| Purpose:I: To Investigate the feasibility and accuracy of grey scale contrast-enhanced ultrasonography in diagnosis of renal artery stenosis;II: To Investigate the optimal parameters of grey scale contrast-enhanced ultrasonography in diagnosis of renal artery stenosis.Methods:The study was divided into two parts:Part one: Varying extents of renal artery stenosis were established in 13 New Zealand rabbits by ligation of left renal artery. Routine ultrasonography, grey scale contrast-enhanced ultrasonography and CTA detection of renal artery were done before (T0) and 5 d, 10 d, 15 d, 20 d (T5, T10, T15, T20) after operation. The rabbits were divided into four groups according to the results of CTA. Group I: renal artery stenosis<50%; Group II: renal artery stenosis 50%～69%; Group III: renal artery stenosis 70%～99%; Group IV: total obstruction of renal artery. Time-intensity curve (TIC) of renal cortex and medulla was obtained using grey scale contrast-enhanced ultrasonography. Parameters of TIC in varying extents of renal stenosis were compared with that before operation (normal control group). The parameters include①AT: arrive time of contrast agent (the time interval from injection of contrast agent to the time when contrast agent arrive renal cortex and medulla);②TTP: time to peak (the time interval from initial enhancement of renal cortex and medulla to the time when perfusion of contrast agent reach the peak level);③PBD: difference between peak and base intensity;④β: base to peak ascending slope. Correlation between changes of grey scale contrast-enhanced ultrasonographic indicators in varying extents of renal stenosis and routine ultrasonographic indicators was analyzed.Part two: Varying extents of renal artery stenosis were established in 10 New Zealand rabbits by ligation of left renal artery. Grey scale contrast-enhanced ultrasonography and CTA detection were performed 5 d, 10 d, 15 d, 20 d (T5, T10, T15, T20) after operation. The optimal parameter obtained by TIC in part one was considered to be standard indicator for renal artery stenosis diagnosing. Then diagnoses of renal artery stenosis in different time point were done using TIC method. The results of grey scale contrast-enhanced ultrasonography and CTA in different time point were compared respectively, with CTA as golden standard. Sensitivity, specificity, false negative rate, false positive rate, positive predictive value, negative predictive value, as well as coincidence rate were analyzed in order to evaluate clinical value and the optimal parameters of grey scale contrast-enhanced ultrasonography in diagnosis of renal artery stenosis farther.Result:Part one:I: Animal model establishingUltrasonography had been performed successfully in 11 rabbits before operation (11/13). The study was completed in 9 of the 11 rabbits.II: Results of CTAGroup I, 4 rabbits; group II, 3 rabbits; group III, 1rabbit, group IV, 1rabbit in T5 time point. Group I, 2 rabbits; group II, 3 rabbits; group III, 3 rabbits, group IV, 1rabbit in T10 time point. Group I, 1 rabbit; group II, 4 rabbits; group III, 2 rabbits, group IV, 2 rabbits in T15 time point. Group I, 1 rabbit; group II, 3 rabbits; group III, 3 rabbits, group IV, 2 rabbits in T20 time point. Results of CTA in diagnosis of varying renal artery stenosis were: group I, n=8; group II, n=13; group III, n=9; group IV, n=6.III: Results of grey scale contrast-enhanced ultrasonographyDuring grey scale contrast-enhanced ultrasonography, the two-dimensional image and time-intensity curve did not change when renal artery stenosis was less than 50%. In rabbits with renal artery stenosis more than 50%, renal cortex and medulla enhanced slowly, and the degree of enhancement was lower than normal rabbits. The ascending branch of time-intensity curve rose slowly, AT and TTP prolonged, and PBD decreased. No enhancement was observed in rabbits with total renal artery occlusion. Of all the parameters of grey scale contrast-enhanced ultrasonography in renal cortex, only PBD decreased dramatically in group I in comparison with control group (11.43±1.15 vs 10.19±1.20, P<0.05). No differences of AT, TTP andβbetween group I and control group were observed (P>0.05); The same statistic results were obtained when group II was compared with control group and group I, respectively. Except for TTP (P>0.05), PBD andβdecreased, AT prolonged (P<0.05) in group II; In comparison with control group and group I, AT and TTP prolonged, PBD andβdecreased in group III (P<0.05). Except forβP>0.05), AT and TTP prolonged, PBD decreased in group III when compared with group II (P<0.05).Results of grey scale contrast-enhanced ultrasonography in renal medulla were similar with that in renal cortex except for TTP, which dramatically prolonged in group II when compared with control group and group I, whereas no statistic differences of TTP were observed in renal cortex.IV: Correlation between renal cortical AT, TTP, PBD,βand intra-renal artery RIThe Pearson correlation coefficient between renal cortical AT, TTP, PBD,βand intra-renal artery RI were: r = -0.9973, -0.9695, 0.9566,0.9976, respectively. P values for r were 0.0027, 0.0305, 0.0434, and 0.0024 by hypothesis testing (P<0.05).Part two:I: Animal model establishingThe study was performed in 9 of 10 rabbits.II: Results of grey scale contrast-enhanced ultrasonographyDiagnostic criteriaDiagnostic criteria of AT (s) were: group I, 4.5±0.5 (4～5); group II, 6.5±0.5 (6～7); group III, 8.5±0.5 (8～9). Diagnostic criteria of PBD (dB) were: group I, 14±1 (13～15); group II, 11±1 (10～12), group III, <10; group IV, no renal enhancement (no contrast agent perfusion) which indicated total renal artery occlusion.Diagnostic results use single indicatorAT: Group I, 2 rabbits; group II, 3 rabbits; group III, 3 rabbits; group IV, 1 rabbit in T5 time point. Group I, 2 rabbits; group II, 2 rabbits; group III, 3 rabbits; group IV, 2 rabbits in T10 time point. Group I, 2 rabbits; group II, 2 rabbits; group III, 3 rabbits; group IV, 2 rabbits in T15 time point. Group I, 2 rabbits; group II, 1 rabbit; group III, 4 rabbits; group IV, 2 rabbits in T20 time point. The results of AT in diagnosing of varying renal artery stenosis were: group I, n=8; group II, n=8; group III, n=13; group IV, n=7.PBD: Group I, 3 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 1 rabbit in T5 time point. Group I, 2 rabbits; group II, 4 rabbits; group III, 1 rabbit; group IV, 2 rabbits in T10 time point. Group I, 2 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 2 rabbits in T15 time point. Group I, 2 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 2 rabbits in T20 time point. The results of PBD in diagnosing of varying renal artery stenosis were: group I, n=9; group II, n=13; group III, n=7; group IV, n=7.Diagnostic results use two indicatorsThe diagnostic results using two indicators were: Group I, 2 rabbits; group II, 2 rabbits; group III, 2 rabbits; group IV, 1 rabbit in T5 time point. The diagnosis which was made by AT was not coincidence with that by PBD in 2 rabbit. Group I, 2 rabbits; group II, 2 rabbits; group III, 1 rabbit; group IV, 2 rabbits in T10 time point. The diagnoses which were made by AT were not coincidence with that by PBD in 2 rabbits. Group I, 2 rabbits; group II, 2 rabbits; group III, 2 rabbits; group IV, 2 rabbits in T15 time point. The diagnosis which was made by AT was not coincidence with that by PBD in 1 rabbit. Group I, 2 rabbits; group II, 1 rabbit; group III, 2 rabbits; group IV, 2 rabbits in T20 time point. The diagnoses which were made by AT were not coincidence with that by PBD in 2 rabbits. The results of two indicators in diagnosing of varying renal artery stenosis were: group I, n=8; group II, n=7; group III, n=7; group IV, n=7. The diagnoses which were made by AT were not coincidence with that by PBD in 6 rabbits in total.III: Diagnostic results of CTAGroup I, 3 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 1 rabbit in T5 time point. Group I, 3 rabbits; group II, 3 rabbits; group III, 1 rabbit; group IV, 2 rabbits in T10 time point. Group I, 2 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 2 rabbits in T15 time point. Group I, 2 rabbits; group II, 3 rabbits; group III, 2 rabbits; group IV, 2 rabbits in T20 time point. The results of CTA in diagnosing of varying renal artery stenosis were: group I, n=10; group II, n=12; group III, n=7; group IV, n=7.IV: Compare results between grey scale contrast-enhanced ultrasonography and CTAConclusions:①Except for renal cortical TTP in 50%～69% stenosis group, all of the other parameters of grey scale contrast-enhanced ultrasonography both in renal cortex and medulla were changed dramatically when renal artery stenosis more than 50% (moderate to severe stenosis), with AT and TTP prolonged, PBD andβdecreased.②The more severe of stenosis, the more obvious of changes of parameters. No statistical differences of renal cortical TTP in group II were observed when compared with control group and group I, as well as no statistical difference of renal corticalβbetween group III and group II was obtained, which indicated that TTP andβwere less accurate than AT and PBD in estimating extents of renal artery stenosis. The value of TTP andβin estimating extents of renal artery stenosis was not confirmed.③Intra-renal artery RI was highly negative correlation with renal cortical AT and TTP, whereas positive correlation with renal cortical PBD andβwhen renal artery stenosis existed.④Renal cortical AT have to some extent clinical value in diagnosis of renal artery stenosis. But maybe the error in measuring AT, the sensitivity, specificity, coincidence rate of AT in estimating extents of renal artery stenosis are inconsistent and lower than that of PBD.⑤Renal cortical PBD is better with higher sensitivity, specificity, coincidence rate and lower false positive rate, false negative rate in estimating extents of renal artery stenosis if criteria are chosen appropriately.⑥Compared with renal cortical PBD, two indicators can not increase the sensitivity, specificity, coincidence rate of diagnosis in estimating extents of renal artery stenosis.
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