MR扩散加权成像在肾功能评价中的应用

目的探讨MR扩散加权成像在肾功能评价中的价值。方法健康志愿者15例作为对照组,慢性肾病(chron ic k idney d isease,CKD)患者32例(其中肌酐正常组12例,肌酐升高组20例)作为研究组。分别测量各例的表观扩散系数(apparent d iffusion coeffic ient,ADC)并与血清肌酐水平及肌酐清除率对比分析。结果15例志愿者在扩散敏感梯度系数(b值)取50、100、400 s/mm2时平均ADC值分别为(405.366±35.964)×10-5mm2/s、(339.646±23.059)×10-5mm2/s、(254.532±13.676)×10-5mm2/s。CKD组病例中肌酐正常组分别ADC值为(336.622±12.879)×10-5mm2/s、(308.142±20.998)×10-5mm2/s、(211.398±14.604)×10-5mm2/s,肌酐升高组分别为(307.717±84.930)×10-5mm2/s、(265.415±57.754)×10-5mm2/s、(201.672±26.411)×10-5mm2/s,ADC值均低于正常对照组(肌酐正常组与正常对照组比较的t值分别为9.720、5.190、11.093,P值均<0.05;肌酐升高组与正常对照组比较的t值分别为6.533、7.382、10.864,P值均<0.05)。肌酐升高组病例的平均血清肌酐水平为(828.490±699.350)μmol/L,肌酐升高组病例的ADC值与血清肌酐水平负相关,但无统计学意义(b值分别为50、100、400 s/mm2时相关系数分别为-0.272、-0.283、-0.023,P值均>0.05)。肌酐升高组病例的平均肌酐清除率为(15.405±14.541)m l/m in,该组病例的ADC值与肌酐清除率呈弱正相关(b值分别为50、100、400 s/mm2时相关系数分别为0.511、0.430、0.335,P值均<0.05,ADC值与肌酐清楚率呈正相关,但相关关系不密切)。结论对肾脏进行扩散加权成像及ADC值测量是1种有一定潜力且无创的肾功能评价的手段。     

Contrast-enhanced MR angiography utilizing parallel acquisition techniques in renal artery stenosis detection

Significant renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension and/or renal impairment. It is caused by either atherosclerosis or fibromuscular dysplasia. Correct and timely diagnosis remains a diagnostic challenge. MR angiography (MRA) as a minimally invasive method seems to be suitable for RAS detection, however, its diagnostic value widely differs in the literature (sensitivity 62-100% and specificity 75-100%). The aim of our prospective study was to compare the diagnostic value of contrast-enhanced MRA utilizing parallel acquisition techniques in the detection of significant RAS with digital subtraction angiography (DSA).A total of 78 hypertensive subjects with suspected renal artery stenosis were examined on a 1.5 Tesla MR system using a body array coil. Bolus tracking was used to monitor the arrival of contrast agent to the abdominal aorta. The MRA sequence parameters were as follows: TR 3.7 ms; TE 1.2 ms; flip angle 25°; acquisition time 18 s; voxel size 1.1 mm × 1.0 mm × 1.1 mm; centric k-space sampling; parallel acquisition technique with acceleration factor of 2 (GRAPPA). Renal artery stenosis of 60% and more was considered hemodynamically significant. The results of MRA were compared to digital subtraction angiography serving as a standard of reference.Sensitivity and specificity of MRA in the detection of hemodynamically significant renal artery stenosis were 90% and 96%, respectively. Prevalence of RAS was 39% in our study population.Contrast-enhanced MRA with high spatial resolution offers sufficient sensitivity and specificity for screening of RAS.     

Diffusion-weighted echo-planar MR imaging in differential diagnosis of brain tumors and tumor-like conditions

We assess diffusion-weighted MR images in the differential diagnosis of intracranial brain tumors and tumor-like conditions. Heavily diffusion-weighted (b = 1100 or 1200 s/mm²) axial images were obtained with single-shot echo-planar technique in 93 patients with pathologically confirmed various intracranial tumors and tumor-like conditions with diffusion gradient perpendicular to the images. We compared signal intensity of the lesions with those of gray and white matter, and cerebrospinal fluid (CSF). In 29 cases (31.1 %) the lesions were isointense to gray and/or white matter. However, 5 cases (5.4 %) showed extremely increased signal intensity: two epidermoid cysts; two chordomas; and one brain abscess. The entire portion of a tumor was markedly hyperintense in 10 cases (10.8 %): four malignant lymphomas; four medulloblastomas; one germinoma; and one pineoblastoma. A CSF-like hypointense signal was seen in many cystic tumors, and cystic or necrotic portions of tumors. A neurosarcoid granulation was the only solid lesion showing characteristically a hypointense signal like CSF. The combination of markedly hyperintense and hypointense signals was seen generally in hemorrhagic tumors. Diffusion-weighted echo-planar MR imaging is useful in the differential diagnosis of brain tumors and tumor-like conditions, and suggests specific histological diagnosis in some cases. Received: 30 July 1999; Revised: 2 November 1999; Accepted: 9 December 1999     

Diffusion-weighted MR imaging findings of kidneys in patients with early phase of obstruction

Background

Diffusion-weighted (DW) magnetic resonance (MR) imaging is an MR technique used to show molecular diffusion. The apparent diffusion coefficient (ADC), as a quantitative parameter calculated from the DW MR images. The purpose of this study is to evaluate the ability of DW MR imaging in early phase of obstruction due to urolithiasis.

Materials and methods

Twenty-six patients with acute dilatation of the pelvicalyceal system detected by intravenous urography were included in this study. MR imaging was performed using a 1.5 T whole-body superconducting MR scanner. DW imaging can be performed using single-shot spin–echo, echo-planar imaging (EPI) sequences with the following diffusion gradient b values: 100, 600, 1000 s/mm². Circular region of interest (ROI) was placed in the renal parenchyma for the measurement of ADC values in the normal and obstructed kidney. For statistical analyses, Paired t test were used.

Results

In spite of obstructed kidneys had the lower ADC values compared to normal kidneys, these alterations were statistically insignificant.

Conclusion

We did not observe significantly different ADC values of early phase of obstructed kidneys compared to normal kidneys.     

Diffusion-weighted MR imaging in leukodystrophies

Leukodystrophies are genetically determined metabolic diseases, in which the underlying biochemical abnormality interferes with the normal build-up and/or maintenance of myelin, which leads to hypo- (or arrested) myelination, or dysmyelination with resultant demyelination. Although conventional magnetic resonance imaging has significantly contributed to recent progress in the diagnostic work-up of these diseases, diffusion-weighted imaging has the potential to further improve our understanding of underlying pathological processes and their dynamics through the assessment of normal and abnormal diffusion properties of cerebral white matter. Evaluation of conventional diffusion-weighted and ADC map images allows the detection of major diffusion abnormalities and the identification of various edema types, of which the so-called myelin edema is particularly relevant to leukodystrophies. Depending on the nature of histopathological changes, stage and progression gradient of diseases, various diffusion-weighted imaging patterns may be seen in leukodystrophies. Absent or low-grade myelin edema is found in mucopolysaccharidoses, GM gangliosidoses, Zellweger disease, adrenomyeloneuropathy, L-2-hydroxyglutaric aciduria, non-ketotic hyperglycinemia, classical phenylketonuria, Van der Knaap disease and the vanishing white matter, medium grade myelin edema in metachromatic leukodystrophy, X-linked adrenoleukodystrophy and HMG coenzyme lyase deficiency and high grade edema in Krabbe disease, Canavan disease, hyperhomocystinemias, maple syrup urine disease and leukodystrophy with brainstem and spinal cord involvement and high lactate.     

Diffusion-weighted MR imaging of the breast: Advantages and pitfalls

The aim of this paper is to review all clinical applications of diffusion weighted MR imaging (DWI) for breast pathology. The challenge of DWI is to obtain the best compromise between lesion detection and characterization. Technical factors affecting lesion characterization and detection are detailed including the effect of contrast administration, the choice of number of b and of b_max, the variation of diagnostic performance according to the type and the size of lesion studied.     

Diffusion-weighted MR imaging (DWI) in the evaluation of epidural spinal lesions

Introduction Epidural spinal cord compression is one of the most critical emergency conditions requiring medical attention and requires prompt and adequate treatment. The aim of our study was to assess the role of diffusion-weighted magnetic resonance (MR) imaging (DWI) in the diagnosis and differentiation of epidural spinal lesions. Methods Three patients with epidural lymphoma, two with sarcoma and three with epidural metastatic disease were imaged on a 1.5T MRI unit. DWI was performed using navigated, interleaved, multi-shot echo planar imaging (IEPI). Three region of interest (ROI)-measurements were obtained on corresponding apparent diffusion coefficient (ADC) maps, and the mean ADC value was used for further analysis. The cellularity of tumors was determined as the N/C ratio (nucleus/cytoplasma ratio) from histological samples. The ADC values and N/C ratios of lesions were compared using a Kruskal-Wallis test. Results The mean ADC of the lymphomas was 0.66 × 10⁻³ mm²/s, that of the sarcomas was 0.85 × 10⁻³ mm²/s and the ADC of the metastatic lesions was 1.05 × 10⁻³ mm²/s; however, the differences were not statistically significant. Mean N/C ratios in the lymphoma, sarcomas and metastases were 4:1, 2:1, and 2.6:1, respectively, with a statistically significant difference between the groups (p < 0.025). Conclusion Although not statistically significant due to the small patient sample, our results clearly show a tendency toward decreased diffusivity in neoplastic lesions with higher cellularity. The data from our study suggest that DWI is a feasible and potentially useful technique for the evaluation of epidural lesions that cause spinal cord compression on a per-patient basis.     

Diffusion-weighted imaging and proton MR spectroscopy in the characterization of acute disseminated encephalomyelitis

Introduction Acute disseminated encephalomyelitis (ADEM) is usually a monophasic illness characterized by multiple lesions involving gray and white matter. Quantitative MR techniques were used to characterize and stage these lesions. Methods Eight patients (seven males and one female; mean age 19 years, range 5 to 36 years) were studied using conventional MRI (T2- and T1-weighted and FLAIR sequences), diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (MRS). Apparent diffusion coefficient (ADC) values and MRS ratios were calculated for the lesion and for normal-appearing white matter (NAWM). Three patients were imaged in the acute stage (within 7 days of the onset of neurological symptoms) and five in the subacute stage (after 7 days from the onset of symptoms). Results ADC values in NAWM were in the range 0.7–1.24×10⁻³ mm/s² (mean 0.937 ± 0.17 mm/s²). ADC values of ADEM lesions in the acute stage were in the range 0.37–0.68×10⁻³ mm/s² (mean 0.56 ± 0.16 mm/s²) and 1.01–1.31×10⁻³ mm/s² (mean 1.24 ± 0.13 mm/s²) in the subacute stage. MRS ratios were obtained for all patients. NAA/Cho ratios were in the range 1.1–3.5 (mean 1.93 ± 0.86) in the NAWM. NAA/Cho ratios within ADEM lesions in the acute stage were in the range 0.63–1.48 (mean 1.18 ± 0.48) and 0.29–0.84 (mean 0.49 ± 0.22) in the subacute stage. The ADC values, NAA/Cho and Cho/Cr ratios were significantly different between lesions in the acute and subacute stages (P < 0.001, P < 0.027, P < 0.047, respectively). ADC values were significantly different between lesions in the acute (P < 0.009) and subacute stages (P < 0.005) with NAWM. In addition, NAA/Cho and Cho/Cr ratios were significantly different between lesions in the subacute stage and NAWM (P < 0.006, P < 0.007, respectively). Conclusion ADEM lesions were characterized in the acute stage by restricted diffusion and in the subacute stage by free diffusion and a decrease in NAA/Cho ratios. Restricted diffusion and progressive decrease in NAA/Cho ratios may help in staging the disease.     

Diffusion-weighted imaging properties of uterine fibroids pre- and post-uterine fibroid embolisation

Objective

To determine the change in apparent diffusion coefficient (ADC) of uterine fibroids following uterine fibroid embolisation (UFE), and if the ADC change correlates with either volume loss or degree of contrast enhancement post-UFE.

Materials and methods

This study was approved by our institutional review board with waiver of consent. The pelvic MRI examinations, including diffusion-weighted MRI (DWI) using 4 b-values, of 50 consecutive patients prior to and 6 months post-UFE were analyzed. The volume, ADC and amount of enhancement were calculated for each fibroid both pre- and post-UFE. The percent residual enhancement for each fibroid was categorized as either: no (0–1%) residual enhancement or residual (>1%) enhancement. Statistical analysis compared ADC, enhancement and volume for each fibroid pre- and post-UFE using paired t-tests and Pearson correlation coefficients.

Results

The mean ADC of all (n = 88) fibroids pre-UFE was 1.30 ± 0.20 × 10⁻³ mm²/s, and increased to 1.68 ± 0.24 × 10⁻³ mm²/s post-UFE (p < 0.0001). Lower pre-UFE ADC correlated with greater ADC change post-UFE (r = −0.50; p < 0.0001). There was no correlation between ADC change and volume change post-UFE (r = 0.07; p = 0.59). However, fibroids with no residual enhancement post-UFE had larger ADC change than those with residual enhancement (p = 0.003).

Conclusion

The ADC of fibroids rises post-UFE. ADC change post-UFE is associated with the degree of loss of enhancement and may therefore be valuable in predicting response to treatment in pre-procedural counseling.     

High resolution MR imaging in patients with symptomatic middle cerebral artery stenosis

Purpose

High resolution magnetic resonance imaging (HRMRI) has been used as an imaging modality to depict the intracranial artery wall. The aim of this study was to compare images of the vessel wall between symptomatic and asymptomatic atherosclerotic plaques of the middle cerebral artery (MCA) using HRMRI.

Materials and methods

From September 2009 to August 2010 we prospectively screened consecutive patients for MCA stenosis using time-of-flight (TOF) MR angiography. We studied 14 patients with symptomatic MCA stenosis and 16 patients with asymptomatic MCA stenosis. The HRMRI protocol included three different scans: T1-, T2-, and proton density (PD)-weighted black blood MRI. The cross-sectional images of the MCA wall on HRMRI were compared between the two groups based on the degree of stenosis, remodeling ratio, outward or inward remodeling, plaque signal intensity, plaque surface irregularity, and presence of an intact inner wall.

Results

The degree of MCA stenosis and the ratio of plaque thickening to patent lumen in the symptomatic group were significantly higher than in the asymptomatic group. Outward remodeling of the stenotic area in symptomatic group was significantly higher than that seen in the asymptomatic group, and the reverse was true for inward remodeling of the stenotic area (it was significantly higher in the asymptomatic group compared to the symptomatic group). T2- and PD-weighted high signal foci, eccentric wall thickening, and plaque volume in the stenotic area were all similar between the two groups.

Conclusions

HRMRI has the potential to distinguish between atherosclerotic plaques in symptomatic and asymptomatic MCA stenoses.     

肾动脉狭窄的影像学诊断及其研究进展

肾动脉狭窄常导致缺血性肾功能不全以及顽固性高血压,严重影响了患者的生存质量.因此,该疾病的早期、准确诊断对于患者的病情和预后判断具有重要意义.目前,评估的主要方法包括有创性和无创性两类:前者主要包括数字血管造影、血管内超声和压力导丝检测;后者主要包括多普勒超声、CT血管成像、磁共振血管成像、放射性核素肾图和声脉冲辐射力成像等.本文就近年来肾动脉狭窄各类诊断方法的优缺点及研究进展作一综述,旨在为今后临床工作中选择合适的评估方法提供依据.     

Diffusion-weighted MR imaging of pleural fluid: differentiation of transudative vs exudative pleural effusions

The aim of this study was to evaluate the ability of diffusion-weighted MRI in differentiating transudative from exudative pleural effusions. Fifty-seven patients with pleural effusion were studied. Diffusion-weighted imaging (DWI) was performed with an echo-planar imaging (EPI) sequence (b values 0, 1000 s/mm²) in 52 patients. The apparent diffusion coefficient (ADC) values were reconstructed from three different regions. Subsequently, thoracentesis was performed and the pleural fluid was analyzed. Laboratory results revealed 20 transudative and 32 exudative effusions. Transudates had a mean ADC value of 3.42±0.76×10^–3 mm²/s. Exudates had a mean ADC value of 3.18±1.82×10^–3 mm²/s. The optimum cutoff point for ADC values was 3.38×10^–3 mm²/s with a sensitivity of 90.6% and specificity of 85%. A significant negative correlation was seen between ADC values and pleural fluid protein, albumin concentrations and lactate dehydrogenase (LDH) measurements (r=–0.69, –0.66, and –0.46, respectively; p<0.01). The positive predictive value, negative predictive value, and diagnostic accuracy of ADC values were determined to be 90.6, 85, and 88.5%, respectively. The application of diffusion gradients to analyze pleural fluid may be an alternative to the thoracentesis. Non-invasive characterization of a pleural effusion by means of DWI with single-shot EPI technique may obviate the need for thoracentesis with its associated patient morbidity.     

移植肾动脉狭窄的介入治疗

目的 探讨移植肾动脉狭窄介入性治疗的方法和疗效。方法 7例肾移植术后肾动脉狭窄的病人,经股动脉或腋动脉入路行狭窄肾动脉的球囊扩张或支架置入术。结果 7例病人中3例行单纯球囊扩张术（2例经股动脉,1例经腋动脉）,4例同时行球囊护张和支架置入（2例经股动脉,2例经腋动脉）。治疗后5例病人血压恢复正常,2例口服降压药恢复正常。随访9－36个月,6例未见狭窄,仅1例支架入术后9个月出现移植肾动脉再狭窄。给予球囊扩张,血流基本恢复。结论 球囊扩张和（或）内支架入仍然是移植肾动脉狭窄的安全有效的方法之一,术后再狭窄的预防和处理需要进一步探讨。     

MR血管壁成像对大脑中动脉深穿支梗死的初步研究

目的探讨大脑中动脉(MCA)深穿支梗死灶位置及数目与MCA动脉粥样硬化之间的关系。方法前瞻性收集2014年3月—2017年6月期间北京天坛医院脑血管病中心收治的急性脑梗死病人。经DWI证实,存在MCA深穿支供血区急性梗死灶的病人49例,其中男45例,女4例,年龄28~73岁,平均(55.5±10.6)岁。所有病人均于发病2周内行颅内大动脉3D高分辨MRI(HR-MRI)检查,即血管壁成像(VWI)。按照HR-MRI所示MCA有无斑块,将所有病人分为2组。采用Mann-Whitney U检验和χ~2检验分别比较2组之间脑梗死病灶位置和数目的差异。结果 2组间年龄、性别、高血压、糖尿病、高血脂等临床资料差异均无统计学意义(均P0.05)。HR-MRI显示MCA有斑块病人30例(61.2%),MCA无斑块病人19例(38.8%)。MCA有斑块组梗死灶最低层面为第2.5(1.0,3.3)层,MCA无斑块组梗死灶最低层面为第3.0(2.0,4.0)层,2组间梗死灶最低层面差异有统计学意义(Z=-2.084,P=0.037)。MCA有斑块组中,深穿支单发病灶者19例(63.3%),多发病灶者11例(36.7%);MCA斑无块组中,19例均为单发病灶(100%)。2组间单发病灶数目差异有统计学意义(P0.05)。结论 MCA动脉粥样硬化斑块与其深穿支供血区梗死灶的位置和数目有关,有助于进一步探讨深穿支区梗死的发病机制。     

DWI和~1H-MRS在肝纤维化中的诊断价值

目的:探讨扩散加权成像(DWI)与氢质子波谱分析(1 H-MRS)在肝纤维化中的诊断价值。方法:使用腹腔注射CCl4溶液法诱导建立兔肝纤维化模型并进行DWI和1 H-MRS检查。DWI使用SE-EPI序列(b1=0s/mm2,b2=600s/mm2),1 H-MRS使用单体素点分辨波谱分析(PRESS)序列(TR 1500ms,TE 35ms),测量表观扩散系数(ADC)值及胆碱(Cho)和脂质(lipid)波峰下面积的比值(Cho/lipid)。以病理学肝纤维化分期为基础,将兔划分为无肝纤维化组(S0)、轻度-中度纤维化组(S1-S2)和重度纤维化及肝硬化组(S3-S4),比较不同组间ADC值和Cho/lipid变化规律。结果:随肝纤维化程度加重,ADC值依次降低(P<0.01),Cho/lipid依次升高(P<0.05);重度纤维化及肝硬化组与另两组ADC值及Cho/lipid差异均具有统计学意义(P均<0.05)。结论:DWI和1 H-MRS具备一定的定量肝纤维化及检测重度纤维化及肝硬化的能力。     

肾动态显像在动脉粥样硬化性肾动脉狭窄支架置入治疗中的价值

目的 探讨99Tcm-DTPA肾动态显像评价和预测经皮腔内肾动脉支架置人术(PTRAS)治疗动脉粥样硬化性肾动脉狭窄(ARAS)的疗效.方法 成功接受PTRAS治疗的单侧ARAS患者76例,分别于术前2周内和术后6个月进行99Tcm-DTPA肾动态显像,利用Gates法测定患侧GFR.根据肾动脉造影结果将狭窄程度分为轻度(50％～69％)、中度(70％～89％)、重度(≥90％)狭窄;根据术前GFR测定结果将患肾功能分为Ⅰ级(GFR≥30 ml/min)、Ⅱ级(15 ml/min≤GFR＜ 30 ml/min)和Ⅲ级(GFR＜ 15 ml/min).通过对比患者术前与术后6个月肾GFR与血压变化情况对PTRAS进行疗效判定.采用SPSS 13.0软件对数据分别进行t检验、x2检验、Fisher精确概率法检验和多元logistic回归分析.结果 术前重度狭窄患者患肾GFR低于轻中度狭窄患者[(19.48±11.56)ml/min与(26.79±15.34) ml/min,t =2.262,P=0.027].PTRAS术后血压改善者占32％( 24/75),无变化者占68％(51/75).术前患肾功能为Ⅰ、Ⅱ级患者术后高血压改善率为39.62％( 21/53),高于肾功能为Ⅲ级患者的13.64％ (3/22),x2=4.825,P=0.028;多因素分析示术前患肾功能分级是影响患者术后血压改善的惟一因素(OR=0.465,P=0.032).PTRAS术后GFR改善者占22.37％ (17/76),无变化者占68.42％ (52/76),降低者占9.21％ (7/76);在血压改善组与未改善组患者中,GFR改善的比率分别为33.33％ (8/24)和17.65％ (9/51),但差异无统计学意义(Fisher精确概率检验,P=0.081).结论 肾动态显像可以客观评价单侧ARAS患者PTRAS术后患肾GFR变化,并可预测术后血压改善情况.     

移植肾动脉狭窄介入治疗

目的探讨移植肾动脉狭窄(TRAS)介入治疗的方法、疗效和安全性。方法经股动脉入路对12例TRAS患者行介入治疗,包括经皮血管腔内成形术(PTA)和支架置入术。患者从肾移植术后至出现肾动脉狭窄症状平均5.5个月(4～15个月),以手术前后血压、血肌酐、动脉狭窄程度作为判断疗效的指标。结果本组4例行单纯球囊(长20～40mm,直径5～7mm)扩张,5例于PTA后置入支架,3例直接置入支架。PTA术后2例(17%)复发狭窄,行支架置入术;支架术后3例再发狭窄,再次行PTA后无复发。12例患者先后共置入9枚球囊扩张式支架,1枚为自膨式支架。介入治疗前肾动脉狭窄率为65%～95%,术后狭窄率降为10%～25%;平均血压由术前175/105mmHg,降至术后140/80mmHg;平均血肌酐水平由术前475.5μmol/L降至术后118.5μmol/L;术后随访3～48个月(平均9个月),12例中最终治愈4例,改善5例,好转2例,无效1例。手术成功率100%,术中未发生血栓、出血、移植肾栓塞等严重并发症。结论TRAS的介入治疗安全有效,选择恰当入路,合理选择和组合运用PTA与支架置入术,可有效提高TRAS的远期疗效和手术成功率。     

Aldosteronoma coexisting with renal artery stenosis in secondary hypertension

A case of secondary hypertension due to an aldosteronoma coexisting with renal artery stenosis is reported. Tumor resection resulted in an immediate but short-lived clinical relief. Follow-up aortography revealed progressive arterial stenosis and infrarenal aortic occlusion. Differential renal venous renin and renal scintigraphy suggested renovascular hypertension. It is necessary to search for a second curable lesion if hypertension remains uncontrollable after surgical correction of an apparent cause.     

Collateral circulation in stenosis or occlusion of the renal artery

The abdominal angiograms of 381 patients were critically reexamined for the existence of collateral circulation in cases of renal artery stenosis or occlusion. Typical renal artery stenosis was found in 39 patients; among these, 17 had a collateral circulation, which was extrarenal in 15 and intrarenal in two. Collateral circulation involving the lumbar arteries was most common. In two patients a collateral circulation was established via the inferior mesenteric artery.     

Drug-eluting stents in renal artery stenosis

Because of higher acute and long-term success rates compared with balloon angioplasty alone, percutaneous stent implantation has become an accepted therapy for the treatment of atherosclerotic renal artery stenosis. Restenosis rates after successful renal stent placement vary from 6 up to 40%, depending on the definition of restenosis, the diameter of the treated vessel segment and comorbidities. The safety and efficacy of drug-eluting stents for the treatment of renal-artery stenosis is poorly defined. The recently published GREAT study is the only prospective study, comparing bare-metal and sirolimus-coated low profile stent systems in renal artery stenosis, showing a relative risk reduction of angiographic binary in-stent restenosis by 50%. This is an opinion paper on indications, current treatment options and restenosis rates following renal artery stenting and the potential use of drug-eluting stents for this indication.