the role of ultrasound (US) in distinguishing retropharyngeal abscess from adenitis in children. METHODS: Eleven infants and children had clinical symptoms suggestive of retropharyngeal infection. Radiographic evaluation included, lateral neck radiography (11/11), contrast-enhanced neck CT (10/11), contrast-enhanced neck MR (1/11), and real time US (11/11) patients. US was used to characterize masses as solid (adenitis) or complex (abscess) and for guiding intraoperative aspiration and drainage. RESULTS: Contrast CT and MR showed findings suspicious for abscess in all 11 cases. Only three children had surgically drainable abscesses. CT numbers within inflammatory masses did not distinguish adenitis from abscess. US was able to correctly diagnose abscess or adenitis in each case. CONCLUSION: Lateral neck radiography and contrast CT identify and localize retropharyngeal inflammatory masses in children. US, but not CT, distinguishes between adenitis and abscess and aids in intraoperative aspiration and drainage.     

64层螺旋CT结合后处理技术对肝移植术后并发症的评估

目的:探讨64层螺旋CT结合后处理技术在肝移植术后评估的应用价值.方法:选取50例(男40例、女10例)肝移植术后患者,行64层螺旋CT平扫、四期增强扫描及CTA检查,由两位放射科医师对图像进行评估,内容包括肝实质、血管、胆道情况及有无转移.将结果与彩超及临床随访行对照分析.结果:CT检查示:肝动脉并发症3例、门脉并发...     

卵巢纤维瘤的CT及MRI诊断

目的:探讨螺旋CT、MRI对卵巢纤维瘤的诊断价值。方法:回顾性分析经手术病理证实的8例卵巢纤维瘤CT、MRI征象,7例行CT扫描,1例行MRI检查。结果:8例患者均表现为盆腔内单侧边界清楚的肿块,其表现可分为三类:单纯肿块型5例,1例小肿瘤密度均匀,4例大的肿瘤密度不均匀,增强后肿瘤不强化或轻度强化;囊变型2例,肿瘤内见囊性密度及信号影;合并其他肿瘤型,1例合并同侧卵巢粘液性囊腺瘤。结论:卵巢纤维瘤CT、MRI表现呈多样化,动态增强扫描可提高诊断符合率。     

Cross-sectional imaging of idiopathic solitary renal vein varix: report of two cases

Two cases of solitary renal vein varices are reported which presented as incidental findings on abdominal computed tomography (CT) and were initially thought to represent retroperitoneal lymph nodes. Contrast-enhanced CT, magnetic resonance imaging (MRI), and Doppler ultrasound (US), all demonstrated the vascular nature of these masses suggesting the correct diagnosis. When a rounded soft tissue density mass is seen on noncontrast-enhanced CT either in or contiguous to the renal hilum, a renal vein varix must be excluded. Doppler US, MRI, or dynamic contrast-enhanced CT should be done to exclude a renal varix as the cause.     

Feasibility of MR urography in neonates and infants with anomalies of the upper urinary tract

The aim of this study was to evaluate the feasibility and diagnostic potential of dynamic MR urography (MRU) in neonates and infants with sonographically detected abnormalities of the upper urinary tract. Thirty infants (age range 5 days to 3 years, mean age 7.9 months; male:female: 22:8) underwent MRU using T2 and contrast-enhanced dynamic T1-weighted sequences. The results were compared with the findings of ultrasound ( n=30), intravenous urography (IVU, n=19) and/or scintigraphy ( n=25) based on the criteria suggestive of obstructive uropathy. Oral sedation was sufficient to perform MRU with diagnostic quality in 20 of 21 patients younger than 1 year; 9 older patients needed intravenous sedation. Diagnosis of the 66 renal units (58 kidneys, 29 successful examinations) included normal systems (contralateral units), duplex systems, vesico-ureteral reflux, obstructive megaureter, ureteropelvic junction obstruction and accompanying renal parenchymal disease, with complex pathology in 10 patients. Magnetic resonance urography demonstrated anatomy better than IVU, particularly the renal parenchyma, (ectopic) ureters, and poorly functioning dilated systems. Magnetic resonance urography was superior to US in showing ureteral pathology. Tiny cysts in dysplastic kidneys were better seen by US. Gadolinium-enhanced dynamic MRU allowed accurate assessment of obstruction applying IVU criteria. Here MRU matched IVU results, and most of the scintigraphic findings. Magnetic resonance urography can be performed in young infants with diagnostic quality using oral sedation. Magnetic resonance urography correctly depicts anatomy and allows assessment of the urinary tract better than US and IVU, with additional functional information. Magnetic resonance urography thus has the potential to replace IVU for many indications.