Abdominal Aortic Aneurysm
Abnormal focal dilation of the abdominal aorta exceeding 3 cm in diameter, most commonly occurring infrarenally, with risk of rupture and life-threatening hemorrhage.
History Taking: Abdominal Aortic Aneurysm (AAA)
Opening the Consultation
Start broad, then funnel in. Many AAAs are asymptomatic and found incidentally—the patient may have been told about a "swelling" or sent from a screening ultrasound. Alternatively, they may present acutely with pain, which changes your entire approach.
Practical opener:
"Can you tell me what brought you in today? / 你今日點解嚟睇醫生呀？(nei5 gam1 jat6 dim2 gaai2 lei4 tai2 ji1 sang1 aa3?)"
Symptom Analysis (SOCRATES)
- "Where exactly is the pain? Can you point to it?" / 邊度痛？你可唔可以指俾我睇？(bin1 dou6 tung3? nei5 ho2 m4 ho2 ji5 zi2 bei2 ngo5 tai2?)
- Central abdominal / epigastric / periumbilical pain is classic for AAA [1][2]
- Back or flank pain suggests posterior wall involvement or retroperitoneal leak [2]
- Pelvic or groin pain suggests distal aortic rupture near iliac bifurcation with lumbar nerve irritation [2]
Why this matters: The location of pain helps localise the aneurysm segment and, critically, helps differentiate ruptured from non-ruptured AAA and from other causes of acute abdomen.
- "When did the pain start? Was it sudden or gradual?" / 幾時開始痛？係突然定係慢慢嚟？(gei2 si4 hoi1 ci2 tung3? hai6 dat6 jin4 ding6 hai6 maan6 maan2 lei4?)
- Sudden onset (within seconds) → think rupture, infarction, haemorrhage [3][4]
- Gradual onset over weeks/months → expanding aneurysm compressing surrounding structures [2]
Why this matters: Catastrophic onset pain is a hallmark of ruptured AAA [4]. Pain onset within seconds should trigger immediate assessment for haemodynamic instability.
- "Does the pain go anywhere else?" / 痛有冇去到其他地方？(tung3 jau5 mou5 heoi3 dou3 kei4 taa1 dei6 fong1?)
- Back: classic for AAA (posterior wall compression or retroperitoneal haemorrhage) [1][2]
- Groin/thigh: distal aneurysm compressing lumbar plexus / genitofemoral nerve [2][3]
- Shoulder tip: suggests intraperitoneal haemorrhage (less common, anterior rupture) [4]
This is where you differentiate "just a big aorta" from a surgical emergency:
- Shock symptoms: "Have you felt faint, dizzy, or collapsed?" / 有冇頭暈、眼前發黑、或者暈低咗？(jau5 mou5 tau4 wan4, ngaan5 cin4 faat3 hak1, waak6 ze2 wan4 dai1 zo2?)
- Limb ischaemia: "Have you noticed any change in colour, coldness, or pain in your legs or toes?" / 你對腳有冇變色、凍、或者痛？(nei5 deoi3 goek3 jau5 mou5 bin3 sik1, dung3, waak6 ze2 tung3?)
- Constitutional symptoms: "Any fevers, night sweats, weight loss, loss of appetite?" / 有冇發燒、夜晚出汗、體重下降、冇胃口？
- GI bleeding: "Have you vomited blood or passed black tarry stools?"
- Aortoenteric fistula → massive GI bleeding (rare but catastrophic) [7]
- Haematuria: "Any blood in your urine?"
- Aorto-ureteric fistula [7]
- "Has the pain been getting worse, better, or staying the same?"
- Progressive worsening → rapid expansion or impending rupture [2]
- Rapid expansion defined as >1.0 cm/year or >0.5 cm/6 months [1][8]
- Pain that suddenly eases after initial severe episode → posterior rupture with retroperitoneal tamponade (do NOT be falsely reassured) [2]
Don't be fooled by transient pain relief
In posterior aortic wall rupture, the retroperitoneal haematoma may temporarily tamponade the bleeding, causing pain to subside. This does NOT mean the patient is improving—it means the retroperitoneum is containing the bleed... for now. Always maintain a high index of suspicion. [2]
- Pain worse with movement → peritoneal irritation (if ruptured) [4]
- Pain unrelated to meals, position changes, or micturition helps exclude GI and urological causes
- "On a scale of 0-10, how bad is the pain?" / 0到10分，你覺得幾痛？(ling4 dou3 sap6 fan1, nei5 gok3 dak1 gei2 tung3?)
- Severe and acute abdominal pain is characteristic of rupture [2]
- Does the pain wake you from sleep? Interfere with daily activities?
| System | Key Questions | Why It Matters |
|---|---|---|
| Cardiovascular | Claudication history (calf/buttock pain on walking)? Chest pain? Palpitations? Previous MI/stroke? | AAA patients have diffuse atherosclerosis; 95% have associated atherosclerosis [1][9]. Claudication history also helps distinguish embolic vs thrombotic limb ischaemia. |
| Peripheral vascular | Cold extremities? Colour changes in toes? Rest pain in legs? | Blue toe syndrome from distal embolization [2][7]. Also screen for femoral/popliteal aneurysms (62% of popliteal aneurysm patients have AAA; 82% of femoral aneurysm patients have AAA) [2] |
| Respiratory | SOB? History of COPD? | COPD is strongly associated with smoking; important for operative risk assessment [2] |
| GI | Haematemesis? Melaena? Change in bowel habit? | Rule out aortoenteric fistula and other causes of acute abdomen [7] |
| Urological | Haematuria? Loin pain? Urinary symptoms? | Rule out renal colic, aorto-ureteric fistula [7] |
| Neurological | Lower limb weakness, numbness, paraesthesia? | Spinal cord or nerve root compression from large AAA or haematoma |
Risk Factors, Comorbidities & Background History
High risk (actively ask about each):
- Elderly + Male + Caucasian [1][2][9]
- Smoking (single most important modifiable risk factor; also accelerates expansion rate) [1][2][8]
- "Have you ever smoked? How many cigarettes per day and for how many years?" / 你有冇食煙？食咗幾耐？一日幾多支？(nei5 jau5 mou5 sik6 jin1? sik6 zo2 gei2 noi6? jat1 jat6 gei2 do1 zi1?)
- Atherosclerosis (IHD, PVD, cerebrovascular disease) [1][9]
- Hypertension [1][2][9]
- Family history of AAA [1][2]
- Presence of other large artery aneurysms (iliac, femoral, popliteal) [1][2]
Moderate risk:
- Connective tissue diseases: Marfan's syndrome, Ehlers-Danlos syndrome type IV [1][7][9]
- Diabetes (paradoxically may ↓ expansion rate but still a risk factor for atherosclerosis) [2][8]
- Hyperlipidaemia [10]
Why this matters for the exam: The examiner expects you to systematically screen for cardiovascular risk factors. AAA is essentially a manifestation of systemic vascular disease. Asking about smoking is non-negotiable.
- Hypertension, IHD, stroke/TIA, PVD, AF
- Diabetes mellitus
- COPD (smoking association + affects operative fitness)
- Connective tissue disorders
- Previous DVT/PE (thrombophilic state)
- Known AAA — if so, when was it diagnosed? What size? Who is following up? Last ultrasound?
- Previous AAA repair (open or EVAR) → risk of endoleak, graft infection, aortoenteric fistula [11]
- Previous vascular surgery (bypass grafting, angioplasty)
- Previous abdominal surgery (may affect surgical approach)
- Antihypertensives (type, compliance — BP control is critical)
- Antiplatelets (aspirin, clopidogrel) — bleeding risk in rupture
- Anticoagulants (warfarin, DOACs) — bleeding risk, need reversal agent awareness
- Statins — cardiovascular risk management
- NSAIDs — renal implications, can confuse pain picture
- Beta-blockers — may slow aneurysm expansion (theoretical benefit)
- "Do you have any drug allergies?" / 你有冇藥物敏感？(nei5 jau5 mou5 joek6 mat6 man5 gam2?)
- Specifically ask about contrast allergy (important for CTA planning) [2]
- Latex allergy (if surgical intervention anticipated)
- "Does anyone in your family have an aneurysm or have they died suddenly from a blood vessel problem?" / 你屋企人有冇血管膨脹或者突然因為血管問題過身？
- Family history of AAA is a significant independent risk factor [1][2]
- Sudden death in a male relative >50 (may represent undiagnosed ruptured AAA)
- Connective tissue disorders in family (Marfan's, Ehlers-Danlos)
- Smoking (quantify in pack-years; cessation is the single most important intervention for small AAAs) [8]
- Alcohol (liver disease → coagulopathy if surgical)
- Occupation and functional baseline — critical for operative planning
- "Can you walk up a flight of stairs without stopping?" / 你行唔行到一層樓梯唔使停？(nei5 haang4 m4 haang4 dou2 jat1 cang4 lau4 tai1 m4 sai2 ting4?)
- Exercise tolerance is a proxy for cardiac fitness
- Living situation — who is at home? Can they care for you post-operatively?
- ADL independence — important for prognostication and surgical decision-making
| Differential | Key Differentiating Question | Expected Finding if Alternative Dx |
|---|---|---|
| Aortic dissection | "Is the pain tearing in nature? Did it start between your shoulder blades?" / 痛嘅感覺係咪好似撕裂咁？有冇去到背脊中間？ | Sudden tearing pain radiating to back, often interscapular. May have asymmetric BP/pulses. [5][9] |
| Renal colic | "Does the pain go from your back around to your groin? Any blood in urine?" | Loin-to-groin colicky pain, haematuria, restless patient (cf. peritonitis: patient lies still) [4] |
| Acute pancreatitis | "Does the pain go straight through to your back? Is it worse after eating or drinking alcohol?" | Epigastric pain radiating to back, relieved by sitting forward, alcohol/gallstone history [4][5] |
| Ruptured HCC | "Do you have a history of hepatitis B or liver disease?" | Especially important in Hong Kong given high HBV prevalence. Younger age, known CLD. [6] |
| Acute MI | "Any chest tightness, jaw pain, or arm pain?" | May present with epigastric pain. ECG and troponin will differentiate. |
| Ruptured ectopic pregnancy | "When was your last period? Any chance of pregnancy?" (in women of childbearing age) | Amenorrhoea, vaginal bleeding, positive pregnancy test [6] |
| Peritonitis (e.g. PPU) | "Is the pain worse when you move or cough?" | Board-like rigidity, history of peptic ulcer disease, NSAID use [5] |
Hong Kong-Specific Tip
In Hong Kong, ruptured HCC must always be considered in the differential of a middle-aged patient presenting with sudden abdominal pain and shock—especially given the high prevalence of Hepatitis B. Don't anchor on AAA without excluding this. [6]
These findings mandate immediate senior escalation and surgical consultation:
| Red Flag | Significance |
|---|---|
| Sudden severe abdominal/back pain + hypotension + pulsatile mass | Classical triad of ruptured AAA (~50% have all three) [1][6] |
| Haemodynamic instability (tachycardia, hypotension, altered consciousness) | Active bleeding; permissive hypotension (SBP 80-100) and prepare for emergency repair [6] |
| New-onset severe back/flank pain in known AAA patient | Impending rupture until proven otherwise [1][2] |
| Rapid expansion (>1 cm/year or >0.5 cm/6 months on surveillance) | Indication for urgent surgical repair [2][8] |
| Acute limb ischaemia (6 P's: pain, pallor, pulselessness, paraesthesia, paralysis, perishing cold) | Distal embolization from mural thrombus [2][7] |
| Signs of retroperitoneal bleeding (Cullen's, Grey Turner's, Fox's, Bryant's signs) | Late signs of significant haemorrhage [2][6] |
| Massive GI bleeding in patient with previous AAA repair | Aortoenteric fistula — surgical emergency [7][11] |
Common OSCE Pitfalls
-
Forgetting to ask about smoking. This is the single most important modifiable risk factor. In an OSCE, failing to ask about smoking for an AAA case is an easy way to lose marks.
-
Not screening for other aneurysms. 62% of patients with popliteal aneurysm have an associated AAA; 82% of femoral aneurysm patients have AAA. [2] Ask: "Have you ever been told you have a swelling or aneurysm anywhere else?"
-
Anchoring on AAA and missing aortic dissection. Both can present with sudden abdominal/back pain. Ask about the character (tearing vs. constant deep pain) and check for asymmetric pulses.
-
Being falsely reassured by temporary pain relief in posterior rupture (retroperitoneal tamponade effect). [2]
-
Forgetting contrast allergy when CTA is the next investigation step.
-
Not asking about functional baseline and exercise tolerance — this directly impacts operative decision-making. A patient who cannot walk up stairs is a different surgical candidate from a marathon runner.
-
Ignoring medications, particularly anticoagulants and antiplatelets, which critically affect bleeding risk and perioperative management.
-
Not asking family history. AAA has a significant genetic component — a first-degree relative with AAA confers significant risk. [1][2]
| Question You Ask | Why the Examiner Cares |
|---|---|
| Smoking history | Shows you understand the #1 modifiable RF; also relevant to COPD/operative fitness |
| "Any previous aneurysm or swelling in your groin/behind your knee?" | Demonstrates knowledge that 20% of AAA patients have associated aneurysms elsewhere [1][9] |
| "Any pain, coldness, or colour change in your toes?" | Shows awareness of distal embolization (blue toe syndrome) as a complication [2][7] |
| "Has anyone in your family had an aneurysm?" | Shows awareness of genetic risk and screening implications [1][2] |
| "What size was your aneurysm last measured at?" | Shows understanding of size-based management thresholds (≥5.5 cm → elective repair, < 5.5 cm → surveillance) [8][9] |
| "How far can you walk? Can you climb stairs?" | Demonstrates awareness that functional status determines operative candidacy |
| "Any history of Marfan's syndrome or similar conditions?" | Shows awareness of connective tissue disease aetiology in younger patients [1][9] |
| Asking about previous AAA repair/graft | Opens the door to discussing endoleak, graft infection, and aortoenteric fistula — high-yield OSCE content [11] |
"Mr Chan is a 72-year-old retired gentleman who presented today to Queen Mary Hospital's Emergency Department with a 3-hour history of sudden-onset severe central abdominal pain radiating to his back.
He describes the pain as constant, deep, and 9 out of 10 in severity. He felt lightheaded and nearly collapsed at home. He denies any tearing quality to the pain, haematemesis, melaena, haematuria, or acute limb symptoms. He has not had any fevers, weight loss, or recent trauma.
His past medical history is significant for a known 4.8 cm infrarenal abdominal aortic aneurysm diagnosed 2 years ago on screening ultrasound (last measured 6 months ago at 4.8 cm), hypertension for 15 years, hyperlipidaemia, type 2 diabetes mellitus, and COPD.
His past surgical history includes a right inguinal hernia repair 10 years ago. He has had no previous vascular procedures.
His regular medications include amlodipine 5 mg daily, atorvastatin 40 mg daily, metformin 500 mg BD, aspirin 80 mg daily, and salbutamol inhaler PRN. He reports no known drug allergies, including no contrast allergy.
His family history is notable for his father who died suddenly aged 68 from a "burst blood vessel in his abdomen" — likely ruptured AAA. His mother had hypertension and died of a stroke aged 75. No known connective tissue disorders in the family.
Socially, he is a 50 pack-year ex-smoker who quit 3 years ago. He drinks alcohol socially, approximately 2-3 units per week. He lives with his wife in a flat with a lift. Prior to today, he was independently mobile and could walk approximately 200 metres on flat ground before stopping due to breathlessness (limited by COPD rather than claudication). He could manage one flight of stairs slowly.
In summary, this is a 72-year-old gentleman with known AAA, multiple cardiovascular risk factors, and a strong family history, presenting with sudden severe abdominal pain and near-syncope — I am concerned about possible rupture or rapid expansion of his known AAA. I would like to request urgent surgical review, establish large-bore IV access, send bloods including group and cross-match for 6 units, and arrange for urgent bedside FAST scan while considering CT angiography if haemodynamically stable."
High Yield Summary
Key takeaways for AAA history taking in the OSCE:
-
Definition: True aneurysm = full-thickness dilation >50% of normal diameter (i.e., >3 cm); 97% are infrarenal; 95% associated with atherosclerosis [1][9].
-
Risk factors you MUST ask: Smoking (pack-years), hypertension, family history of AAA, known other aneurysms, connective tissue disease, male sex, age >65.
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Classical triad of ruptured AAA: Severe abdominal/back pain + hypotension + pulsatile abdominal mass (present in ~50%) [1][6].
-
Size matters: < 5.5 cm → surveillance; ≥5.5 cm → elective repair; symptomatic or rapidly expanding at any size → urgent repair [8][9].
-
Don't forget: Screen for associated peripheral aneurysms (62% of popliteal, 82% of femoral aneurysm patients have AAA) [2]; ask about limb ischaemia (blue toe syndrome); ask about contrast allergy for CTA.
-
Key differentials to exclude: Aortic dissection, ruptured HCC (important in HK), renal colic, acute pancreatitis, acute MI, ruptured ectopic pregnancy [5][6].
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Escalation triggers: Haemodynamic instability, new severe pain in known AAA, acute limb ischaemia, massive GI bleeding post-AAA repair.
Active Recall - History Taking
[1] Lecture slides: GC 199. Pulsating abdominal mass aortic aneurysm.pdf (p4-5) [2] Senior notes: felixlai.md (Abdominal aortic aneurysm section) [3] Senior notes: Ryan Ho Fundamentals.pdf (p275-276, Approach to the Acute Abdomen) [4] Senior notes: Ryan Ho GI.pdf (p97, p101-102, Causes of Central Abdominal Pain and Approach to the Acute Abdomen) [5] Lecture slides: GC 195. Lower and diffuse abdominal pain RLQ problems; pelvic inflammatory disease; peritonitis and abdominal emergencies.pdf (p44) [6] Senior notes: Ryan Ho Cardiology.pdf (p222-223, p227, Abdominal Aortic Aneurysms and Ruptured AAA) [7] Senior notes: maxim.md (Vascular surgery, AAA section) [8] Senior notes: maxim.md (Management, conservative and surgical indications) [9] Senior notes: Ryan Ho Cardiology.pdf (p222-223, AAA epidemiology and features) [10] Senior notes: Ryan Ho Endocrine.pdf (p125, ASCVD risk factors) [11] Senior notes: felixlai.md (Upper GI bleeding section — aortoenteric fistula post-AAA repair)
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