Clinical Study Of Acoustic Radiation Force Impulse Imaging In Lupus Nephritis

Background and objectiveSystemic lupus erythematosus (SLE) is a multisystemic autoimmune disorder, predominantly affecting kidney, eventually lead to renal failure which is main cause of death in SLE patients. The most common and serious visceral impairment of SLE is acute or chronic nephritis, nephrotic syndrome, etc. There is no obvious clinical symptoms in the early stage of renal damage due to kidneys have strong compensatory capacity. Renal biopsy is the gold standard for diagnosis of lupus nephritis (LN). The pathological damage of LN varying from glomerular minor lesion to widely diffuse proliferative lesions, even glomerulosclerosis may occur. Since different pathologic types with distinctive prognosis, early to know pathological type is of great significance for predicting prognosis and guiding clinical treatment. However, due to invasive and postoperative complications make its application restricted.Conventional ultrasonography can only assess kidney qualitatively by providing information on the size, shape, internal echo and color Doppler ultrasound, rather than quantitatively evaluating the damage extent of renal tissue. Some studies have shown that the elasticity or hardness of biological tissue associated closely with its biological characteristics. In other words, the pathological change of tissue is correlated with hardness alteration. Therefore, the ultrasound elastography can provide more clinical information on kidney.Ultrasound elastography which can be divided into static ultrasound elastography and dynamic ultrasound elastography is a new technology used for the diagnosis of parenchymal organs diseases, and currently is the most widely used elastography in clinical application. The VTQ of acoustic radiation force imaging (ARFI) can generate shear wave in the target tissue via acoustic radiation, can objectively capture quantitative information on hardness by calculating the shear wave velocity, mainly applied to abdominal and superficial organs. The values of shear wave velocity (SWV) vary according to hardness of different organs, and thus quantify tissue elasticity can evaluate the elastic compliance.In this study we use the VTQ to detect elastic parameters of right renal lower pole in patients with LN, which can judge the degree of renal impairment indirectly and provide quantitative information of renal impairment for clinical application. It can develop better therapeutic regimen of immunological intervention to protect kidneys, control diseases and delay declining progress of renal function. Materials and methods1. Patients dataFrom September2010to January2013,53lupus nephritis patients (46female and7male) and57healthy volunteers (47female and10male) were evaluated by using VTQ examinations of ARFI. The mean ages of the subjects in these groups were38.82±13.67and36.50±11.24respectively. Lupus nephritis patients were divided into group LN1, LN2, LN3and LN4according to pathological grouping and were divided into group LNa, LNb, LNc and LNd according to clinical pattern. Renal function and serum creatinine of healthy volunteers in the control group were within normal range, without proteinuria, hematuria, and other symptoms of renal damage. Body mass indexes (BMI) of all subjects were within the normal range (18-25).2. MethodsConvex array probe with3.0-4.5MHz was selected for both conventional ultrasound and ARFI by using the Siemens Acuson S2000ultrasonic diagnosis system. First gray scale ultrasound and color Doppler ultrasound for the routine examination of right kidney were used, then ARFI. Taking the maximum cross section of long axis for the right kidney coronal position, start VTQ, the sampling frame is placed into the renal parenchyma in the inferior pole of right kidney, the long axis of sampling frame directing perpendicular to the renal capsule as much as possible, to measure the shear wave velocity (m/s) of the tissue in the sampling frame. Every same part was tested five times and was taken average. All the checks were completed within2days before renal biopsy.3. Statistical analysisSPSS18.0software was used for statistical analysis. Measurement data were expressed as the mean and standard deviation. Single factor analysis of variance was applied in the intergroup comparison. Pearson rank correlation test was applied in the correlations. Receiver operator characteristic (ROC) curve analysis to determine the sensitivity and specificity, and the area under the ROC curve (Az value) is compared. The McNemar test was used in the difference of sensitivity and specificity. Taking P<0.05for the difference was statistically significant.Results1. The comparison of SWV mean between the LN group and the control group:the SWV mean values of LN group and control group were (3.39±0.42) m/s and (2.98±0.36) m/s, the difference between the two groups was statistically significant (P<0.05).2. The ROC curve analysis of LN group and control group:compare the SWV mean values of LN group and control group, then construct ROC curve to obtain the cutoff value, set3.14m/s as cutoff value, implying that the sensitivity and specificity of SWV for diagnosis of LN were67.90%and73.70%, Az value is0.77.3. Correlation analysis of SWV1n and pathological type:Pearson rank correlation test for SWVln and LN1, LN2, LN3, LN4groups, there was statistically significant difference between the groups, and there was significant positive correlation between SWV and the four groups (r=0.304, P<0.05). More severe the pathological type, the higher of SWV value.4. Correlation analysis of SWV1n and clinical type:Pearson rank correlation test for SWVln and LN1, LN2, LN3, LN4groups, there was no statistically significant difference between the groups(r=0.129, P>0.05), there was no correlation between SWV and clinical type.5. The relationship of pathological and clinical type:the pathological types of53patients with LN including Ⅱ, Ⅲ, Ⅳ and Ⅴ, the cases of each group was9(16.98%),6(11.32%),34(64.15%) and4(7.55%) respectively. The clinical manifestations including nephrotic syndrome, nephritic syndrome, renal insufficiency, and occult nephritis, each accounts for23(43.40%),15(28.30%),9(16.98%) and6(11.32%) respectively. There was significant heterogeneity and diversity between the pathological and clinical type.ConclusionsPathological changes including immunological complex deposition, glomerulosclerosis and interstitial fibrosis occur in the progress of LN, leading to tissue hardness increase and elasticity decrease on a macro level. ARFI has objective, non-invasive, quantitative and repeatable characteristics, can provide quantitative indexes of renal impairment for rational therapeutic regimen of immunological intervention, control diseases and slow deterioration of renal function.