| BackgroundArthrosclerosis is one of the most common causes of renal artery stenosis (RAS). In spite of that Takayasu arteritis was reported as the major cause of RAS in China and other Asian countries, it has been demonstrated that atherosclerotic renal artery stenosis (ARAS) has become the predominant cause of RAS, instead of Takayasu artcritis nowadays in China.Renal dysfunction and renovascular hypertension (RVHT) are two major clinical manifestations of RAS. ARAS is an important cause of renal failure in developed countries, but no significant improvements in renal function has been demonstrated from percutaneous renal revascularization in these patients.The mechanisms leading to renal dysfunction in ARAS are unclear. Rcnovascular hypertension results from the activation of renin-angiotensin-aldosterone system due to anatomic stenosis of renal artery. After administration of captopril, an angiotensin-converting enzyme(ACE) inhibitor, glomerular filtration rate(GFR) will asymmetrically decrease because of dilatation of efferent arteriole. Captopril renal scintigraphy (CRS), based on this mechanism,can be used to diagnose RVHT.Few domestic studies about the mechanism of renal dysfunction and the value of CRS on RVHT in patients with ARAS have been reported.Objective1. To investigate the relationship between the severity degree of renal artery stenosis and single kidney glomerular filtration (SKGFR) obtained by renal scintigraphy. 2. To evaluate the value of CRS in the diagnosis of RVHT resulting from atherosclerotic renal artery stenosis and analyze the relative factors on the influence of examination.Materials and MethodsThis study was conducted from Jan 2003 to Aug 2006 and 55 patients with atherosclerotic renal artery stenosis included. Renal scintigraphy was performed within 14 days before or after renal arteriography. 28 patients of them, clinically diagnosed as RVHT, also underwent captopril renal scintigraphy 1 to 5 days later.22 hypertensive patients whose renal artery is normal or stenosis less than 50% on renal arteriography were considered as control group.The arteriographic results were assessed by an experienced cardiologists.The diameter stenosis≥50% was defined as significant renal artery stenosis.Renovascular hypertension are defined as those who have renalstenosis equal or more than 50% by arteriography, history of hypertension and 3 or more antihypertensive agents taken at the time of study. Renal scintigraphies were performed with 99mTc-DTPA. The analysis of images was independently dealed by two nuclear radiologists who were blinded to the results of arteriography. Regions of interest were drawn around each kidney on both views with background region below the renal region. The body surface area corrected glomerular filtration rate and renography were automatically produced.ACE inhibitors were discontinued 24～48 hours before captopril renal scintigraphy, other antihypertensive medications were discontinued 24 hours prior to the procedure. The positive diagnostic criteria is any one item of follow: A. increased time to maximum (Tmax)≥6minutes; B. a small and poorly functioning kidney (＜30% uptake with Tmax≤2min) that shows no change in captopril renal scintigraphy; C, reduction in relative uptake greater than 5% after captopril intake; D. 10% decrease in calculated GFR after captopril renal scintigraphy compared with the basic scintigraphy.Results1. The relationship between the severity degree of renal artery stenosis and SKGFR from renal scintigraphy.(1) The comparison of SKGFR of the kidneys with renal artery stenosis with that of the contralateral kidneys in unilateral renal artery stenosis patients①The SKGFR of the stenosed kidneys in 32 patients with unilateral renal artery stenosis was significantly decreased compared to the contralateral kidneys (25.0±11.6ml/min vs. 30.5±9.0ml/min, P=0.039).②The SKGFR of kidney with artery stenosis≤90% in 23 patients with unilateral renal stenosis was 29.2±10.6ml/min and the SKGFR of the contralateral kidney was 28.8±8.1 ml/min. The difference between the two side of kidneys was not statistically significant (P=0.894).③The SKGFR of kidney with severe artery stenosis (≥90%) was 17.0±9.4ml/min and 33.7±10.2ml/min compared to the contralateral kidney The difference was statistically significant (P=0.001).(2) The comparison of SKGFR in bilateral and unilateral renal stenosisThe SKGFR in 23 patients with bilateral renal stenosis and 32 patient with unilateral renal stenosis were 21.0±11.0ml/min and 27.0±10.7ml/min. The difference is statistically significant (P=0.002).(3) The relationship of severity degree of renal stenosis and SKGFR in patients with ARAS.55 patients (110 kidneys) were divided into three groups according to severity degree of renal artery narrowing.There were 34 cases in normal or mild renal lesion group, 30 cases in mild stenosis group (renal stenosis at 50%～69%), 46 cases in moderate stenosis group (≥70%). The mean SKGFRs of kidneys were 30.0±9.2ml/min, 28.4±10.8ml/min, 18.84±10.3 ml/min, respectively. No significant difference in SKGFR was observed between normal /mild lesion group and mild stenosis group(P=0.521). The SKGFRs in the moderate stenosis group was statistically significant lower than that in normal/mild renal lesion group or mild stenosis group (P＜0.001).2. The values of CRS in the diagnosis of RVHT(1) The comparison of diagnosing value using different standards in renal stenosis in ASAS patientsThe sensitivity and specificity of CRS for the diagnosis of RVHT were 71.4% and 72.7% when the renal diameter stenosis＞50% used as the criteria for RVHT.When renal Stenosis≥70% as the criteria,the sensitivity and specificity were 73.3% and 57.1%.(2) The comparison for diagnosis of RVHT using different standards by CRSThe sensitivity of glomerular filtration rate decrease≥10% in captopril renal scintigraphy as the criteria in diagnosing RVHT was 46.0%, which is significant higher than that Of other three criteria (35.7%, 17.9% and 14.3%, P＜0.05). The specificity was 86.0% which was not statistically significant different from other criteria(P＞0.05).(3) The comparions of CRS for the diagnosis of RVHT in bilateral or unilateral renal stenosis and renal functionThe sensitivity of CRS for the diagnosis of RVHT was 57.1% in patient with bilateral renal artery stenosis and 85.7% in patients with unilateral renal stenosis.The difference was not statistically significant(P＞0.05). The sensitivity of CRS on the diagnosis of RVHT in the group of moderate decreased GFR was not significant different from the goup of mild dcreased GFR(78.9% vs. 55.6%, P＞0.05). (4) The safety of CRSNo clinically significant hypotension or uncomfortable symptoms happened during CRS examination.Conclusion1. The SKGFR of kidney with renal artery stenosis was significantly decreased compared to that of contralateral kidney in unilateral renal stenosis patients, and was related to the severity degree of renal artery stenosis in renal scintigraphy.2. The SKGFR of patients with bilateral renal artery stenosis was significant lower than that of unilateral renal artery stenosis patients.3. A 10% decrease in calculated GFR of ipsilateral kidney after captopril intake is the most useful single criteria in captopril renal scintigraphy when DTPA used.4. The sensitivity of CRS for the diagnosis of RVHT may be influenced by renal function, bilateral or unilateral renal artery stenosis.5. Captopril renal scintigraphy is a safe and clinically valuable method for diagnosing RVHT in ARAS patients. |
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