| Background:Diabetic nephropathy(DN) accounts for the majority of renal diseases that lead to end stage kidney disease, and gradually increases. Presently, Microalbuminuria is one of important evidences for the diagnosis of DN. When microalbuminuria occurs,the impairment of renal is irreversible. In fact, changes like mesangial expansion and hemodynamic changes occurs before microalbuminuria, so a safe、convenient、effective technique to find these changes is clinically important.Contrast-enhanced ultrasound(CEUS)to assess the renal blood flow quantitatively is a new imageology method. Ultrasound contrast agent is free of nephrotoxicity and has a similar size with erythrocyte, which make it excellent for evaluating blood perfusion. Up to now, lots of methods studies about this technique and its application in diseases have been reported. The main agent adminstration methods for this technique were bolus injection and constant injection with burst technique. Both methods were reported effective for evaluating the renal blood perfusion quantitatively, and further studies were done in acute renal failure in animal and chronic renal disfunction in human. Effective parameters to explain the hemodynamic changes were different in each article.Objective:1.To compare bolus injection and replenishment using contrast-enhanced ultrasound in evaluating renal blood perfusion;2.To study the effectiveness of contrast-enhanced ultrasound in evaluating renal blood perfusion changes in early diabetic rats, and which parameters are sensitive.Materials and methods:1.MaterialsUltrasound system:LOGIQ9medical system ultrasound of GE,10L line probe, equipment with coded pulse inversion harmonic imaging and Time-intensity analysis.Contrast agent:SonoVue(?) from Italy Bracco company.P-Aminohippuric Acid (PAH):Analytic ally pure, Japan TIC company.Animals:20New Zealand rabbits, male, weighing2～2.5kg;50SpragueDwley rats,8month, weighing252±12g. All the animal were supplied by XINQIAO hospital animal center.2.ProtocolsFor bolus injection and replenishment methods, dopamine was administrated with the dose of0.5、2.0、5.0μg.kg-1.min-1to change renal blood perfusion. Bolus injection and continuous injection-burst-replenishment method with real-time low mechanical index contrast-enhanced ultrasound were performed for each change, the latter method needed to disrupt microbubbles using0.5mechanical index pulse, then recorded the replenishment.Meanwhile maintain the blood and urine samples to detect P-Aminohippuric Acid clearance rate to calculate effective renal plasma flow(ERPF),which was taken as the standard renal blood flow. Analyzing raw time-intensity curves of dynamic imagings, We can get absolute peaking intensity(A)、time to peak(TTP)、and curve ascending gradient(Upslope) from fitting curve. Paired samples T test were performed for each parameter before and after dopamine administration, and also correlation analysis between each parameter and ERPF.For evaluating the renal hemodynamic changes in early diabetic rats, Rats were divided into control group、STZ-treated group(S)and STZ-treated group(F), STZ was injected intraperitoneally to induce type I diabetic in STZ-treated group, those failed to reach glucose level of16.7mmol/L were in STZ-treated group(F).On day before STZ treatment and Day11、Day30、Day46、Day61, CEUS was performed, and24h urinary albumin excretion(UAE) and histopathology observations were done to confirm the lesion degree of diabetic nephropathy. Analyse the raw time-intensity curves to obtain A and TTP in cortex and medulla, Upslope was defined as the ratio of A and TTP, Ratio-A、Ratio-TTP were the ratio between cortex and medulla. One-way analysis of variance for each parameter in three groups were done to get the significant parameters. Results:1. Enhanced images for bolus infusion and replenishment method:After bolus injection, enhancement occurred along kidney segment arteries'interlobar arteries'arcuate arteries'cortex'medulla, then the whole kidney was enhanced, and the inverse direction for degrading. Enhancement of replenishment was similar to that of bolus injection. The ascending branch of raw TIC curve of bolus method was straight line, that of replenishment ascended to turn point then gradually reach to the peak piont.2. Statistic results for bolus infusion and replenishment method:A、TTP and ERPF increased significantly with the increased dose of dopamine. When bolus injection, the relation coefficient between A and ERPF was0.85, the relation coefficient between TTP and ERPF was-0.92;When replenishment, the relation coefficient between A and ERPF was0.66, the relation coefficient between TTP and ERPF was-0.72,all p=0.00; When bolus injection, there was no statistic correlation between Upslope and ERPF, when replenishment,the relation coefficient between Upslope and ERPF was0.66,p=0.00.3.24h UAE and histopathology observation:After STZ administration,24h UAE of STZ-treated group(S) increased with the development of diabetes, on Day60,it is significantly increased compared to the other two groups. on dayll and day30, glomerulus hypertrophy and capillaries within glomerulus expanding can be observed. On day46and day61, the lesions characterize by mesangial expanding and glomerular basement membrane thickening.4. Evaluating the renal hemodynamic changes in early diabetic rats:there were no significant differences for A and TTP among three groups at each time point. Upslope in cortex on day11、day30、day61and that in medulla on day30、day61showed significantly increases compared to the control group; Ratio-A was always greater than1in control and STZ-treated group(F), on day11、day46、day61,it was lower than1in STZ-treated group(S), and there was significant differences compared to the other two groups on day46and day61.Ratio-TTP was significantly decreased in STZ-treated group(S) on day46compared to the control group. Conclusions:1. Both bolus and replenishment contrast-enhanced ultrasound can evaluating the kidney blood perfusion effectively,bolus method is more accurate and convenient.2. Contrast-enhanced ultrasound can evaluating the kidney hemodynamic changes in early diabetic rats, Ratio-A、Ratio-TTP、Upslope in cortex and medulla were effective TIC parameters, and Ratio-A is specially sensitive. |
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