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Table 1: show preoperative and postoperative diameters of the examined veins at the wrist and elbow

Maturation, from the diameter aspect considering diameter more than 4 mm measured by ultrasound, it occurred in 84.9% of the arterio-venous fistulas at the wrist and in 100% of the arterio-venous fistulas at the elbow at the 7^th day post operatively. On the 14^thday postoperatively, 82.5% of arterio-venous fistulas at wrist and 94.3% of the arterio-venous fistulas at the elbow reached the minimal maturation diameter, and on the 1^st month postoperatively, 100% of the wrist and elbow arterio-venous fistulas reached the minimal diameter for maturation. As regard the volume of blood flow, the preoperative measurement was very low and not used for comparison, but post-operative data was used for comparison. At the 7^thday postoperatively mean volume of flow with standard deviation was 496.8 ± 256.4 ml/min at the wrist and 968.8 ± 328.4 ml/min at the elbow; on the 14^th postoperative day, mean flow volume with standard deviation 528.39 ± 265.36 ml/min at the wrist and 1094.65±415.00 ml/min at the elbow; on the 1^st month postoperatively, mean hemodynamic arterio-venous fistula value was 580.3 ± 254.53 ml/min at the wrist and 1138.6 ± 588.72 ml/min at the elbow; and on the 2^nd month, it was 684.71 ± 269.59 ml/min at the wrist and 1194.62 ± 584.61 ml/min at the elbow and lastly on the 3^rd month, it was 697.36 ± 238.43 ml/min at the wrist and 1172.28 ± 566.9 ml/min at the elbow. Statistical significance was detected for hemodialysis arterio-venous fistula flow volume at the wrist around the 7^th day postoperatively (p = 0.009) but no other statistical significance detected in other measurements at the wrist or elbow (p > 0.05). Assessment of maturation by using blood flow volume, considering 400 ml/min as the minimal value, in this study only 59.4% of arterio-venous fistula at the wrist reach minimal maturation flow volume but all the fistulas reach minimal maturation flow volume at the elbow after the 7^th day postoperatively. On the 14^thday postoperatively, about 74.9% of arterio-venous fistulas at the wrist reach the minimal maturation flow volume while about 90.9% of elbow arterio-venous fistula reached the minimal maturation flow volume, on 1^stmonth postoperatively, 100 % of wrist and elbow hemodialysis arterio-venous fistulas had volume of blood flow more than 400 ml/min. As regard the time of maturation (including both venous diameter and volume flow) in this study both HAVF at the wrist and elbow show minimal criteria of maturation at the end of the first month. As regard the complications that detected post operatively many complications detected post-operative, table 2 summarizes the number of normal and complicated cases and table 3 summarizes the frequency of each complication detected in the study as well as table 4 summarizes the site of the lesion in relation to the type of complication.

Table 2: Frequency and percentage of normal and complicated fistulae

The patient population consisted of 31 normal fistulas (68.9%) and 14 complicated fistulas (31.1%). Complications varying from thrombosis to stenosis, infection, venous hypertension, and aneurysm formation (table3)

Table 3: Frequency and percentage of different complications

From this table, the most common complication was thrombosis (Figure 1) followed by stenosis (Figure 2) as the second common complication, with equal incidence of aneurysm formation (Figure 3) and infection as third complication (Figure 4 and 5), with least incidence of complication was venous hypertension.

Figure 1: B-Mode shows total occluded basilic vein (arrows).

Figure 2: The cephalic vein show short segment of stenosis of the cephalic vein with subsequent aliasing of the post-stenotic flow

Figure 3: Color Doppler ultrasound: shows color swirl of large pseudoaneurysm at the basilic vein

Figure 4: Multiple subcutaneous abcesses at the left arm; Figure 5: Subcutanous edema (cobble stone appearance)

Table 4: Site of complication in relation to its type

The following table shows the relation between the types of fistula constructed to the type of complication seen

Table 5: Relation between type of fistula and type of complication

From this table the most type of fistula associated with complication was the radio-basilic followed by the brachio-cephalic while the brachiocephalic type associated with less incidence of complication.

DISCUSSION

The recent expansion of replacement therapy for end stage renal disease leads to increase number of patients that require permanent hemodylasis arterovenous fistula (vascular access). The vascular access has became the most widely used mean for end-stage renal disease patients on regular hemodialysis ⁹. Many types of hemodylasis arterio-venous fistulas are known, but the most widely used one is that created with autogenous material, because they have very good primary and secondary patency than those fistulas created with synthetic graft¹⁰. Catheters or grafts liable for many complications that lead to early failure of the vascular access. These complications includes higher incidence of thrombosis, infection, ischemia, and occlusion secondary to initimal hyperplasia, providing higher morbidity and mortality rates for the patients when compared with an autogenous HAVF¹¹. According to the National Kidney Foundation, the best vascular access for hemodialysis is the Native HAVF^{7, 10}.There is variation in the literature about the minimal diameter of the vein to be used in hemodylasis arterio-venous fistula, some consider 1.8 mm as the lowest limite while others consider 2 mm as the lowest diameter^{12, 13, 14}. Nearly the same controversy about the diameter of the donor artery is present many author consider it should not be less than 2 mm while others use 1.8 mm, however 2.0 mm diameter is the most widely accept lower limit. Malovrh¹⁵, found significant increase in the risk of early failure of the hemodialysis arterio-venous fistula when the donor artery diameter is less than 1.6 mm. The most important factor for maintenance of the vascular access patency is the periodic follow up, as early detection of complication and access dysfunction leads to early intervention with subsequent reduction of access failure¹⁶.Doppler ultrasonography is the best modality for post operative follow up and early detection of complications as standard techniques used to assess arterio-venous fistula flow and anatomy have many major limitations. These techniques include indicator dilution techniques, clinical assessment, and pulsed-wave Doppler alone without ultrasonographic imaging do not give detailed anatomical information¹⁷.Some authors considered color Doppler ultrasonography is more superior for assessment of the vascular access patency and abnormalities than angiography which considered the gold standard technique for imaging the abnormalities of the vascular access. As color Doppler ultrasonography provides functional and morphological information’s about the vascular access, in addition it is bedside examination, non invasive, cheap, could be used as guide for further interventional procedures and not use ionizing radiation or radiocontrast material. For these advantages color Doppler ultrasonongraphy considered the first imaging modality and first investigation in assessment of autogenous arterio-venous fistula dysfunction¹⁶.In this study, the radio-cephalic fistula was the most common type of the AVF represent about 48.89 % followed by brachio-cephalic about 24.44 % and lastly brachio-basilic about 26.67 % of cases. These results agree with Keith and Melih¹⁸, as they reported that most common type of hemodialysis arterio-venous fistula is radio-cephalic followed by brachio-cephalic and lastly brachio-basilic.In this study, the age of the fistulae maturation, was variable with more than 50 % reach maturation as regard the diameter and flow volume after one week, and about 80% reach maturation by the end of the 2^nd week, with all fistulas reach maturation by the end of the first month, This not agree with the study done in 2007 by Lynda¹⁹, who stated that the arterio-venous fistula maturation occurs usually within the first two weeks after the operation. From that early evaluation of the AVF maturation is very important and should be started immediately after AVF creation. In the other hand our results agree with the results obtained by Jeferson et al.¹⁰, as they reported that maturation of arterio-venous fistula usually occurred in a variable period from 4-12 weeks. In this study complicated arterio-venous fistula was detected in 14 patients (31.1%) while 31 patients had uncomplicated AFV (68.9%). Complication varies from thrombosis which is the most common complication to venous hypertension which is the least common complication. Thrombosis detected in 5 patients (11.11%), stenosis in 4 patients (8.89%), aneurysmal formation in 2 patients (4.44%), venous hypertension in 1 patient (2.22 %) and infection in 2 patients (4.44 %), These results similar to the resulted obtained by Iftikhar Ahmed et al.²⁰.The results of this study demonstrated that 5 patients out of 45 had thrombotic lesions, which represents the majority of our complicated cases. Most of them (4 patients) were detected at the venous side of the fistula, while only one case had arterial side thrombosis. Which goes together with Lumsden et al.²¹, that proved that the most common cause of vascular access failure is venous thrombosis. And similar with results obtained by Culp K et al.²², in which they found thrombosis was the most common complication and consider the Color Doppler ultrasound the modality of choice for differentiating partial from complete thrombosis and detect the length of the thrombosed segment that could not be assessed by venography or angiography. Also this agree with the results obtained by Elcheroth et al.²³, as they found thrombosis is the most common complication and considered color Doppler ultrasound is sufficient for diagnosis of thromobosis that appear as anechoic or hypoechoic clot within the vessel with absence of blood flow noted during pulsed or color Doppler study. However Khaled M.¹⁷, found that stenosis was more common than thrombosis in this study. In present study, low volume of blood flow was measured in all complicated patients in cases suffering from thrombotic lesions. The National Kidney Foundation: Dialysis Outcomes Qualitative Initiative Guidelines (NKF-k/DOQI, 2006)²⁴also stated that a decrease in hemodialysis vascular access blood flow is a powerful predictor of vascular access thrombosis. In one duplex ultrasonography study of 831 PTFE grafts and 477 AV fistulae, flow volumes less than 80 ml/min in PTFE grafts and less than 800 ml/min in AV fistulae were shown to be predictive of graft failure Paun et al.²⁵The second most common complication in the present study was stenosis, 4 cases detected representing about 8.89 %., most of these detected at the anastomotic site (3 cases) and only one case detected at the venous site. This agree with Van Tricht et al.²⁶, they found graft stenosis usually develop in the venous outflow tract at the site of anastomosis between the graft and the vein and it is usually the underlying cause for thrombosis. But less than the results obtained by Culp K et al.²² and by Daniel et al.²⁷.The location of the stenotic segment differs from one study to another. In our study, 3 stenotic segments were found at the region of AVF, one in the venous limb distally this agree with the results obtained by Hill and Donato²⁸, but not agree with results obtained by Sullivan KL et al.²⁹, in which venous site stenosis was the most common site. Color Doppler ultrasonography by measuring the resistance of blood flow at the level of the AVF can detect stenosis very early and should be used for follow up. In normal AVF the waveform pattern is usually biphasic which represent low resistance flow with high diastolic flow. So, any change in the pattern of this waveform when compared with the previous examination denote the presence of vascular access dysfunction as well as change in the pattern of the waveform from biphasic to triphasic which means high resistant flow indicate vascular access dysfunction Matsui et al.³⁰.Not easy to identify presence of stenosis with maintained blood flow; in these cases the measurements of the peak systolic velocity with continuous follow up and comparison can detect stenosis very early and help in decision making for the next step of management. When the peak systolic velocity less than 300 cm / sec present with maintained flow, follow up of the vascular assess flow is very important to detect any drop of the flow which means vascular access dysfunction Federico et al.³Pseudoaneurysms were easily to diagnosed clinically by the presence of pulsatile mass with systolic murmur. However, Color Doppler ultrasound is the modality of choice for detecting the lesion and determined its extent as well as the presence of any thrombus inside Wiese P and Nonnast DB.¹⁴.Out of the examined cases in our study 2 patients had pseudoaneurysm (4.44%), both at the venous side of the AVF. Our results were low than these obtained and published by Daniel et al.²⁷ who found that 7 patients out of 51 with a percentage of 13.72% had pseudoaneurysms at the AVF. Venous hypertension results from arterialization of the venous system proximal to an arteriovenous fistula with central venous occlusion, Moore³¹. Our study included 1 patients with venous hypertension (2.22%) due to central venous stenosis.

CONCLUSION

Color Doppler ultrasound is a safe, bedside examination, non invasive technique and available that accurately allows the preoperative mapping of the vessels by measuring their diameters and exclude any obstructing or stenosis cause as well as normal assessment of the vascular anatomy. After that the patients suitable for hemodylasis arterio-venous fistula will be selected and postoperatively will subjected to color Doppler ultrasonography follow up to assess hemodynamical and morphological changes. Adding more advantage for color Doppler ultrasonography, is free from ionizing radiation and not use radiocontrast material as well as its low price so, suitable for all patients. Post operatively color Doppler ultrasound plays a very important role in assessment of HAVF morphology and hemodynamic. With subsequent early detection of complications and vascular access dysfunction leading to rapid intervention to save the access rather than forming new one. It is excellent in detection of lumen patency, narrowing and formed thrombus as well as detect the hemodnamical changes that may appear before morphological changes and so, pick up the complication very early.

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