Infected vascular graft and mycotic aneurysm

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Vascular graft and endograft infection is microbial contamination of prosthetic arterial material or surrounding tissue. An infected arterial aneurysm, historically called mycotic despite often being bacterial, is infection-driven destruction and dilatation of a native arterial wall.

Infection follows peri-operative inoculation, extension from an adjacent bowel or wound focus, or bloodstream seeding. Staphylococci dominate many graft infections; enteric Gram-negative organisms, streptococci, enterococci, Salmonella and fungi occur according to site and exposure.

Low-grade infection can be deceptively quiet. Recurrent bacteraemia, back or groin pain, loss of appetite, weight loss, a small sinus or unexplained inflammatory markers may precede pseudoaneurysm, thrombosis, fistulation and rupture.

Care requires infection physicians, vascular surgeons, radiologists and microbiology. Antimicrobials reduce bloodstream burden, but unstable infected anatomy and retained devitalised prosthesis usually require urgent procedural source control.

Key points

Ask about every arterial graft, stent, bypass and endovascular repair, including implantation date, groin wound problems and recent bacteraemia.
Vascular graft infection may present months or years later with fever, weight loss, vague pain, recurrent bloodstream infection or a draining sinus.
CT angiography is the urgent anatomical investigation for suspected aneurysm, perigraft complication, rupture or fistula.
Take several peripheral blood-culture sets before antibiotics when stable and send multiple deep operative specimens rather than superficial sinus swabs.
FDG PET-CT or labelled-leucocyte imaging can support diagnosis of indolent graft infection when cross-sectional findings are equivocal.
Definitive treatment usually requires removal or exclusion of infected material, debridement and reconstruction planned by an experienced vascular service.
Endovascular stenting may control life-threatening bleeding as a bridge but can leave infection behind and needs a definitive follow-up plan.
Antibiotic selection and duration depend on organism, anatomy, removal completeness, new graft material, allergy and renal function.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Operative inoculation

Skin or environmental organisms contaminate prosthetic material during implantation and later establish deep biofilm infection. in susceptible exposed adults.

Bloodstream seeding

Sustained staphylococcal, Salmonella or other bacteraemia adheres to graft surfaces or damaged atherosclerotic arterial wall. in susceptible exposed adults.

Contiguous extension

Groin wound infection, bowel communication, vertebral infection or adjacent collection spreads directly onto graft and anastomosis.

Aorto-enteric communication

Mechanical erosion and infection create a fistula between aortic reconstruction and bowel, introducing enteric flora and catastrophic bleeding risk.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Biofilm persistence
Adherent organisms become embedded in protective matrix on prosthesis, reducing immune access and antimicrobial susceptibility. during active invasive disease.
2
Arterial-wall destruction
Inflammation and microbial enzymes weaken media and adventitia, forming an infected aneurysm or rapidly expanding pseudoaneurysm.
3
Anastomotic failure
Infected sutures and surrounding tissue lose integrity, causing leak, dehiscence, haemorrhage and graft-enteric fistulation. during active invasive disease.
4
Thrombotic and embolic injury
Inflamed grafts thrombose or shed infected debris, compromising limb, renal, mesenteric or cerebral circulation. during active invasive disease.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Aortic pain syndromeRed flag

Persistent focal chest, back or abdominal pain with fever or bacteraemia suggests infected aneurysm or perigraft inflammation and warrants urgent CTA.

Groin graft infectionRed flag

Pain, erythema, swelling, discharge, lymph leak, bleeding or a sinus over a femoral graft may communicate directly with prosthetic material.

Late constitutional illness

Weight loss, anorexia, night sweats and raised CRP months after repair can represent indolent biofilm infection rather than malignancy alone.

Recurrent bacteraemiaRed flag

Repeated isolation of the same organism after apparently adequate therapy suggests a colonised graft, infected aneurysm or occult fistula.

Aorto-enteric fistulaRed flag

A self-limited sentinel gastrointestinal bleed, sepsis or polymicrobial blood culture in an aortic-graft recipient is a surgical emergency warning.

Perfusion complicationRed flag

Cool painful limb, absent pulse, abdominal pain out of proportion or focal neurology may indicate graft thrombosis, septic embolus or branch compromise.

Red flags requiring action

Sentinel haematemesis or melaena in a patient with an aortic graft can precede catastrophic aorto-enteric haemorrhage.
Sudden severe chest, back, abdominal or groin pain with hypotension suggests aneurysm or anastomotic rupture.
Expanding pulsatile swelling, wound bleeding or exposed graft needs immediate vascular review without bedside probing.
Persistent Staphylococcus aureus or Salmonella bacteraemia with focal aortic pain demands vascular imaging.
Gas, enlarging perigraft fluid, pseudoaneurysm or loss of tissue planes on CT supports deep infection and mechanical failure.
New limb ischaemia, mesenteric symptoms or neurological deficit may reflect embolisation, thrombosis or compromised reconstruction.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
CT angiographyFirst step
Why
Define aneurysm morphology, perigraft fluid or gas, pseudoaneurysm, fistula, thrombosis, branch perfusion and rupture.
Interpretation and limitations
This is the first urgent anatomical test in suspected deep vascular infection; arterial and portal phases may be needed when enteric fistulation is considered.
02
Peripheral blood cultures
Why
Identify the organism before treatment and demonstrate persistent or relapsing bloodstream infection.
Interpretation and limitations
Obtain at least two and preferably three sets when stable; repeat after therapy until clearance and never dismiss credible S aureus growth.
03
Full blood count, CRP, renal, liver and lactate
Why
Measure inflammation, haemorrhage, organ dysfunction and suitability for contrast, surgery and antimicrobial doses.
Interpretation and limitations
Normal inflammatory markers do not exclude indolent biofilm infection; falling haemoglobin or rising lactate escalates concern for bleeding or malperfusion.
04
FDG PET-CT
Why
Localise metabolically active graft infection and remote septic foci when routine CT is inconclusive in a stable patient.
Interpretation and limitations
Focal intense uptake is more concerning than diffuse postoperative activity; recent implantation and sterile inflammation complicate interpretation.
05
Microbiology from surgery
Why
Establish deep causative organisms and susceptibilities at debridement or graft explantation.
Interpretation and limitations
Send multiple separately labelled tissue, graft and pus samples before antiseptic contamination; request prolonged or molecular testing after prior antibiotics.
06
Endoscopy only after vascular planning
Why
Assess gastrointestinal bleeding or fistulation when it can be performed safely and will alter management.
Interpretation and limitations
A negative endoscopy cannot exclude an aorto-enteric fistula; avoid delaying CTA and operative control in a haemodynamically unstable patient.
07
Echocardiography and metastatic imaging
Why
Find an upstream endocardial source or haematogenous complications in sustained bacteraemia.
Interpretation and limitations
S aureus, enterococci and persistent bacteraemia require echocardiographic assessment; image spine, joints or viscera according to focal symptoms.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Sterile postoperative change

Expected early perigraft fluid and inflammation should regress; enlarging collections, gas, pseudoaneurysm or matching bacteraemia favour infection.

Non-infected graft thrombosis

Technical stenosis or progressive vascular disease causes ischaemia without systemic infection, though thrombosis and infection can coexist.

Retroperitoneal malignancy

Tumour can cause weight loss, pain and a soft-tissue mass but lacks characteristic perigraft communication and bloodstream microbiology.

Vertebral infection

Spondylodiscitis causes focal back pain and fever and may be either an alternative focus or contiguous complication of aortic infection.

Inflammatory aneurysm

Immune-mediated periaortitis creates pain and wall thickening without microbial cultures, perigraft gas or septic deterioration. on focused clinical assessment.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01BLEEDControl suspected rupture or fistulaFirst stepShock, sentinel or active gastrointestinal bleeding, abrupt severe pain or graft-site haemorrhage is present.

1Call vascular surgery and activate major-haemorrhage support immediately; use ABCDE, large-bore access, crossmatch and balanced blood-component resuscitation.
2Obtain cultures quickly and give broad intravenous therapy active against likely skin and enteric organisms under the local emergency protocol.
3Proceed to urgent CT angiography if sufficiently stable, but do not delay operative or endovascular haemorrhage control for exhaustive investigation.
4DefinitiveDocument whether endovascular treatment is definitive or a bridge, because retained infected tissue requires prolonged therapy and reassessment.

02STABLEConfirm indolent graft infectionThere is chronic pain, sinus, constitutional illness, unexplained inflammation or recurrent bacteraemia without immediate rupture.

1Clarify graft type, operative reports, wound history and prior isolates; examine graft course and distal perfusion without probing a sinus.
2Take multiple peripheral blood cultures and obtain CT angiography to assess graft, anastomoses, adjacent bowel and collections.
3Use PET-CT or labelled-leucocyte imaging through the vascular infection team when anatomy remains uncertain and the result will change intervention.
4Agree the operative and sampling strategy before starting antibiotics if stable enough, while treating promptly if sepsis or progression develops.

03CONTROLRemove infected vascular materialDeep prosthetic infection, infected aneurysm, pseudoaneurysm, fistula or uncontrolled bacteraemia is established.

1Plan explantation or exclusion, radical debridement and in-situ or extra-anatomical reconstruction according to anatomy and physiological reserve.
2Take several deep samples during source control and communicate prior antimicrobial exposure to the laboratory.
3Use temporary endovascular sealing selectively for catastrophic bleeding or prohibitive risk, with explicit surveillance for persistent infection.
4Assess limb, renal, bowel and spinal perfusion after reconstruction and respond immediately to ischaemia or compartment syndrome.

04DIRECTComplete directed infection treatmentDeep cultures and procedural findings define organism, retained material and source-control completeness.

1Narrow to the safest bactericidal agent with reliable bloodstream and tissue activity, adjusting dose for renal function, body size and susceptibility.
2Set duration jointly; extensive debridement, retained prosthesis and new material commonly require weeks of intravenous or highly bioavailable treatment.
3DefinitiveConsider long-term suppressive therapy only when definitive removal is impossible, with documented limitations, toxicity plan and relapse triggers.
4Arrange clinical, inflammatory-marker, culture and imaging follow-up because recurrence may present after apparent early improvement.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Treats sepsis while CTA and emergency vascular source control proceed.

Empirical severe graft-infection regimen

Give the locally approved intravenous combination after blood cultures, covering likely staphylococci and Gram-negative or enteric organisms according to anatomical site and healthcare exposure.

Select with infection specialists; document immediate beta-lactam allergy, renal function, recent resistant isolates and whether bowel fistulation or fungal risk changes coverage.

Provides targeted bactericidal therapy after cultures show susceptible staphylococci.

Flucloxacillin for MSSA

Give 2 g intravenously every four hours for confirmed methicillin-susceptible Staphylococcus aureus bloodstream or deep graft infection, with specialist-defined total duration.

Monitor liver, renal function, full blood count and sodium burden; ongoing positivity mandates renewed search for retained graft, abscess or endocarditis.

Covers resistant Gram-positive infection until a more specific active agent can be selected.

Vancomycin

Use local weight-based intravenous loading and renal-adjusted maintenance with measured serum exposure when MRSA or a defined severe beta-lactam constraint requires it.

Review concentrations, kidney function and nephrotoxins frequently; underexposure fails while excessive exposure causes avoidable renal injury.

Provides a defined parenteral option for susceptible Salmonella bacteraemia involving arterial tissue.

Ceftriaxone for susceptible invasive Salmonella

Give 2 g intravenously once daily when invasive Salmonella vascular infection is susceptible and the infection team selects ceftriaxone, generally as part of a prolonged source-control plan.

Susceptibility and travel history are essential; assess biliary effects, interaction with calcium infusions, allergy and whether oral step-down is microbiologically reliable.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Aneurysm rupture

Progressive arterial-wall destruction causes sudden internal haemorrhage, shock and death unless vascular control is immediate. without timely definitive management.

Aorto-enteric fistula

Communication with bowel produces occult sepsis, sentinel bleeding and later massive gastrointestinal haemorrhage. without timely definitive management.

Graft thrombosis

Luminal clot acutely compromises limb or organ perfusion and can threaten reconstruction, bowel, kidney or spinal cord.

Septic emboli

Infected thrombus travels distally, producing arterial occlusion, abscess, digital ischaemia or metastatic infection. without timely definitive management.

Relapsing bacteraemia

Retained biofilm or incompletely debrided tissue causes repeated bloodstream infection after apparently adequate antimicrobial courses. without timely definitive management.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Record haemodynamics, haemoglobin, lactate, abdominal or back pain and distal perfusion frequently during acute assessment.
Repeat blood cultures until clearance and obtain new sets before changing therapy for recurrent fever.
Monitor wound, sinus, graft exposure and reconstruction without bedside probing or superficial sampling.
Track renal, liver and haematological toxicity and serum concentrations required by the selected antimicrobials.
Assess limb, bowel, renal and spinal-cord perfusion after vascular intervention and investigate any new deficit urgently.
Trend CRP and imaging findings as adjuncts; neither alone proves sterilisation of retained prosthetic material.
Provide long-term surveillance with explicit instructions for recurrent fever, focal pain, bleeding, wound change or limb ischaemia.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Mycotic does not mean fungal

The historical term describes an infected aneurysm of any microbial cause; bacterial pathogens are much more common.

Sentinel bleeding matters

A brief apparently resolved gastrointestinal bleed may reflect temporary thrombus over an aorto-enteric fistula before exsanguination.

Superficial swabs mislead

A sinus swab reflects colonising skin flora and cannot replace multiple deep graft and tissue specimens obtained during source control.

Endovascular rescue has limits

A covered stent can stop catastrophic bleeding, but placing more foreign material into infection may require later explantation or suppression.

Salmonella seeks damaged arteries

Invasive non-typhoidal Salmonella can seed atherosclerotic aorta, so persistent bacteraemia with focal pain deserves CTA.

Normal CRP is not clearance

Low-grade biofilm infection can persist with modest markers; microbiology, anatomy and clinical trajectory carry greater weight.

11Common pitfallsFrequent interpretation and management errors.

01
Do not reassure after a sentinel gastrointestinal bleed in an aortic-graft recipient.
02
Do not delay CTA while repeatedly treating recurrent bacteraemia without finding its source.
03
Do not probe an exposed or bleeding groin graft at the bedside.
04
Do not base definitive therapy on a superficial sinus swab.
05
Do not assume endovascular haemorrhage control has eradicated infection.
06
Do not label prolonged suppression as cure when infected prosthetic material remains.