Fistula Stenosis Research Articles

Detection of Abnormal Wall Shear Stress and Oscillatory Shear Index via Ultrasound Vector Flow Imaging as Possible Indicators for Arteriovenous Fistula Stenosis in Hemodialysis.

The arteriovenous fistula (AVF) is an essential vascular access for hemodialysis patients. AVF stenosis may occur at sites with abnormal wall shear stress (WSS) and oscillatory shear index (OSI), which are caused by the complex flow in the AVF. At present, an effective method for rapid determination of the WSS and OSI of the AVF is lacking. The objective of this study was to apply an ultrasound-based method for determination of the WSS and OSI to explore the risk sites of the AVF. In this study, the ultrasound vector flow imaging technique V Flow was applied to measure the WSS and OSI at four different regions of the AVF to detect and analyze the risk sites: (i) anastomosis region, (ii) curved region, (iii) proximal vein and (iv) distal vein. Twenty-one patients were included in this study. The relative residence time was calculated based on the measured WSS and OSI. The curved region had the lowest WSS; the anastomosis region had a significantly higher OSI (p < 0.05) compared with the venous regions, and the curved region had a significantly higher RRT (p < 0.05) compared with the proximal vein region. V Flow is a feasible tool for studying WSS variations in AVF. The possible risk site in the AVF may be located in the anastomosis and curved regions, where the latter could present a higher risk for AVF stenosis.

Tensor decomposition and machine learning for the detection of arteriovenous fistula stenosis: An initial evaluation.

Duplex ultrasound (DUS) is the most widely used method for surveillance of arteriovenous fistulae (AVF) created for dialysis. However, DUS is poor at predicting AVF outcomes and there is a need for novel methods that can more accurately evaluate multidirectional AVF flow. In this study we aimed to evaluate the feasibility of detecting AVF stenosis using a novel method combining tensor-decomposition of B-mode ultrasound cine loops (videos) of blood flow and machine learning classification. Classification of stenosis was based on the DUS assessment of blood flow volume, vessel diameter size, flow velocity, and spectral waveform features. Real-time B-mode cine loops of the arterial inflow, anastomosis, and venous outflow of the AVFs were analysed. Tensor decompositions were computed from both the 'full-frame' (whole-image) videos and 'cropped' videos (to include areas of blood flow only). The resulting output were labelled for the presence of stenosis, as per the DUS findings, and used as a set of features for classification using a Long Short-Term Memory (LSTM) neural network. A total of 61 out of 66 available videos were used for analysis. The whole-image classifier failed to beat random guessing, achieving a mean area under the receiver operating characteristics (AUROC) value of 0.49 (CI 0.48 to 0.50). In contrast, the 'cropped' video classifier performed better with a mean AUROC of 0.82 (CI 0.66 to 0.96), showing promising predictive power despite the small size of the dataset. The combined application of tensor decomposition and machine learning are promising for the detection of AVF stenosis and warrant further investigation.

Factors affecting the primary patency of native arteriovenous fistulas after ultrasound-guided percutaneous transluminal angioplasty

Objective By analyzing the clinical history, laboratory test indexes, and intraoperative ultrasound imaging data of patients receiving ultrasound-guided percutaneous transluminal angioplasty (UG-PTA) for the first time, the application value of UG-PTA in the treatment of peripheral stenosis of autogenous arteriovenous fistula (AVF) and the related factors affecting postoperative patency were investigated. Methods A total of 381 patients with dysfunction of radio-cephalic AVF were treated with UG-PTA from June 2017 to September 2019. According to the inclusion and exclusion criteria, 199 patients were included in this study. Baseline characteristics of patients, including demographic, clinical, and laboratory data, were collected. Kaplan–Meier’s survival curve was used to demonstrate the cumulative primary patency rate of UG-PTA. Univariate and multivariate Cox regression analysis was performed on clinical, anatomic, biochemical, and medication variables to identify the predictors of postintervention primary patency. Results The early technical success rate of UG-PTA was 98.4% (375/381). One hundred and ninety-nine patients, with an average age of 52.9 years, were analyzed, 97 of whom were males (48.7%). The median follow-up duration was 21 months. No major complication was observed. Postintervention primary patency rates were 87.7%, 75.8%, and 60.0% at 6, 12, and 24 months, respectively. A previously failed AVF (HR, 1.935, 95% CI 1.071–3.494; p = .029) and an increased level of parathyroid hormone (HR per 100 pg/mL increase, 1.105; 95% CI 1.014–1.203; p = .004) were identified as independent negative predictors of primary patency of UG-PTA. Conclusions UG-PTA is a safe and effective method for the treatment of peripheral stenosis of AVF. Previously failed AVF and elevated parathyroid hormone levels are associated with lower primary patency rate.

Comparison of drug-coated balloon angioplasty versus common balloon angioplasty for arteriovenous fistula stenosis: A systematic review and meta-analysis.

Drug-coated balloons (DCBs) have been used in dialysis patients with arteriovenous fistula (AVF) stenosis, but whether DCBs have advantages over ordinary balloons is still controversial. A meta-analysis was designed to investigate the safety and efficacy of DCBs and common balloons (CBs) in the treatment of AVF stenosis. We searched the PubMed, EMBASE, and China National Knowledge Internet (CNKI) databases for randomized controlled trials that evaluated the comparison of DCB angioplasty versus CB angioplasty for AVF stenosis in dialysis patients and reported at least one outcome of interest. The results showed that the DCB group had a higher first-stage patency rate of the target lesion 6 months [odds ratio, OR = 2.31, 95% confidence interval, CI: (1.69, 3.15), p < .01] and 12 months [OR = 2.09, 95% CI: (1.50, 2.91), p < .01] after surgery. There was no statistically significant difference in all-cause mortality between the two groups at 6 months [OR = 0.85, 95% CI: (0.47, 1.52), p = .58] and 12 months [OR = 0.99, 95% CI: (0.60, 1.64), p = .97]. Compared with CB, DCBs as a new endovascular treatment for AVF stenosis have a higher primary patency rate of target lesions and can delay the occurrence of restenosis. There is no evidence that DCB can increase the mortality of patients.

The Role of Drug-Coated Balloon in Haemodialysis Arteriovenous Fistula Stenosis Management.

Arteriovenous fistula (AVF) stenosis is a common problem leading to dialysis access dysfunction. The conventional balloon (CB) is the most commonly used device during angioplasty but suffers from poor durability of results due to neointimal hyperplasia-mediated recurrence. The drug-coated balloon (DCB) is an adjunct to balloon angioplasty that reduces neointimal hyperplasia, thereby improving post-angioplasty patency. Despite the heterogeneity of DCB clinical trials to date, the evidence suggests that DCBs of different brands are not necessarily equal, and that patient selection, adequate lesion preparation and proper DCB procedural technique are important to realize the benefit of DCB angioplasty.

Polymer-coated paclitaxel-eluting stents for the treatment of stenosed native arteriovenous fistulas: Long-term results from the ELUDIA study.

Percutaneous transluminal angioplasty is the preferred treatment of stenosed failing arteriovenous fistulas (AVF) but is hampered by increasing rates of vascular restenosis because of development of myointimal hyperplasia. This multicenter observational study of polymer-coated low-dose paclitaxel-eluting stents (ELUvia stents by Boston Scientific) in stenosed AVF undergoing hemoDIAlysis (ELUDIA) was jointly conducted in three tertiary hospitals from Greece and Singapore. Failure of AVF was defined according to K-DOQI criteria and significant fistula stenosis (>50%DS by visual estimate) was determined with subtraction angiography. Patients were considered for ELUVIA stent insertion based on significant elastic recoil following balloon angioplasty for the treatment of a single vascular stenosis within a native AVF. The primary outcome measure was sustained long-term patency of the treated lesion/fistula circuit defined as successful stent placement with resumption of uninterrupted hemodialysis and without significant vascular restenosis (50%DS threshold) or other secondary interventions during follow-up. Some 23 patients received the ELUVIA paclitaxel-eluting stent (eight radiocephalic, 12 brachiocephalic, and three transposed brachiobasilic native AVFs). Mean AVF age at the time of failure was 33.9 ± 20.4 months. Treated lesions included 12 stenoses at the juxta-anastomotic segment, nine at the outflow veins, and two cephalic arch lesions with a mean diameter stenosis of 86 ± 8%. Median stent diameter and length used were 7 mm and 40 mm, respectively. After a median follow-up period of 20 months, some 18 stents out of 23 cases remained patent (cumulative rate 78.3%) without any clinical or imaging evidence of recurrent stenosis. Estimated primary patency of the ELUVIA stents was 80.6% and of the corresponding fistula circuit 65.1% at 2 years by Kaplan-Meier methods. This observational study has shown promising long-term results of polymer-coated paclitaxel-eluting stents for the treatment of failing arteriovenous fistulas. Large-scale controlled studies are necessary.

Contrast Venography Versus Intravenous Ultrasound in Hemodialysis Arteriovenous Access Dysfunction

Contrast Venography Versus Intravenous Ultrasound in Hemodialysis Arteriovenous Access Dysfunction

Cost-Effectiveness of Drug-Coated Balloon Angioplasty versus Plain Old Balloon Angioplasty for Arteriovenous Fistula Stenosis.

To compare the cost-effectiveness of drug-coated balloon angioplasty (DCB) versus plain old balloon angioplasty (POBA) for treatment of arteriovenous fistula (AVF) stenosis. A Markov model was created to compare DCB versus POBA for AVF stenosis over a 2-year time horizon from a United States payer's perspective. Probabilities related to complications, restenosis, retreatment, and all-cause mortality were obtained from published literature. Costs were calculated using Medicare reimbursement rates and data from published cost analyses, inflation-adjusted to 2021. Health outcomes were measured with quality-adjusted life years (QALY). Probabilistic and deterministic sensitivity analyses were performed with a willingness-to-pay threshold of $100,000/QALY. Base case calculation showed better quality-of-life outcomes but increased cost with POBA compared to DCB, with an incremental cost-effectiveness ratio of $27,413/QALY, making POBA the more cost-effective strategy in the base case model. Sensitivity analyses showed that DCB becomes cost-effective if the 24-month mortality rate after DCB is no more than 3.4% higher than that after POBA. In secondary analyses where mortality rates were equalized, DCB was more cost-effective than POBA until its additional cost reached more than $4213 per intervention. When modeled from a payer's perspective over 2years, the cost utility of DCB versus POBA varies with mortality outcomes. POBA is cost-effective if 2-year all-cause mortality after DCB is greater than 3.4% higher than after POBA. If 2-year mortality after DCB is less than 3.4% higher than after POBA, DCB is cost-effective until its additional cost per procedure exceeds $4213 more than POBA. HISTORICALLY CONTROLLED STUDY.: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Prospective, randomized, multicenter clinical study comparing a self-expanding covered stent to percutaneous transluminal angioplasty for treatment of upper extremity hemodialysis arteriovenous fistula stenosis

Use of a covered stent after percutaneous transluminal angioplasty (PTA) was compared to PTA alone for treatment of upper extremity hemodialysis patients with arteriovenous fistula (AVF) stenoses. Patients with AVF stenosis of 50% or more and evidence of AVF dysfunction underwent treatment with PTA followed by randomization of 142 patients to include a covered stent or 138 patients with PTA alone. Primary outcomes were 30-day safety, powered for noninferiority, and six-month target lesion primary patency (TLPP), powered to test whether TLPP after covered-stent placement was superior to PTA alone. Twelve-month TLPP and six-month access circuit primary patency (ACPP) were also hypothesis tested while additional clinical outcomes were observed through two years. Safety was significantly non-inferior while six- and 12-month TLPP were each superior for the covered stent group compared to PTA alone (six months: 78.7% versus 55.8%; 12 months: 47.9% versus 21.2%, respectively). ACPP was not statistically different between groups at six-months. Observed differences at 24 months favored the covered-stent group: 28.4% better TLPP, fewer target-lesion reinterventions (1.6 ± 1.6 versus 2.8 ± 2.0), and a longer mean time between target-lesion reinterventions (380.4 ± 249.5 versus 217.6 ± 158.4 days). Thus, our multicenter, prospective, randomized study of a covered stent used to treat AVF stenosis demonstrated noninferior safety with better TLPP and fewer target-lesion reinterventions than PTA alone through 24 months.

THROMBECTOMY IN PATIENTS WITH THROMBOSIS OF ARTERIO-VENOUS FISTULA: CASE SERIES

Introduction. Thanks to the use of renal replacement therapy at the current stage of medical development, complete medical and social rehabilitation of patients with end-stage chronic renal failure is possible. The key to effective programmed hemodialysis is the formation of adequate permanent vascular access. Ensuring the optimal use and functioning of permanent vascular access is a multidisciplinary challenge. Currently, none of the known options for permanent vascular access is ideal, but a native arteriovenous fistula meets the requirements to a greater extent. Complications from vascular access for hemodialysis remain relevant for their solution today. The most common complication of vascular access is thrombosis of an arteriovenous fistula. For patients with chronic renal failure who are on programmed hemodialysis, thrombosis of vascular access is a great danger, which ultimately can lead to the impossibility of further hemodialysis and is the main reason for hospitalization and high mortality of this contingent of patients and needs an urgent solution.&#x0D; Clinical cases. 17 patients underwent thrombectomy from the subcutaneous "fistula". vein of the upper extremity. The age of the patients was 49.0 (44.0-61.0) years. By gender, the studied patients were distributed as follows: women - 9 (53%), men - 8 (47%). Among 17 (100%) operated patients, 12 (71%) had late thrombosis, 5 (29%) had early thrombosis of arteriovenous fistula,. Of 5 (100%) patients with early thrombosis of arteriovenous fistula, thrombectomy was effective in 2 (40%) patients (p=0.038). On the other hand, in 12 (100%) patients with late thrombosis of arteriovenous fistula, thrombectomy was successful in only 4 (33%) cases.&#x0D; Discussion. The cause of thrombosis of any vascular anastomosis is primarily hyperplasia of the neointima due to the proliferation of smooth muscle cells of the vascular wall. This circumstance leads to the formation of stenosis of the anastomosis, and as soon as the stenosis values become hemodynamically significant (&gt; 50% of the lumen of the vessel), the risk of developing thrombosis increases by more than 50%. Thrombectomy alone is insufficient to restore patency of the permanent vascular access in the long term, as flow-limiting stenosis is present in more than 85% of cases.&#x0D; Conclusions. Neointimal hyperplasia is the main cause of progressive stenosis of arteriovenous fistula and subsequent thrombosis. Thrombectomy is indicated for thrombosis of arteriovenous fistula in the early postoperative period (up to 30 days after arteriovenous fistula formation). Thrombectomy alone is not enough to restore the patency of the permanent vascular access in the long term, and the final treatment requires its reconstruction at an early stage or the creation of a new arteriovenous fistula.

Identification and Validation of Hub Genes in the Stenosis of Arteriovenous Fistula.

Arteriovenous fistula (AVF) is the most widely used hemodialysis vascular access in China. However, stenosis of the AVF limits its use. The mechanism of AVF stenosis is currently unknown. Therefore, the purpose of our study was to explore the mechanisms of AVF stenosis. In this study, we identified the differentially expressed genes (DEGs) based on the Gene Expression Omnibus (GEO) dataset (GSE39488) between venous segments of AVF and normal veins. A protein-protein interaction (PPI) network was constructed to identify hub genes of AVF stenosis. Finally, six hub genes (FOS, NR4A2, EGR2, CXCR4, ATF3, and SERPINE1) were found. Combined with the results of the PPI network analysis and literature search, FOS and NR4A2 were selected as the target genes for further investigation. We validated the bioinformatic results via reverse transcription PCR (RT-PCR) and Western blot analyses on human and rat samples. The expression levels of the mRNA and protein of FOS and NR4A2 were upregulated in both human and rat samples. In summary, we found that FOS may play an important role in AVF stenosis, which could be a potential therapeutic target of AVF stenosis.

Retracted: Risk Factors of Arteriovenous Fistula Stenosis of Patients with Maintenance Hemodialysis.

[This retracts the article DOI: 10.1155/2022/2968122.].

Retracted: Role and Mechanism of Epithelial-Mesenchymal Transition Mediated by Inflammatory Stress-Induced TGF-β1 in Promoting Arteriovenous Fistula Stenosis.

[This retracts the article DOI: 10.1155/2022/9454843.].

A deep learning algorithm to quantify AVF stenosis and predict 6-month primary patency: a pilot study.

A deep convolutional neural network (DCNN) model that predicts the degree of arteriovenous fistula (AVF) stenosis and 6-month primary patency (PP) based on AVF shunt sounds was developed, and was compared with various machine learning (ML) models trained on patients' clinical data. Forty dysfunctional AVF patients were recruited prospectively, and AVF shunt sounds were recorded before and after percutaneous transluminal angioplasty using a wireless stethoscope. The audio files were converted to melspectrograms to predict the degree of AVF stenosis and 6-month PP. The diagnostic performance of the melspectrogram-based DCNN model (ResNet50) was compared with that of other ML models [i.e. logistic regression (LR), decision tree (DT) and support vector machine (SVM)], as well as the DCNN model (ResNet50) trained on patients' clinical data. Melspectrograms qualitatively reflected the degree of AVF stenosis by exhibiting a greater amplitude at mid-to-high frequency in the systolic phase with a more severe degree of stenosis, corresponding to a high-pitched bruit. The proposed melspectrogram-based DCNN model successfully predicted the degree of AVF stenosis. In predicting the 6-month PP, the area under the receiver operating characteristic curve of the melspectrogram-based DCNN model (ResNet50) (≥0.870) outperformed that of various ML models based on clinical data (LR, 0.783; DT, 0.766; SVM, 0.733) and that of the spiral-matrix DCNN model (0.828). The proposed melspectrogram-based DCNN model successfully predicted the degree of AVF stenosis and outperformed ML-based clinical models in predicting 6-month PP.

Comparison of percutaneous transluminal angioplasty and surgical revision after intraoperative dilatation with biliary tract probes for arteriovenous fistula stenosis at juxta-anastomosis.

Percutaneous transluminal angioplasty (PTA) is widely used for stenosis of vascular access (VA) for hemodialysis. We aimed to evaluate the effectiveness of both PTA and surgical revision after intraoperative dilatation with biliary tract probes for juxta-anastomotic stenosis in autogenous radiocephalic arteriovenous fistulas (RCAVFs). We performed a retrospective analysis of PTA and surgical revision after intraoperative dilatation with biliary tract probes; these were the first interventions after RCAVF establishment in 112 patients with juxta-anastomotic stenosis. Anatomical (number of stenoses) and clinical variables (age and gender of the patient, time of hemodialysis, AVF age, presence of diabetes mellitus, and cause of end-stage renal disease) were reviewed. Technical success, clinical success, and post-intervention primary patency were evaluated. Our study enrolled 35 patients in the PTA group and 77 patients in the surgical revision group. Clinical and technical success rates of both groups were 100%. There were no complications, such as bleeding or hematomas. Using the Kaplan-Meier method, the post-intervention primary patency rates at 3, 6, 9, 12, 18, and 24months in the PTA group were 100%, 94.28%, 77.1%, 60%, 54.29%, and 45.71%, respectively, and those in the surgical revision group were 100%, 94.81%, 92.2%, 90.91%, 81.82%, and 76.62%, respectively. The post-intervention primary patency rates at 9-24months in the surgical revision group were significantly higher than those in the PTA group (χ2 = 19.04, p < 0.0001). The post-intervention long-term primary patency rate of surgical revision after intraoperative dilatation with biliary tract probes is higher than that of PTA for the first intervention of patients with juxta-anastomotic stenosis in RCAVFs. The surgical revision method is safe and effective, especially in hospitals that have not yet carried out PTA.

Hyperglycemia Induces Endothelial Dysfunction through Hedgehog Signaling-Mediated TNF-α Production

Abstract: When patients with diabetic factors undergo hemodialysis with an arteriovenous fistula (AVF), the fistula is prone to stenosis with unclear mechanism. As a dynamic barrier between the blood and the vessel wall, the endothelium is easily damaged by molecules in the blood, and the mechanism between its dysfunction and the pathogenesis of AVF is still unclear. In this study, we aimed to investigate the mechanism of endothelial dysfunction, and the interventions of endothelial function to rescue of AVF stenosis. We investigated the release of inflammatory cytokine TNF-α from endothelial cells during AVF stenosis in Diabetes Mellitus, the mechanism of endothelial dysfunction, and the improvement of endothelial cell function to rescue of AVF stenosis after the implementation of interventions in clinical collected data, animal models, and cell-based studies. Our study finds high glucose stimulation could induce inflammatory cytokine TNF-α overproduction and dysfunction of endothelial cells. SMO expression was upregulated in high glucose stimulated endothelial cells, indicating activation of hedgehog signaling. Inhibition of SMO expression either by genetically knockdown or with its inhibitor Cyclopamine (Cyc) efficiently reduced the release of TNF-α and partially reverted the endothelial dysfunction in vitro and in vivo. GLI1 was further confirmed to be a downstream effector of SMO to induce the expression of TNF-α, and its inhibitor could block this effect. This study provides a new perspective that SMO-GLI1 axis as a promising therapeutic target for reducing the release of inflammatory cytokine TNF-α and alleviating endothelial cell dysfunction to prevent AVF stenosis in diabetic patients. Keywords: arteriovenous fistula stenosis; endothelial cell dysfunction; hedgehog signaling pathway; high glucose; inflammatory cytokine. Disclosures: No relevant conflicts of interest to declare. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Risk Factors of Arteriovenous Fistula Stenosis of Patients with Maintenance Hemodialysis.

To investigate the risk factors of arteriovenous fistula stenosis in maintenance hemodialysis patients. A total of 80 patients with maintenance hemodialysis in our hospital from January 2017 to January 2022 were included. According to the stenosis degree of the arteriovenous fistula, patients were divided into a stenosis group (n = 35) and an unobstructed group (n = 45). Laboratory examination data, such as the demographic characteristics of patients, past medical history, the use of traditional Chinese medicine (TCM), the TCM for improving blood circulation to promote blood circulation and remove blood stasis, and cellular immune function, were collected. Multivariate Logistic regression analysis was used to analyze the influencing factors. There was no significant difference in the age, sexuality, body mass index, proportion of patients with coronary heart disease, cephalic vein diameter, radial artery diameter, albumin, fibrinogen, and blood calcium levels between the two groups (P > 0.05). Compared with the unobstructed group, the stenosis group had higher rates of diabetes and hypertension as well as significantly higher levels of platelets, parathyroid hormone, and D-dimer (P < 0.05). The proportion of TCM application in the stenosis group was 28.6% (10/35), which was significantly lower than that in the unobstructed group 57.8% (26/45). The difference was statistically significant (χ 2 = 6.785, P=0.009). The levels of CD3+ (37.5 ± 5.1% vs. 42.0 ± 4.8%), CD4+ (35.7 ± 3.2% vs. 39.6 ± 3.1%) and CD4+/CD8+ (1.4 ± 0.3 vs. 2.4 ± 1.0) in the stenosis group were significantly lower, while CD8+ level was significantly higher (26.8 ± 5.1% vs. 18.5 ± 6.2%) than that in the unobstructed group (P < 0.001). Logistic regression analysis indicated that the usage of TCM was an independent risk factor for arteriovenous fistula stenosis after adjustment for other factors (odds ratio [OR] 0.302; 95% confidence interval [95% CI] 0.100-0.896; P=0.039). Less use of traditional Chinese medicine for activating blood circulation and removing blood stasis and poor cellular immune function are important factors affecting the function of the arteriovenous fistula in patients with maintenance hemodialysis, which is worthy of clinical attention.

Comparing non-invasive diagnostic methods for arteriovenous fistula stenosis: a prospective study.

International guidelines recommend screening for arteriovenous fistula (AVF) stenosis using various non-invasive methods. We evaluate different non-invasive AVF flow measurements for detecting AVF stenosis. Twenty-three haemodialysis patients with suspected AVF stenosis are enrolled based on abnormal physical signs or high venous pressure during dialysis. Ultrasound dilution, urea dilution, Doppler ultrasonography, and fistulography are performed on all patients. The accuracy of three non-invasive methods is compared. Fistulography reveals AVF stenosis in 18 patients, 12 of whom have severe stenosis (greater than 50% stenosis in diameter). Concerning the location of the stenosis lesions, eight are at the inflow site, six at the outflow site, and four on both sites. Receiver operating characteristic curve analysis shows that Doppler ultrasonography has a high discriminative ability and the averaged areas under the curves are 0.933 (95% confidence interval [CI]; 0.81 to 0.99) for stenosis and 0.929 (95% CI 0.82-0.99) for severe stenosis. The sensitivity of each method for the prediction of access stenosis using ultrasound dilution, urea dilution, and Doppler ultrasonography is 73%, 73%, and 80%, respectively. The respective specificity of each method is 40%, 80%, and 100%, respectively. Physical examination (PE) shows an 80% sensitivity and 80% specificity in the detection of AVF stenosis. The combination of Doppler ultrasound with PE produces the highest sensitivity (93%) for detecting AVF stenosis. Doppler ultrasound combined with physical examination is more accurate than other non-invasive methods for detecting AVF stenosis.

Pentoxifylline decreases the activity of the nucleotide-binding oligomerization domain-like receptor protein 3 pathway: potential role for preventing arteriovenous fistula stenosis.

This study aimed to determine the effect of pentoxifylline (PTX) on the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome pathway and its role in preventing arteriovenous fistula (AVF) failure. Vein samples were collected from AVF failure patients and from patients who underwent surgical AVF as a control. The expressions of CD34 and NLRP3 in AVF tissues were detected by immunohistochemistry and Western blotting. Arteriovenous fistula rat models were established by the end-to-end anastomosis of the common carotid artery and external jugular vein. The AVF models were divided into the following groups: AVF, AVF + PTX, AVF + uraemia and AVF + uraemia + PTX. Six weeks after surgery, the AVF tissues in each group were collected to detect the expressions of CD34, NLRP3, caspase-1 and interleukin (IL)-1β by immunohistochemistry, Western blotting and real-time polymerase chain reaction. The expressions of NLRP3 and CD34 in human AVF failure tissues were significantly higher than those in normal veins (p < 0.001), indicating that NLRP3 was upregulated in patients with AVF failure. In our animal study, the veins in the AVF + uraemia group exhibited heavy hyperplasia, and the boundary between the media and the adventitia was not clear. However, PTX alleviated this hyperplasia. Compared with the AVF models, the AVF + uraemia models had much higher expressions of NLRP3, caspase-1, IL-1β and CD34 (p < 0.001). However, PTX had the opposite effect against uraemia on the NLRP3 inflammasome pathway at both the gene and protein levels. Our findings provide new insights that show that PTX can decrease the activity of the NLRP3 inflammasome pathway in AVF models. Pentoxifylline has the potential as a drug for preventing intimal hyperplasia and AVF failure.

S3617 Gastrocolic Fistula After Roux-en-Y Gastric Bypass: A Case Report

Introduction: Gastric Fistula is a well-recognized complication after Roux-en-Y gastric bypass (RYGB). We present a rare case of gastro-colic fistula that occurred many years following a RYGB. Case Description/Methods: Our patient is a 68-year-old female nursing home resident with a past medical history of hypertension, diabetes, stroke, chronic ventilator-dependent respiratory failure and retrocolic RYGB surgery in 2001 who presented with dark maroon stool. The patient’s vitals were stable, abdominal exam was benign, and she had a gastrostomy tube in place (remnant stomach). Laboratory workup showed a Hgb of 6.4 mg /dl. Upper endoscopy showed ulceration and stenosis of gastro-jeujenostomy and gastro colic fistula. The fistula was intubated and showed feculent material from the transverse colon(Figure A,B). The biopsies of the ulcers revealed chronic inflammation. Computed tomography (CT) imaging with oral and IV contrast showed contrast filling in transverse colon and changes consistent with gastro colic fistula(Figure C,D). General surgery and bariatric surgery were consulted. However, she was not a candidate for surgical intervention due to her overall condition. She was discharged to a nursing home after management with a proton pump inhibitor (PPI) along with a blood transfusion. Discussion: Fistulous complications occur in up to 1- 6% of patients who undergo RYGB surgeries. This is historically related to incomplete division of gastric tissue upon creation of gastric pouch. However, with new stapler technology, the staple line is completely divided and the chances of fitulous complications are signficantly decreased. Gastro-jeujenal anastomosis ulcer, leaks, and chronic infection might be contributing to contemporary fistulas. Like ulcers, most gastro gastric fistulas present with epigastric abdominal pain, oral intolerance, failure to thrive and/or bleeding. The patient was not a candidate for surgery due to her overall medical condition. Had the patient been a surgical candidate, exploratory laparoscopy with en-bloc resection of the fistula and reconstruction would have been the definitive surgical treatment for her gastro colic fistula. It is strongly recommended that clinicians take a multi-disciplinary approach to this rare, but critical complication of bariatric surgery to ensure overall patient health optimization.Figure 1.: (A) Gastric pouch to transverse colon fistula, (B) Contrast seen in descending colon, (C) Gastric pouch to transverse colon fistula, (D) Transverse colon visualized through the fistulous tract.