Diagnosis of renal artery stenosis and renovascular hypertension

Percutaneous Endovascular Therapy of Renal Artery Stenosis: Technical and Clinical Developments in the past Decade

Renal artery stenosis may initiate or exacerbate arterial hypertension and/or renal insufficiency. During the last decade, technical improvements of diagnostic and interventional endovascular tools have led to more widespread use of endoluminal renal artery revascularization and broader indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig in 1978, numerous single-center studies have documented the benefits of percutaneous renal revascularization. In the early 1990s, stent implantation was added to the interventionist's armamentarium for treating renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. The metaanalysis of 3 randomized studies comparing balloon angioplasty with best medical therapy found intervention to be beneficial for blood pressure control but not for preservation of renal function. Despite the absence of randomized studies, there is mounting evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has a positive impact on blood pressure control and renal function. This article summarizes the technical improvements in these endovascular tools during the last decade and gives an overview concerning their clinical impact on renal artery revascularization.

Renal artery stenosis: epidemiology, clinical manifestation, and percutaneous endovascular therapy

Renal artery stenosis may cause or deteriorate arterial hypertension and/or renal insufficiency. Technical improvements of diagnostic and interventional endovascular tools have lead to a more widespread use of endoluminal renal artery revascularization and extension of the indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig in 1978, numerous single-center studies have reported the beneficial effect of percutaneous transluminal renal angioplasty, and since the early 1990's stenting of renal artery stenosis caused either by atherosclerosis or by fibromuscular dysplasia. This article summarizes the impact of technical improvements of endovascular tools on interventional techniques during the last decade and gives an overview concerning the clinical impact of renal artery revascularization. Despite the absence of sufficient randomized studies, there is nonetheless evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has an impact on blood pressure control, renal function, and left ventricular hypertrophy.

Percutaneous endovascular therapy of renal artery stenosis: technical and clinical developments in the past decade

Renal artery stenosis may initiate or exacerbate arterial hypertension and/or renal insufficiency. During the last decade, technical improvements of diagnostic and interventional endovascular tools have led to more widespread use of endoluminal renal artery revascularization and broader indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Gruntzig in 1978, numerous single-center studies have documented the benefits of percutaneous renal revascularization. In the early 1990s, stent implantation was added to the interventionist's armamentarium for treating renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. The meta-analysis of 3 randomized studies comparing balloon angioplasty with best medical therapy found intervention to be beneficial for blood pressure control but not for preservation of renal function. Despite the absence of randomized studies, there is mounting evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has a positive impact on blood pressure control and renal function. This article summarizes the technical improvements in these endovascular tools during the last decade and gives an overview concerning their clinical impact on renal artery revascularization.

Reliability of contrast enhanced sonography with harmonic imaging for detecting early renal scarring in experimental pyelonephritis in a porcine model: preliminary results

PURPOSE

Contrast medium enhanced harmonic ultrasound is a recently developed ultrasound technique that improves the assessment of renal parenchymal vascularity. We performed a preliminary study to define the ability of contrast enhanced ultrasound with harmonic imaging to detect and localize renal scars in a porcine model of experimentally induced pyelonephritis.

MATERIALS AND METHODS

Vesicoureteral reflux was surgically induced in 10 pigs weighing 10 kg. with the contralateral kidney serving as a control. Approximately 4 weeks after the creation of vesicoureteral reflux cystography confirmed reflux. Infection was induced by placing a suspension of paraffin broth impregnated with Escherichia coli in the bladder of each pig. At 4 to 8 weeks (mean 6.5) after the induction of infection a radiologist blinded to the side of the previous procedure performed conventional gray scale ultrasound, color Doppler ultrasound and contrast enhanced ultrasound with harmonic power imaging. The animals were sacrificed; the kidneys were inspected and tissues from the upper, mid and lower poles were sent for culture and histological examination. Histology results were compared with the findings of the 3 ultrasound modalities.

RESULTS

All 10 pigs survived the surgical procedures with no complications. Post-contrast harmonic ultrasound images were available in 9 pigs (18 renal units). Harmonic ultrasound revealed decreased blood flow in 11 renal units, including the upper pole in 7, lower pole in 3, and upper and lower poles in 2. Renal tissue cultures were positive in 11 renal units (6 refluxing units). Histological findings revealed fibrosis in 10 renal units (8 refluxing units). Harmonic ultrasound findings in these 10 renal units showed 9 with changes consistent with inflammation or scars. Using histological results as the gold standard for renal injury harmonic ultrasound was more sensitive than gray scale ultrasound for detecting renal injury with 90% sensitivity, 75% specificity, 81% positive predictive value and 85% negative predictive value.

CONCLUSIONS

Preliminary results indicate that contrast enhanced ultrasound with harmonic imaging is a sensitive method for determining renal scarring without the need for radiation exposure. It may be prove to be a useful adjunct for evaluating children who present with urinary tract infection.

Cortical thickness: an early morphological marker of atherosclerotic renal disease

BACKGROUND

Although kidney size is still the most commonly used morphological parameter, it is not sensitive enough for early detection of atherosclerotic renal disease (ARD). The purpose of this work was to evaluate morphological abnormalities on both post-stenotic and contralateral kidneys, by using spiral computed tomography angiography (CTA).

METHODS

Spiral CTA was performed in 49 hypertensive patients. Renal diameters, renal length, and cortical thickness were measured in 26 post-stenotic kidneys, 26 contralateral kidneys and 46 control kidneys. Mean cortical thickness, cortical area, and medullary length were calculated.

RESULTS

The right and left control kidneys were of comparable morphology. The post-stenotic kidneys showed significant cortical atrophy. The contralateral kidneys also underwent cortical disease, as judged by comparison with control kidneys. A threshold of 800 mm2 was identified for the cortical area that allowed us to distinguish control kidneys from post-stenotic kidneys. Similarly, a threshold of 8 mm was identified for mean cortical thickness. Renal length was still within normal range in all kidney groups. The measurement of superior pole segments appeared to be more sensitive than measurement at other locations for identifying significant intrarenal lesions. There was no significant correlation between clinical and morphological parameters.

CONCLUSIONS

These results suggest that cortical parameters are more sensitive for early diagnosis of ARD than kidney size. Cortical atrophy should be a useful marker for guidance for revascularization.