How should a fluid collection near a dialysis access be managed, comparing an arteriovenous fistula (AVF) versus an arteriovenous graft (AVG), and what is the appropriate duration of intravenous antibiotics if the AVG is retained versus removed?

Management of Fluid Collections Near Dialysis Access: AVF vs AVG

Immediate Assessment and Diagnosis

For any fluid collection near a dialysis access, obtain blood cultures and aspirate/drain the collection for Gram stain and culture before initiating antibiotics, then start broad-spectrum empiric antibiotics immediately and refer urgently to a vascular surgeon. 1

Key Diagnostic Steps

• Physical examination remains the primary diagnostic tool for assessing infection, looking specifically for erythema, skin breakdown, purulent discharge, or exposed graft material 1
• Radiologic imaging (duplex ultrasound ± CT scan) should be used to confirm the diagnosis and characterize the fluid collection 1
• The presence of gas within the collection on CT imaging is a strong predictor of infection (P = 0.001), though imaging alone cannot definitively distinguish infected from sterile collections 2

Critical Differences: AVF vs AVG Management

Arteriovenous Fistula (AVF) Infection

• AVF infections are rare and can often be managed with antibiotics alone plus drainage of any fluid collection 1, 3
• The AVF itself is typically preserved unless there is extensive tissue destruction or sepsis 1, 3
• Surgical consultation should focus on drainage of the fluid collection while maintaining fistula patency 1

Arteriovenous Graft (AVG) Infection

AVG infections require a more aggressive surgical approach based on the extent of infection: 3

• Total graft excision: When the patient presents with sepsis or the entire graft is bathed in purulent material 3
• Subtotal graft excision: When all graft material is removed except a small oversewn cuff on the underlying patent artery 3
• Partial graft excision: When only the infected portion is removed and a new graft is rerouted through adjacent sterile tissue 3

The infection rate for AVG (11-20%) is substantially higher than AVF (1-4%) during their expected periods of use 1

Antibiotic Duration Guidelines

If AVG is Retained (Partial Excision with Rerouting)

• Administer IV antibiotics for 4-6 weeks based on culture sensitivities 1
• This extended duration accounts for the retained prosthetic material serving as a nidus for persistent infection 1
• Strict follow-up of culture results with appropriate antibiotic adjustment is essential 1

If AVG is Completely Removed

• Administer IV antibiotics for 2-3 weeks after complete graft excision 1, 4
• Duration should be guided by clinical resolution of infection signs (fever resolution, normalized WBC, clinical improvement) rather than complete radiographic resolution of fluid collections 4
• Antibiotics can be stopped after 3-5 days if no signs of systemic inflammation persist and adequate source control was achieved 4

If AVF is Retained (Typical Scenario)

• Administer IV antibiotics for 2-3 weeks with drainage of the fluid collection 1, 4
• The native vessel is less prone to persistent infection compared to prosthetic material 3
• Clinical parameters (resolution of fever, normalized inflammatory markers, catheter output <10-20 cc/day if drain placed) guide discontinuation 4

Surgical Decision Algorithm

Follow this stepwise approach: 1, 3

1. Assess severity of presentation:

   • Sepsis/bacteremia → Total AVG excision required 3
   • Localized infection without systemic signs → Consider partial excision or drainage 3

2. Evaluate extent of graft involvement:

   • Entire graft bathed in pus → Total excision 3
   • Limited segment infected with adjacent sterile tissue → Partial excision with rerouting 3

3. Consider future access options:

   • Limited remaining access sites → Attempt graft salvage if clinically safe 1
   • Multiple alternative sites available → Lower threshold for complete excision 1

4. Identify offending organism:

   • S. aureus, Gram-negative bacteria, or fungal organisms → Monitor closely for metastatic complications (endocarditis, spinal abscess, septic arthritis) with echocardiography and MRI as indicated 1

Temporary Access Management

• Place a tunneled cuffed dialysis catheter for interim hemodialysis access if the infected access must be abandoned 1
• If systemic infection or bacteremia is present, treat the infection first before placing a tunneled catheter 1
• A temporary non-tunneled catheter can be used for immediate dialysis needs while treating active infection 1

Common Pitfalls to Avoid

• Never remove the drain and continue antibiotics alone for a persistent fluid collection - this is inappropriate management 1, 4
• Do not delay surgical consultation - infected AVG requires timely surgical assessment to prevent progression to sepsis 1
• Avoid prolonging antibiotics based solely on residual imaging findings - small residual collections are common after successful treatment and do not require extended therapy if clinical parameters have normalized 4
• Do not assume all fluid collections are infected - even with advanced imaging, specificity for infection is only 39% 2
• Never place a tunneled catheter in the setting of active bacteremia without treating the infection first 1