Surgery MCQs Q31

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SURGERY • VASCULAR

A 24-year-old IV drug user presents with a 2-week history of gradually increasing swelling in the left groin. He is afebrile, pulse 74/min. On examination, the swelling is non-tender but shows expansile pulsation. No regional lymphadenopathy is noted.

What is the most likely diagnosis?

A Ectopic testis

B Lipoma

C Psoas abscess

D Enlarged lymph nodes

E Femoral artery aneurysm

The most likely diagnosis is Femoral artery aneurysm (often a pseudoaneurysm in this patient population).

Decoding the Stem

1

CLUE "Groin swelling + expansile pulsation + IV drug abuse"

TRANSLATION This combination strongly indicates a vascular lesion.

Explanation

E. Femoral Artery Aneurysm: ✅ Correct. Expansile pulsation is the hallmark clinical sign of an arterial aneurysm. In IV drug users, repeated accidental arterial puncture leads to pseudoaneurysm formation, which typically presents as a pulsatile mass in the groin.

C. Psoas Abscess: ❌ Incorrect. While common in IV users, it typically presents with fever, hip flexion, and localized pain. It does not show expansile pulsation.

D. Enlarged Lymph Nodes: ❌ Incorrect. Lymphadenopathy (often due to infection in IV users) presents as firm, discrete or matted masses that are not pulsatile.

A & B. Ectopic Testis / Lipoma: ❌ Incorrect. Neither of these conditions exhibits vascular features like pulsation.

🧠 Clinical Pearls

Sign/Factor	Clinical Significance
Expansile Pulsation	Pathognomonic for Aneurysm
Transmitted Pulsation	Solid mass overlying a large vessel
IV Drug Use Risk	High risk for Pseudoaneurysm

Integrated Clinical Questions

1. What is the anatomical difference between a true aneurysm and a pseudoaneurysm?

Answer: A True Aneurysm involves all three layers of the vessel wall (intima, media, adventitia). A Pseudoaneurysm (False Aneurysm) is a breach in the wall where blood is contained by surrounding connective tissue.

2. What is the investigation of choice to confirm the diagnosis?

Answer: Duplex Ultrasound (Doppler) is the initial investigation of choice to assess flow and confirm the vascular nature of the mass.

3. Why are IV drug users specifically at risk for femoral pseudoaneurysms?

Answer: Due to accidental or intentional arterial puncture during attempts to inject into the femoral vein, leading to a persistent leak from the artery.

4. What are the common complications of a femoral aneurysm?

Answer: Rupture (life-threatening hemorrhage), thrombosis (causing acute limb ischemia), and distal embolism.

5. How can you clinically distinguish transmitted vs. expansile pulsation?

Answer: Place two fingers on the mass: if they move apart with each pulse, it is expansile (aneurysm). If they move upwards only together, it is transmitted (solid mass over a vessel).

⚡ Exam Pearls

• Expansile pulsation = Aneurysm (must not miss).
• IV Drug Use: Classic risk factor for pseudoaneurysm.
• Differentiate: Abscess is painful; Lymph nodes are firm/non-pulsatile.

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