Clinical Application Of CTA For Arteriovenous Fistula Of Upper Extremity In Dialysis Patients

Objective:(1)To summarize the CTA imaging characteristics and it’s key points of differential diagnosis on arteriovenous fistula(AVF)complications in hemodialysis patients under different scanning techniques.(2)To analyze the problems in clinical CTA examination of AVF complications in hemodialysis patients,and summarize the main points for improving the examination techniques.Materials and Methods:Using the hospital information system,the clinical and CTA imaging data of upper limb AVF complications of 26 dialysis patients(35 person-times,Dec.2014 to Aug.2018)in our hospital were collected,included general clinical data(age,sex,fistula usage time,etc.),other examination results(physical examination,ultrasound,DSA,etc.),CTA scanning technical parameters(scanning position,scanning mode,etc.)and original imaging data.An analysis team assessed the image quality,and used volume rendering(VR),maximum intensity projection(MIP)and common measuring tools to analyze the following items: vascular variation,AVF anastomosis show and stenosis grading,CT differential value ratio between the two ends of anastomosis,pathological changes of venous outflow tract and arterial inflow tract,small distal branch display and CT value of upper limb muscles in different groups.Then the consistency diagnosis were given based on comprehesive analysis with clinical physical examination and other examinations.According to the examination technology and imaging performance,those data were summarized and analyzed.Correlation between CT differential value ratio and stenosis grading of AVF anastomosis was analyzed.Paired T test was performed to detect the difference of CT value in various groups of upper limb muscles.On the basis of summarizing CTA characteristics and key points of differential diagnosis in AVF complications,the main problems and improving suggestions about clinical scanning options were conducted.Results:(1)Different postures and scopes,uncertain position of medication,different threshold setting and trigger CT values,with or without pre-contrast scan and various enhanced scanning stagings were showed in those 35 examinations.No motion artifact was found.2 external artifacts and 14 uneven filling of contrast media could be seen.2cases image quality were unqualified.(2)Vascular variation was found in 5 patiens(19.23%,5/26 cases),mainly belonging to axillary vein branch variation(4/5 cases).(3)The CTA manifestations of AVF complications were closely related to the scanning schemes,included:(1)Excepting the cases of CTV or that the fistlua was not scanned,the visualized effects of the fistula(31 imaging of 26 patients)were shown as level 0,level 1,and level 2,which accounted for 19.35%,19.35% and 61.29%,respectively.Among level 2 displaying cases,moderate stenosis and mild stenosis were3 and 5,respectively.(2)Excepting the cases of incomplete or blurred venous images,pathological changes of venous outflow tract,such as enlargement,tumor-like dilatation,stenosis,thrombosis,calcification and collateral circulation appeared in different combinations in the forearm and elbow drainage veins,besides 8 cases of pseudo-stenosis of cephalic vein in the upper arm,5 cases of pseudo-stenosis of subclavian vein and 3 cases of pseudo-stenosis of left cephalic vein were found.(3)About the changes of arterial outflow tract,4 cases were difficult to diagnose because of blurred development and 1 case was found of brachial artery pseudoaneurysm among all the 35 cases.(4)Stenosis was the most common lesion of internal jugular vein,accounting for 82.35%(14/17 cases),which might involve the brachiocephalic or subclavian veins,could also be accompanied with thrombosis,collateral circulation and local dilatation.(5)Vascular access imaging blurred and multiple distal branches of AVF were displayed in 2 caces.soft tissue swelling were displayed in 4 cases.(6)Four types of imaging manifestations difficult to identy were related to scanning techniques,including uneven venness of venous filling,thin and light vessels,venous collateral circulation and nodular high density,.(4)The higher the difference ratio of CT value between the two ends of AVFanastomotic stoma,the more severe the stenosis(the R value = 0.51,P value < 0.05);According to the degree of stenosis(normal,mild and moderate group),inconsistent between CTA imaging and dialysis effect was found in one patient.whose CTA showed moderate stenosis,but CT difference ratio was only 0.07,and the follow-up dialysis effect was satisfactory.According to the average CT value of different muscle groups,the CT enhancement value of the forearm muscle group on the internal fistula side was lower than that of the healthy side,and the radial side muscle group was more obvious.CT strengthening value of lateral muscle group of upper arm is higher than that of healthy side,and CT strengthening value of medial muscle group is lower than that of healthy side.However,there was no statistical difference among those groups of muscle(P > 0.05)).Conclusion:(1)The casual CTA examination option of hemodialysis fistula has caused its imaging performance to be complex,so the technology need to be standardized.Double upper limbs straight up,Palm to palm,injection of contrast agent in healthy side,control of the total amount of contrast agent and scanning speed,might be beneficial to clear angiography.(2)AVF complications,such as stenosis,thrombosis,enlargement,tumor-like dilatation and collateral circulation,were complicated shown on CTA,systematic and holistic analysis were very necessary so as to identify some of the imaging signs.(3)There were potential application values of measurement on the difference ratio of CT values at both ends of anastomotic stoma and regional muscle’s CT enchanced value for the analysis of abnormal changes of hemodynamics at both ends of anastomotic stoma and the local muscle perfusion after AVF.