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Aortoenteric Fistula (AEF)

Key Points:

  • Mortality Rate: 60% to 100%.

Primary AEF:

  • Incidence: 0.04% to 0.07%.
  • Demographics: Common in older males (M:F = 3:1).
  • Most common location:
    • D3 & D4 (54%).
    • Esophagus (28%).
    • Small and large bowel (5%).
    • Stomach (2%).
  • Most common cause: Atherosclerotic aortic aneurysms.

Secondary AEF:

  • Incidence: Higher than primary AEF (0.36-1.6%).
  • Type 1 (Graft Enteric Fistula):
    • Erosion of the proximal aortic suture into the adjacent bowel.
    • Massive GI bleed.
  • Type 2 (Aortoenteric Erosions - AEE):
    • Aortic graft mechanically erodes into the overlying bowel without forming a fistula.
    • Causes chronic GI bleeding.

Classic Triad (Only in 11%):

  1. GI Bleeding.
  2. Pulsating abdominal mass.
  3. Abdominal pain.
  4. Intermittent Herald Bleeds: More common (94%).
  5. Positive Blood Culture: 85% (Most common organism: Staphylococcus aureus).

Diagnosis:

  • Exploratory Laparotomy: Gold standard with 100% sensitivity and specificity.
  • First Line Investigations: CT and UGIE.

CT Scan Findings:

  • Most Specific Signs:
    • Extravasation from aorta to the bowel lumen.
    • Enteric contrast in periaortic space.
  • Post-Surgical Indicators:
    • Periaortic gas persisting after 3-4 weeks.
    • Periaortic fluid persisting after 3 months (suggests infected graft).

Complications:

  • Most dreaded complication of extra-anatomic bypass in AEF:
    • Aortic stump blowout (5% to 25%).

Questions:

  1. MC organism isolated from AEF site is:

    • A) Streptococcus
    • B) E. coli
    • C) Staphylococcus
    • D) Klebsiella

    Answer: C) Staphylococcus

  2. Classical triad of symptoms in AEF is:

    • A) GI bleeding + Palpable abdominal mass + Pain
    • B) GI bleeding + Pulsating abdominal mass + Jaundice
    • C) Pulsating abdominal mass + Jaundice + Pain
    • D) GI bleeding + Pulsating abdominal mass + Pain

    Answer: A) GI bleeding + Palpable abdominal mass + Pain

  3. Most specific signs for an AEF on CT is:

    • A) Enteric contrast found in the periaortic space
    • B) Periaortic soft tissue edema
    • C) Periaortic fluid
    • D) Periaortic stranding

    Answer: A) Enteric contrast found in the periaortic space