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ABSTRACT: To determine the accuracy and repeatability of ultrasonography (US) with the ellipsoid formula in calculating the renal volume.
The renal volumes in 20 volunteers aged 19-51 years were determined by using US with the ellipsoid formula and magnetic resonance (MR) imaging with the voxel-count method by two independent observers for each modality. The observers performed all measurements twice, with an interval between the first and second examinations. The voxel-count method was the reference standard. Repeatability was evaluated by calculating the SD of the difference (method of Bland and Altman).
Renal volume was underestimated with US by 45 mL (25%) on average. A comparable underestimation was found when the ellipsoid formula was applied to MR images. This indicates that the inaccuracy of US renal volume measurements (a) occurred because the kidney does not resemble an ellipsoid and (b) was not primarily related to the imaging modality. Intra- and interobserver variations in US volume measurements were poor; the SD of the difference was 21-32 mL. For comparison, the SD of the difference in reference-standard measurements was 5-10 mL.
Use of US with the ellipsoid formula is not appropriate for accurate and reproducible calculation of renal volume.
Radiology 07/1999; 211(3):623-8. · 5.73 Impact Factor
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ABSTRACT: Percutaneous transluminal angioplasty (PTA) for ostial atherosclerotic renal-artery stenosis has poor results. Angioplasty with stent placement (PTAS) may be more effective. We undertook a randomised prospective study to compare PTA with PTAS in patients with ostial atherosclerotic renal-artery stenosis.
Patients with ostial atherosclerotic renal-artery stenosis were assigned to receive PTA or PTAS. Secondary PTAS was allowed if PTA failed immediately or during 6 months' follow-up. Analysis was by intention to treat.
42 patients were assigned PTA and 43 were assigned PTAS, but one patient in the PTAS group was excluded from the study. Primary success rate (<50% residual stenosis) of PTA was 57% (24 patients) compared with 88% (37 patients) for PTAS (difference between groups 31% [95% CI 12-50]). Complications were similar. At 6 months, the primary patency rate was 29% (12 patients) for PTA, and 75% (30 patients) for PTAS (46% [24-68]). Restenosis after a successful primary procedure occurred in 48% of patients for PTA and 14% for PTAS (34% [11-58]). 12 patients underwent secondary stenting for primary or late failure of PTA within the follow-up period: success was similar to that of primary PTAS. Evaluation based on intention to treat showed no difference in clinical results at six months for PTA or PTAS.
PTAS is a better technique than PTA to achieve vessel patency in ostial atherosclerotic renal-artery stenosis. Primary PTAS and primary PTA plus PTAS as rescue therapy have similar outcomes. However, the burden of reintervention after PTA outweighs the potential saving in stents, so primary PTAS is a better approach to use.
The Lancet 02/1999; 353(9149):282-6. · 38.28 Impact Factor
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ABSTRACT: In this in vitro study, the accuracy and repeatability of magnetic resonance imaging (MRI) and ultrasound (US) in assessing renal length and volume were determined. US and MR images of 20 cadaver pig kidneys were obtained twice and evaluated by two observers for each modality. The fluid displacement method provided the "gold standard." Renal volumes were calculated from the US and MR images using the ellipsoid formula. Additional volume calculations after segmentation of the kidney on MR images were done using the voxel-count method. Volumes calculated with the ellipsoid formula resulted in an average of 24% underestimation (range 5%-48%) of the renal volume for both US and MRI. With the voxel-count method, no significant deviation from the true renal volume was encountered. Repeatability was also greatest with the voxel-count method. Measuring renal length, repeatability was, again, better with MRI compared to US. For reliable calculation of renal size in vitro, MRI with use of the voxel-count method is preferred.
Ultrasound in Medicine & Biology 07/1998; 24(5):683-8. · 2.29 Impact Factor
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ABSTRACT: Ischemic nephropathy due to bilateral renovascular disease (RVD) is increasingly recognized as cause of end-stage renal failure in the elderly, but a reliable non-invasive method of detection is nor available. Angiotensin converting enzyme inhibition (ACEi) may impair renal function in such patients, but a prospective study of its diagnostic validity has not been undertaken. We studied the effects of controlled exposure to ACEi on plasma creatinine in 108 patients at risk for severe bilateral atherosclerotic RVD, and compared the findings with subsequent angiography. ACEi was given for two weeks, or, to avoid acute renal failure, for four days if plasma creatinine had increased by 20% or more. If after two weeks of ACEi plasma creatinine had not increased by > or = 20%, while blood pressure was still elevated, plasma creatinine was remeasured after blood pressure control by addition of diuretics. The severity of RVD was scored by the stenosis grade of the best perfused kidney. Fifty-two patients had severe bilateral RVD, defined as > or = 50% stenosis to both kidneys (N = 23) or a solitary functioning kidney (N = 29). Of the others, 21 had less severe bilateral RVD, 20 unilateral RVD, and 15 no apparent RVD. Basal plasma creatinine was higher in severe bilateral RVD (median 170 mumol/liter, range 85 to 654 mumol/liter) than in the others (122 mumol/liter, 62 to 675 mumol/liter; P < 0.01), but not discriminative due to a large variability. The increase during ACEi was correlated with the degree of RVD (r = 0.53, P < 0.001). In 69 patients ACEi caused at least a 20% increase in plasma creatinine, in 26 cases by four days, in 31 after two weeks, and in 12 only after blood pressure control by diuretics. Among these were all 52 patients with severe bilateral RVD, 15 of the 41 patients with lesser forms of RVD, and two with normal renal arteries. Thus, in this selected population the criterion of > or = 20% rise in plasma creatinine upon ACEi was 100% sensitive to detect severe bilateral RVD, while its specificity was 70%. No case of acute renal failure was encountered, and plasma creatinine always recovered after stopping ACEi. In conclusion, controlled exposure to ACEi in these patients is safe, and ACEi-induced increase in plasma creatinine is a very sensitive detector of severe bilateral RVD in a high risk population.
Kidney International 04/1998; 53(4):986-93. · 6.61 Impact Factor
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ABSTRACT: To determine the best projection angles for imaging the renal artery origins in profile.
A mathematical model of the anatomy at the renal artery origins in the transverse plane was used to analyze the amount of aortic lumen that projects over the renal artery origins at various projection angles. Computed tomographic (CT) angiographic data about the location of 400 renal artery origins in 200 patients were statistically analyzed.
In patients with an abdominal aortic diameter no larger than 3.0 cm, approximately 0.5 mm of the proximal part of the renal artery and origin may be hidden from view if there is a projection error of +/-10 degrees from the ideal image. A combination of anteroposterior and 20 degrees and 40 degrees left anterior oblique projections resulted in a 92% yield of images that adequately profiled the renal artery origins. Right anterior oblique projections resulted in the least useful images.
An error in projection angle of +/-10 degrees is acceptable for angiographic imaging of the renal artery origins. Patients sex, site of interest (left or right artery), and local diameter of the abdominal aorta are important factors to consider.
Radiology 11/1997; 205(1):115-20. · 5.73 Impact Factor
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ABSTRACT: To compare spiral computed tomographic (CT) angiography with optimized digital subtraction angiography (DSA) for accurate detection and quantification of renal artery stenosis.
In 71 consecutive patients with possible renovascular hypertension, spiral CT angiography was performed of the renal arteries before DSA. Optimized DSA (performed with projection angles calculated from axial spiral CT source images) was used as the standard. Two independent observers evaluated spinal CT angiograms for the presence and grade of renal artery stenosis. Sensitivity, specificity, and interobserver variability were calculated.
With spiral CT angiography, all 166 renal arteries and accessory arteries were identified correctly by both reviewers. Overall sensitivity and specificity for assessment of stenoses of grade 0 (none), grade 1 (1%-49%), grade 2 (51%-99%), and grade 3 (occlusion) were 97% and 100%, 92% and 98%, 96% and 96%, and 100% and 100%, respectively. Agreement was strong between spiral CT angiographic and DSA findings in assessment of all grades of stenosis (kappa coefficient, 0.9 and 0.9, respectively) for the two observers.
Spiral CT angiography enabled accurate assessment of renal artery stenosis in patients with possible renovascular hypertension and may assist in selecting patients for interventional treatment.
Radiology 11/1997; 205(1):121-7. · 5.73 Impact Factor
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ABSTRACT: To describe anatomic features pertinent to patient selection and graft design for transfemoral endovascular aneurysm management (TEAM) of the infrarenal aorta using computed tomographic (CT) angiography.
A prospective noncomparative analysis of 102 spiral CT scans of the abdominal aorta of patients with abdominal aortic aneurysms was performed. From the original CT data set, slices were reconstructed perpendicular to the vessel axis (central lumen line) at a 10 mm interval. In these reconstructed slices, diameter measurements were performed. Vessel length was measured along the central lumen line. In each patient possibilities for TEAM were analyzed.
Because of technical reasons, 36 scans were excluded from the analysis. Of the remaining 66 patients, 18 could potentially be treated with a bifurcated endovascular device. The infrarenal aortic diameter-to-iliac artery diameter ratio was less than 2 in most patients. The vessel segments judged to be adequate for endovascular graft anchoring had a noncylindrical shape in the majority of cases.
Only a minority of patients with abdominal aortic aneurysms can at this stage be treated with an endovascular graft. The ideal endovascular graft should be a combination of rigid and flexible components. The proximal and distal attachment systems should have some flexibility with an intrinsic maximum diameter while the midsection of the graft can be relatively rigid.
Journal of Vascular Surgery 09/1997; 26(2):231-7. · 3.21 Impact Factor
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ABSTRACT: To determine the in situ location and distribution of the renal artery origins in the transverse plane with computed tomography (CT).
CT scans of the paired main renal arteries in 200 patients (89 men, 111 women) were retrospectively reviewed. The locations of the renal artery origins, defined on the basis of their optimal profile angles, and the angle between them were measured. The degree of aortic atherosclerosis was graded in 119 of the 200 patients.
The origins of 400 paired main renal arteries were identified. A statistically significant difference was found between the average best profile angle on the right (24 degrees [range, 26 degrees-70 degrees]) and that on the left (5 degrees [range, -75 degrees to 38 degrees]) (P < .001). Truly laterally located renal arteries were seen on the right in 11 (5%) of 200 right renal arteries and on the left in 56 (28%) of 200 left renal arteries. One hundred eighty-six (93%) of 200 right ostia and only 40 (20%) of 200 left ostia were in an anterolateral location. One hundred four (52%) of 200 left ostia and three (2%) of 200 right ostia were in a posterolateral location. The prevalence of truly opposite renal arteries was 17%. The average profile angle between the renal artery origins was 161 degrees (range, 72 degrees-225 degrees) and was significantly larger in women (P = .001). No relationship was found between ostial location and patient age or atherosclerotic grade.
In the transverse plane, the location of the origin of the right renal artery tended to be anterolateral and of the left renal artery tended to be posterolateral or lateral. The variation in location and distribution width was great.
Radiology 04/1997; 203(1):71-5. · 5.73 Impact Factor
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Nederlands tijdschrift voor geneeskunde 02/1997; 141(1):65-6.
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ABSTRACT: To evaluate short-term effect of Transfemoral Endovascular Aneurysm Management (TEAM) on aortic diameters and volumes after aneurysm exclusion, using CT-angiography.
Analysis of preoperative, 1 week postoperative and 6 months postoperative CT measurements.
University Hospital.
Nine patients treated with an endovascular tube prosthesis.
True cross-sectional diameters of the aorta and the aneurysm, volume of the infrarenal aortic lumen, of the thrombus and of the iliac arteries and length of the aorta and of the endovascular prosthesis.
CT-angiography detected shrinkage of the aneurysm in seven patients. Aneurysm growth was observed in one patient with persistent flow outside the graft and in one patient with fully thrombosed aneurysm sac. In the two patients with increasing thrombus volume, the volume of the aortic lumen decreased.
Although successful aneurysm exclusion can be confirmed by maximum aneurysm diameter measurement, changes in aortic lumen volume and thrombus volume may be more appropriate to discriminate successful from failed exclusion.
European Journal of Vascular and Endovascular Surgery 09/1996; 12(2):182-8. · 2.99 Impact Factor
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ABSTRACT: To evaluate a discrepancy between the location of renal artery stenoses on intraarterial digital subtraction angiographic (DSA) images and that on spiral computed tomographic (CT) angiograms.
The spiral CT angiograms and intraarterial DSA images of 40 consecutive patients with atherosclerotic renal artery stenoses were examined retrospectively. Stenoses were classified as truncal or ostial. The atherosclerotic changes in the abdominal aorta were graded.
Fifty-eight stenoses were demonstrated. In 48 ostial stenoses, there was no discrepancy in the location of the stenoses on spiral CT angiograms and DSA images. In 10 patients, spiral CT angiography showed an ostial lesion, whereas DSA demonstrated an apparent truncal lesion. Most of these stenoses ("pseudotruncal" ostial stenoses) were in patients with severe aortic atherosclerotic disease.
A renal artery stenosis at or within 10 mm of an atherosclerotic aorta at DSA may be diagnosed as an ostial stenosis.
Radiology 07/1996; 199(3):637-40. · 5.73 Impact Factor
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ABSTRACT: We implanted transluminal stents in 24 hypertensive patients with a critical atherosclerotic ostial renal artery stenosis (28 arteries). Immediate revascularisation was successful in all. Follow-up angiography at 6 months, available in 18 patients, revealed restenosis twice. In another patient restenosis was suspected and confirmed by angiography at 2 months. Hence, the total restenosis rate was 3 of 19 patients (16%) and 3 of 23 arteries (13%). Two patients developed renal insufficiency due to cholesterol embolism. In the remaining 22 patients renal function improved (n = 8) or stabilised (n = 14). Although all had to resume antihypertensive treatment, blood pressure normalised in 15 patients, improved in one, remained unchanged in five and worsened in one.
The Lancet 10/1995; 346(8976):672-4. · 38.28 Impact Factor
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ABSTRACT: The purpose of this work was to assess the optimal scan delay for spiral CT angiography (SCTA) of the renal arteries in achieving optimal vascular contrast enhancement and to compare the utility of a delay based on these bolus injection versus that of a fixed scan delay.
Seventy patients underwent renal artery SCTA with a 140 ml bolus of contrast agent injected a 3 ml/s. In 35 patients (Group A), a fixed scan delay of 27 s was used; in the other 35 (Group B), the scan delay was based on the transit time (TTest) of a test bolus injection. The scan delays in this group were set at TTest + 5 s (n = 5), TTest + 10 s (n = 8), TTest + 15 s (n = 4), or TTest + 20 s (n = 18). For all 70 patients, the time intervals between TRA (time to scanning the renal arteries) and TMax (time to maximum aortic enhancement after 140 ml bolus injection) were calculated, after which it was determined in which group of patients TRA occurred closest to TMax. Linear regression and mean squared error (MSE) were used for statistical analysis.
For Group A, mean TRA and TMax were 38 and 50 s, respectively. Mean (TRA - TMax) was -12 s with MSE of 185.76. For Group B, mean TRA and Tmax were 45 and 52 s. Mean (TRA - TMax) values were -15, -12, -11, and -1 s for scan delays of TTEST + 5 s, TTEST + 10 s, TTest + 15 s, and TTEST + 20 s, respectively, with MSEs of 253.80, 158.00, 137.50, and 30.00.
SCTA of the renal arteries was best performed with a scan delay of TTEST + 20 s. However, analysis of our data showed that similar results could be expected with a delay of 44 s.
Journal of Computer Assisted Tomography 22(4):541-7. · 1.22 Impact Factor
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ABSTRACT: To describe short-term complications during stent placement for atherosclerotic renal artery ostial stenosis.
Sixty-one arteries in 50 patients were treated with Palmaz stents. Nineteen patients had a single functioning kidney, 23 had a bilateral stenosis, which was stented bilaterally in 11, and 8 had a unilateral stenosis. The complications were grouped as those related to the catheterization procedure, those related to stent placement, and those possibly related to either category. The complications were divided into those with severe clinical significance (SCS), those with minor clinical significance (MCS), and radiological-technical complications (RTC). The stent placement procedures were ordered chronologically according to examination date and the complications were tabulated per group of 10 patients.
Five (10%) SCS, 5 (10%) MCS, and 8 (16%) RTC occurred in 50 patients. The catheterization procedure led to 2 SCS, 3 MCS, and 1 RTC. Stent placement gave rise to 7 RTC. Three SCS and 2 MCS could have been related to either catheterization or stent placement. More SCS occurred in the first group of 10 patients than in the following groups.
Renal artery stent placement for atherosclerotic ostial stenosis has a considerable complication rate and a learning curve is present. The complications related to the actual stent placement were without clinical consequences.
CardioVascular and Interventional Radiology 20(3):184-90. · 2.09 Impact Factor
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