What are the signs of impending abdominal aortic aneurysm (AAA) rupture?

Signs of Impending AAA Rupture

Any patient with a known AAA presenting with acute abdominal, back, or flank pain should be presumed to have impending rupture and requires immediate ICU admission with urgent repair within 24-48 hours. 1

High-Risk Clinical Features

Pain Characteristics (Primary Warning Sign)

• Acute onset pain in the abdomen, back, or flank is the cardinal symptom of impending rupture 1
• Pain may radiate to the groin 1
• Recurrent or refractory pain identifies patients at highest risk of progression to complete rupture 1
• The presence of pain attributable to the AAA warrants ICU admission regardless of aneurysm size 1

Physical Examination Findings

• Tenderness to palpation overlying the AAA in the abdomen, back, or flank indicates impending rupture 1
• A pulsatile abdominal mass has only 47.1% sensitivity, so its absence does not exclude impending rupture 2
• Hypotension has poor sensitivity (30.9%) for detecting impending rupture and typically indicates complete rupture has already occurred 2

Critical Imaging Findings on CT

Intramural Signs (Indicate Impending Rupture)

CT findings suggesting the aneurysm wall is failing but has not yet completely ruptured: 3, 4

• Preserved integrity of the aortic wall on imaging despite acute pain presentation 1
• Intramural hematoma visible on non-contrast CT phase 1
• Focal discontinuity or irregularity of calcification in the aneurysm wall 3, 4
• Hyperattenuating crescent sign (acute hemorrhage within aneurysm wall or thrombus) 3, 4

Extraluminal Signs (Indicate Contained or Complete Rupture)

• Pleural or peritoneal effusions, particularly if increasing on serial imaging 1
• Perivascular hematoma sealed off by retroperitoneal structures 1
• Contrast extravasation indicating active bleeding 1

Important Clinical Distinctions

Contained vs. Free Rupture

• Contained rupture patients remain hemodynamically stable because bleeding is temporarily sealed by surrounding structures (pleura, pericardium, retroperitoneum) 1
• Free rupture leads to rapid hemodynamic collapse and death, with mortality reaching 54% at 6 hours and 76% at 24 hours 1
• Fewer than half of patients with free rupture arrive at the hospital alive 1

Size Considerations

• Symptomatic aneurysms require urgent treatment regardless of diameter 1
• Saccular AAAs can rupture at smaller sizes than fusiform aneurysms (25% of saccular AAAs presenting acutely were <5.5 cm) 1
• Women experience rupture at smaller diameters than men (mean 5.0 cm vs. 6.0 cm) 1

Common Pitfalls to Avoid

• Do not rely on the classic triad (pain, hypotension, pulsatile mass) as it is present in only 25-50% of cases 5
• Do not wait for hemodynamic instability to diagnose impending rupture—this indicates complete rupture has already occurred 1
• Do not dismiss symptoms in patients with smaller aneurysms (<5.5 cm), especially women and those with saccular morphology 1
• Classic symptoms (abdominal pain 61.7%, back pain 53.6%, syncope 27.8%) have poor sensitivity, and their absence does not rule out impending rupture 2

Immediate Management Algorithm

1. Any AAA patient with acute pain → Immediate ICU admission 1
2. CT with non-contrast phase followed by contrast to detect intramural hematoma and contrast leaks 1
3. Arterial blood pressure monitoring and tight BP control 1
4. Urgent repair within 24-48 hours to prevent progression to free rupture 1
5. Consider endovascular repair when anatomically feasible, as it may have lower mortality than open repair in this setting 1