A 28-year-old woman undergoes femoral artery catheterization for coronary angiography. Six hours post-procedure, she develops a pulsatile mass in the groin with pain and mild swelling. Doppler ultrasound confirms a 2.5 cm pseudoaneurysm of the femoral artery with a 4 mm neck. She is hemodynamically stable with intact distal pulses. What is the most appropriate next step in management?

Explanation

## Clinical Context Post-catheterization pseudoaneurysm of the femoral artery is a known complication. This patient is hemodynamically stable with a small-to-moderate pseudoaneurysm (2.5 cm) and narrow neck (4 mm), making her an ideal candidate for **percutaneous thrombin injection**. ## Management Algorithm for Femoral Pseudoaneurysm ```mermaid flowchart TD A[Post-catheterization femoral pseudoaneurysm]:::outcome --> B{Hemodynamically stable?}:::decision B -->|No| C[Hemorrhagic shock]:::urgent C --> D[Urgent surgical repair]:::action B -->|Yes| E{Neck diameter?}:::decision E -->|< 6 mm| F[Percutaneous thrombin injection]:::action E -->|≥ 6 mm| G[Compression repair or surgery]:::action F --> H[Ultrasound follow-up at 1 week]:::action G --> I[Surgical repair]:::action ``` ## Key Point: **Percutaneous thrombin injection is the first-line treatment for hemodynamically stable femoral pseudoaneurysms with a neck diameter < 6 mm.** Success rate exceeds 95% with minimal morbidity. ## High-Yield: Pseudoaneurysm management depends on: | Feature | Observation | Compression | Thrombin | Surgery | |---------|-------------|-------------|----------|----------| | **Hemodynamic stability** | Required | Required | Required | Any | | **Neck diameter** | Any | < 10 mm | < 6 mm | Any | | **Size** | < 2 cm preferred | Any | Any | Any | | **Success rate** | ~10% | 60–80% | > 95% | 100% | | **Recurrence** | High | 5–10% | < 2% | Rare | ## Clinical Pearl: Thrombin injection works by **direct thrombus formation within the pseudoaneurysm sac**, sealing it from the arterial system. The narrow neck (4 mm) ensures thrombin stays contained and does not embolize distally. ## Mnemonic: **"THROMBIN for THIN necks"** — Thrombin injection is ideal when the pseudoaneurysm neck is **thin** (< 6 mm). ## Warning: **Do NOT observe pseudoaneurysms > 2.5 cm or with wide necks.** Risk of rupture and thromboembolism increases with size. Compression repair is second-line if thrombin fails or is contraindicated.