Chronic kidney disease (CKD) is one of the growing diseases in the world in 2017, 850 million people were living with this disease which was about 2 times the number of diabetic patients and about 20 times the number of AIDS patients at that time [1]. Although the age-standardized mortality of most of the common chronic diseases such as cancer and cardiovascular diseases (CVD) were decreased in the past few decades, the CKD are increasing and it’s estimated to become the 3^rd cause of death in 2040 [2]. Chronic renal failure (CRF) is one of the most prevalent diseases in the world and it results from damage to kidney cells which happens as a result of many causes especially in elderly patients. There are five stages for CRF which depend of the level of glomerular filtration rate (GFR) and the extend of renal cells damaged, the normal GFR is 60 ml/min and when this GFR becomes less than 15ml/min/1.73m² it is often called an end-stage renal disease (ESRD) [3] as shown in Table 1 (CKD) [4]. 

Table 1: Classification of chronic kidney diseases

In this stage water and toxins are accumulated in the body therefore the best way to get rid of these toxins, is by means of dialysis especially in ESRD. Therefore dialysis is an artificial way to remove toxins, excess water and other waste products from the body, although this procedure can not completely replace normal kidney function but it can help to some extent by the mean of diffusion and ultra-filtration [5]. The main two types of dialysis are peritoneal dialysis and hemodialysis, in this study concentration is on the hemodialysis, and in order to prepare these patients for hemodialysis sessions which they undergo periodically. 

About 4 million people are living with kidney replacement therapy (KRT) and hemodialysis constitutes about 69% of these KRT and 89% of all dialysis. Dialysis technology started to develop since 1960 especially in first world countries but the accessibility to hemodialysis differ from country to country regarding cost, outcomes…etc.

According to national guidelines arteriovenous fistula (AVF) is the preferred method for dialysis because of low rate of failure, cost, complications, good patency when it becomes mature in addition to low infection rates and reduced need for intervention in contrast with central venous catheter also knows as double lumen catheter. 

Preoperative evaluation of vessel is very important in order to select an appropriate site to improve the surgical outcome [6]. Brescia-Cimino shunt is still the most commonly used arteriovenous fistula although it has been reported to be associated with failure rates hovering around 20% in some centers. Complications substitute; thrombosis, hemorrhage, infection and aneurysm. The autogenous AVF showed higher rates of patency in many studies. 

In autogenous fistulae anastomoses will be done between the artery and the vein, there are four types of these anastomoses, end artery to end vein (end-end) anastomosis, end artery to side vein (end-side) anastomosis, side artery to end vein (side-end) anastomosis and lastly side artery to side vein (side-side) anastomosis as shown in Figure 1. 

Figure 1: Types of anastomoses between the arteries and veins for AVF.

The AVF can be divided into two types autogenous and non-autogenous fistulae, when all the materials used is native, autogenous AVF is constructed otherwise a non-autogenous fistula will be placed but usually this is not preferred because of high rates of failure. Usually, surgeons prefer autogenous over a prosthetic graft.

Furthermore, surgeons prefer creating fistulae with distal vessels just to preserve the proximal vessels for future vascular accesses and operations.

There are many factors that have a role in maturation of AVF including age, sex, blood markers… etc. as shown in Figure 2. 

Figure 2: Factors that are associated with maturation of AVFs

According to the above figure, age has the main role in the outcome of AVF, therefore the older the patient, the more prevalence for bad outcome or failure and this fact has been approved by many studies [7]. This may be due to change in the histological difference of the vessel’s wall between younger and older patients especially the difference in the intima-media with radial arteries which resulted in early failure of radio cephalic AVF [8].

Regarding the gender, many researchers believe that the males has a larger vessels diameter in comparison to females, but on the other hand many studies rejected this allegations and concluded that there is no differences between the two genders regarding diameter [9], but for patency the evidences are less strong.

Another cause of AVF dysfunction is coagulation factor, most of these failures happened as a result of stenosis which happened slightly distal to the site of anastomosis and this phenomenon is called “swing segment” [10]. There are two types of swing segments (distal and proximal) the distal swing segment is the segment of the native vein that is mobilized during radio-cephalic AVF, brachiocephalic, and transposed brachial-basilic fistula creation. A proximal swing segment occurs in the basilic vein near the axillary region during transposition surgery [11]. 

Inflammatory activity is one of the factors that lead to obstruction of the vessel after AVF as a result of infiltration of the lining epithelium by macrophages and lymphocytes, atherosclerosis also can lead to disruption of the lining epithelium and eventually to obstruction of the vessel [12].

Serum lipid profile’s role in the maturation of AVF or its failure is not known, in some studies the lipid profile was the same in functional and those who have atherosclerosis in other studies taking lipid lowering agents such as statin drugs with folic acid had a role keeping the patency of AVF without thrombosis [13].

Vein diameter is another factor that has a role in the success of AVF, and there is a positive correlation between the diameter of vein and the success of AVF and this depends on the velocity of flow of blood and the lumen diameter, normally dilatation happened due to shear stress of the blood, therefore inadequate vessels used to conduct blood may be associated with failure of the AVF [14]. 

Regarding the effect of Diabetes mellitus (DM) on the outcome of AVF, the changes which happens in this disease cause failure AVF, among these pathological changes, change in metabolism, pro-thrombotic situations, damage to endothelial layer, in addition to inflammation all of these factors will accelerate the process of stenosis [15]. 

Endothelial dysfunction also can occur in patients with DM as a result of imbalance between the constricting and vaso-dilatory effect of endothelium, endothelial dysfunction is also a part of the mechanism which happened in many diseases such as hypertension (HT), hyperlipidemia especially hypercholesterolemia in addition to DM [16] Environmental factors also may have a role in endothelial dysfunction, such as tobacco smoking, air pollution, all of these factors will eventually lead to atherosclerosis which will impair the process of remodeling of the vessel and then change in blood flow through it [17].

Regarding hypertension which is also one of the important risk factors which has an effect on the maturation of AVF, the acceptable mechanism is that hypertension lead to impairment of endothelial function and this lead to decrease the relaxation of the wall which results in an inflammatory process and eventually infiltration of the blood vessel [18]. Macrophages and T cells have the main role in these inflammatory processes which is triggered by the sheering stress of fistula creation therefore some studies suggest using immunosuppressive with sirolumus and prednisolone which decreases neointimal hyperplasia during AVF maturation [19]. Other studies showed no correlation between AVF maturation and hypertension and diabetes mellitus [20]. 

Peripheral vascular disease (PVD) resulted from atherosclerosis which develops gradually from accumulation of lipids and inflammatory cells along the inner walls of the arteries, with other factors such as coronary artery diseases and cerebrovascular diseases PVD which is one of the main causes of atherothrombosis which usually developed at the ruptured plaque situated at the afflicted part of artery, sometimes atherosclerotic plaques formed at the bifurcation sites of the vessels as a results of protection mechanisms of the damaged sites [21] therefore one of the main cause of AVF failure is thrombosis [22]. 

Smoking and high eosinophil count are among other factors which have influence on the outcome of AVF and a study showed the smoking as an independent factor for AVF failure in this study which had been done on 141 patients thrombosis was found in 60 patients and 81 had not [23] Other studies showed the effect of smoking on the outcome of AVF failure even with the normal level of hemoglobin [24]. 

Obesity has an impact on the AVF through several mechanism, obesity is risk factor for many conditions including atherosclerosis, hyperlipidemia, coronary artery diseases and diabetes mellitus, also mechanically as vessels in the forearm are more difficult to reach due to thickness of fat layer in the skin [25] On the other hand some studies showed that obesity doesn’t prevent successful autogenous AVF and may protect the forearm venous vessels from damage (iatrogenic) that occur before the onset of hemodialysis therapy [26].

Approximately 500 patients in Erbil governorate are receiving long-term hemodialysis, resulting in an annual health care expenditure in excess of around $250,000. Approximately 25% of these costs result from efforts to maintain access site patency. Clinical protocols to optimize patency and function of hemodialysis access sites could lead to substantial reduction in both patient morbidity and health care costs. It is well established that arteriovenous fistulas exhibit superior long-term function compared with prosthetic arteriovenous grafts. Furthermore, arteriovenous fistulas result in fewer infectious and ischemic complications in contrast to prosthetic arteriovenous grafts.

According to researcher’s knowledge, no similar study has been done in Erbil city and because of the importance of this topic, this study was done.

OBJECTIVES:

• Identify the socio-cultural characteristic of patients enrolled in this study.

• Determine the different sites for fistula and their success rate.

• Clarify the outcome of arteriovenous fistula according to gender and time of follow up.

• Determine the association between types of arterio-venous fistula and its outcome.

• Find the association between risk factors and chronic diseases and the outcome of AVF.

A prospective study has been carried out for data of patients referred to Cardiovascular and Thoracic Surgery Department at Hawler Teaching Hospital, EMC Cardiac Center and Rizgary Teaching Hospitals in Erbil city in Kurdistan Regional Government (KRG) of Iraq for permanent hemodialysis access from November 2020 to November 2022. These three hospitals serve a population of approximately 2,900,000 inhabitants of Erbil governorate, and neighboring villages of Dohuk, Sulaymaniyah and Kirkuk cities in addition to Mosul city, reaching up to 3,500,000 inhabitants.

The case notes and operating room records of all patients who have had arteriovenous fistula creation from November 2020 and November 2022 has been retrieved and analyzed for age, gender, race, indication for arteriovenous fistula, complications, outcomes, comorbidities and cause of end-stage renal disease. Three patients whose records were incomplete were excluded from the study. The data were analyzed using Statistical Package for the Social Sciences (SPSS) software version 26 and results were presented in graphs and tables with p-value taken as ≤ 0.05 as statistically significant. The early outcome will be taken as within 8 weeks of the arteriovenous fistula, and late outcome will be taken as more than 8 weeks.

• Outcomes which will be Measured:

• Maturity of the fistula; signified by significant palpable thrill and venous varicosities.

• Postoperative complications: hemorrhage, hematoma and aneurysm.

• Rates of wound infections postoperatively and with multiple uses in hemodialysis sessions before 8 weeks after maturation of the fistulae and after 8 weeks.

A prospective imaging protocol was used preoperatively to increase arteriovenous fistula success rate. This experience will be compared with that in patients in whom permanent hemodialysis access were created less than 8 weeks prior to their visit, before implementation of liberal preoperative doppler ultrasound scanning and venography. Demographic data will be compiled including; age, gender, race, indication for arteriovenous fistula, complications, comorbid conditions and cause of end-stage renal disease.

The unit of Cardiovascular & Thoracic Surgery has been performing arteriovenous fistula for hemodialysis, although the outcome of its creation in the centers has not been analyzed. This study seeks to audit the procedure at the department to evaluate the early and late outcomes with a view to identify areas requiring improvement.

Initially, these patients are sent for their first few sessions of hemodialysis with a double lumen prior to their referral to the Department of Cardiothoracic & Vascular Surgery in ECC Erbil Cardiac Center and Rizgary Teaching Hospitals, which both are situated in southeast and east of Erbil city, respectively. 

Preoperative evaluation included careful assessment of the vascular anatomy, the non-dominant upper extremity was preferred for creation of arteriovenous fistula site; however, the final decision was ultimately determined according to size and quality of the vessels intraoperatively. Arterial examination included pulse assessment, performance of Allen’s test, and bilateral upper extremity blood pressure measurements. Venous examination included inspection and palpation of the cephalic vein at the wrist and upper arm, and the basilic vein at the elbow, with a tourniquet in place. If an acceptable vein was apparent at the wrist that transmitted a percussed wave a distance up the forearm, a radio-cephalic fistula was planned.

If physical examination failed to disclose an adequate vessel or there was uncertainty regarding the quality or continuity of the vein for arteriovenous fistula (i.e., history of multiple venipunctures), patients underwent doppler ultrasound scanning, which was performed by a registered radiologist in an accredited and registered radiology center and/or clinic. Patients were examined while reclining, with the arm dependent. Warm ultrasound gel applied, and veins were insonated with a 5 or 7 MHz scanning probe. Doppler ultrasound scanning was initiated at the wrist before and proximal venous tourniquet occlusion at the mid-forearm. Veins were assessed for ease of compressibility, distensibility, diameter, thickness, continuity, and depth below the skin. The tourniquet was then moved to the arm, and the forearm veins were followed proximally. The acceptable threshold diameter for vein use was 2.5 cm or greater.

Measurements of vein diameter was recorded from the ultrasound scans at representative sites, including wrist, distal forearm, mid-forearm, proximal forearm, antecubital fossa, distal upper arm, mid-upper arm and proximal upper arm. Axillary and subclavian veins were assessed for patency. Brachial, radial and ulnar arteries were evaluated for calcification. Segmental pressure and velocity wave forms were obtained, diameter of radial artery at the wrist and brachial artery immediately above the antecubital fossa was also determined.

Venography was performed selectively if no suitable vein identified at doppler ultrasound scanning. Venography was also performed if the only suitable vein identified at doppler ultrasound scanning was upper basilic vein, to confirm that no usable forearm or upper arm cephalic vein had been overlooked. Unexplained edema of the upper extremity, presence of subcutaneous collateral veins across the shoulders and chest, or extensive history of central venous cannulation also mandated venography to exclude central vein stenosis or occlusion. A superficial vein in the hand or forearm was cannulated, contrast agent was injected, and, with sequential tourniquet placement, the venous circulation from the superficial veins to the superior vena cava was imaged, to assess diameter and continuity.

The choice of access configuration was made on the basis of results of clinical examination and imaging. Local or regional anesthetic techniques was selected on the basis of the site of the planned procedure and the preferences of the surgeon and patients. Most hemodialysis access procedures were followed up in the outpatient clinic within 7 to 10 days postoperatively, and then around 40 days until the fistula was significantly mature enough for cannulation for hemodialysis.

• Maturation of Vessel and its Failure:

Normally the fistula matures in 3 to 6 weeks and failure is detected before (early outcome) and after (late outcome) 8 weeks postoperatively by lacking significant thrill on palpation or mechanical sound on auscultation or no flow on doppler U/S. The early period after arteriovenous fistula creation is very important in determining the failure of the fistula. Failure is mostly due to thrombosis and lack of maturation exercise (as clenching and unclenching the fist) and to a lesser extend wound infection, these can be seen in early outcomes. As for late outcomes thrombosis and aneurysmal dilatation are the reasons why they may fail, due to low blood pressure and atherogenic factors during cannulation of the fistula.

Information regarding cannulation dates was obtained from 2 regional dialysis centers, one in Hawler Teaching Hospital Hemodialysis Center and one neighboring the West Emergency Hospital of Erbil. Each dialysis center has a database that records dates of dialysis sessions. Functional maturation is defined as time from the operative procedure to initiation of sustained hemodialysis (cannulated on 3 occasions) via the index access. 

• Surgical Technique:

The surgeries were performed by the author, as well as the supervisor who was assisted by the author and in vice versa as well. Each patient was seen in the clinic, where physical examination was performed, where the non-dominant upper extremity was chosen if available. During the examination arterial pulsation and venous distensibility were assessed and the site of arteriovenous fistula was chosen. The most distal usable site (excluding the snuff box) was chosen. All the procedures were carried out in the operating room under local anesthesia or regional anesthesia, using lidocaine infiltration of 1%. End of the cephalic vein to the side of the radial artery anastomosis was performed, and for selected number of patients in case of inadequate or not usable distal forearm a radio-cephalic fistula or brachial artery to transported basilic vein fistula will be done, using 5-0, 6-0 or 7-0 prolene suture material in continuous parachute technique anastomosis. Patients with inadequate veins because of recent thrombosis seen, were deferred and then evaluated after two weeks until the veins were distensible clinically before surgery. Equipment as handheld doppler ultrasound and color flow doppler ultrasound were used before and after arteriovenous fistula creation as well as a stethoscope for auscultating the turbulent flow by the fistula created.

• Arteriovenous Fistula Patency:

Interpretation of the doppler ultrasound of fistula is initially started by visualizing the flow of artery used in the fistula created and the venous flow as well, then the turbulence the artery made in the created fistula with its flow. Then the artery’s caliber proximally and distally to see if there is any sort of steal-syndrome, not to affect the hand. Indeed, patients with known diabetes showed smaller calibers in their arteries those were used in the fistula created, denoting various degrees of steal-syndrome that affected their hands in sense of ischemia as cold hand, small ulcerative lesions and poor vasculature of their hands, in addition to, insufficient high and lower arches of their hands. Furthermore, presence of atheroma and atheromatous changes in the arteries were evaluated for patency of the fistula. Detection of aneurysmal dilatation of the veins was looked for thoroughly not to end up with steal-syndrome. In some cases, where anastomosis was too small to feed the vein which ended up with insufficient flow to the vein appeared small in caliber only to result in no maturation of the fistula and failure. Finally, detection of subcutaneous edema, hematoma, seroma and presence of infection deep in the surgical site were done.

• Outcome Measures:

The primary end point was detection of turbulent flow to the vein that engorged the vein but not ended up with an aneurysmal dilatation by doppler ultrasound after 8 weeks not accompanied by extensive subcutaneous edema that was debilitating the patient’s life style with no upper limb ischemia as well. Palpable thrill and distal pulse of the used limb upon palpation on each patient’s visit to the outpatient clinic postoperatively.

• Data Collection:

The required information for this study was collected with a pre-designed questionnaire preoperatively and postoperatively as follows:

• Preoperatively; general information of the patients is recorded in the first part of the questionnaire. Information being (age, gender, race, cause of end stage kidney disease and primary vascular access for hemodialysis used).

• Postoperatively; clinical information of the patients, including; assessment of the upper limb, which artery and veins used for fistulae, complications (thrombosis, aneurysm, infection, hematoma and hemorrhage) and outcomes (successful and unsuccessful).

• Statistical Analyses:

The general information of the patients was presented in mean (SD) or number (%). The prevalence of clinical outcomes and patency are detrained in number and percentage. The comparison of patency prevalence and clinical outcomes between two types of techniques was examined in Pearson Chi-squared test. The significant level of difference was determined in a P-value of < 0.05. The data were analyzed by using Statistical Package for Social Sciences 26 (SPSS 26) for Windows operating system.

• Ethical Consideration:

The protocol of this study is presented to the Health Ethics Committee of the College of Medicine, Hawler Medical University. In this study, the confidentiality of the personal information of the patients is protected throughout the study steps. In addition, the patients who were asked had the option of rejection to participate the study.

85 patients were included in this study 39 (46%) of them were males and 46(54%) of them were females, their age ranged from 13 to 83 years with a mean of 54.76 ± 14.4 as shown in Figure 3. 

Figure 3: Ratio of male to female enrolled in this studyNearly 28% of the cases’ ages were in the 60-69 age group followed by those in the age group 50-59 years, the least age group enrolled in this study was the 80-90 age groups as shown in Figure 4. 

Figure 4: Distribution of patients according to age groups

Most of the functional AVF were in the 50-59 age group, on the other hand the highest failure rate of AVF was in the 60-69 age group and also the highest death occured in the 50-59 age group but there was no statistical significant association between these variables as shown in Figure 5. 

Figure 5: Association between age group and the outcome of AVF.

About half of cases were from Erbil city followed by those patients from other parts of Iraq especially Baghdad as shown in Figure 6.

Figure 6: Place of living of cases enrolled in this study.

The types of AVF were Lt. radio cephalic end-side in near one third of cases of cases (31.8%), followed by Lt. brachiocephalic end-side (27.1%), Rt. brachiocephalic median cubital, cephalic + basilic vein end-side were the least type done for AVF (1.2%) as shown in Figure 7. 

Figure 7: Distribution of cases of AVF according to its type

For the first type of AVF in the above figure, male cases were more than female cases (43.6% vs21.7%), while for the 2^nd type female cases were more than male cases (39.1% vs 12.8%) as shown in the Figure 8. 

Figure 1: Distribution of cases according to type of AVF and gender.

About 80% of cases were followed up in 2021 though out the whole year, only 20% of cases were followed up in 2022 and most of cases were followed up in the 1^st quarter of that year as shown in Table 2. 

Table 2: Date of follow up of cases according the quarter of years.

Upon observing the outcome of the procedure nearly three quarters of the cases were functional (75.3%), about 15% of cases were non-functional, and only about 10% of cases were deceased as shown in Figure 9. 

Figure 9: Distribution of cases according to the outcome of AVF.

There was no significant difference between both genders regarding the outcome of AVF procedure in this study as shown in Figure 10.

Figure 10: Distribution of cases regarding the outcome of AVF procedure and gender.

On studying the risk factors of the patients before AVF operation, hypertension was the main risk factor present in these patients, followed by Diabetes mellitus, ischemic heart disease constituted the least portion of these risk factors as shown in Figure 11.

Figure 11: Risk factors for the patients enrolled in this study

On comparying the statistical tests between the above risk factors and the outcome of the AVF operation, there was statistical significant association between these two variables, HTN had an impact to aid fistulae to mature and DM lead to failure of the fistulae created, by infection and small caliber arteries, according to this study as shown in Table 3

Table 3: Association between risk factors and the outcome of arterio-venous fistula

                *Fisher’s Exact Test

34 cases of AVF procedure outcome were from Erbil City, but at the same time the number of non-functional and deceased one were (9 and 6) respectivily, and there was no significant relation between the AVF procedure outcome and place of living of cases as shown in Figure 12.

Figure 12: Outcome of AVF procedure according to the place of living of cases.

With observing the time of follow up after the AVF procedure in weeks, we see that the highest time for follow up was in 40-51 weeks followed by those between 11-21 weeks, the least time for follow up was between 61 to 71 weeks, therefore we can say that only about 8 percent visited for follow up as early outcome as shown in Figure 13.

Figure 13: Time of following up in weeks after the AVF procedure.

Although most of the follow ups were done after 40 to 49 weeks from time of operation, followed by those which had follow up after 10 to 19 weeks, no statistically significant association was found between these two variables as shown in Table 4. 

Table 4: Times of follow up in weeks

Fischer’s Exact Test

All the complications found in those patients whose AVF was failed after the procedure except one case who developed infection after the procedure but later on resolved with a functional AVF, Thrombosis was the main cause of failure in this study followed by infection, technical failure came in the 3^rd place, bleeding was the least complication happened as a complication of AVF as shown in Figure 14. 

Figure 14: Time of follow up in weeks after the AVF procedure.

In this study male to female ratio was 0.85:1, although there was no statistical significant association between gender and the functional outcome of AVF, in some studies female gender was found to be associated with non-maturation functional AVF, while the history of kidney transplant, using calcium channel blockers and low hemoglobin level all of these factors were associated with successful functional maturation [27] In the United States of America yearly near 500,000 people develop chronic kidney diseases which eventually lead to renal failure or kidney replacement therapy about 45% were females, this gender has different level of renal function for the same value of serum creatinine, they lose kidney function over a prolonged period of time or more slowly than males, females are less likely to initiate dialysis with AVF in place, also they were more prone to access failure as well as for complications such as steal syndrome [28]. 

Regarding the age distribution in this study, approximately more than half of the cases were between 50 and 70 years of age, but at the same time no statistically significant association was found between the age groups and the functionality of AVF, this outcome was in line with a study of (meta-analysis) which was done on the researches between 1^st January 2000 to 31 Dec 2005 which concentrated on the age groups (<65, 65-79, >80) depending on primary and secondary functional patency of AVF found that age has no effect on the usability, primary and secondary patency of radio-cephalic and brachiocephalic AVF, therefore even patients with >80 years old age can be suitable for surgical placement [29]. 

In a study done on 245 patients which were followed for 4 years, this study was published in PubMed which followed the patients up with AVF for 4 years showed that patency rate will decrease year after year by (79.5% to 48%) also it showed that it was not the time of follow up but also other factors played role such as patients undergoing dialysis have better fistula patency, also this study showed that the patency will increase with dialysis, some of the patients had risk factors such as hypertension and diabetes mellitus, but these risk factor had no effect on the patency or failure of the AVF according to the outcome of the above study [30]. 

In this study left radio-cephalic end-side AVF came in the first place regarding the number of procedures which have been done, followed by Lt. brachiocephalic end-side AVF, although there was no statistically significant association with the outcome of AVF whether to be functional or not, this result was inconsistent with a study that performed for 213 patients in which primary functional patency was followed after one year the result showed increasing brachiocephalic AVF creation reduced the reliance on radio-cephalic AVFs which resulted in increased primary functional patency at 1 year [31].  Other studies showed that there is a complex interaction of factors that affect the outcome of AVFs therefore careful selection of the site of procedure and the best technique, treatments and follow up protocols all these factors have effects on the outcome of the procedure [32].  In one review article study in PubMed and related bibliographic which focused on primary failure rate in addition to primary patency rates after 1 and 2 years respectively, found that proximal AVF presented low to moderate primary failure and primary and secondary patency rates with acceptable complications [33]. 

As hypertension came in the first place as a risk factor for AVF in this study followed by DM and Chronic kidney disease, there was a statistically significant association found between hypertension and diabetes mellitus and the outcome of AVF, from 68 hypertensive patients 58 of them had functional AVF, and this may be due to the high pressure in the vessels which usually associated with high patency rate and eventually functional AVF, but out of 31 diabetic patient only 15 of them had functional AVFs, and this is due the reason why DM usually is associated with increased risk of infection and eventually failure of the AVF.

Diabetes mellitus came in the 2^nd place as a risk factor for the outcome of AVFs, this was in line with a study done in Geneva University Hospital on 119 patients with early failure AVFs, these patients underwent creation of 148 native AVFs in the forearm and upper arm, the result showed that failure mostly happened in the forearm, women and those with diabetes mellitus, and the results was statistically significant [34]. 

Ischemic heart disease in this study also had a role as a predictive variable for the outcome and failure of many cases of the AVFs, but when searching the literatures for this parameter, there was no specific research mentioning IHD as a predictive value for the outcome of AVFs, however they were explaining thrombosis which is also one of the end results of IHD, in a study which evaluates the risk factors for AVFs in those patients undergoing hemodialysis, 36 patients were included, in which doppler ultrasonography was done in three situation one before AVFs the second after that and the last one when the patient develops AVF failure, many parameters were studied, for instance; biochemical, hematological and the coagulation system, it was found that about one third of the patients (10 patients ) developed thrombosis between day 1 and day 73 after performing AVFs, also it was detected that female gender, thrills, quality of vein, peak systolic and end-diastolic velocity of the radial artery in snuffbox region and the cephalic vein diameter in the Brescia–Cimino region all of these factors were associated with thrombosis with statistically significant association which was in line with the outcome of this study[35]. 

In this study only 15.3% developed complications which eventually lead to failure this was inconsistent with a study done on 273 patients of them 184 developed complication (67.6%), these complications occur more in the left side and the rate of these complications increased with age (P<0.05) [36]. 

Regarding the complications which were responsible for failures in this study, thrombosis was the 1^st cause of these failures followed by infection, this was in line with a study done in Christian Medical College and Hospital in which thrombosis accounts for 18.6% of all cases as late complication [37]  In addition to, a review study done in 2005 found that thrombosis was the 1^st major cause of AVF failure and this was usually due to technical errors like twisting of the vessels which lead to turbulence in flow of blood and eventually lead to formation of thrombosis[38]. This study also was in line with our current study in which technical factor had a role in the outcome of functionality for AVFs.

Infection came in the 2^nd place as a complication for AVF, it’s said that usually infection accounts for 20% of all complications of AVF [39]. Cellulitis creates most of these infections which appears as a local erythema and edema and its treatment is not difficult, other more difficult types of infections are associated with anatomical abnormalities such as aneurysms, hematomas or abscesses which usually can be treated surgically with drainage [39]. The output for infection as a complication in this study was in line with a study done in India in which also infection was the 2^nd cause of complication and failure of AVF and accounted for 3.4% of all complication [37]. 

Technical factor was also one of the factors that was behind failure of a few cases in this study although the researcher didn’t find any study with this factor as a prediction for failure of AVF. On the other hand, many studies referred to stenosis as an indicating factor that was usually blamed as a causative factor of failure of AVF. Therefore, in a study which have been done on 155 patients, 52% of them showed subsequent stenosis therefore percutaneous transluminal angioplasty was indicated, these patients were followed for at least one year (2 or 3 years), and primary patency was less than secondary patency rate [40]. 

LIMITATION OF THE STUDY:

• Sample size was too small therefore; it was not possible to find significant association between the variables except for hypertension and diabetes mellitus.

• The complications were found only in those who had failure in the outcome of AVF therefore not studied in full functional AVF or they don’t develop complications.

The authors declare that they have no conflict of interest

No funding sources

The study was approved by the HMU – College of Medicine, Erbil, Iraq

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